volume 47 no. 4 octobervolume 48 no. 1 jan - mar...

Volume 47 No. 4 October - December 2015Volume 48 No. 1 Jan - Mar 2016

No. 1Vol. 48 Jan - March 2016

JLST Vol. 48 No. 102Jan - Mar 2016

It is a good news for the consumer that the Food Safety and

Standards Authority of India (FSSAI) has notied some amendments to

standards for labelling which is expected to offer clarity to consumers on the

kind of vegetable oils/ fats used in the food products.

In June 2015, the FSSAI had proposed amendments to the food

safety and standards (Packaging and Labelling) regulations 2011 regarding

declarations of class titles related to labelling of edible oils, edible fats, trans

fats in various foods. After taking suggestions from stakeholders, FSSAI has

now made regulations to further amend the FSSAI (Packaging and

Labelling) regulations of 2011.

According to this, the new regulations will be called the Food Safety

and Standards (Packaging and Labelling) second amendment 2016. They

will be enforced after their publication in the ofcial gazette.

Under the new regulations, the following changes have been made :

(a) Labelling of Vegetable oil and vegetable fats will be separated

and will be different.

(b) Every package of edible oils, inter-esteried fat, margarine and

fat spread and packaged food in which fats and oils emulsion is used as an

ingredient shall declare the quantity of trans fat content and saturated fat

content on the label.

With best regards and wishing you happy reading.

From Editors Desk

ABSTRACT

Six blend samples were prepared by physical

mixing of cardanol-based epoxy resin (CER) with

varying concentrations of carboxyl-terminated

polybutadiene (CTPB) ranging between 0-25 weight

percent. The CER resin was prepared by the reaction

of cardanol-based novolac-type phenolic (CNP) resin

and epichlorohydrin in basic medium at 120°C. The

CNP resin was synthesized by reacting cardanol and

formaldehyde (mole ratios 1:0.8) with organic

sulphonic acid as catalyst (1 wt%) at 120°C for 5

hours. The initial pH of the reaction mixture was 5.0

which reduced to a value of 2.6 after 5 hours of

reaction. The lms of these blends were cured by

using 40 wt% polyamide with the total amount of the

blend and evaluated for their chemical resistance

characteristics for a period of one year. The chemical

resistance properties were improved signicantly of

cured lms containing 15 wt% CTPB in CER resin.

These studies have been found to be suggestive for

their use in eco-friendly heavy duty protective

coatings.

Keywords : Cashew nut shell liquid (CNSL),

epoxy resin, carboxyl-terminated polybutadiene

(CTPB), blend, polyamide, thermal stability, chemical

resistance.

INTRODUCTION

Biomass-derived phenolic compound such as

cardanol, a distillate of cashew nut shell liquid

(CNSL), can be regarded as a versatile and valuable

raw material for polymer production for coating

applications. This phenolic compound contains 15-

carbon chains with variable unsaturation degrees and

meta substituted in the aromatic ring. By far the

greatest amount of work on polymeric materials,

Studies on the chemical resistance of the films of blends of distilled CNSL-based epoxy resin and CTPB

1 2 3Kavita Srivastava , A. K. Rathore and Deepak Srivastava *1Department of Chemistry, V.S.S.D. College, Kanpur – 208 002 (U.P.), India.

2 3Department of Chemical Engineering, School of Chemical Technology, Department of Plastic Technology, School of Chemical Technology

H. B. Technical University (Formerly H. B. Technological Institute), Kanpur - 208 002 (U.P.), India.

derived from CNSL or cardanol, has been with their

use in the manufacture or modication of phenolic

resins [1-4] particularly base catalyzed resoles and

acid catalyzed novolacs. The cardanol based

novolac-type phenolic resins may further be modied

by epoxidation with epichlorohydrin to duplicate the

performance of such phenolic-type novolacs [5].

Having several outstanding characteristics, epoxy

resins show low impact resistance in their cured state

[6-11] which minimizes their usage in specialty

coatings. To alleviate this deciency, epoxy resins are

modied by the incorporation of reactive liquid rubber

viz., CTBN, HTBN, VTBN, ATBN, etc. [12-15] without

signicant loss in other properties, particularly

mechanical properties [12, 13]. The materials

produced by blending these liquid rubbers are not

very economical and therefore, attempts have been

made to produce very low cost blends with liquid

rubber, carboxyl-terminated polybutadiene (CTPB)

with comparable properties having improved

chemical & thermal properties for producing eco-

friendly heavy duty protective coatings, in the present

investigation.

