Hifax flexible polypropylene used in geomembrane applications

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Overview

LyondellBasell Industries is one of the world’s largest polymers, petrochemicals and fuels companies. We are the global leader in polyolefins technology, production and marketing; a pioneer in propylene oxide and derivatives; a significant producer of advanced fuel products; and the operator of one of North America’s largest full-conversion refineries. Through research and development, LyondellBasell develops innovative materials and technologies that deliver exceptional customer value and products that improve quality of life for people around the world. Headquartered in The Netherlands, LyondellBasell (www.lyondellbasell.com) is privately owned by Access Industries.

Thermoplastic olefins (TPOs) produced using LyondellBasell’s proprietary Catalloy process technology are utilized by many industries for the production of a variety of customer applications, including automotive, single ply roofing and geomembranes. Resins from the Catalloy process are part of LyondellBasell’s advanced polyolefins product line and are produced using technology which incorporates rubber and polypropylene in the reactor, enabling high levels of rubber to be evenly dispersed throughout the polymer matrix. The resulting resins have a unique range of properties with a combination of softness and mechanical properties. Marketed under the Hifax trade name, these resins can be produced with Shore A hardness as low as 75.

Hifax flexible polypropylene resins are utilized by customers in geomembrane applications due to the unique combination of mechanical toughness, flexibility, barrier properties and environmental resistance they possess. Customers have found that these products, when used as building blocks, form the critical backbone of their geocomposite compounds. Due to their high levels of rubber content, Hifax resins can be combined with other olefins, mineral fillers and stabilizers without a significant reduction in mechanical properties. Their crystallinity is very low, providing outstanding resistance to environmental stress cracking even at elevated temperatures.

Hifax resins can be processed using popular sheet conversion processes such as round die extrusion, horizontal slot die extrusion, calendaring and extrusion coating. Membranes produced from Hifax TPO resins may also be recycled for use in alternative markets or utilized for energy production by incineration. Products produced using LyondellBasell’s Catalloy process technology are becoming the materials of choice for producers of geomembrane applications because of their unique mechanical property performance, their environmental advantages over other materials, their flexibility of use and their ease of handling during the manufacturing process.

Why our customers use Hifax TPO resins for geomembranes:

Attributes

Plasticizer-free

Low specific gravity

Heat weldable on site

Flexible TPOs high in rubber content

Excellent resistance to root and hydrostatic puncture

Formability to soil movements

Can be modified with UV stabilizers for excellent UV and thermal characteristics

High tear resistance

Hifax TPO resins can be converted using a variety of technologies

Flat die extrusion

Calendering

Blown film process

As polyolefins, these grades have extremely good environmental profiles during manufacture as well as in use and through disposal, making them attractive candidates for the replacement of other membrane raw material alternatives with less favorable environmental characteristics.

Geomembrane applications for which our customers have used Hifax TPO resins:

Waste management

Municipal solid waste landfill caps

Waste water treatment reservoirs and floating covers

Water containment

Aquaculture ponds

Decorative and golf course pond liners

Water conveyance

Canal liners

Storage reservoirs

Storm water ponds

Industrial

Floating covers to control evaporation

Tunnel liners

Waste reservoirs

Note: it is the owner’s responsibility to determine and test for material suitability for each application and installation.

Physical properties

Physical properties: Flexible TPO building blocks used to produce geomembranesProduct Name/ Test

Description Durometer MFR Flexural Modulus

Tensile Strength @ Break

Elongation @ Break

Brittleness Temperature

Vicat Softening Temp (A50 (50 °C/h 10 N))

Unit Shore A g/10 min MPa MPa % °C °C

Test Method ASTM D2240 ISO 133 (230 °C, 2.16 kg) ISO 178 ISO 527 ISO 527 ASTM D746 ISO 306

Hifax CA 10 A Minimally stabilized building block*

89 0.6 80 20 >800 <-70°C 56

*Additional stabilizers will be required for specific applications

CBR puncture (DIN 54307) with yield point

Geomembranes produced using Hifax TPO exhibit exceptional resistance to puncture, an important characteristic when root resistance is important.

Coefficient of linear thermal expansion

The coefficient of linear thermal expansion of geomembranes produced using Hifax TPO is comparable to PVC-P liners and is significantly lower than those produced with polyethylene. CLTE testing indicates that TPO-based membranes would have a lower tendency than other olefin liners to have excessive movements due to extreme weather conditions that could lead to improper seam alignment or overlap and unnecessary stresses.

Technical data

Comparative friction angles

Liners produced using Hifax TPO exhibit a higher friction angle than polyethylene-based liners, enabling greater soil/liner interface stability at steeper slopes during installation.

PVC

Hifax

LLDPE

HDPE

CLT

E X

10-

5/ºC

Temperature (ºC)

5

10

15

20

25

30

50403020

Normal Stress

Shea

r St

ress

Hifax 30°

LLDPE 22°

HDPE 18°

0.00 50 100 150

0.5

1.0

1.5

2.0

2.5

3.0

3.5PVC-P

Hifax

Flexible PE

HDPE

Displacement (mm)

Load

per

uni

t th

ickn

ess

(kN

)/mm

Multi-axial elongation performance

Geomembranes produced from Hifax resins show high extensibility, which enables high conformance characteristics. A multi-axial elongation test executed on a welded membrane demonstrates the strength of the weld without adhesives. Liners produced using Hifax resins have a wide seaming and installation temperature window.

