成型方法对PE-UHMW摩擦磨损性能的影响

采用对比试验的方法分别对模压成型法、机筒成型法制备的超高分子量聚乙烯(PE-UHMW)进行摩擦磨损性能研究。结果表明,采用机筒成型的PE-UHMW试样的磨合期较短,稳定区间摩擦系数为模压成型PE-UHMW试样摩擦系数的62.4%,机筒成型的PE-UHMW试样在载荷、转速变化的条件下摩擦系数表现更稳定;磨损量都呈现先快速增大后缓慢上升再快速增大的趋势,试验60 min后,模压成型PE-UHMW试样的磨损量为1.4 mg,机筒成型试样的磨损量为1.2 mg,机筒成型PE-UHMW试样的耐磨性能优于模压成型PE-UHMW试样;对试样摩擦磨损试验后的表面形貌的SEM分析表明,模压成型的PE-UHMW试样的摩擦机理主要为粘着磨损和疲劳磨损;机筒成型的PE-UHMW试样的摩擦机理以磨粒磨损和疲劳磨损为主,后期转化为粘着磨损。机筒成型的PE-UHMW试样摩擦磨损过程中的磨粒起到自润滑及减摩剂的作用,其热力学及力学性能优于模压成型的PE-UHMW试样。     

氮化硼改性超高分子量聚乙烯的摩擦学性能研究

通过高速球磨、热压成型制备超高分子量聚乙烯/氮化硼（PE-UHMW/BN）复合材料,研究了PE-UHMW/BN的硬度、摩擦学性能和力学性能。结果表明,BN的加入可以提高复合材料的屈服强度,但会降低复合材料的拉伸断裂应力和断裂伸长率,BN含量为3%（质量分数,下同）时,BN对PE-UHMW基体的屈服强度的提升效果最明显,同时对基体拉伸应力和断裂伸长率的影响最小;加入BN能明显降低PE-UHMW基体的摩擦系数,PE-UHMW/BN复合材料的摩擦系数随着BN含量的增加而下降,3%的BN对基体润滑性能的提升效果最明显,复合材料的摩擦系数相比纯PE-UHMW下降了60%,在BN含量为7%时润滑效果下降;在PE-UHMW基体中加入不超过3%的BN纳米片可以提高材料表面硬度,进而有效提高材料的抗磨损能力,但添加量为7%时由于团聚效应材料的表面硬度相对下降,材料磨损加剧,耐磨损能力下降。     

黏度法测定超高分子量聚乙烯分子量的研究

为验证ASTM D4020–2011和GB/T 1632.3–2010是否适合测定我国常用超高分子量聚乙烯(PE-UHMW)的黏均分子量以及探讨奥氏黏度计能否代替乌氏黏度计测定PE-UHMW的黏均分子量,研究了黏度法测定PE-UHMW分子量的影响因素,包括黏度计与毛细管内径的选择、溶液浓度与溶剂的选择、抗氧剂的作用、实验温度的控制以及数据处理方法等。实验结果表明,十氢萘是配制PE-UHMW溶液的较佳溶剂,PE-UHMW溶液的浓度与毛细管流出时间分别控制在0.008～0.050 g/(100 mL)与80.0～140.0 s较为合适,加抗氧剂能有效防止PE-UHMW的氧化降解,选用毛细管内径为0.55 mm的奥氏黏度计可满足使用要求。     

超高分子量聚乙烯加工改性研究进展

综述了近几年超高分子量聚乙烯(PE-UHMW)加工改性的研究进展,从流动改性、加工工艺和机械模具改进等方面详细论述了改善PE-UHMW加工性能、实现PE-UHMW顺利加工的方法,并对未来PE-UHMW的加工改性研究方向进行了展望。     

不同结构氢化丁腈橡胶的性能研究

从氢化度和丙烯腈含量角度对不同结构氢化丁腈橡胶(HNBR)的性能进行研究。结果表明:在HNBR丙烯腈含量相同的条件下,随着HNBR氢化度的升高,填料的分散性降低,胶料的混炼升温速率减慢,流动性降低,硫化速率变慢,硫化胶的定伸应力下降,拉断伸长率提高,压缩永久变形增大,高氢化度HNBR硫化胶可采用二段硫化来提升抗压缩永久变形性能;在HNBR氢化度相同的条件下,随着HNBR丙烯腈含量的增大,填料的分散性提高,胶料的混炼能耗和排胶温度显著降低,流动性提高,焦烧时间延长,硫化胶的定伸应力和拉伸强度提高,拉断伸长率降低,耐油性能显著提高,压缩永久变形增大。     

减摩耐磨超高分子量聚乙烯改性研究进展

超高分子量聚乙烯(PE-UHMW)优异的耐磨性使其在工程领域和生物领域得到广泛的应用.综述了减摩耐磨PE-UHMW改性的研究成果,重点阐述无机填料填充改性、接枝改性、辐照交联改性、表面沉积改性等方法对PE-UHMW摩擦磨损性能的改善,并对这些方法的优缺点进行了总结,最后展望了减摩耐磨PE-UHMW改性研究和应用的前景.     

