karnataka state council of science and technology

Karnataka State Council of Science and Technology

Indian Institute of Science Campus, Bengaluru 560 012

A Project Report On

MECHANICAL BEHAVIOR OF WOOD PLASTIC COMPOSITES (Project Ref. No. 39S0534)

Under

Student Project Programme

(39th Series 2015-16)

Submitted by:

Under the Guidance of

Prof. H. M. Kadlimatti

2015-2016

DEPARTMENT OF MECHANICAL ENGINEERING

SHRI B.V.V. SANGHA’S

BASAVESHWAR ENGINEERING COLLEGE (AUTONOMOUS)

VIDYAGIRI, BAGALKOT- 587102

KRUTIKA NAGDA 2BA12ME041

AMIT DESAI 2BA12ME011

MALLIKARJUN V M 2BA12ME048

LOHIT RATHOD 2BA12ME042

SHRI B.V.V. SANGHA’S

BASAVESHWAR ENGINEERING COLLEGE (AUTONOMOUS)

BAGALKOT- 587102

DEPARTMENT OF MECHANICAL ENGINEERING

2015-2016

CERTIFICATE

This is to certify that the project entitled “Mechanical Behavior of Wood Plastic

Composites”, sponsored by Karnataka State Council of Science and Technology

(KSCST), Indian Institute of Science Campus, Bengaluru 560 012 (Project Ref. No.

39SBE0534) under Student Project Programme (39th Series 2015-16) is a bonafide work

carried out by Ms. Krutika Nagda, Mr. Amit Desai, Mr. Mallikarjun V M, and Mr.

Lohit Rathod, bearing University register numbers 2BA12ME041, 2BA12ME011,

2BA12ME048 and 2BA12ME042 respectively as a part of their final year BE project

during 2015-16.

PROJECT GUIDE H.O.D PRINCIPAL

Prof H.M.KADLIMATTI Dr. S. N. KURBET Dr. R. N. HERKAL

INDEX

Contents Page No.

Acknowledgement …………………………………………………………..i

Abstract……………………………………………………………………...ii

List of Tables………………………………………………………………..iii

List of Figures…………………………………………………………......iv-vi

Chapter 1 Introduction……………………………………………………..1-3

1.1 Background and Motivation

1.2 Objectives

1.3 Outline of the project

Chapter 2 Literature Survey……………………………………………….4-23

2.1 Properties of Teak Wood

2.2 Properties and types of Plastics used

2.2.1 Properties of LDPE

2.2.2 Properties of HDPE

2.2.3 Properties of PVC

Chapter 3 Experimental Method…………………………………………24-39

3.1 Materials used

3.2 Methodology

3.3 Testing

3.3.1 Compression and Tensile tests

3.3.2 Water Absorption test

3.4 Results and Discussion

3.4.1 Compression test results

3.4.2 Tensile test results

3.4.3 Microstructure of WPC

Chapter 4 Conclusion…………………………………………………….40-41

Chapter 5 Scope for Future Work………………………………………….42

Chapter 6 References and Links ……………………………………………43

6.1 References

6.2 External Links

i

ACKNOWLEDGEMENT

It is with great pleasure and pride that we represent this report before you.

During planning and designing of this project we received support and

encouragement from various quarters.

At first I express my deep felt gratitude to Almighty God for His uncountable

blessings, which made it possible for us to see through the turbulence and complete

the project work.

We are deeply indebted to our project guide Prof. H. M. Kadlimatti for his

advices and whole hearted support and very valued constructive ideas that has driven

us to complete the project successfully.

We also express our gratitude to our beloved Principal Dr. R. N. Herkal,

Head of the Mechanical Department Dr. S. N. Kurbet and our project coordinators

Prof. G. K. Patil and Prof. B. S. Vivekanand for all the guidance they have

provided.

We would also like to express our gratitude to all the Faculty members

And supporting staff of Mechanical Engineering Department for their support

provided during the project work.

We gracefully acknowledge the financial support provided by the Karnataka

State Council (KSCST), IISc Campus, Bengaluru to carry out this project

successfully.

At last, we would like to take this our foremost duty to thank all those persons

who helped us and were a source of encouragement.

ii

ABSTRACT

Plastic nowadays has been a common need in day to day life. From using a toothbrush to

installing pipelines plastic has a vital role to play. One side it is a boon to the mankind but when

the coin is turned it is causing a serious hazard to the living beings. It was observed that the strength

and hardness of the polymeric materials have been increased with the addition of wood powder

available as a carpentry waste. Wood has long been used by the plastics industry as inexpensive

filler to increase strength and stiffness of thermoplastic or to reduce raw material costs. During the

late 1980’s, research and industries began investigating high filler levels and coupling agents to

encourage interaction between the wood and thermoplastic component. An improved

sophistication in processing and formulation lead to development of wood plastic composites

(WPC) that exhibit synergistic material properties. Wood plastic composites consists primarily of

wood and thermoplastic polymers. Specimens were prepared with different plastics like Low-

density polyethylene (LDPE), High-density Polyethylene (HDPE), Polyvinyl chloride (PVC)

and waste wood. Different compositions were tried as to know the amount of wood that can be

combined with plastic. Composites with PVC couldn’t be produced as it started to burn upon

heating. Compression and tensile tests were carried out using Universal Testing Machine for the

prepared specimens and results were compared. The microstructure of the surface of the specimen

were studied using Scanning Electron Microscope. Hence composite materials made from waste

wood powder and waste plastic would result in better utilization of solid waste.

Most of the physical and mechanical properties of wood plastic composites depend

mainly on the interaction developed between wood and thermoplastic materials. The strength of

wood plastic composites (WPC) varies from composition to composition. The mechanical

properties are more effective for the composite specimens having more fibrous content. Among

the different types of wood plastic composites made of LDPE, HDPE and combined plastic waste

(LDPE+HDPE), the mechanical behavior of samples made of LDPE is the greatest followed by

specimens made of combined plastic waste and HDPE. The moisture absorption of wood plastic

composites is vary less compared to wood.

Keywords- LDPE, HDPE, PVC, Compression and Tensile Test.

