Small range 文档类型:"3"

Totally found 45 items.

  • [期刊] Drawing behavior and mechanical properties of ultra-high molecular weight polyethylene blends with a linear polyethylene wax
    Ultra-high molecular weight polyethylene (UHMWPE; M-w = 103 kg/mol) is blended with a low molecular weight, linear polyethylene (PEwax; M-w = 1 kg/mol) and the solid state drawing behavior and mechanical properties are explored. The results indicate that the low molecular weight polyethylene wax acts as a solvent for the UHMWPE which leads to an improvement in rheological properties and the maximum attainable draw ratio of the blends. The maximum attainable Young's modulus of the drawn films increases with more than a factor 2 without removal of the solvent. Moreover, it is found that the maximum attainable tensile strength of the drawn blends also increases significantly from similar to 1 GPa to similar to 1.5 GPa upon addition of 60 wt% of the PEwax. Based on these results, a new route is proposed for the processing of highly oriented polyethylene, which has certain characteristics in common with both melt spinning and solution spinning but, in fact, is neither of the two. (C) 2018 Elsevier Ltd. All rights reserved.
  • [期刊] Efficacy of polyethylene wax, sucrose fatty acid ester and lime dips in delaying postharvest browning of rambutan.
    The efficacy of several surface coatings and lime dip in reducing water loss and browning of rambutan (Nephelium lappaceum L.) fruit was examined. Dipping fruit for 5 min in polyethylene wax (Super size Z) at 2:1, 1:1 and 1:2 dilution with water comparably reduced weight loss and delayed browning of the fruit. However, fruit developed off-flavors. On the other hand, sucrose fatty acid esters at 0.1-0.5% did not reduce weight loss but decreased fruit browning. L* and a* values did not correlate with browning scores. Lime as 2% solution was not effective in reducing weight loss and browning. It was concluded that storage at a low but non-chilling temperatures (approximately 13 degrees C) and high RH is required to reduce fungal spoilage, retard water loss and to slow browning.
  • [期刊] Synthesis of polyynes (and ene-ynes) segments by dechlorination reactions of chlorinated polyethylene wax and chlorinated docosane
    High density polyethylene oligomers and docosane (C_(22)H_(46)) were subjected to a photochlorination reaction to a chlorine content above 70% as checked by thermogravimetry. The resulting chlorinated materials were dehydrohalogenated by potassium hydroxide in different conditions with simple reaction routes. It is shown by FT-IR, C~(13)-NMR and electronic spectroscopy that soluble low molecular weight polymers were formed having polyyne-ene and polyene-yne segments. These new soluble polymeric materials are of potential interest both in the field of optics and electronics as well as in the understanding the cosmochemical problem of the molecules in interstellar space.
  • [期刊] Influence of polyethylene wax on wear resistance for polyurethane composite material under low speed water-lubricated conditions
    The water lubricated bearing is one of the most important components in machine systems, and significantly affects safe operation. Poor lubrication makes it very difficult to ensure good wear resistance in water lubricated bearings, especially at low speed or in complex load conditions. However, polyethylene wax (PEW) offers good self lubricating performance, which may provide lubrication and the required wear resistance in water lubricated bearing materials. In this reported study, a new water lubricated bearing composite material comprised of polyurethane (PU) and a small amount of PEW were fabricated to improve the wear resistance of the PU based water lubricated bearings. The wear behavior of the PU PEW composite material and the PU material was investigated at low speed and at different load conditions at room temperature using the CBZ 1 friction and wear tester. The wear resistance of these materials was evaluated based on the experimental results of the friction coefficient and wear morphologies. The experimental results indicated that the PEW additive was heated by the developed friction and was deposited on the surface of the composite material to form a lubricant film with good lubricity. As a result, the load bearing capacity of the lubricant film was improved, which effectively improved the lubrication conditions of the composite material, thereby improving the wear resistance and decreasing the effect of the load. These results suggest that this study may provide a novel approach for improving the wear resistance and lubrication condition of PU based water lubricated bearings.
