短纤维-橡胶复合材料动态力学性能研究

研究了短纤维与基质的粘合水平及短纤维的取向，用量等因素对尼龙－天然橡胶和聚酯－氯丁橡胶复合材料的动态力学性质的影响。结果表明：橡胶中加入短纤维可使低温下损耗角正切减小，高温下损耗角正切增大；短纤维与基质粘合程度越高，短纤维取向度越高，填充量越大，则对复合材料的动态力学性能的贡献越大，用等效界面厚度来评价粘合水平有一定意义。     

粘合性能对短纤维-氯丁橡胶复合材料耐热性的影响

该文以尼龙短纤维为例研究了短纤维的不同用量及其粘合性能对短纤维-CR复合材料的力学性能和耐热老化性能的影响；并研究了尼龙短纤维-CR复合材料的耐溶胀性能。实验结果表明：随着尼龙短纤维用量的增加，短纤维-CR复合材料的硬度、撕裂强度、20％定伸应力不断提高；短纤维与橡胶基质的粘合好，耐溶胀性能明显提高，对橡胶的补强效果更好，复合材料的耐热老化性能提高。     

短纤维取向对短纤维/天然橡胶复合材料性能的影响研究

研究短纤维取向度和取向角对短纤维/天然橡胶复合材料性能的影响。结果表明:短纤维取向度和取向角越大,在该方向上复合材料综合性能越好,并且表现出了各向异性的特性;短纤维胶料流动性较差,基质变形受到很大限制。通过建立实验系统实现了对短纤维取向的定性表征。     

动态热力学分析法评估短纤维/橡胶复合材料界面粘合效果

采用动态热力学分析法评估短纤维／橡胶复合材料（SFRC）界面层的粘合效果。其基本原理为；使用动态热力学分析仪测定SFRC的损耗因子（tanδ），依据公式计算出表征材料界面粘合强度的参数α。试验结果表明。α值越大，材料的界面粘合效果越好，SFRC的拉伸强度、撕裂强度和耐磨性能也越好，但拉断伸长率减小。该方法具有操作简单、数据精确和周期短等优点。     

预处理PA6短纤维与橡胶复合材料的研究

用一种新方法处理的尼龙－６短纤维与橡胶复合，研究了纤维的分散性，长度保持率，取向参数及粘合性能与复合材料抗溶胀性和宏观力学性能的关系。提出了制约该复合体系力学性能的关键是纤维的分散性的观点，并对该复合体系的临界体积分数及断裂机理提出了见解。     

菠萝叶短纤维补强NR复合材料的加工性能和动态力学性能

研究菠萝叶短纤维补强NR复合材料的加工性能和硫化胶的动态力学性能。结果表明，菠萝叶短纤维的加入使复合材料在加工过程中所需的剪切力比NR大，短纤维含量越大，越不容易混炼；菠萝叶短纤维的加入改善了胶料的粘弹性，使其挤出胀大效应减弱；复合材料的模量比NR高得多，且随短纤维加入量的增大而提高。     

短纤维补强氯丁橡胶的性能研究

研究短纤维种类和用量对短纤维/氯丁橡胶(CR)复合材料中短纤维取向和分散以及复合材料粘合性能和溶胀性能的影响.结果表明:随着短纤维用量的增大,短纤维/CR复合材料的相对交联密度和短纤维取向度均增大,抗溶胀性能提高,取向度大小顺序为芳纶短纤维、聚酯短纤维、锦纶66短纤维和短切棉纤维;聚酯纤维与CR基体的粘合性能最差,短切棉纤维在CR中分散性最差;短纤维/CR复合材料的性能呈现出明显的各向异性.     

聚碳酸酯动态黏弹性能与分子取向态的关系

将双酚A型聚碳酸酯（PC）注射成型,基于流动残余应力与分子取向关系的讨论,利用光学双折射法表征样品中的平均分子取向,并考察其动态力学性能。结果表明,近浇口取向大于远浇口,且分子取向态与其动态黏弹性参数间存在关联。当选取损耗角正切值（tanδ）=1的损耗模量值时,发现更高的积分双折射值对应更小的损耗模量,即取向越大动态黏度越小;当储能模量选取玻璃态平台末端值时,尽管双折射值与储能模量的关系受自由体积因素干扰相对不明朗,但材料依然表现出弹性随取向增加而增加的整体趋势。     

新型胶乳预处理尼龙短纤维体系的研究

采用特软羧基丁苯胶乳(苯乙烯质量分数为40％)和丙烯酸类胶乳(HST2073A型胶乳)对尼龙短纤维进行预处理，考察了预处理剂配方对短纤维橡胶复合材料(SFRC)性能的影响，得出了最适预处理液配方；把预处理短纤维应用于轮胎胎面胶中，通过性能测试比较了不同预处理短纤维-橡胶复合材料的力学性能；通过分析复合材料拉伸断面扫描电镜图，初步探讨了预处理在复合材料中的粘合机理。     

短纤维在轮胎部件中的取向方法

国产预处理尼龙短纤维自１９９４年投产以来，已在近百家橡胶厂应用于胶带、胶管等多种制品。遗憾的是，至今未正式用于轮胎。本人应一些厂家要求，谈谈这方面的一些看法。一、短纤维取向对轮胎部件性能的影响短纤维在橡胶中的分散、粘合和取向等是用好短纤维－橡胶复合材料的关键技术。短纤维取向方式及其实施方法对轮胎部件的性能、整个轮胎的使用性能有重要的影响，所以应引起足够的重视。原则上说，预处理尼龙短纤维适用于工程胎（越野胎）也可用于普通载重胎；适用于子午胎也可用于斜交胎；适用于胎面也可用于胎侧、胎圈等部件，可提高…     

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.     

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.     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.