iii

List of Tables

Table No. 2.1 Mechanical and physical test results 7

Table No. 2.2 Properties of the boards 12

Table No. 2.3 Composition of various polypropylene/wood

flour composites

14

Table No. 2.4 Mechanical properties of WPCs 14

Table No. 2.5 Rate of water absorption and equilibrium

moisture of WPCs

15

Table No. 2.6 Polymers used in the study 16

Table No. 2.7 Experiments performed on two-roll mill 20

Table No. 3.1 Compression Test Results 36

Table No. 3.2 Tensile Test Results 37

Table No. 3.3 Moisture absorption Test Results 38

iv

List of Figures

Figure No. 1.1 Sources of Plastic 2

Figure No. 2.1 Tensile strength of MDF/Waste plastic composite

specimen as a function of fiber mass fraction at room

temperature and humidity 4

Figure No. 2.2 Tensile modulus of MDF/Waste plastic composite



Figure No. 2.3 Flexural strength of MDF/Waste plastic composite



Figure No. 2.4 Surface Roughness 7

Figure No. 2.5 Typical surface profiles of the samples average modulus

of elasticity of samples made from 60% and 80% fibers

and particles. 8

Figure No. 2.6 Thickness swelling for 2hr water soaking test 8

Figure No. 2.7 Average roughness (Ra) roughness values of the samples 9

Figure No. 2.8 Stress strain curve with 4% ionomer compared to nest

HDPE/maple compound 16

Figure No. 2.9 MOE (a) & MOR (b) of the wood plastic composites as a

function of ionomer content. The arrows indicate the

content above which the materials are too ductile for the

MOR to be evaluated with the method. 17

Figure No. 3.1 Drying of Wood powder in sunlight 25

v

Figure No. 3.2 Drying of wood powder in hot air oven 25

Figure No. 3.3 Heating of graphite crucible for melting of plastic 26

Figure No. 3.4 Mould for compression test specimens 26

Figure No. 3.5 Mould for tensile test specimens 27

Figure No. 3.6 Specification of WPC specimens for compression 28

Figure No. 3.7 Specifications of WPC specimens for tensile 28

Figure No. 3.8 UTM used for testing of WPC 28

Figure No. 3.9 Scanning Electron Microscope 28

Figure No. 3.10 Compression test result for WPC of composition LDPE-

75% & Wood-25% 29

Figure No. 3.11 Compression test result for WPC of composition LDPE-

80% & Wood-20% 29

Figure No. 3.12 Compression test result for WPC of composition HDPE-

75% & Wood-25% 30

Figure No. 3.13 Compression test result for WPC of composition HDPE-

80% & Wood-20% 30

Figure No. 3.14 Compression test result for WPC of composition

Combined (LDPE+HDPE) Plastic 75% & Wood-25% 31

Figure No. 3.15 Compression test result for WPC of composition

Combined (LDPE+HDPE) Plastic 80% & Wood-20% 31

Figure No. 3.16 Tensile test result for WPC of composition LDPE-75% &

Wood-25% 32

Figure No. 3.17 Tensile test result for WPC of composition LDPE 80% &

Wood 20% 32

vi

Figure No. 3.18 Tensile test result for WPC of composition Combined

(LDPE+HDPE) Plastic 80% & Wood-20% 33

Figure No. 3.19 Microstructure of WPC having composition LDPE-75%

& Wood-25% 33

Figure No. 3.20 Microstructure of WPC having composition LDPE-80%

& Wood-20% 34

Figure No. 3.21 Microstructure of WPC having composition 75% HDPE

– 25% Wood 34

Figure No. 3.22 Microstructure of WPC having composition 80% HDPE

– 20% Wood 35

Figure No. 3.23 Microstructure of WPC having composition 75%

LDPE+HDPE – 25% Wood 35

Figure No. 3.24 Microstructure of WPC having composition 80%

LDPE+HDPE – 20% Wood 36

Figure No. 3.25 Bar chart representing the comparison of compressive

strengths of WPC 38

Figure No. 3.26 Comparison of average values of samples of water

absorption 39

Figure No. 5.1 Outdoor decking 40

Figure No. 5.2 Railings 40

MECHANICAL BEHAVIOR OF WOOD PLASTIC COMPOSITES

DEPT. OF MECHANICAL ENGG, BEC, BAGALKOT 1

Chapter 1 INTRODUCTION

Wood-plastic composites (WPCs) are composite materials made of wood fiber/wood flour

and thermoplastic(s) (includes Low Density Polyethylene (LDPE), High Density Polyethylene,

(HDPE), Polypropylene (PP), and Poly Vinyl Chloride (PVC) etc.).

1.1 Background and motivation

Plastic pollution involves the accumulation of plastic products in the environment that

adversely affects wildlife, wildlife habitat, or humans. Plastics that act as pollutants. The

prominence of plastic pollution is correlated with plastics being inexpensive and durable,

which lends to high levels of plastics used by humans. However, it is slow to degrade. Plastic

pollution can unfavorably affect lands, waterways and oceans. Living organisms, particularly

marine animals, can also be affected through entanglement, direct ingestion of plastic waste,

or through exposure to chemicals within plastics that cause interruptions in biological

functions. Humans are also affected by plastic pollution, such as through the disruption of

the thyroid hormone axis or hormone levels. About 300 million tons of plastic is produced

globally each year, only about 10 % of that is recycled. India generates 5.6 million metric tons

of the waste plastic annually.

Modernization and progress has had its share of disadvantages and one of the

main aspects of concern is the pollution it is causing to the earth – be it land, air, and water.

With increase in the global population and the rising demand for food and other essentials,

there has been a rise in the amount of waste being generated daily by each household. This

waste is ultimately thrown into municipal waste collection centers from where it is collected

by the local municipalities for further disposal into the landfills and dumps. However, either

due to resource crunch or inefficient infrastructure, not all of this waste gets collected and

transported to the final dumpsites. Added to this if the management and disposal is improperly

done, it can cause serious health impacts. Plastic waste is a major environmental and public

health problem in India, particularly in the urban areas. Plastic shopping or carrier bags are one

of the main sources of plastic waste in our country. Plastic bags of all sizes and color dot the

city‘s landscape due to the problems of misuse and overuse and littering in India. Besides this

visual pollution, plastic bag wastes contribute to blockage of drains and gutters, are a threat to

https://en.wikipedia.org/wiki/Composite_material

https://en.wikipedia.org/wiki/Polypropylene

https://en.wikipedia.org/wiki/PVC

https://en.wikipedia.org/wiki/Environment_(biophysical)

https://en.wikipedia.org/wiki/Wildlife

https://en.wikipedia.org/wiki/Wildlife_habitat

https://en.wikipedia.org/wiki/Pollutant

https://en.wikipedia.org/wiki/Thyroid_hormone

https://en.wikipedia.org/wiki/Hormone



aquatic life when they find their way to water bodies, and can cause livestock deaths when the

livestock consume them. Furthermore, when filled with rainwater, plastic bags become

breeding grounds for mosquitoes, which cause malaria. In addition, plastics take many years

(20-1000) to degrade and hence pose a disposal challenge.

We have become so accustomed to the ubiquitous presence of plastic that it is difficult

to envision life when woods and metals were the primary materials used for consumer

products. Plastic has become prevalent because it is inexpensive and it can be engineered with

a wide range of properties. Plastics are strong but lightweight, resistant when degraded by

chemicals, sunlight, and bacteria, and are thermally and electrically insulating. Plastics have

become a critical material in the modern economy; the annual volume of plastics produced

exceeds that volume of steel. The world's annual consumption of plastic materials has

increased from around 5 million tons in the 1950s to nearly 300 million tons today. [9]

Fig. 1.1 Sources of plastic waste



1.2 Objectives

1. To produce wood plastic composites of different compositions by using thermoplastics

(LDPE, HDPE and PVC) and wood flour.

2. To test the wood plastic composite specimens for different mechanical properties (Tensile,

compression), microstructure and water absorption test.

1.3 Outline of the project

This project contains 6 chapters. Chapter 1 is general introduction to the project in

which motivation and background of the project, the specific objectives which were met in

accomplishing this goal are discussed. In chapter 2, the literature survey has been carried out

on various National and International research papers published about wood plastic

composites. The chapter 3 explains about the production and testing of wood plastic specimens

prepared in which the characteristics of the materials (wood and types of plastics), the

methodology used for the production of wood plastic composite specimens, the different types

of tests carried out to find the mechanical properties and the results obtained by the tests

(compression, tensile, water absorption and microstructure) are discussed in detail. Chapter 4

deals with the conclusions that could be drawn from the project. Chapter 5 deals with scope

for future work. The related references and links are listed in chapter 6.



Chapter 2 LITERATURE SURVEY

Composite specimens of prismatic shapes were produced through melt bending the

wood fibers and waste plastic, followed by injection moulding. The tensile and flexural

properties of the specimen were determined at room temperature and humidity, oven dried and

water soaked conditions and low and high temperatures. The influence of a coupling agent on

the tensile and flexural properties of some of the specimens had also been evaluated. The waste

plastics from a Kerbside collection considered in this study had 4 categories, namely HDPE

waste, Janitorial waste, Kerbside waste I and Kerbside waste II. Maleated propylene wax was

used as a coupling agent in some of the specimens produced. The medium density fibers used

in this study were commercial fibers which were brown in color with widths varying from 15

to 40m, lengths ranging from 1.5 to5 mm, density of 400kg/m3 and a nominal tensile strength

and stiffness of 125-150 MPa and 2.5-4 GPa, respectively. HDPE waste, Janitorial waste and

Kerbside waste I were melt blended without wood fibers and width 0, 20, 30 and 40% by mass

of wood fibers. Compounding was performed in a laboratory sigma blade mixer with a capacity

of 50g. The tensile and flexural properties of the MDF/Waste plastic composites at room

temperature and humidity were determined using Universal Testing Machine.

