Stress-crack resistance, of polyethylene

The homopolymer finds a variety of uses, as an adhesive component, as a base for chewing gum, in caulking compounds, as a tackifier for greases, in tank linings, as a motor oil additive to provide suitable viscosity characteristics and to improve the environmental stress-cracking resistance of polyethylene. It has been incorporated in quantities of up to 30% in high-density polyethylene to improve the impact strength of heavy duty sacks. 

Soares JBP, Abbott RF, Kim JD (2000) Environmental stress cracking resistance of polyethylene the use of CRYSTAF and SEC to establish structure-property relationships. J Polym Sci Part B Polym Phys 38(10) 1267-1275... 

Bec Becker, G., Braun, D. Kunststoff Handbuch 4, Polystyrol. Carl Hanser Verlag, Munich, 1996. OOSoa Soares, J. B. P., Abbott, R. F., Kim, J. D. Environmental stress cracking resistance of polyethylene The use of CRYSTAF and SEC to establish structure-property relationships. J. Polym. Sci. Part B-Polym. Phys. 38 (20(X)) 1267-1275. 

An important application for polybntylene is plumbing pipe for both coimnercial and residential use. The exceUent creep resistance of polybntylene aUows for the manufacture of thiimer wall pipes compared to pipes made from polyethylene or polypropylene. Polybutylene pipe can also be used for the transport of abrasive fluids. Other applications for polybutylene include hot melt adhesives and additives for other plastics. The addition of polybutylene improves the environmental stress cracking resistance of polyethylene and the impact and weld line strength of polypropylene. Polybntylene is also used in pack aging applications. 

Other applications include hot-melt adhesives and additives for other plastics. The addition of polybutylene improves the environmental stress cracking resistance of polyethylene and the impact and weld line strength of polypropylene. Polybutylene is also used in packaging applications. 

ASTM D 2561 Standard Test Method for Environmental Stress Cracking Resistance of Blow Molded Polyethylene Containers. ASTM F1248 Environmental Stress Cracking Resistance of Polyethylene... 

Environmental Stress Cracking n The formation of internal or external cracks in a plastic caused by tensile stresses well below its short-time strength, and induced by exposure to heat, solvent vapor, or chemically active solutions. ASTM Test F 1248 describes the measurement of the environmental stress-cracking resistance of polyethylene pipe in the presence of a surface-active agent. Other ASTM tests treating this subject are D 1693, D 2561, D 2951, and, in Section 15.03, F 484, F 791, and F 1164. 

One non-standardized approach to testing for notch sensitivity and stress cracking resistance of polyethylene pipes is offered by the Full Notch Creep Test (FNCT) and Notched Constant Tensile Load. Here, a square test bar with a circumferential notch is loaded at 95°C In a wetting bath at constant tensile load [266]. 

PP/PA (polypropylene/polyallomer). These plastics are similar to polyethylene, but each unit of their chains has a methyl group attached. They are translucent, autoclavable, and have no known solvents at room temperature. They are slightly more susceptible than polyethylene to strong oxidizing agents. They offer the best stress-cracking resistance of the polyolefins. Products made of polypropylene are brittle at ambient temperature and may crack or break if dropped from benchtop height. 

Schellenberg J, Fienhold G (1998) Environmental stress cracking resistance of blends of high-density polyethylene with other polyethylenes. Polym Eng Sci 38(9) 1413-1419... 

Kurelec, L. et al. (2005). Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene. Polymer, Vol. 46 (2005), p>p. 6369-6379... 

Chemical resistance is essentially unchanged, except that environmental stress crack resistance of such polymers as polycarbonate and polyethylene is markedly increased by glass reinforcement. 

Figure 13.31 Environmental stress cracking resistance (ESCR) plotted against strain-hardening modulus for a range of EIDPEs, both catalyst based with broad molecular weight distribution, and bimodal. Points labelled reproducibility are repeated tests on the same sample. (Reproduced from Kurelec, L, Teeuwen, M., Schoffeleers, El. et al. (2005) Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene. Polymer, 46, 6369. Copyright (2005) Elsevier Ltd.)...

Polyethylene resistance increases with increasing density in general PE-HD is more resistant than PE-LD or PE-LLD. With increasing density, the stress cracking resistance of linear polyethylene decreases. Bimodal polyethylene grades exhibit higher resistance than mono-modal grades. 

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