The uniaxial tension (loading and unloading), creep and relaxation experiments on high density polyethylene (HDPE) have been
carried out at room temperature. The stress–strain behavior of HDPE under different strain rates, creep (relaxation) behavior
at different stress (strain) levels have been investigated. These experimental results are used to compare the simulation
results of a unified state variable theory, viscoplasticity theory based on overstress (VBO) and a macro-mechanical constitutive
model for elasto-viscoplastic deformation of polymeric materials developed by Boyce et al. (Polymer 41:2183–2201, 2000). It is observed that elasto-viscoplasticity model by Boyce et al. (Polymer 41:2183–2201, 2000) is not good enough to simulate stress–strain, creep and relaxation behaviors of HDPE. However, the aforementioned behaviors
can be modeled quantitatively by using VBO model. 相似文献
A high density polyethylene geomembrane (GMB) stabilized with hindered amine (light) stabilizers (HALS or HAS) is immersed in four chlorinated water solutions with a simulated free chlorine concentration range of 0.5–5 ppm at five different temperatures (25, 40, 65, 75, and 85 °C) for 70 months. Standard and high pressure oxidative induction time (OIT) tests are performed to monitor antioxidants depletion while melt flow index, tensile, and stress crack resistance (SCR) tests are conducted to monitor degradation in physical and mechanical properties. Degradation in the GMB properties occurred shortly after immersion in chlorinated water at all temperatures except at 25 °C. Increasing the free chlorine concentration resulted in faster degradation of the tensile properties and SCR. The predicted time to nominal failure based on SCR ranges between 25 years at 40 °C and 5 years at 85 °C in chlorinated water (with 0.5 ppm free chlorine). A comparison between the degradation in SCR of this GMB and a GMB with a different resin and without HALS shows significant difference in their performance in chlorinated water but not in other incubation media. 相似文献
A hybrid structure of single-crystal silicon (Si) and high-density polyethylene (HDPE) was developed as a new substrate for infrared lenses by using precision press molding. A thin HDPE film was used to laminate a silicon wafer and their interface was directly bonded by the silane cross-link. The HDPE film is easy to be hot-embossed to form three-dimensional surface microstructures and the silicon wafer provides a high stiffness for the hybrid substrate. The infrared (IR) optical properties of the hybrid substrate were examined by two kinds of measurements, transmittance and image sharpness. Interestingly, the transmittance measurement result shows that the IR transmittance of the hybrid substrate is higher than that of Si itself in some region of wavelength. The imaging test result shows that the hybrid substrate is capable to produce similar image quality as Si itself. These results strongly demonstrate that the developed Si–HDPE hybrid substrate is a promising alternative substrate material for IR lens. 相似文献
A series of octyltetramethyldisiloxane‐containing ethylene copolymers, poly(ethylene‐co‐OO7) (abbreviated as E‐co‐OO7), are prepared from vanadium catalyzed copolymerization of ethylene with 1‐oct(7‐en)yl‐3‐octyl‐1,1,3,3‐tetramethyldisiloxane (or OO7) macromonomer. The copolymers containing different silicone contents are employed as composite lubricants for high‐density polyethylene (HDPE). The influences of the silicone content in the copolymer and that of the added copolymer amount in the blend on the bulk and surface properties of the blends are systematically investigated. The results show that E‐co‐OO7 exhibits superior overall performance in comparison with conventional lubricants silicone masterbatch and polyethylene wax. Compared to HDPE control, 10 wt% E‐co‐OO7 addition increases the melt flow rates by 49%, increases the elongation at break from 740 to 860%, increases the water‐contact angle from 90° up to 108°, lowers the coefficient of friction from 0.072 to 0.049, lowers the specific wear rate from 11 × 10?3 to 5.6 × 10?3 mm3 Nm?1. The impact strength and high temperature thermal stability are also slightly improved. The measured Si/C atomic ratios demonstrate the sufficient silicone enrichment on surface of the blends. E‐co‐OO7 with 23.5 Si? O? Si per 1000 C gives the best internal lubrication, and E‐co‐OO7 with 29.7 Si? O? Si per 1000 C gives the best external lubrication.