Fig. 2.1 Tensile strength of MDF/Waste plastic composite specimen as a function of fiber mass fraction at room

temperature and humidity (Jayaram et.al, 2004)



It was observed that the type of wood fiber, the thermoplastic matrix, any additives used and

the method of specimen produce influence the tensile strength of the resulting composite

specimen. Tensile moduli of MDF/waste plastic composite mostly increased with the

increasing fiber content except for 20% MDF/HDPE waste composites (Fig 2.1).

Fig.2.2 Tensile modulus of MDF/Waste plastic composite specimen as a function of fiber mass fraction at room

temperature and humidity (Jayaram et.al, 2004)

Flexural strength of MDF/waste plastic composites increase with the addition of

medium density fibers in all the way plastic composites except MDF/Kerbside waste I and an

increase in the fiber content causes an increase in the flexural modulus of all the waste plastic

composites (Fig 2.2 and 2.3). The addition of 1% Epolene to the 40% MDF/Kerbside waste II

composites improve their mechanical performance. It has been hypothesized that the maleic

anhydride units in Epolene bond with the lignocellulosic fibers, while the polymer chain in

Epolene entangles with the polymer chains of the plastic matrix leading to the improvement in

mechanical properties. The mechanical properties with oven dried and water soaked conditions

were also determined. It was observed that oven dried specimens displayed very little variation

whereas water soaked specimens showed degradation in mechanical properties. In this study

we observed that plastic from the post-consumer waste stream can be utilized to make

composite materials with useful mechanical properties.



Fig 2.3 Flexural Stength of MDF/Waste plastic composite specimen as a function of fiber mass fraction at room

temerature and humidity (Jayaram et.al, 2004)

Higher fiber content improved mechanical properties of the composites with

MDF/HDPE waste composites being the greatest followed by MDF/Janitorial waste

composites and then MDF/Kerbside waste I composites. The properties of 40 %

MDF/Kerbside waste II composites are only slightly lower than those of MDF/HDPE waste

composites due to the addition of 1% Epolene. (Jayaram et al, 2004). [1]

In the study carried out by Wechsler et al, 2006, specimens having 60% and 80%

particle fiber of pinus radiata were mixed with polypropylene and four different additives,

namely Structor TR 016 which is a coupling agent, CIBA blue pigment (Irgalite), CIBA anti-

microbial agent (IRGAGUARD F3510) as fungicide, CIBA UV Filter coating (TINUVIN

123S), and their combinations. On obtaining the results the work static bending properties of

the samples were improved as above additives were added to the fiber and particle based

composites. Micrographs were taken on scanning electron microscope (SEM) and it was

revealed that coupling agent and pigment resulted in more homogeneous mixture of the wood

and plastic. When average surface roughness and maximum surface roughness were evaluated,

the samples with particle based wood had rougher surface characteristics than with fiber based.

There was no significant influence on addition of additives.

The Wood particles and fibers were dried in an oven before they were mixed with

polypropylene. First plastic material was put into mixer rotating at 75 rpm having a



temperature of 165 °C for 2 min followed by adding the chemicals for each type of material.

In the next step particles or fibers were added into the mixture and rotated for another

3 min completing a total mixing time to 5 min. Mixed samples then were pressed in a

hot press with a 20 by 20 cm platen capacity. Each batch of sample was pressed using

a temperature of 165°C and a pressure of 40 bar for 5 min. The press was cooled off while

the samples were still under compression before they were removed and conditioned in a

cl imate chamber with a temperature of 201C and a relative humidity of 55%. Average

target thicknes of the panel was 2.5 mm. Modulus of elasticity (MOE) and modulus of

rupture (MOR) of the samples were determined on a Comten Testing Unit equipped with

a load cell with a capacity of 2000 kg.

Surface roughness (Fig 2.4) of the samples was also determined using a stylus-type

profilometer. A portable stylus equipment consisted of a main unit and pick-up which had

a skid-type diamond stylus with 5 mm tip radius and 901 tip angle. The vertical

displacement of the stylus was converted into electrical signal and digital information.

Different roughness parameters such as average roughness and maximum roughness can

be calculated from that digital information and profile of the surface can be developed.

Table 2.1 Mechanical and physical test results (Wechsler et.al, 2006)

Panel type Static bending (MPa) Water Absorption (%) Thickness swelling (%) Surface roughness (mm)

Fiber based samples



MOE MOR 2 h 24 h 2 h 24 h Ra Rma

x

A 2,109 11.80 3.21 8.33 11.3 18.6 1.98 16.7

1 B 3,560 18.74 5.73 12.84 5.2 13.3 4.05 33.84 C 3,208 14.53 5.11 6.53 5.4 8.9 4.48 33.94 D 2,778 14.28 4.79 10.96 5.8 11.8 4.09 32.11 E 2,155 12.74 5.22 9.49 3.9 11.0 3.54 28.35

Particle based samples

A 2,058 12.01 4.76 8.82 5.5 12.5 5.84 41.6

8 B 3,034 13.90 6.67 14.71 6.7 12.2 6.61 66.43 C 3,254 14.60 4.07 7.50 3.8 5.9 6.70 49.07 D 2,656 14.10 7.19 15.36 7.9 13.4 8.11 50.18 E 2,191 12.89 7.46 14.61 7.5 12.1 6.96 57.78

Fig 2.4 Surface Roughness (Wechsler et.al, 2006)

Fig 2.5 Typical surface profiles of the samples average modulus of elasticity of the samples made from

60% and 80% fibers and particles. (Wechsler et.al, 2006)

Average MOE value of the samples containing 60% and 80% wood fiber without having

any chemicals was found 2109 MPa. When these samples were added coupling agent

bending properties of the samples increased to 3560 MPa which is 38% higher than

that of the specimen made without any chemicals. Panel types C, D, and E having

chemicals also improved MOE values of the samples as compared to those of made with

combination of plastic and wood fiber. However, panel type D which was added UV

filter in the form of flakes and pallets showed only. This could be due to non-

homogeneous mixture of three elements, namely wood fiber, plastic, and UV filter. Fiber-

based panels manufactured with coupling agent pigment had the lowest MOE values.



Fig 2.6 Thickness swelling for 2hr water soaking test (Wechsler et.al, 2006)

Fig 2.7 Average roughness (Ra) roughness values of the samples. (Wechsler et.al, 2006)

Fiber-based panels had only 3.3% higher MOE values than that of particle-based samples

at 95% confidence level. However, fiber-based panels containing coupling agent had

significantly higher MOE than those of specimens manufactured from particle- based using

the same chemicals. The particles and fibers from radiata pine along with different chemicals

as additives were used to make experimental WPC panels. The surface roughness parameters

obtained from the samples resulted in significantly different Ra and Rmax values than those of

particle based ones. [2]

Kamdem et al., (2004) focused on the properties of wood plastic composites made of recycled

HDPE and wood flour from CCA-treated wood removed from service. The feasibility of using



recycled plastic and wood particles from chromated copper arsenate (CCA)-treated wood

removed from service was investigated in this study. CCA pressure-treated red pine lumber

removed from service after 21 years utilization was Wiley milled to wood flour and blended

with virgin or recycled high-density polyethylene at 50:50 wood flour-to-plastic weight ratios.

