Apparatus for Testing the Combined Effects of Deformation and Chemical Exposure on Polymeric Liners

Abstract

A new experimental apparatus was developed for determining the combined effects of mechanical stress and chemical exposure on the long-term durability of polymeric liners, which are widely used in civil and environmental engineering applications. The apparatus is capable of bending and holding up to 12 coupon-type specimens at predetermined levels of deflection while simultaneously exposing the specimens to a chemical solution bath. The apparatus was used to study the effects of three levels of deformation of 0.0, 0.03, and 0.08 mm/mm normalized deflection at the midspan of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) specimens (3.2×12.7×63.5 mm or 0.13×0.50×2.50 in.). The bent specimens were immersed in deionized water, chlorine (3 or 800 mg/L) or trichloroethylene (TCE) (3 or 1,000 mg/L) solution baths. The specimens were then stored at a constant temperature (23, 50, or 80°C/73, 122, or 176°F) for a predetermined period of 1,250, 2,500, 3,750, and 5,000 h. Results of the tests indicate that neither TCE nor chlorine affect the modulus of elasticity of the tested HDPE and LDPE materials, whereas deformation at 8% normalized deflection (in deionized water and the chemical solutions) reduced the flexural modulus of elasticity of HDPE. In addition, elevated temperature (80°C) combined with deformation had a notable effect on the ultimate strength of HDPE and elevated temperature only (80°C) made all of the LDPE specimens fail.