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排序方式: 共有124条查询结果,搜索用时 15 毫秒
81.
Many controversial issues have recently been associated with plasticized poly(vinyl chloride) (pPVC) used in building applications, mainly for flooring. One of them has to do with the health impact of some plasticizers and thermal stabilizers based on heavy metal compounds. Recent advances in the synthesis of polyolefins based on metallocene catalysts can yield similar flexibility for formulations as is now available for those based on pPVC. Polyolefin copolymers are considered to be possible replacements for pPVC. The soil burial test has demonstrated that highly filled polyolefin elastomer formulations having a significant percentage of post-consumer polyolefins (up to 60% in laboratory conditions) have interesting properties from the biodegradation point of view. They are more resistant to microorganisms’ attack than plasticized flooring formulations based on PVC that are currently used, even in a very harsh environment as soil, where complex mixtures of microorganisms are present. The effect of microorganisms’ attack after soil burial was evaluated by visual examination, weight loss, water absorption and changes in mechanical properties. 相似文献
82.
Gang?Liu Yan-feng?Li Feng-yuan?YanEmail author Zhen-xing?Zhao Lin-cheng?Zhou Qun-ji?Xue 《Journal of Polymers and the Environment》2005,13(4):339-348
Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO2 and TiO2 at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO2 contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO2 and TiO2, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area. 相似文献
83.
Water transport in polylactic acid (PLA), PLA/ polycaprolactone copolymers, and PLA/polyethylene glycol blends 总被引:1,自引:0,他引:1
Georgette L. Siparsky Kent J. Voorhees John R. Dorgan Kevin Schilling 《Journal of Polymers and the Environment》1997,5(3):125-136
Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester, and water vapor permeability may have a significant
influence on the rate of degradation. A method is devised to use bags prepared from PLA films and filled with molecular sieves
to determine the water vapor permeability in the polymer, its copolymers with caprolactone, and blends with polyethylene glycol.
The “solution-diffusion” model is used to determine the permeability parameters. These include the solubility coefficient,S, a measure of the equilibrium water concentration available for hydrolysis and the diffusion coefficient,D, which characterizes the rate of water vapor diffusion into the film under specific conditions. Values ofS andD at 50‡C and 90% relative humidity ranged from 400 × 10-6 to 1000 × 10-6 cm3 (STP)/(cm3 Pa) and 0.20 × 10-6 to 1.0 × 10-6 cm2/s, respectively. TheS andD coefficients were also measured at 20 and 40‡C and compared to those of other polymers. The degree of crystallinity was found
to have little influence on the measured permeability parameters. The heat of sorption, δHS, and the activation energy of diffusion, ED, were used to show that the permeability process is best described by the “water cluster” model for hydrophobic polymers.
Finally, the diffusion coefficient is used to compare the rate of water diffusion to the rate of water consumption by ester
hydrolysis. Results indicate that hydrolytic degradation of PLA is reaction-controlled. 相似文献
84.
Effect of Poly(Vinyl Alcohol) and Polyethylene on the Growth of Red Pepper and Tomato 总被引:2,自引:0,他引:2
Poly(vinyl alcohol) (PVA) and polyethylene (PE) were blended with a soil for cultivation, and their effects were investigated on the growth behavior of red pepper and tomato by examining the stems, the leaves, and the roots. PVA retarded the growth of red pepper significantly even at a concentration as low as 0.05%. The roots were depauperated more than the stems and the leaves. Tomato was also affected by PVA but to a lesser extent than red pepper. In contrast, the presence of both round pieces (10 mm diameter) of PE film and powdery PE influenced negligibly the growth of red pepper as well as that of tomato up to 35 wt% in soil. 相似文献
85.
液相法芒硝制碱中苛化废渣的利用 总被引:2,自引:0,他引:2
研究了用液相法芒硝制碱的苛化废渣制取轻质CaCO3的工艺及用轻质CaCO3填充母料对聚乙烯进行改性。试验结果表明,本研究所制取的轻质CaCO3的质量符合GB4794-84一级品规格,用其制成母料对低密度聚乙烯填充改性,不仅可消除苛化废渣对环境的污染,降低聚乙烯制品的生产成本,而且可在制品的拉伸强度、断裂伸长率和冲击强度降低不多的情况下,提高制品的硬度、弹性模量、热稳定性及耐蠕变性。 相似文献
86.
Explosion flame propagation characteristics and overpressure distribution of low density polyethylene (LDPE) dust and ethylene hybrid mixture were investigated under N2 inerting conditions using a custom-designed 12 L cylindrical explosion tank. The results showed that a small amount of ethylene could promote the explosion characteristics of LDPE dust. N2 inerting had different inhibitory effects on the explosion flame of LDPE dust and its mixture with ethylene. The explosion overpressure strength of the LDPE dust/ethylene hybrid mixture decreased with increasing N2 concentration. The overall suppression effect of N2 on the explosion overpressure of the LDPE dust was better than that of the LDPE dust/ethylene hybrid mixture explosion. As the ethylene concentration increased from 0% to 2.5%, the limiting oxygen concentration decreased by 13% oxygen. This small amount of ethylene restricted the traditional inerting process. The study conclusions can provide further scientific basis for the inerting and explosion proofing design of production process equipment involving LDPE dust. 相似文献
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90.
ERT技术界定卫生填埋场边界的试验研究 总被引:2,自引:1,他引:1
界定卫生垃圾填埋场边界有助于场地环境的维护和管理,采用电阻率二维层析成像技术中的3种装置排列(测深、温纳、偶极-偶极)对高阻体上表面特征进行试验模拟,并通过电阻率二维层析成像技术对垃圾填埋场边界的电性特征进行研究,在此基础上开展了现场勘查. 结果表明:在由测深和温纳2种装置排列所得到的二维反演图像中,高阻体的上表面与高阻区相切,误差达到25%,表明2种排列不能进行精确定位;而偶极-偶极的反演图像中高阻体的上表面在低阻区与高阻扩散末端的分界点上,反演精度较高,误差在5%以内. 相似文献