The blended materials were compression molded into panels and the physical and mechanical

properties characterized. Samples containing particles from recycled CCA-treated pine

exhibited flexural bending properties higher than those made with either particles from virgin

pine or recycled urea formaldehyde bonded particleboard. The higher modulus of elasticity

and modulus of rupture from CCA-treated material were attributed to the increased thermal

coefficient of the solid deposits rich in copper chromium and arsenic present in the cell wall

of the recycled CCA-treated wood. The biological durability and the photo-protection

properties were improved for samples containing recycled CCA-treated wood.

Chromated copper arsenate (CCA)-treated wood removed from service has been

proposed as a source of raw materials for wood composites such as particleboard (PB),

fiberboard, oriented strand board (OSB), laminated veneer lumber (LVL) and wood cement

bonded products. The problems associated with this recycling option are the toxic fumes and

air borne particles produced during the cutting and machining of wood containing heavy

metals and the air quality during the hot pressing of the composites. Occupational exposure

to copper, chromium, and arsenic from wood sawdust may constitute a health hazard.

Another issue with the use of treated wood as raw materials for traditional wood

composites is the adhesion. The quality of the adhesion of CCA-treated wood surfaces

depends on the surface properties of treated wood and the type of adhesives. It is well

documented that the presence of CCA solid residues on the surface of treated wood interfere

negatively with phenol formaldehyde adhesive and result in products with reduced mechanical

and physical properties.

Wood-Virgin Pine (VP), recycled urea formaldehyde(UF) bonded PB, and recycled

CCA-treated red pine wood with 6 kg/m3 CCA total oxides retention were used to produce

sawdust. Untreated kiln dried red pine boards with an average moisture content of 12% and

CCA-treated red pine (Pinus resinosa Ait) poles removed after 21 years in service.



Fine powder of virgin high-density polyethylene (HDPE) and post-consumer recycled

HDPE were obtained from commercial source. Oven dried wood particles with moisture

content less than 3% and HDPE were blended for 10 min to produce a homogenous mixture

in a 10l high-intensity laboratory mixer from Papen Meier. About 800 g of the oven dried

blended furnish mixture was poured in an aluminum mould placed between two steel plates.

The surfaces of caul plates were sprayed with mineral oil releasing agent to reduce the

adhesion between the wood composites and the caul plates. An oil heated press with a nominal

maximum pressure level up to 800 psi was used for the compression molding. The press

platens were maintained at 200 °C and the press cycle consisted of two phases. The first phase

involved the heating of the mould assembly to 200 °C for 8 min. After the mould assembly

reached the desired temperature the press was slowly closed for 2 min. The objective of a slow

closing of the press is to maintain contact with the mould assembly as furnish began to melt

in order to facilitate the flowing of the thermoplastic within the mould. It reduces the

probability of the formation of internal air voids in the panel during the release of gases that

may cause undesirable defects.

Boards made of virgin HDPE and CCA exhibit the higher value of the MOE. MOE

(Modulus of Elasticity) values of samples made with HDPE and pine was statistically similar

to the value of board made with HDPE and PB. However, MOE of virgin HDPE and PB was

also comparable to the MOE value of board containing recycled CCA-treated particles. The

high value of the MOE of samples containing CCA-treated wood particles compared to VP

particle may be due to the presence of solid deposits containing copper chromium and arsenic

oxides. For recycled HDPE, MOE of boards made with recycled CCA-treated particles was

statistically similar to the MOE of boards containing particles from VP and statistically higher

than board made with particles from PB. The MOR (Modulus of Rupture) of boards made

with virgin HDPE was higher than that of boards made with recycled HDPE, the same trend

was observed for MOE. The MOR of boards containing recycled CCA-treated wood was

statistically higher than for samples with VP or PB. The values of the MOE of samples made

with virgin HDPE were higher than that of recycled HDPE. The recycled HDPE used for this

experiment contained mixed polymers, which induced some miscibility problems. The MOE

of samples made with particles from UF particleboard and from VP particles were similar.

The same pattern was observed for MOR; with the high MOR for samples made virgin HDPE



and recycled CCA treated wood. No significant difference was found between the impact

strength of samples containing recycled HDPE; virgin HDPE with particles from CCA-treated

wood and virgin HDPE with VP particles. Only boards made with virgin HDPE and particles

from PB exhibit low impact energy.

Thickness swelling (TS) at 21 °C for 2 h immersion vary from 1.11 to 2.09%. After

24 h at 21 °C TS increase from 2.10 to 3.10%. Samples made with particle from PB have the

lowest TS while those made with particles from VP for both virgin and recycled HDPE

exhibited the highest value of TS. The same trend was observed with the TS test performed at

40 °C. Regardless of the type of polymer, TS of samples containing VP particles was higher

than that of samples with particles from CCA-treated wood. The TS increases with the

temperature. The difference between the values of TS of samples made with particle from

CCA-treated wood and particles from UF particleboard was not significant. The presence of

thermoset resin such as urea formaldehyde or CCA treatment may contribute to reduce the

thickness swell of WPC. Further investigations are needed to clarify the reduction of TS for

recycled wood.

Table 2.2 Properties of boards (Kamdem et.al, 2004)

Description

Density

(kg/m3) MOE (1000 psi) MOR (psi)

Unnotched impact

strength (J/m)

HDPE-Pine 1000a ^ 17b 123.8 ̂ 23B 2267.5 ̂ 200B 286.3 ^ 18A HDPE-CCA 1024 ^ 20 144.3 ̂ 24A 2731.2 ̂ 317A 315.1 ^ 20A HDPE-PB 1018 ^ 20 132.7 ̂ 8AB 2226 ̂ 57B 257.3 ^ 58B Rec-Pine 1021 ^ 10 82.7 ̂ 9CD 1670 ̂ 120D 358.5 ^ 10A Rec-CCA 1043 ^ 13 94 ̂ 4C 2024 ̂ 80C 337.5 ^ 15A Rec-PB 1010 ^ 13 72.3 ̂ 10D 1440.4 ̂ 190E 285.6 ^ 21A

Compression molding was used to manufacture WPCs using particles from VP,

recycled PB and CCA-treated utility poles retired from services and virgin and recycled HDPE

powder. Increased strength properties, anti-photo degradation and decay resistance were

observed with samples made with particles from CCA-treated wood. The increase in strength

properties was due to the increase in heat diffusion attributed to the presence of copper

chromium and arsenic complexes in the CCA-treated wood. The low photo-degradation of

WPC samples containing recycled CCA-treated wood was also attributed to the presence of



copper and chromium in wood particles. The WPC containing copper, chromium and arsenic

treated wood exhibit a high level of decay resistance attributed to the presence of toxic copper

and arsenic in particles. The level of As obtained by using a laboratory leaching test was

relatively high compared to the minimum level required for drinking water, suggesting that

the use of such products will be limited for applications with minimum exposure to water and

human beings. [3]

In the study conducted by Shu-Kai et al.,(2008), Wood–plastic composites (WPCs)

underwent cyclic dimensional changes due to periodic absorption and desorption of moisture,

and the resulting loss of mechanical integrity can be ameliorated using a coupling agent.

Another solution is better processing. They examined injection-molded, polypropylene (PP)-

based wood–plastic composites and investigated why the rate of moisture absorption can be

reduced by changing extruder operating conditions. At a given wood content, the mechanical

properties were found to be similar, but the use of high screw rotation speeds, whether in the

co-rotation or counter rotation modes, and long residence times gave lower rates of moisture

absorption even in the absence of a coupling agent.

Maple wood flour (Maple 8010), of 80-mesh size (about 177 lm), was provided by

American Wood Fiber, while the polymer used was BP Amoco’s polypropylene homo-

polymer PP1246 (melt flow index = 20 g/10 min at 230 LC and 2.16 kg, ASTM D1238). Since

wood is a biomaterial, and since the rate of water absorption is closely related to the quality

of wood flour, batch-to-batch differences between different bags of wood flour may affect

experimental results.

