The thermooxidative degradation of poly-(oxymethylene) copolymer (CPOM-Y) powder was studied in air in 150

The processing of ultrahigh molecular weight polyethylene (UHMWPE) by the addition of polypropylene (PP) and high-density polyethylene (HDPE) was investigated. The results show that the addition of PP improves the processability of UHMWPE more effectively than does the addition of HDPE. UHMWPE/PP blends can be effectively processed with a twin-roller and general singlescrew extruder. In the extrusion of UHMWPE/PP blends, PP is enriched at the surface of the blend adjacent to the barrel wall, thus increasing the frictional force on the wall; the conveyance of the solid down to the channel can then be carried out. The melt pool against the active flight flank exerts a considerable pressure on the UHMWPE powder in the passive flight flank, which overcomes the hard compaction of UHMWPE. The PP penetrates into the gaps between the particles, acting as a heat-transfer agent and adhesive, thus enhancing the heat-transfer ability in the material.

The capillary flow properties and morphologies of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were studied. The results show that UHMWPE is difficult to process. The melts flowed unsteadily at lower shear rate. With 10wt% PP contained in the UHMWPE/PP blends, the apparent melt viscosity was much lower than that of UHMWPE. When the PP content increased to 20 and 30wt%, no pressure vibration occurred throughout the whole shear rate range. Microstructure analysis showed that PP prefers to locate in the amorphous or low crystallinity zones of the UHMWPE matrix. The flowability of UHMWPE increased substantially with the addition of PP. The addition of PE could not effectively reduce the chain entanglement density of UHMWPE. The improvement of processability of UHMWPE by the addition of PE was rather limited.

This paper explores anti-wear properties and wear mechanism for ultrahigh molecular weight polyethylene (UHMWPE) and ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends, which were prepared by melt extruding through a single-screw extruder, and were conducted sliding wear tests with MM-200 wear tester by sliding against 45# steel ring of a surface roughness about 0.015 m. Results show that anti-wear properties of UHMWPE are improved notably by blending with appropriated content of polypropylene (PP). The coefficients of friction and wear rate of UHMWPE/PP blend are much lower than those of pure UHMWPE during sliding. Partly oxidized transfer film of UHMWPE is formed on the surface of the steel counterpart. No transfer film but fine powders can be found on the steel ring surface sliding against the UHMWPE/PP blend. Long duration sliding causes fatigue failure of UHMWPE and many big spalls are produced around the counterpart edge, while the amount of debris from UHMWPE/PP blends does not show apparent increase with sliding time. DSC analysis reveals that the surface temperature of UHMWPE is higher than that of UHMWPE/PP blend during sliding. 'Shish-kebab' crystal is formed in the worn surface of UHMWPE/PP blend due to the long time shearing, stretching and annealing effect during sliding. The improvement of wear resistance is probably due to the rod shape debris existing between the contact surface of UHMWPE/PP and the counterpart, which helps to reduce the friction and wear efficiently.

采用紫外光谱、XPS研究了羧甲基纤维素型高分子表面活性剂在硅胶/水界面上的吸附形态,结果表明随着高分子表面活性剂溶液浓度增大,分子在硅胶表面的吸附由单层逐渐变为多层,生成半胶束结构。