Note 1: Critical friction angles dry Ottawa sand vs. liners (ASTM D 5321)

Note 2: Testing was conducted on a basic geomembrane. Friction-angle performance may change based on the additives utilized with the Hifax TPO building blocks or the texture of the liner.

0

1000

2000

3000

4000

0 50 100 150Strain (%) ASTM D5616

HifaxPVC-P

LLDPE

Reinforced Hifax

HDPE

(28)

(21)

(14)

(7)

Tested per ASTM D 696. Test performed on typical samples provided by our customers

1 mm sheet produced from a Hifax TPO

In Table 1, results of a test conducted using aqueous solutions saturated with some chemicals are reported. Each chemical was tested at saturation in water (=conc.), and then a saturated aqueous mixture of these chemicals was tested.

Chemical resistance of Hifax TPOs

In many applications where Hifax resins could be considered for use, chemical resistance is often a key selection criterion. Since the backbone of Hifax resins is polypropylene, these resins in general have an excellent balance of chemical resistance and physical performance properties. Many of the Hifax resin grades are, however, modified with significant amounts of a rubbery component which gives them the desired flexibility. Therefore, it is critical to understand that the chemical resistance of Hifax resins is different from that of traditional homopolymer and copolymer polypropylene.

It is important to note that the degree of attack on any material is influenced by a number of variable factors, including, but not limited to, concentration of the chemical(s), mechanical stresses, temperature, aeration, velocity of flow, duration of exposure, possible chemical reaction with other compounds, size of the test sample and different additive packages. In practical applications these stress factors are also in combination with each other. Therefore, the information on the following tables is offered only as a guide. It is recommended that a sample of the specified item be tested under actual or simulated service conditions.

Chemical Classes Chemical Resistance

Acids Inorganic e.g., hydrochloric acid, nitric acid, dilute sulfuric acid good resistance

Bases Organic e.g., amines good resistance

Bases Inorganic e.g., sodium hydroxide, calcium hydroxide, ammonium hydroxide good resistance

Alcohols e.g., methanol, n-propanol, ethylene glycol good resistance

Heavy Metals e.g., mercury, lead, cadmium good resistance

Salts e.g., sodium chloride, potassium bromide, cupric sulfate, calcium carbonate good resistance

Acids Organic e.g., acetic acid, stearic acid marginal resistance

Volatile/Semivolatile Organics e.g., ketones, aldehydes, esters, amides, ethers, other oxygenated solvents

marginal resistance

Oil and Grease marginal resistance

Strong Oxidizers e.g., potassium permanganate, potassium dichromate, chlorine, bleach, chlorine dioxide, perchloric acid, peroxides

marginal resistance

Aliphatic Halogenated Hydrocarbons e.g., trichloroethylene, methylene chloride, chloroform, other chlorinated solvents

Poor

Aromatic Halogenated Hydrocarbons e.g., dichlorobenzene, other chlorinated solvents

Poor

Aliphatic Hydrocarbons e.g., butane, pentane, hexane, light petroleum ethers Poor

Aromatic Hydrocarbons e.g., benzene, toluene, xylene Poor

Table 2: Chemical resistance of Hifax CA 10 A to various classes of chemicals

Tested for 120 days at 50 °C. Conc. PPM. Weight Gain % Ultimate Tensile, MPa Ultimate Elongation %

Control n/a n/a 22.6 840

Water n/a n/a 22.0 800

NaCl 2,000 0.10 21.1 815

Methyl Ethyl Ketone (MEK) 1,000 0.18 20.4 775

o-Xylene 150 1.10 21.5 840

Trichlorethylene (TCE) 475 2.00 24.7 835

Toluene 475 2.25 19.1 775

Toluene +2% NaCl 475 2.50 18.9 765

Mix various 3.70 19.2 805

Table 1: Chemical resistance of specimens based on Hifax CA 10 A in aqueous solutions

In Table 2, an indication of the chemical resistance of Hifax resins to classes of chemicals is given. Samples of the specified item should be tested in all cases.

Chemical resistance

LyondellBasell Industries

LyondellBasell is privately owned by Access Industries

Adflex, Catalloy and Hifax are trademarks owned or used by LyondellBasell group companies. Adflex and Hifax are registered in the U.S. Patent and Trademark Office.

Before using a LyondellBasell product, customers and other users should make their own independent determination that the product is suitable for the intended use. They should also ensure that they can use the LyondellBasell product safely and legally. (Material Safety Data Sheets are available from LyondellBasell at lyondellbasell.com). This document does not constitute a warranty, express or implied, including a warranty of merchantability or fitness for a particular purpose. No one is authorized to make such warranties or assume any liabilities on behalf of LyondellBasell except in writing signed by an authorized LyondellBasell employee. Unless otherwise agreed in writing, the exclusive remedy for all claims is replacement of the product or refund of the purchase price at LyondellBasell’s option, and in no event shall LyondellBasell be liable for special, consequential, punitive or exemplary damages.

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