WPC samples were compounded using a Leistritz Micro-27 twin-screw extruder; half

the samples were processed with co-rotation screws, and the other half were processed with

counter-rotation screws. The materials were fed into the extruder with K-Tron loss-in-weight

powder and pellet feeders. The compounded WPC pellets were dried at 85 °C for 6 h and then

injection molded using a Battenfeld injection molding machine to produce standard ASTM

samples. The tensile and stiffness properties and also the impact strengths of these samples

were measured using an Instron 5869 universal testing machine and a BLI impact tester,

respectively. The rate of water absorption of the WPCs was determined using a ‘‘blot and

weigh” method. Three weighed samples were taken from each batch to conduct this test. The



optical properties of the WPCs were measured using a Macbeth Color-eye 7000 color meter.

These tests were conducted courtesy of GE Plastics (now SABIC Innovative Plastics) in

Washington, WV.

It was observed that the tensile modulus lies between 4 and 5 GPa with the counter

rotating screws, perhaps, giving a slightly higher modulus under the same processing

conditions and coupling agent content. On the other hand, the tensile strength appears not to

depend on the processing conditions employed. Though, as expected, tensile strength values

do increase as the coupling agent content is increased. The reversed notch Izod impact strength

of WPCs also increases with the loading level of PP-g-MA, but counter-rotating screws give

slightly lower values, and this is consistent with the modulus measurements since stiffer

materials usually possess lower impact strength. In general, though, all the samples show

similar mechanical properties.

Table 2.3 (Shu Kai et.al, 2008) Table 2.4 (Shu Kai et.al, 2008)

A long residence time and higher screw speeds not only result in smaller particulate sizes in

the compounded WPCs, they also lower the rate of water absorption. The reduction in moisture

absorption rate ranges from 10% to 40%, and this happens without a change in the mechanical

properties of the WPCs. It was found that the density of the WPCs is decreased under severe

compounding conditions, and this offers a clue to the reason for the observed reduction in the

rate of water absorption. It is speculated that moisture absorption rate decreases when severe

compounding conditions are employed because these cause the loss of hydrophilic volatile

organic compounds contained in the WPCs. The rate of water absorption between the third and



the 36th day of water immersion and the equilibrium moisture content obtained from these

figures are listed in fig below. [4]

Table 2.5 Rate of water absorption and equilibrium moisture of WPCs (Shu Kai et.al, 2008)

In the study conducted by Tieqi Li et al, (2006), the structure and mechanical properties

of wood flour composites with HDPE/ionomer blends as matrices were studied at a fixed wood

loading of 60% by weight. It was found that toughness and strength properties of the

composites can be improved significantly by adding ionomers of different types and contents.

The enhancement in the interfacial interaction was observed through short-time creep analysis.

The interfacial interaction and the structure of the matrix phase were characterized through the

melting behavior using differential scanning calorimetry (DSC) and with small strain

oscillatory tests on the melts using a Dynamic Mechanical Analyzer. Both the sodium and zinc

ionomers were found to be immiscible with the HDPE in matrix. The immiscible characteristic

was correlated with the interfacial load transfer efficiency as revealed by the creep tests. The

past decade has seen fast and steady growth of wood plastics industry. Among many reasons

for the commercial success, the low cost and reinforcing capacity of the wood fillers provide

new opportunities to manufacture composite materials. Certain problems, however, are

challenging the further application of the wood plastics technology owing to some intrinsic

properties of wood such as its hydrophilic nature and relatively poor thermal stability of the

lignin cellulose components. Efforts are being made to improve the compatibility between the

wood filler and the matrix polyolefin resins. Moisture sensitivity and related dimensional

stability and aging performance are also topics of intensive research.

Wood fillers used in this work are grade 14010 maple flour from American Wood

Fiber. The HDPE and ionomer resins are listed in Table 2.6. The properties were provided by

the suppliers unless stated otherwise. The HDPE resin and the wood flour were used as



received. The ionomer resins were used immediately after being taken out of the package

without drying.

Table 2.6 Polymers used in the study (Tieqi Li et.al, 2006) Legend Melt index Density (kg/m3) Flexural modulus Melting point Vicat softening Elongation Supplier and (g/10 min) (MPa) (LC) point (LC) at break resin grade

ASTMD-1238 D-792 ASTMD-790

ASTM D638

HDPE 0.3 946 940a – – Equistar LB01000 NaR 0.9 940 49 78 51 660 Dupont Surlyn 8120 NaS 1.0 950 30 70 47 555 Dupont Surlyn 8350 ZnL 1.0 960 178 86 60 510 Dupont Surlyn 9120 ZnH 4.5 970 358 82 57 335 Dupont Surlyn 9150

The composites containing 60% by weight of wood fillers and the ionomer of either

0%, 2%, 4%, 8%, 12%, 16%, 24%, 32%, or 40% based on the total weight of the composites

were compounded with a Brabender mixer with roller rotors and then compression molded into

plates. The neat resin mixtures were first introduced into the mixer soaked at 180 °C for

melting. The wood flour was then added into the melted resin mixture with the rotor speed

varying between 5 and 20 rpm. The composition was subsequently mixed for 3 min at 35 rpm

and 3–5 min at 20 rpm after the ampere meter gets stabilized. The compound was then

compression-molded into plaques of 4 mm thickness at 180°C with a maximum nominal

pressure of 7.5 MPa using a non-matched mold.

Flexural tests were performed on the samples of 12.7 mm in width and the as-molded

thickness of around 4 mm conforming to the ASTM D790 standard using 6 defect-free

specimens from the same plate for each formulation. The modulus of elasticity (MOE) was

determined on the strain range between 0.1% and 0.5%. Only the results of specimens that

break below or close to 5% strain are studied for Modulus of Rupture (MOR), strain at break

(eb) and the strain energy at break (Emax). Notched Izod impact experiments were carried out

following the ASTM D256 standard. The room temperature short-time creep properties were

studied by a TA Q800 Dynamic Mechanical Analyzer using a three-point bending fixture of

50 mm span. The sample of 12.7 mm width was brought to the fixed stress level of 5 MPa in

shorter than 6s, let deformed at the stress level for 10 min, and then allowed to recover for 20

min.

Flexural and impact properties Fig. 2.8 reports the typical stress–strain curves of the

maple flour/HDPE/ionomer composites in the flexural tests as compared to the neat

HDPE/maple used. As shown in the figure, the composites containing 4% of the sodium

ionomers deform and break in the way similar to the straight blend of HDPE and maple. Fig.



2.9 illustrates the MOE and MOR of the composites with different ionomer contents. From

fig.2.9a it can be seen

Fig. 2.8 Stress strain curve with 4% ionomer compared to nest HDPE/maple compound (Tieqi Li et.al 2006)

That the ionomers improve MOE at low ionomer contents. With the further increase in the

ionomer content, there is a general trend for MOE to decrease with increasing ionomer content

for all the ionomers studied.

Fig.2.9 MOE (a) and MOR (b) of the wood plastic composites as a function of ionomer content (Tieqi Li et.al,

2006)

When ionomer content is higher than 24% in the matrix, the composites with the Nar

ionomer, which has higher modulus, show higher MOE than the composites with the NaS



polymer. In the contrast to the case of MOE, MOR of the composites shows a simpler

dependence on the moduli of the ionomers. As shown in fig 9b, the zinc composites have higher

MOR values than the sodium composites. The ZnL polymer, which has the highest modulus

among the ionomers studied, results in the highest MOR for the composites while the softest

ionomer, NaS, gives the lowest MOR value for the composites.