MATERIALS AND METHODS

Materials

Cardanol (M/s Satya Cashew Pvt. Ltd., Chennai),

formaldehyde (40% solution), p-toluene sulphonic

acid, sodium hydroxide, epichlorohydrin (All from M/s

Thomas Baker Chemicals Ltd., Mumbai), polyamide

resin (M/s Parikh Resins Ltd., Naya Ganj, Kanpur)

(Amine value : 240-400 mgKOH/g) and carboxyl-

terminated polybutadiene (CTPB) was procured from

Vikram Sarabhai Space Research Centre (VSSRC),

Trombay, Mumbai.


Methods

Synthesis of cardanol-based novolac-type phenolic (CNP) resin : Cardanol, procured from open market, was distilled under reduced pressure at 206C. The puried cardanol was checked for its iodine value, viscosity, specic gravity etc. These values resembled the values given in our previous publication [16]. Cardanol-based novolac type phenol ic resin (molar rat io of cardanol-to-formaldehyde : 1:0.8) with p-tolune sulphonic acid (PTSA), as catalyst (0.5 wt% based on cardanol), at 120°C for 5 hours was prepared as per the method given in our previous work [16]. Samples were drawn at regular intervals of 45 minutes from the reaction mixture for determining the free-phenol (as per ASTM standard D 1312-56) and free-formaldehyde content (as per ISO standard 9397). The reaction product was cooled and dried under vacuum at 60°C overnight before purication by column chromatography. A resin solution prepared with n-hexane, charged to the silica gel column chromatographic purication, was adopted main ly to remove the unreacted components, impurities etc. from the methylolated cardanol. Purication was effected using the eluent mixture of ethyl acetate.

Epoxidation of CNP resin : The CNP resin, thus formed, was epoxidized by a method similar to the method as adopted by our previous group [16]. The C N P w a s t r e a t e d w i t h m o l a r e x c e s s o f epichlorohydrin and 40% solution of sodium hydroxide at 120°C for about 10 hours. The formed product was vacuum distilled for the removal of excess of epichlorohydrin. The resulting viscous product was stored for further analysis. The epoxide equivalent weight (EEW) of cardanol-based epoxidized novolac resin (CER) resin was found to be 330 eq/g, as determined by a method given in our previous work [16].

Table 1: Sample designation.

S. No. CERresin(wt%)

CTPB(wt%)

Sample Code

1.

2.

3.

4.

5.

6.

100

95

90

85

80

75

0

5

10

15

20

25

CNE10

CNE95

CNE91

CNE81

CNE82

CNE 27

Preparation of blends of CER resin with CTPB : The prepared epoxy resin (CER) was mixed physically with varying concentration of CTPB ranging between 0-25 wt % with an interval of 5 wt%. All the samples were designated according to Table 1. Fourier-transform infra-red (FTIR) spectroscopic analysis : Fourier-transform infra-red (FTIR) spectra of the prepared blend samples were recorded on a Perkin Elmer FTIR spectrophotometer, (Model: RX-1), using KBr pellet for cured materials, in the wave length range

-1of 400-4000 cm . Sodium chloride (NaCl) pellets were used to get the spectra of uncured material.

Curing of blends of CER resin with CTPB : The cure temperature of the blends of CER/CTPB was measured by taking a small quantity of blend sample into shallow aluminum pan sealed by an aluminum cover of differential scanning calorimeter (DSC) (TA, Instrument, USA; Model DSC Q20), in dynamic and isothermal

-1 mode, at heating rate of 10C min to identify the cure temperature and time for the completion of the curing reactions. For curing the samples, polyamide (40 wt% of total weight of blend of epoxy/CTPB) was used as curing agent during the studies. Data related to cure schedule for different blend samples are summarized in Table 2.

Blen d S amp le

T i ( ºC)

To n se t ( ºC )

TP

( ºC ) Ts to p (ºC)

FF (J m ol -1 )

atc u re

(m in)

CE R10

68.2 92 .8 149.8 227 .6 103.1 321

CE R95

68.8 85 .2 152.5 207 .4 87.3 300

CE R91

72.2 90 .6 149.8 218 .7 65.8 282

CE R81

66.6 88 .4 146.5 215 .4 117.8 252

CE R82

64.3 78 .1 147.1 216 .6 68.7 264

CE R72

69.4 97 .2 149.2 218 .2 63.3 270

Table 2: DSC results of unmodified and CTPB-modified CER resin cured at 150ºC with 40 wt% polyamide.


