EVM/PLA共混发泡材料泡孔结构和性能的研究

以乙烯-醋酸乙烯酯橡胶(EVM)和聚乳酸(PLA)共混物为基体材料,经模压发泡制备了共混发泡材料。研究了EVM/PLA不同共混比、硫化剂(DCP)、发泡剂(AC)和白炭黑用量以及不同发泡时间对EVM/PLA共混物发泡材料泡孔结构和物理机械性能的影响。结果表明,随PLA组分的减少,白炭黑和DCP用量的增加,泡孔逐渐减小,均匀度增加,孔壁增厚,材料的密度、拉伸强度和拉断伸长率呈升高趋势,发泡倍率呈降低趋势。随发泡剂AC用量的增加,泡孔壁变薄,平均泡孔尺寸变化不大,材料的密度、拉伸强度和拉断伸长率呈降低趋势,发泡倍率增加。随硫化时间的延长,泡孔尺寸变小,孔壁增厚、发泡倍率逐渐下降,拉伸强度先增大后减少,拉断伸长率先下降后上升。     

发泡剂用量对EVM/PLA共混物性能的影响

选用乙烯-醋酸乙烯酯橡胶(EVM 700)与聚乳酸(PLA)为基体材料,过氧化二异丙苯(DCP)为交联剂,偶氮二甲酰胺(AC)为发泡剂,采用模压发泡法制备了橡塑共混型发泡材料,研究了发泡剂用量对材料发泡性能和阻尼性能的影响。结果表明,共混物呈现大量微孔围绕少数大孔的梯度泡孔结构。随着AC用量的增加,泡孔数量增多,泡孔壁变薄,泡孔尺寸变化不大;压缩强度和发泡密度呈降低趋势,发泡倍率呈升高趋势。AC用量为4份时,材料阻尼性较好。     

泡沫密度对乙烯-乙酸乙烯酯橡胶发泡材料压缩性能及动态力学性能的影响

以乙烯-乙酸乙烯酯橡胶(EVM)为基体,过氧化二异丙苯(DCP)为硫化剂、偶氮二甲酰胺(AC)为发泡剂,制备了不同泡沫密度的EVM发泡材料,研究了EVM混炼胶的硫化及发泡特性,采用体视显微镜表征了发泡材料的微观形貌,并考察了泡沫密度对发泡材料的压缩性能及动态力学性能的影响。结果表明,当DCP选用6份、AC选用3.5份时有利于EVM进行发泡;随着泡沫密度的增加,EVM发泡材料的泡壁逐渐变厚;低密度EVM发泡材料的线性弹性阶段范围较大,随着泡沫密度的增加,EVM发泡材料的应力增大,压缩过程中的线性弹性区逐渐变窄;泡沫密度对EVM发泡材料的玻璃化转变温度、阻尼因子(tanδ)峰值几乎没有影响;随着泡沫密度的增加,在玻璃态下EVM发泡材料的储能模量(G')和tanδ不断增大,而在高弹态下G'增大,但tanδ减小。     

超支化多元醇对乙烯-乙酸乙烯酯橡胶/聚乳酸共混发泡材料性能的影响

选用乙烯-乙酸乙烯酯橡胶（EVM 700）和聚乳酸作为基质材料,以过氧化二异丙苯为交联体系、偶氮二甲酰胺为发泡剂,并添加超支化多元醇,经模压发泡制备出橡塑共混发泡材料,研究了多元醇对发泡材料发泡性能及阻尼性能的影响。结果表明,加入多元醇后体系中的小泡孔长大,材料的泡孔由大小孔穿插的结构变为大小相对均匀的结构;发泡材料的有效阻尼温域拓宽,其中偶氮二甲酰胺用量为4份（质量）时材料的阻尼温域较宽（78.1℃）;发泡材料的压缩强度减小,发泡后的密度减小,发泡倍率增大。     

有机多元醇对乙烯-乙酸乙烯酯橡胶/聚乳酸共混物阻尼性能的影响

通过差示扫描量热仪、扫描电子显微镜和动态黏弹谱仪考察了自制的有机多元醇对乙烯-乙酸乙烯酯橡胶(EVM)/聚乳酸(PLA)共混物的玻璃化转变温度(Tg)、微观形貌及阻尼性能的影响,并探讨了阻尼机理。结果表明,EVM/PLA共混物具有2个Tg,分别对应EVM和PLA的Tg,添加多元醇后可使共混物中EVM与PLA的Tg内移,且多元醇用量的增加使PLA的Tg减小;EVM/PLA共混物的断面粗糙,添加多元醇后断面变得光滑,且随着多元醇用量的增加,PLA富集相颗粒粒径减小,说明多元醇起到增容剂作用,且与PLA具有良好的亲和性;当分别添加10份和30份多元醇时,可使EVM/PLA共混物的有效阻尼温域由66.5℃拓宽到104.8℃和183.3℃;添加多元醇后,EVM/PLA共混物中存在CO、C—O与—OH之间形成的氢键,且C—O与—OH之间形成的氢键在解离时出现"红移"现象。     