The wood composites with HDPE/ionomer blends as matrices have been studied for

the fixed wood loading of 60% by weight. It has been shown that a wide spectrum of

mechanical properties can be achieved with the ionomers. All the ionomers improve the static

strain capacity in terms of strain energy at break. The two sodium ionomers result in a decrease

in MOE but an increase in both strain at break and Izod impact strength. The more rigid zinc

ionomers at low contents are less effective in toughening the HDPE/wood composites but are

proved to be useful in achieving significantly higher MOR. The viscoelasticity and structure of

the wood/ionomer/HDPE composites have been characterized using the creep, DSC and DMA

experiments. It was shown that the ionomers modified the wood-polymer interface and formed

immiscible matrix morphology. A comparison between the matrix blend morphology and the

creep test results indicates that the creep test results indicates immiscible nature between HDPE

and the ionomers can be beneficial. The immiscible nature may allow the ionomer to connect

the wood particles at the content lower than what is necessary to fill in all spaces and hence

play its role in a more cost-effective way than in the cases where the ionomer alone is used as

matrix. [5]

N. Rocha et al., (2009) described an approach to the study of the influence of the nature

and the composition on the performance properties of wood flour/poly vinyl chloride (PVC)

composites. The raw materials were mixed on a two-roll mill. The final composites were

obtained by controlled press moulding. The results indicate that properties such as surface

tension and flexibility do not change significantly with the composition in the chosen

composition range. The color is easily controlled by variation in the content and the type of

wood flour. A thermal and morphological study has been performed on the raw materials and

on the composites to assess the effect of wood flour on the stability of the composites. The

inclusion of wood flour into PVC leads to poorer tensile properties. This effect is related to the

lack of association between the wood flour and the PVC.

The combination of wood and plastics offers potential for the provision of high-value



wood plastic composites (WPC). Thus, the appreciated aesthetic effects of wood can be

transferred to the world of plastics processing. The wood, in the form of fibers or flour, is

usually based on industrial wastes that can be ground. When the loading of wood flour

increases, the cost of the final composites is reduced. Compared to wood, WPC can have a

longer service life with less need for maintenance, less water absorption, better dimensional

stability and less bio deterioration. WPC can be used as a substitute for wood in a variety of applications, including

decking, benches, marina boardwalks, and window and door profiles. The WPC’s performance

can be optimized by controlling the raw materials used (type and quantity of wood and

thermoplastic polymers), the processing, and the additives. For common WPC applications,

the more important properties are mechanical strength, stiffness, impact resistance, density,

and color. In terms of color characteristics, the demands for WPC include materials that do not

stain and can provide a grained natural wood look. The consumer market is looking for more

color variety, especially for dark colored woods. A great diversity of plant residues has been

used in WPC, due to the low cost, high environ-mental acceptance, and good sustainability

features.

The wood flour samples were donated by DPM – Distribuição e Produção de Móveis

(Portugal). Two kinds of wood flour were used: bubinga (Guibourtia Tessmannii) and walnut

(Jugans Nigra). The fibers were ground on a cutting mill (Retsch GmbH SM1) with a 500 lm

stainless steel trapezium shaped sieve.

Poly (vinyl chloride) samples PVCS63 (a suspension grade, with a molecular weight of

approximately 63,000 gmol_1) and PVCS54 (a suspension grade, with a molecular weight of

about 54,000 gmol_1), was supplied by Cires, SA (Estarreja, Portugal).

Stabilox CZ 2973 GN, from REAGENS Deutschland GmbH (Lohne, Deutschland), is a

calcium salt and zinc salt-based soap stabilizer and lubricant. Sodium stearate from Ferro

Indústrias Químicas (Portugal), Lda (Castanheira do Ribatejo, Portugal), was used as a

lubricant. Epoxydised soya bean oil from CECA, SA (Paris-La Défense, France), is a co-

stabilizer and an internal lubricant in PVC formulations. Kane Ace PA210, an acrylic

copolymer (MD-P210-C210) from Kaneka Belgium N.V. (Westerlo-Oevel, Belgium), is an

impact modifier and a lubricant. Wax PE520 (KWPEI 15), a lubricant for plastics, was supplied

by Clariant GmbH (Augsburg, Germany). Decreased to 1000 rpm and the liquid components



were added. The speed was increased to 2000 rpm. When the temperature reached 110 LC, the

cooling was provided and the speed reduced to 1200 rpm. The mixture was taken from the

mixer when the stock temperature was about 50 LC.

Table 2.7 Experiments performed on two-roll mill. (N. Rocha et.al, 2009)

Sample PVC Wood flour wwf (wt%) T (LC) T1H PVCS63 None 0 170 T3H PVCS63 None 0 190 T1HB2.5 PVCS63 Bubinga 2.5 170 T1HB10 PVCS63 Bubinga 10 170 T2HB10 PVCS63 Bubinga 10 180 T3HB20 PVCS63 Bubinga 20 190 T3HB30 PVCS63 Bubinga 30 190 T3HB40 PVCS63 Bubinga 40 190 T3HW20 PVCS63 Walnut 20 190 T3HW30 PVCS63 Walnut 30 190 T3LB30 PVCS54 Bubinga 30 190 T3LB40 PVCS54 Bubinga 40 190

Preparation of two-roll mill sheets: Mixing between the PVC and the wood flour

sample was provided using a two-roll mill (Dr. Collin GMBH-85560 EBEMSBERG, Collin)

for different wood flour contents, between 0% and 40% of the total weight of each composite.

The thickness of the obtained sheets was 0.8 mm.

Press mould composites: The 0.8 mm thick sheets from the two-roll mill were press

molded on a laboratory hydraulic hot press (412BCE, Carver). The molds gave sheets of 2 mm

thickness. The sheets were guillotined to (11 cm)*(11 cm) squares. The sheets were aligned in

order to keep the wood flour particles oriented in the same flow direction. The operating

temperature of the press was the same as that used when the sample was mixed in the roll mill.

Each sample was pressed for 2 min at 4 metric tons of pressure, at the temperature of the press

plates. Then the materials were pressed for 3 min at 27 metric tons. Afterwards the temperature

was decreased to 50 °C and the pressed composite removed from the hot press. Due to processing difficulties that were related to the in-creased viscosity caused by wood

flour, the processing temperature was raised for compositions containing a greater wood flour

content. For the samples coded T3HB40 and T3LB40 it was not possible to obtain sheets,

because of the low shear rates associated with the chosen processing pathway and the high

viscosities arising from the use of the wood flour. PVCS54 was used to establish whether or

not it would be possible to produce a composite sheet in the roll mill. PVCS54 has a lower

viscosity than that of PVCS63.

Conclusions: A small amount of wood flour (2.5 wt. %) is enough to change completely the

appearance of a PVC based material, producing a composite with the appearance of wood. The



darkness of the material increases only slightly with additional increases in the wood flour

content. The color of the material can also be adjusted by controlling the type and the amount

of the wood flour. The wood flour content of the composites has little influence on the composites

properties such as the wettability and the flexural properties of the composites. However, there

is a trend for a decrease in the wettability and in the flexural strength at high wood flour

contents. These properties may be essentially related to the PVC matrix used. The effect is

clearly seen in the flexural behavior of the composites. A lower molecular weight PVC

produces a material with lower flexural compliance, independent of the wood flour content. Thermal and SEM analyses show that the presence of wood flour leads to an increase

in the degradation temperature of the main matrix. However, an initial weight loss is observed,

which may be related to the poor entanglement of the materials, caused by the presence of the

wood flour. The wood flours lead to materials that possess higher thermal endurance.

The experiments concerning the tensile properties of the composite materials showed

that a low content of wood flour creates a more fragile material, breaking just after the yield

point. Increasing the wood flour content leads to a lower tensile strength and elongation at the

yield point and a lower elongation at break. Walnut flour creates a material with better tensile

properties than those provided by the bubinga flour. PVCS54 leads to composites that give

inferior tensile properties relative to those produced PVCS63. [6]

2.1 Properties of Teak Wood

Type of wood used was carpentry waste which was from teak wood widely used to make

furniture. The main properties of teak wood are:

Teak is moderately hard, durable and fire resistant.