Thermal Stability : The thermal stability was determined

by comparing the onset degrada�on temperature (5 %

weight loss) of cured samples by using thermogravimetric

analyzer (TGA) of TA

acure time obtained by curing the sample in air oven at 150ºC.

t : kick-off temperature, where the curing starts; t : temperature where the rst detectable heat is released; i onset

t : temperature of peak position of exotherm; t : temperature of end of curing exotherm; H: heat of curing; t : cure p stop cure

time in minutes.

Instruments (Model Q50 TGA) at a heating rate of -1 10C min in nitrogen atmosphere from ambient to

700ºC. Data related to this, for different blend

samples, are given in Tables 3 and 4.

Weight

loss

(%)

Temperature for

(K)

CER10

CER95

CER91

CER81

CER82

CER72

1 473 247 251 279 246 237

2 436 302 335 351 297 281

3 486 425 444 479 408 396

4 491 410 431 455 398 391

5 503 427 451 472 424 407

6 510 457 483 491 438 417

7 520 457 490 498 462 439

8 528 483 499 507 473 452

9 537 493 508 516 482 475

10 550 518 530 542 502 488

Table 3. : Temperature of 1-10% weight loss in TGA of cured blend samples.


Prepara�on of Panels : The panels were prepared by

applying the blends of CER resin/CTPB samples on sand

blasted steel sheet panels of size 150 mm x 100 mm x 1.25

mm using Bird Film applicator (M/s Sheen Instruments Ltd.,

UK). These panels were further sealed from three sides by

using molten parafn wax.

The dry lm thickness of about 150 micron was

maintained on all the panels. These lms were then

cured as per the cure schedule as determined in

preceding section of cure schedule.

Mechanical Properties : The adhesion and

exibility of the cured lms of the resin was tested by

putting the prepared steel panels into a ¼ inch

mandrel keeping the coated side downward. Then the

two plates, connected to the mandrel, were readily

bent. The bent portion of the panel was examined for

any damage in the lm. The impact resistance of the

cured lm samples was conducted by dropping a

hemi-spherical shaped two-pound weight from 25

inch height over the panels. The tests were carried out

with the uncoated side of the panel facing the falling

weights. Gloss was measured using Triglossometer (Sheen). After watching the lms from 60°angle it was

observed that all the coating lms had good gloss.

The observation taken during the studies are

summarized in Table 5.

Sample

Temperature (°C)

Char Yield (%)

CER10

230

12

CER95 154 04

CER91 178 05

CER81 199 08

CER82 151 05

CER72 134 03

Table 4. : Degradation temperature at 5% weight loss of blends of CER/CTPB coatings in TGA.

Table 5: Mechanical properties cured films of pure CER resin and it's blend with CTPB.

Exposure of Panels to different chemicals : The

panels were examined for a visible change in the

conditions of the lm samples at regular intervals

when immersed in different chemicals like solvents,

acids, and alkalies at ambient temperature for a

period of 12 months. The observations taken during

the studies are summarized in Tables 6 and 7.

RESULTS AND DISCUSSION

Synthesis of CNP and CER resins : The formylation

reaction was carried out with 1: 0.8 mole ratio of

cardanol-to-formaldehyde catalyzed by PTSA. The

initial pH of the reaction mixture was found to be 6.0.

Therefore, under this experimental condition, the

complete formylation might yield resin with high ortho-

ortho linkages for phenolic novolac resin [17]. The

completion of the methylolation reaction was checked

by periodic withdrawal of reaction mixture to analyze

Sample Code

Properties of Films

Transparency ColorGloss

(60 Angle)Scratch

Hardness (kg)Adhesion and

Flexibility

Impact Resistance

(kg.cm)

CER10

CER95

CER91

CER81

CER82

CER72

Smooth andUniform

Smooth andUniform

Smooth andUniform

Smooth andUniform

Smooth andUniform

Smooth andUniform

Brown

Light Brown

Light Brown

Light Brown

Light Brown

Light Brown

68.3

77.6

80.5

90.1

86.4

78.8

3.1

1.8

2.0

1.9

1.6

1.4

Fail

Pass

Pass

Pass

Pass

Pass

40.0

44.1

50.6

65.2

54.8

39.2


free formaldehyde content [17]. The nal pH of the reaction mixture was found to be 2.6 after 5 h of reaction. The decrease of pH in the methylolated cardanol might be ascribed to the formation of monohydroxyl substituted cardanol [18].