超声辅助双螺杆机制备高密度聚乙烯/超高分子量聚乙烯复合材料及性能研究

利用超声辅助双螺杆挤出机制备高密度聚乙烯（PE-HD）/超高分子量聚乙烯（PE-UHMW）复合材料，并考察PE-UHMW含量对复合材料流变性能、结晶行为及力学性能的影响。结果表明，当PE-UHMW的含量不超过2.0 %（质量分数，下同）时，PE-UHMW在PE-HD基体内均匀分散，不存在相分离；由于PE-UHMW的相对分子质量非常大，分子链非常长，缠结程度大，其分子链松驰时间较长，有利于形成结晶前驱体，直至成核，随着PE-UHMW含量的增加，有利于成核，晶核数目明显增加，同时，PE-UHMW与PE-HD的缠结程度变大，约束了PE-HD分子链的运动，使其吸附于晶核心表面，分子链折叠排列形成结晶，最终复合材料体系的结晶度逐渐增大，片晶增厚；加入PE-UHMW后，复合材料的屈服强度、拉伸强度和断裂伸长率均明显提高。     

单螺杆挤出制备活性炭/PE-UHMW微孔管材

采用单螺杆挤出法,使用不同相对分子质量的超高相对分子质量聚乙烯(PE-UHMW),通过改变活性炭与PE-UHMW的比例,制备活性炭/PE-UHMW微孔管材;采用扫描电子显微镜和压汞仪分析了微孔管材的微孔结构和参数,同时还测试了微孔管材的密度和压缩强度。结果表明,PE-UHMW有助于活性炭的挤出,但若其含量过高,很容易将活性炭包覆起来堵塞微孔;采用单螺杆挤出法制备活性炭/PE-UHMW微孔管材,其微孔孔径和开孔率可与传统烧结成型法制备的微孔管材相媲美;微孔管材的密度和压缩强度随组分中的PE-UHMW的相对分子质量的增大而减小,随PE-UHMW含量的增大而减小。     

超高分子量聚乙烯薄膜制备方法与应用

超高分子量聚乙烯（PE-UHMW）是指分子量在100万以上的聚乙烯材料，其分子结构与高密度聚乙烯（PEHD）类似，是一种综合性能较为优异的工程塑料。PE-UHMW薄膜是一种有机高分子膜，是以PE-UHMW为聚合物基体，进行填料或结构改性并加工至一定厚度的新型功能材料，主要分为无孔薄膜及微孔薄膜2种。因其综合性能优异，具有耐冲击、耐低温、耐腐蚀等性能，被广泛应用于纺织、包装、农业、食品、医疗、锂离子电池隔膜等领域。但由于其分子量较高，分子链间存在大量缠结且熔融状态下流动性不佳等特点，使其难以通过常规方法制备出性能优异的薄膜材料。如今，PE-UHMW的制备及加工工艺得到了较为迅速的发展，本文根据PE-UHMW的结构特点，介绍了近年来PE-UHMW薄膜的研究进展、性能优势、常用制备方法以及主要应用。     

PE-UHMW/PP共混物的流动、力学与耐磨损性能研究

将均聚型聚丙烯(PP)、耐磨助剂与超高分子量聚乙烯(PE-UHMW)共混,制备了PE-UHMW/PP共混物,研究了PP含量及耐磨助剂对PE-UHMW/PP共混物流动、力学与耐磨损性能的影响。结果表明,PP能有效地改善PE-UHMW的流动性能,PE-UHMW/PP共混物的维卡软化点和热变形温度均随PP含量的增加而增加;加入耐磨助剂后,当PP的质量分数为50%时,共混物的拉伸强度达到最大,但断裂伸长率最小,且随PP含量的增加,PE-UHMW/PP共混物的冲击性能降低;PP降低了PE-UHMW的耐磨损性能,加入耐磨助剂后保持了PE-UHMW的高耐磨损性能且对共混物的流动和力学性能影响不大。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。