It can be easily seasoned and worked.

It takes up a good polish and is not attacked by white ants.

It doesn’t corrode iron fastenings and it shrinks little.

It is among the most valuable timber trees of the world and its use is limited to

superior works only.

Heart wood is brownish red in color. It darkens as it ages. Sometimes there are dark

patches on it. There is a strange scent in newly cut wood.



Sapwood is whitish to pale yellowish brown in color. It can easily separate from

heart wood.

Wood texture is hard and ring porous.

Density is 720 kg/m3.[7]

2.2 Properties and types of Plastics used

Plastic is a material consisting of any of a wide range of synthetic or semi-

synthetic organics that are malleable and can be molded into solid objects of diverse shapes.

Plastics are typically organic polymers of high molecular mass, but they often contain other

substances. Due to their relatively low cost, ease of manufacture, versatility, and

imperviousness to water, plastics are used in an enormous and expanding range of products,

from paper clips to spaceships.[8] The properties of plastics are defined chiefly by the organic

chemistry of the polymer such as:

Hardness

Density

Resistance to heat

Organic solvents

Oxidation

Ionizing radiation.

In particular, most plastics will melt upon heating to a few hundred degrees Celsius. While

plastics can be made electrically conductive. Low Density Polyethylene (LDPE), High Density

Polyethylene (HDPE) and Polyvinyl Chloride (PVC) were used in the present study.

2.2.1 Properties of LDPE:

Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. Its

most common use is in plastic bags. [10]

It is not reactive at room temperatures.

Quite flexible and tough.

Weaker intermolecular forces, hence lower tensile strength.

Higher resilience

https://en.wikipedia.org/wiki/Synthetic_polymers

https://en.wikipedia.org/wiki/Organic_chemistry

https://en.wikipedia.org/wiki/Malleability

https://en.wikipedia.org/wiki/Molding_(process)

https://en.wikipedia.org/wiki/Organic_polymer

https://en.wikipedia.org/wiki/Molecular_mass

https://en.wikipedia.org/wiki/Thermoplastic

https://en.wikipedia.org/wiki/Monomer

https://en.wikipedia.org/wiki/Ethylene



Because its molecules are less tightly packed and less crystalline due to the side

branches, its density is lower (0.910-0.940 g/cm3).

2.2.2 Properties of HDPE:

High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a

polyethylene thermoplastic made from petroleum. With a high strength-to-density ratio, HDPE

is used in the production of plastic bottles, corrosion-resistant piping and plastic lumber. [11]

Stronger intermolecular forces and tensile strength than LDPE.

Harder and more opaque.

Large strength to density ratio

The density can range from 0.93-0.97 g/cm3

2.2.3 Properties of Poly Vinyl Chloride (PVC):

PVC comes in two basic forms: rigid and flexible. The rigid form of PVC is used in

construction for pipe and in profile applications such as doors and windows. It can be made

flexible by addition of plasticizers (phthalates) and can be used in plumbing, electrical cable

insulation etc. [12]

PVC has high hardness and mechanical properties

Elastic modulus of rigid can reach up to 1500-3000 MPa and of flexible is 1.5-15MPa.

Good insulation because of higher polar nature.

https://en.wikipedia.org/wiki/Polyethylene

https://en.wikipedia.org/wiki/Thermoplastic

https://en.wikipedia.org/wiki/Petroleum

https://en.wikipedia.org/wiki/Plastic_bottles

https://en.wikipedia.org/wiki/Plastic_lumber



Chapter 3 Experimental Setup

3.1 Materials used: Waste plastic bags were collected from retail cloth store and bottles

from cold drink stores. The waste wood powder was obtained as a carpentry waste from Gayatri

Wood Works, Vidyagiri, Bagalkot. The plastic bags fell into a category of LDPE and bottles

in the category of HDPE. The wood powder was found to be of teak wood which is widely

used to make furniture.

The wood waste from carpenter was brought and fine powder was separated from the waste by

sieving process using a sieve of mesh size 1500microns. The size of the particles were

1500microns.

3.2 Method:

Following steps were involved in the preparation

Drying of wood powder: Wood was first dried in the sunlight for 24 hours and further

kept in a hot air oven at 105±5ºC for 24 hours to remove any moisture content in the

wood. This is shown in the Fig 3.1 &3.2.

Melting of thermoplastics in a graphite crucible by placing in resistance furnace

(Fig 3.3) by maintaining the temperature range as follows

1. Low Density Polyethelene(LDPE) (105°C-115°C)

2. High Density Polyethelene(HDPE) (120°C-180°C)

3.Poly Vinyl Chloride(PVC) (100°C-250°C)

Thouroghly mixing ground wood particles and melted thermoplastic. Upon mixing the

mixture is poured into the mould (Fig 3.4 & 3.5) and rammed by applying hand pressure

to the rammer.

Allowing the mould to cool and solidify and followed by demoulding.



Fig. 3.1 Drying of wood powder in sunlight

Fig. 3.2 Drying of wood powder in hot air oven



Fig 3.3 Heating of Graphite Crucible for melting of plastic

Fig 3.4 Mould for compression testing specimens



Fig 3.5 Mould for Tensile testing specimens

3.3 Mechanical Properties of Wood Plastic Composites

3.3.1 Compression and tensile tests

The tensile and compression properties of the waste wood particle and plastic

composites at room temperature were determined for 4 different specimens of a particular

composition by following the ASTM standards (ASTM D638 for tensile & ASTM D3410 for

compression) and testing them in a computer controlled Universal Testing Machine. The

specimen size are shown below (Fig3.6 & Fig 3.7). In addition to this microstructure images

of each composition were obtained using Scanning Electron Microscopy. The microstructures

study explained how the different compositions varied. The images are shown under results

and discussion.

3.3.2 Water absorption test

Before testing, the weight of each specimen was measured and conditioned samples of

each composite type were soaked in distilled water at room temperature for 24 h. Samples were

removed from the water, patted dry and then measured again. Each value obtained represented

the average of 4 samples. The value of the water absorption in percentage was calculated using

the following equation:



WA (t) =𝑊(𝑡)−𝑊0

𝑊0 ×100

Where,

WA (t) - water absorption (%) at time t,

Wₒ - oven dried weight and W (t) is the weight of specimen at a given immersion time t.

Fig. 3.6 Specifications of WPC Fig. 3.7 Specifications of WPC specimens

specimens for compression for tensile

Fig 3.8 UTM used for testing of WPC Fig 3.9 Scanning electron microscope



3.4 Results and Discussions

3.4.1 Compression test results

Fig 3.10. Compression strength of WPC for the composition LDPE-75% & Wood-25%

Fig 3.11. Compression strength of WPC for the composition LDPE-80% & Wood-20%



Fig 3.12. Compression strength of WPC for the composition HDPE-75% & Wood-25%

Fig 3.13. Compression strength of WPC for the composition HDPE-80% & Wood-20%



Fig 3.14. Compression strength of WPC for the composition Combined (LDPE+HDPE)

Plastic 75% & Wood-25%

Fig 3.15. Compression strength of WPC for the composition Combined (LDPE+HDPE)

Plastic 80% & Wood-20%



3.4.2 Tensile test results

Fig 3.16. Tensile strength of WPC for the composition LDPE-75% & Wood-25%

Fig 3.17. Tensile strength of WPC for the composition LDPE 80% & Wood 20%



Fig 3.18. Tensile strength of WPC for the composition Combined (LDPE+HDPE)