The novolac based epoxy resin was synthesized by reaction with epichlorohydrin (ECH). The number of glycidyl groups per molecule in the resin was dependent upon the number of phenolic hydroxyls in the starting novolac, the extent to which they were reacted and the extent to which the lowest molecular species were polymerized during synthesis. Theoretically, all the phenolic hydroxyls might be reacted, but in practice all of them did not react because of steric hindrance [17]. The reaction between ECH and novolac resin might be thought to proceed in a similar fashion as in the work given by Lee and Neville [17]. The epoxide group of ECH reacted with phenolic hydroxyls under the alkaline medium and formed chlorohydrin ether which underwent dehydrochlorination reaction and resulted in to glycidyl ether. The structure of the epoxy resin (refer Scheme 1) may be proposed on the basis of the procedure as adopted in our previous publication [16] for epoxidized novolac resin where novolac resin was prepared with cardanol and formaldehyde ratio of 1:0.5.

FTIR spectroscopic analysis of CNP and CER -1resins : A peak at 1090 cm (Fig. 1) was observed in

methylolated cardanol due to the C-O stretching from CH OH. It has also been found that the intensity of peaks 2

-1 -1at 1583 cm (C=C, str), 3011 cm (C-H str of alkene) and -1717 cm (C-H out-of-plane deformation) remained

a lmost unaffec ted which ind ica ted that the polymerization has taken place through substitution of CH OH and not through the double bonds in the side 2

-1chain. The band at 3321 cm for sample CFN , might be 81

due to the presence of hydroxyl groups in the methylolated cardanol. The small peaks near 908 and

-1717 cm might be due to three adjacent hydrogen atoms in the benzene nuclei. The peak appearance near 717

-1cm (Fig.1) indicated the ortho- and para- substitution at benzene nuclei. The preceding spectral data was found to identical with that given in the literature [19-21]. The FTIR spectrum of uncured CER sample is shown in Fig. 2. The characteristic band of the oxirane ring was

-1observed near 912 and 848 cm .

FTIR analysis of uncured and cured blend samples

: The peaks related to oxirane functionality -1

appeared near 911 and 848 cm (Fig. 2). When

CTPB is added to pure epoxy resin, these peaks

disappeared and new peaks appeared near 913 -1

and 851 cm (Fig. 3). The peaks appeared near 911 -1

and 848 cm (Fig. 2) might overlap these peaks.

-1 Thepeaks near 1725 cm due to carbonyl stretching

were also seen in the spectrum of uncured blend system

(Fig. 3). These observations clearly indicated that there

occurred no chemical interaction between the oxirane

group of epoxy and carboxyl group of CTPB. The epoxy

resin and CTPB remained as a discrete phase in the

uncured stage. However, the addition of CTPB and

polyamide into epoxy caused chemical interaction

between the oxirane ring and the carbonyl function of the

CTPB which resulted complete diminution of the peaks -1 at 911 and 848 cm in cured blend sample (Fig. 4). The

blend also showed appearance of new stretched peaks -1 -1 between 1258-1633 cm and 1048 cm and peak

-1 broadening at 1606 cm due to C-C multiple stretching

[22, 23].

Thermal Stability : The temperatures for 1-10% -1weight loss in TGA at a rate of 10°Cmin for cured

CER/CTPB blend samples are given in Tables 3. From the temperature for a particular degree of weight loss, it is apparent that the thermal stability of blend sample containing 15 wt% CTPB was the greatest amongst all other blend samples containing 5-25 wt% CTPB. The temperature upto 5% weight loss in TGA thermograms have been ignored as these might appear due to presence of impurities in the blends. Thus, the temperatures for 5% weight loss can be treated as an indicating temperature for the thermal stability of the blends and these temperatures have been shown in Table 4. From the table, it is again clear that the blend sample containing 15 wt% CTPB showed the highest initial degradation temperature (IDT), 472K, amongst all other blend samples containing 5-25 wt% CTPB in the blend. Also, the percent char yield was found to be maximum in case of sample CER (Table 4). The blend 81

sample without CTPB content (CER ) showed the 10

maximum degradation temperature (230°C) and char yield (12 %). The formation of more thermally stable blend samples (CER and CER ) might be attributed to 10 81

the presence of aromatic content and formation of more crosslink in the cured blend samples.

Scratch hardness, adhesion, exibility, gloss and

impact resistance of cured lms of blend samples :

Table 5 showed the surface and mechanical

properties of cured lms of blend samples. The

table clearly indicated that the cured lms of blend

samples containing 5-25 wt% CTPB showed

smooth and uniform with semi-glossy surfaces.