EVA/SBR发泡材料的研究

乙烯-醋酸乙烯酯共聚物(EVA)与丁苯橡胶(SBR)共混,用过氧化二异丙苯(DCP)引发交联,偶氮二甲酰胺(AC)发泡,得到了交联闭孔式发泡材料。研究了DCP、AC用量以及发泡温度和发泡时间对其力学性能的影响。研究结果表明:DCP用量为0.6%、AC用量为6%、发泡温度为130℃、发泡时间为15min时,发泡材料具有优异的力学性能。     

EPDM/EVA共混发泡胶料的制备和性能研究

以三元乙丙橡胶（EPDM）和乙烯-醋酸乙烯酯共聚物（EVA）为主体材料,通过模压化学发泡法制得EPDM/EVA共混发泡胶料。研究EPDM与EVA的相容性及其迁移行为,以及采用单因子试验方法研究发泡剂AC用量（0. 5,1,1. 5,2和2. 5份）对EPDM/EVA共混发泡胶料的泡孔尺寸分布、物理性能及止滑性能的影响。结果表明：EPDM/EVA共混比为75/25时,EPDM/EVA共混胶中间层与最外层的EPDM吸光度与EVA吸光度之比相差最大,说明EPDM和EVA的迁移效果最明显,且EPDM不断地向外层迁移;随着发泡剂AC用量的增大,EPDM/EVA共混发泡胶料的平均泡孔孔径和邵尔A型硬度先减小后增大,密度、拉伸强度和撕裂强度减小,回弹值变化不大,止滑性能提高。     

影响乙烯-乙酸乙烯酯橡胶发泡的工艺因素

以偶氮二甲酰胺作为发泡剂,采用膨胀法制备乙烯-乙酸乙烯酯(EVM)橡胶发泡材料,研究了填充系数以及硫化的温度、时间和压力等工艺参数对EVM橡胶发泡过程、泡沫的泡孔质量和物理机械性能的影响。结果表明,EVM胶料的填充系数达到90%以上可以获得表面平整、泡孔均匀的EVM橡胶泡沫,并且在103%时其综合物理机械性能较好。当发泡温度低于165℃时,硫化过程对温度比较敏感,温度较高时发泡过程对温度比较敏感。硫化温度为165～170℃、时间为4～6 min、采用高压硫化更有利于制得性能较好的低密度EVM橡胶泡沫。     

丙烯酸酯橡胶/聚乳酸发泡材料的结构与性能

以偶氮二甲酰胺(AC)为发泡剂制备了丙烯酸酯橡胶(ACM)/聚乳酸(PLA)发泡材料,考察了ACM/PLA(质量比)和AC用量对发泡材料结构与性能的影响。结果表明,随着PLA并用比的增加,发泡材料的泡孔密度减小,泡孔逐渐变大,泡孔壁变薄,邵尔C硬度增大,撕裂强度和拉伸强度均降低,耐老化性能得到改善;随着AC用量的增加,发泡材料的泡孔壁变薄,大泡孔数增加,泡孔大小均匀度降低,密度、邵尔C硬度、拉伸强度和撕裂强度均逐渐降低,并且下降幅度逐渐变小,耐老化性能没有明显变化;发泡材料的压缩应力-应变变化包括较宽的线弹性区域、较窄的泡孔塌陷平台和泡孔壁相互接触后的密实化区域3个阶段。     

PCL/PLA共混材料的结晶行为及对微发泡的影响

基于单因素实验分析方法,研究了工艺参数对聚己内酯(PCL)/聚乳酸(PLA)共混材料结晶行为的影响,并通过间歇微发泡实验,研究结晶对共混材料微发泡行为的影响。结果表明,PCL/PLA共混材料的结晶度和晶体尺寸随着结晶温度及结晶时间的增加而增加;在PCL/PLA共混物微发泡过程中,晶粒能够诱导泡孔成核,且泡孔的长大过程受到晶体的限制,使得微发泡泡孔数目增多,泡孔密度增大,泡孔尺寸更为均匀,改善了PCL/PLA共混物的发泡性能。     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009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、环氧树脂、不饱和聚酯树脂)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。     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.