Plastic80% & Wood-20%

3.4.3 Microstructures of WPC

Fig 3.19 Microstructure of WPC having composition LDPE-75% & Wood-25%



Fig 3.20. Microstructure of WPC having composition LDPE-80% & Wood-20%

Fig 3.21 Microstructure of WPC having composition 75% HDPE – 25% Wood



Fig 3.22 Microstructure of WPC having composition 80% HDPE – 20% Wood

Fig 3.23 Microstructure of WPC having composition 75% LDPE+HDPE – 25% Wood



Fig 3.24 Microstructure of WPC having composition 80% LDPE+HDPE – 20% Wood



Table 3.1 Compression Strength of the Specimens

Type of plastic Composition Peak load (N) Comp Strength

(N/mm2)

1.LDPE ii)75% P-25% W 30900.00 38.13

41573.86 42.24

57970.83 58.80

64506.40 65.54

51.18

iii)80% P-20% W 27900 34.91

27519 28.44

30896 31.93

35472.89 36.66

32.99

2.HDPE i)75% P-25% W 5760 6.13

8158.72 8.48

6917.59 7.19

6157.50 6.40

7.085

ii)80% P-20% W 4980 5.27

5156.9 5.36

5955.46 6.19

5580.238 5.8

5.655

3. Combined LDPE

and HDPE

i)75% P- 25% W 15660.00 16.50

15873.00 18.57

20394.4 21.2

17094.74 17.77

18.51

ii)80% P-20% W 11880.00 12.81

13073.58 13.59

18066.36 18.78

11120.72 11.56

14.185



Fig. 3.25. Bar chart representing the comparison of compressive strengths of WPC

Table 3.2 Average Tensile Strength of Specimens

Type of Plastic Composition Peak load (N) Tensile Strength

(N/mm2)

1. LDPE i)75% P-25%

W

1320 7.09

ii)80% P-20%W 540 2.15

2. HDPE Unable to prepare as the mixture gets solidified before pouring

into the mould

3. Combined i) 80% P-

20%W

840 4.08

ii) 75% P-25%W- unable to prepare as specimen was very

brittle and broke during removal from mould.

0

10

20

30

40

50

60

75%P-25%W 80%P-20%w

STREN

GTH

LDPE HDPE COMBINED PLASTIC



Table 3.3 Water absorption capacity

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 1 2 3 4 5 6 7

Fig. 3.26 Comparison of average values of samples of water absorption

Sl.no Type of

plastic

Description Specimen

Diameter

(cm)

WA(t) in

% for 25

Hours

WA(t) in

% for 50

Hours

WA (t) in

% for

75 Hours

WA(t) in

% for

100 Hours

1 LDPE 75P-25W 3.54 0.044 0.133 0.133 0.177

2 LDPE 80P-20W 3.48 0.013 0.02 0.056 0.08

3 HDPE 75P-25W 3.47 0.078 0.083 0.12 0.19

4 HDPE 80P-20W 3.51 0.023 0.039 0.040 0.08

5 COMBINED 75P-25W 3.52 0.05 0.052 0.098 0.14

6 COMBINED 80P-20W 3.54 0.039 0.041 0.08 0.098



Chapter 4 CONCLUSIONS

The study conducted on the WPC has shown that plastics that are discarded after the

use can be successfully utilized to make composite materials with useful mechanical

properties. The composite specimens were prepared without using any binding agent or

coupling agent as it is important to know the behavior of WPC in absence of agents.

The wood plastic composite specimens were prepared using teak wood powder along

with different plastics by varying composition such as 70 % plastic with 30% wood powder

and 80% plastic with 20% wood powder. After preparing specimens with single plastic (LDPE

or HDPE), specimens were prepared by combining the two plastic (LDPE+HDPE) with equal

distribution. It was observed that, more the wood content more will be the strength and the

point to be considered the most is that it is difficult to prepare specimen having more than 30%

wood due to lack of interfacial bonding and hence binding agents can be used for further

composition.

4 specimens were prepared of each composition and were tested for compression and

tensile strength in a computer controlled Universal Testing Machine. More or less the results

obtained were nearer. The compressive strength of specimens made of LDPE are generally

greatest, closely followed by specimens made of combined plastic waste (LDPE+HDPE) and

WPC samples made of HDPE. The tensile properties of the composite materials showed that a

low content of wood flour creates more fragile materials, breaking just after the yield point.

The graphs were obtained and the results were tabulated. Increasing the wood flour content

leads to more tensile strength. The problems associated with PVC is that the release of toxic

gases upon melting and very low bonding property. The PVC could not be melted as it started

to burn upon melting and no specimens were prepared.

The specimen were tested for water absorption capacity also by immersing the

specimens in water for 100 Hours. Weight of the specimen was observed for every 25 hours

i.e., 25 hours, 50 hours, 75 hours and 100 hours. The rate of water absorption was found to be

significantly lower for wood plastic composites. It was found that more the plastic content

lesser will be the water absorption. The results are tabulated and graphical representations are

made to compare the properties of wood plastic composites prepared.



Finally the conclusion was derived that specimen with composition 50% plastic and

50% wood powder and 60% plastic and 40% wood powder cannot be produced due to lack of

interfacial bonding between plastic and wood powder. Hence to produce the specimen of such

composition, binding or coupling agents are required. The properties of wood change with

moisture content and those of WPC depend a great deal on the manufacturing procedure.



Chapter 5 SCOPE FOR THE FUTURE WORK

WPC are new and rapidly evolving products. They offer a number of advantages,

including flexibility of production and the use of recycled material to create a recyclable

product. Despite the wide array of possible finished forms, the manufacture of WPC is

relatively simple and uniform. WPC have become well-established building materials,

especially for residential decking, Outdoor deck floors, railings, park benches, fences,

landscaping timbers, cladding and siding, moulding and trim are likely to be used for a wider

array of applications in the future.

Fig 5.1 Outdoor decking Fig 5.2 Railings



Chapter 6 REFERENCES AND LINKS

6.1 References

[1] Krishnan Jayaraman, Debes Bhattacharyya (2004), Mechanical performance of wood

fiber-waste plastic composite materials, Resources, Conservation and Recycling, 41 307-

319.

[2] Andrea Wechsler, Salim Hiziroglu (2007), “Some of the properties of the wood-plastic

composites”, Building and environment, 42 2637-2644.

[3] Pascal Kamdem. D, Haihong Jiang, Weining Cui, Jason Freed, Laurent M. Matuana.

(2004), “Properties of wood plastic composites made of recycled HDPE and wood flour

from CCA-treated wood removed from service”, Composites: Part A 35 (2004) 347-355.

[4] Shu-Kai, Rakesh K. Gupta (2008), “Improved wood-plastic composites through better

processing” Composites: Part A 39 1694-169.

[5] Rocha. N, Kazlauciunas. A, Gil. M. H, Concalves. P. M, Cuthrie. J. T, (2009) “Poly (vinyl

chloride)-Wood flour press mould composites: The influence of raw material on

performance properties”.

[6] Teiqi Li, Ning Yan, (2007) “Mechanical properties of wood flour/HDPE/ionomer

composites”, Composites: Part A 38 1-12.

6.2 External links

[7] https://en.wikipedia.org/wiki/Teak

[8] https://en.wikipedia.org/wiki/Plastic

[9] http://gurumavin.com/study-renewable-plastic-made-from-carbon-dioxide-and-plants

[10] https://en.wikipedia.org/wiki/Low-density_polyethylene

[11] https://en.wikipedia.org/wiki/High-density_polyethylene

[12] https://en.wikipedia.org/wiki/Polyvinyl_chloride

https://en.wikipedia.org/wiki/Teak

https://en.wikipedia.org/wiki/Plastic

http://gurumavin.com/study-renewable-plastic-made-from-carbon-dioxide-and-plants

https://en.wikipedia.org/wiki/Low-density_polyethylene

https://en.wikipedia.org/wiki/High-density_polyethylene

https://en.wikipedia.org/wiki/Polyvinyl_chloride

karnataka state council of science and technology

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