The blend samples showed improved impact

resistance than that of pure epoxy resin. The

adhesion and exibility improvement may be

thought due to the presence of some dissolved

rubber particles inside the epoxy matrix. The


decrease of cross-link density might also be an indicative of improved exibi l i ty whereas cavitations of rubber particles inside the epoxy matrix improved the impact resistance of the lms of blend samples. This table also indicated that the lm of pure epoxy, CRE was harder than the lm of blend samples10 .

The addition of CTPB decreased the hardness due to increase in exibility of resin lms.

Chemical Resistance : The acid and alkali resistance of cardanol based epoxidized novolac resin

and their blends with CTPB have been shown in Table 6. It is clear from the Table 6 that lms of coating based on epoxy with 15 wt% CTPB have offered the maximum resistance towards different concentrations of acids and alkalies as compared to the cured lms of other epoxy and its blend samples. This behaviour might be attributed due to greater reactivity of epoxy and liquid rubber.

Table 6 : Comparative acid and alkali resistance of films of the blends of CER resin with CTPB showing the period after which the first effect was detected when immersed for 12 months at ambient temperature.

Acids/ AlkaliesSample

Period in Months

CER 10 CER 95 CER 91 CER 81 CER 82 CER 72Sulphuric Acid, 10%

Sulphuric Acid, 25%

Hydrochloric Acid, 10%

Hydrochloric Acid, 25%

Nitric Acid, 10%

Nitric Acid, 25%

Sodium Hydroxide, 10%

Sodium Hydroxide, 25%

Potassium Hydroxide, 10%

Potassium Hydroxide, 25%

Ammonium Hydroxide, 10%

Ammonium Hydroxide, 25%

8

8

9

8

9

8

11

10

11

9

11

10

10

10

10

9

11

10

12

10

12

10

11

10

11

11

11

10

11

11

12

11

12

11

12

11

>12

>12

>12

>12

>12

>12

>12

>12

>12

>12

>12

>12

12

11

10

09

11

10

>12

11

>12

12

>12

>12

11

11

10

08

10

10

12

10

12

11

12

12

Table 7 : Comparative solvent resistance of CER resin films with CTPB showing the period after which the first effect was detected when immersed for 12 months at the ambient temperature.

Acids/ AlkaliesSample

Period in Months

CER 10 CER 95 CER 91 CER 81 CER 82 CER 72Deionized Water

Synthetic Sea Water

Methanol

Acetone

MEK

Tolune

Xylene

MTO

12

10

10

10

11

11

10

12

12

12

12

12

12

12

12

>12

>12

>12

>12

>12

>12

>12

>12

12

11

10

09

11

10

>12

11

11

11

10

08

10

10

12

10

12

12

11

11

11

11

11

11

12


decrease of cross-link density might also be an indicative of improved exibi l i ty whereas cavitations of rubber particles inside the epoxy matrix improved the impact resistance of the lms of blend samples. This table also indicated that the lm of pure epoxy, CRE was harder than the lm of blend samples10 .

The addition of CTPB decreased the hardness due to increase in exibility of resin lms.

Chemical Resistance : The acid and alkali resistance of cardanol based epoxidized novolac resin and their blends with CTPB have been shown in Table 6. It is clear from the Table 6 that lms of coating based on epoxy with 15 wt% CTPB have offered the maximum resistance towards different concentrations of acids and alkalies as compared to the cured lms of other epoxy and its blend samples. This behaviour might be attributed due to greater reactivity of epoxy and liquid rubber.

The effect of different solvents on the surface of the cured lms of pure epoxy and various blend samples of epoxy and CTPB has been shown in Table 7. It is evident from Table 7 that the surfaces of the epoxy and its blends with CTPB were completely unaffected by deionised and synthetic sea water. The exposure of cured lms of blend samples in solvents like acetone, toluene, MEK, methanol, etc. resulted rst change during 10 – 12 months which was more than that for pure epoxy resin. This indicated that the blend samples were more resistant towards solvents than pure epoxy resin. The better thermal stability of the blend samples conrmed the same.

CONCLUSIONS

The FTIR spectroscopic analysis revealed a chemical reaction between the oxirane and the carboxyl group of CTPB. DSC studies showed the exothermal heat of reaction of epoxy crosslinking due to addition of rubber into epoxy matrix. The thermal stability of the cardanol based epoxy resin was increased with the addition of 15 wt% CTPB in epoxy matrix. The lms of coating based on epoxy with 15 wt% CTPB offered the maximum resistance towards different concentrations of acids, alkalies, and solvents as compared to the cured lms of other blend samples. In view of these properties, the prepared blend systems may be recommended for high performance protective coatings.

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