  • [期刊] Boracic polyethylene/polyethylene wax blends and open-cell nickel foams as neutron-shielding composite
    This work shows that mechanical properties, thermal conductivity, and secondary gamma-ray shielding ability can be significantly improved when open-cell nickel foams are embedded into the shielding composites. The boracic polyethylene/polyethylene wax blends and open-cell nickel foam composites (PPNM) are designed and prepared by permeating homogeneous mixed melt fillers into open-cell nickel foams. The ratio of polyethylene and polyethylene wax is investigated to achieve higher filling rate. The quasi-static compressive response of PPNMs and polyethylene/polyethylene wax blends is measured, and the crystallization properties are studied by differential scanning calorimetry. The neutron and secondary gamma-ray shielding abilities of PPNMs are also simulated based on Monte Carlo particle transport method. Results show that the compression strength of PPNMs with boron carbide is slightly improved when compared with polyethylene/polyethylene wax blends. The nickel foams in PPNM composites improve the energy-absorbing efficiency by 30%. The thermal conductivity of PPNMs is 300% higher than polyethylene/polyethylene wax. The calculated results show that neutron-shielding abilities of PPNMs increase as content of boron carbide increases. Moreover, secondary gamma-ray shielding ability of PPNMs containing boron carbide is obviously higher than polyethylene/polyethylene wax. The PPNMs containing boron carbide neutron-shielding materials are proved to have good thermal conductivity, mechanical properties, and radiation-shielding ability.
  • [期刊] Thixotropic properties of multi-functional binder and compaction behaviour of the low alloyed binder-treated powder
    A new multi-functional binder with adhesive and lubricant effect was designed, and the thixotropic properties of the binder components and the resulting binder, the adhesive effect and compaction behaviour of the binder-treated powder were investigated. The results demonstrate that the thixotropic components in the binder are polyethylene wax and microcrystalline wax. With the increase of polyethylene wax content, the critical solid-liquid shear stress of binders decreases gradually. The main lubrication components in the low-pressure and high-pressure stages during the compaction process are found to be polyethylene wax and microcrystalline wax, respectively. The fine metal or graphite additives are effectively bonded on the surface of iron particles and filled in the pits. The green density reaches 7.25 g cm(-3) at 600 MPa when the content of polyethylene wax is 30%. From 400 to 750 MPa, the content of polyethylene wax corresponding to the minimum ejection pressure decreases from 20 to 0%.
  • [期刊] Antifungal Activity of Polyhexamethyleneguanidine Derivatives Introduced into Biodegradable Polymers
    Experiments were conducted to investigate the antifungal activities of polyhexamethyleneguanidine (PHMG) derivatives introduced into polylactide (PLA), polyhydroxybutyrate (PHB) and polycaprolactone (PCL) against Aspergillus niger, Penicillium chrysogenum and Candida albicans. All of the PHMG derivatives inhibited the germination of A. niger and P. chrysogenum. All of the derivatives exerted a much stronger inhibitory effect on the cells of C. albicans. PHMG granular polyethylene wax (at the concentration of 1.0%) has a fungicidal effect. The reduction in the number of yeast cells capable of growing on the surface composites PLA, PHB and PCL with PHMG granular polyethylene wax for 24h was R>2. PHMG derivatives introduced into PLA decreased hydrolases activity in A. niger and P. chrysogenum. All of the PHMG derivatives introduced into all investigated polymers inhibited the hydrolases activity in C. albicans proportionately to concentration. PHMG granular polyethylene wax at a concentration of 1.0% most strongly inhibited hydrolases activity in yeast. The composites produced from PLA, PHB, PCL and this PHMG derivatives can be used in many areas to reduce the growth of yeast. The studied composites can potentially be used for the production of biomedical or packaging materials.Graphical AbstractPHMG derivates introduced into polymer have slightly biocidal properties against molds and strong against yeast. The composites produced from PLA, PHB, PCL and this PHMG derivatives can be used in the many areas to reduce the growth of yeast. The studied composites can potentially be used for the production of biomedical or packing materials.[GRAPHICS].
  • [期刊] HDPE卫浴排水弯管材质研究
    讨论了成核剂、LLDPE、吹塑级HDPE、弹性体POE和EVA,以及PE蜡对注塑级HDPE M80064材料性能的影响,结果表明:成核剂、LLDPE、吹塑级HDPE对材料抗开裂性均有改善但幅度不明显;弹性体POE和EVA能较大幅度提高材料的抗开裂性,POE添加至15%,材料抗开裂时间达到700h左右,但材料的拉伸强度低于20MPa; EVA用量为10%时,材料抗开裂时间可达到900h,材料的拉伸强度为21. 9MPa,材料的韧也得到明显改善; PE蜡减小材料成型时与模具的粘附,解决了长弯管强脱部位的拉伤现象;材料组分为HDPE M80064/成核剂HPN 210M/HDPE 5502/EVA 7350M/PE蜡=59. 8/0. 2/30/10/2,材料的抗开裂时间达到950h,材料性能以及成型性满足卫浴HDPE排水弯管的要求。
  • [期刊] 抗老化透明聚丙烯的制备及性能
    以有机磷酸盐成核剂(NA–11)作为等规聚丙烯(iPP)的透明添加剂,通过对分散剂、抗氧剂的优选,制备了抗老化性能优异的透明iPP材料。通过力学性能、雾度、透光率、热氧老化性能测试和DSC分析等手段研究了分散剂、抗氧剂协同作用对iPP/NA–11 (NiPP)材料力学性能、透明性能、结晶行为和抗老化性能的影响。研究结果表明,当乙撑双硬脂酸酰胺(EBS)作为分散剂时会影响NiPP材料的透明性,而聚乙烯(PE)蜡作为分散剂时NiPP材料的力学性能和透明性能保持较好。以聚乙烯(PE)蜡作为分散剂,添加抗氧剂1010的NiPP材料的抗老化性能优异,但是它的加入会恶化NiPP材料的透明性,NiPP材料的雾度增加了57.78%;添加复合抗氧剂B215的NiPP材料在保持透明性能的同时拥有优异的抗老化性能。NiPP/PE蜡/B215材料的雾度仅为15.0%,经过35d热氧老化后,NiPP材料的拉伸强度保持率为83.75%,弯曲强度保持率为81.36%,缺口冲击强度保持率为72.32%。
  • [期刊] Ethylene Oligomerization and Polymerization by Palladium(II) Methyl Complexes Supported by Phosphines Bearing a Perchlorinated 10-Vertex closo-Carborane Anion Substituent
    The synthesis and ethylene reactivity of the zwitterionic Pd methyl complexes (kappa(2)-P,Cl-PR2CB9Cl9)PdMe-(THF) (7, R = Pr-i; 8, R = Ph) and (kappa(2)-P,O-P(o-OMe-Ph)(2)CB9Cl9)PdMe(THF) (9), which contain the first phosphines appended with anionic 10-vertex perchlorinated closo-carboranes, are described. Complexes 7 and 8 oligomerize ethylene (23 degrees C, 2 atm) to a Schulz-Flory distribution of C-4-C-10 olefins with TOFs of ca. 8000 and 1800 t.o./h, respectively. 8 is ca. 4 times more active than the analogous (kappa(2)-P,F-ortho-PPh2C6H4BF3)PdMe(L) (L = pyridine or collidine) system reported by Jordan and Piers, which produces butenes. Complex 9 reacts with ethylene to yield polyethylene wax (M-n ca. 1000, D ca. 1.5) that is similar to commercial Fischer-Tropsch waxes. The activities of 7-9 are independent of ethylene pressure and the presence of B(C6F5)(3), suggesting that the catalyst resting state is the corresponding (PR2CB9Cl9)PdR(H2C=CH2) adduct. The molecular weights of the oligomer/polymer products are independent of ethylene pressure, which is consistent with an associative chain transfer mechanism. Reaction of 9 with ethylene generates the corresponding ethylene complex (kappa(2)-P,O-P(o-OMe-Ph)(2)CB9Cl9)PdMe(H2C=CH2), which inserts ethylene at -20 degrees C with a barrier (Delta G(insertion)(double dagger)) of 18.1 kcal/mol.