抗冲共聚聚丙烯2500H熔体流变行为研究

采用熔体流动速率仪、螺旋流动长度测试模具、毛细管流变仪和旋转流变仪等仪器,研究了抗冲共聚聚丙烯2500H及对比牌号K8303和3015的熔体流变行为。结果表明,2500H具有较大的分子量和较窄的分子量分布,即分子量大小依次为2500H3015K8303,分子量分布宽窄依次为K830330152500H。当剪切速率为700 s-1时,3015挤出胀大过程出现螺旋畸变现象,而2500H和K8303均未出现熔体螺纹畸变现象。三个样品的熔体流动速率从大到小依次为K830330152500H,其中K8303样品具有更高的熔体流动性。     

挤出级SAN/ASA共混物在毛细管流变仪中的熔体破碎现象

通过毛细管流变仪系统表征了挤出级苯乙烯–丙烯腈塑料与丙烯腈–苯乙烯–丙烯酸酯塑料(SAN/ASA)共混物的熔体破碎现象,研究了加工温度、SAN分子量及其AN含量、ASA分子量和ASA含量对ASA挤出物表面质量的影响。研究发现,随着SAN分子量的增加、SAN中AN含量的增加和ASA分子量的增加,引起聚合物发生熔体破碎的剪切速率(临界剪切速率)都有所减小,更容易出现不稳定挤出和熔体破碎现象;同时,随着SAN分子量的下降,ASA树脂的粘流活化能增加,熔体黏度的温度敏感性增加。随着ASA含量的增加,临界剪切速率亦移向低值区,熔体破碎现象与熔体加工过程储存的弹性能有关。此外,加工温度的提高有利于消除熔体破碎现象。     

聚丙烯3240NC与同类产品的流变性能对比研究

通过熔体流动速率仪、毛细管流变仪和旋转流变仪等手段研究了聚丙烯3240NC及同类牌号产品的流变性能。结果表明,三个样品的熔体流动速率从小到大依次为3240NCK4912R370Y。三个样品的毛细管流变性能和旋转流变性能略有不同,这表明三个样品的分子量及分子量分布也不相同。     

耐热聚乙烯的加工性能

采用高压毛细管流变仪、旋转流变仪和哈克转矩流变仪等研究了几种市售典型的耐热聚乙烯(分别记作PERT-1,PERT-2,PERT-3,PERT-4)的加工性能。结果表明:PERT-4的熔体流动速率(MFR)较低,属于高密度聚乙烯,其他3种PERT的MFR均在0.60 g/10 min左右,属于中密度聚乙烯;PERT-1,PERT-2,PERT-3的相对分子质量分布(M_w/Mn)较窄,PERT-4的M_w/Mn宽,且有较明显的大分子拖尾;各试样在170~205℃条件下的加工稳定性较好;PERT-4对剪切速率最敏感,但对温度敏感性较差,PERT-1的剪切黏度随温度升高降幅最大。     

PC/UHMWPE共混物的流变性能

采用熔融共混的方法 ,制备了两种不同配比的PC/UHMWPE共混物。采用毛细管流变仪和熔融指数仪研究了PC/UHMWPE共混物的流变行为 ,结果表明 :PC/UHMWPE共混物熔体的流变行为呈假塑性流体的特征 ,表观粘度随剪切速率的增加而减小 ,随温度的升高而降低 ;共混物熔体的粘度大于纯PC的粘度。采用悬浮体系模型讨论了两种共混物的流变行为     

PA1212的热性能及流变性能研究

采用DTA/TG方法研究了PA1212的热降解过程,用平板流变仪和XLY-Ⅱ型毛细管流变仪对聚酰胺1212(PA1212)的流变性能进行了研究。结果表明:在氮气中,PA1212最大热降解温度约为431.73℃。PA1212熔体流动行为为假塑性流动,随着温度的升高,非牛顿指数下降,假塑性减弱。比较2种流变仪的测量结果发现:平板流变仪在低剪切速率范围内数据较好,毛细管流变仪则在较高剪切速率范围类比较好,且测定的非牛顿指数偏大。     

几种聚乙烯毛细管流变性能的研究

采用高压毛细管流变仪研究了聚乙烯(PE)在225℃和250℃下的流变行为.结果表明,PE的粘度随着剪切速率的增加而降低,相同结构PE的粘度随熔体流动速率(MFR)的增加而降低;在同一温度和剪切速率下,当MFR相当时茂金属线性低密度聚乙烯(PE-MLLD)的粘度最大、线性低密度聚乙烯(PE-LLD)次之、低密度聚乙烯(P...     

长链支化聚丙烯的流变性能研究

利用反应挤出法制备了长链支化聚丙烯,采用旋转流变仪和毛细管流变仪对纯聚丙烯及其改性聚丙烯进行测试,用流变学理论进行表征。结果表明,聚丙烯加入支化剂后,产生了长支链,分子量增大,分子量分布变宽;在一定范围内,随着支化剂量的增大,其支化程度增加;在低频处,能模量G'比损耗模量G″对长支链的出现及量变更敏感;加入支化剂后熔体强度明显增大,且支化的程度越高熔体强度越大,可拉伸性变小,能有效地改善材料的加工性能。     

聚碳酸酯熔体挤出流动特性的研究

在温度为280～310℃,表观剪切速率为60～900s~(-1)的条件下,应用毛细管流变仪,考察了聚磷酸酯(PC)熔体挤出流动行为及其影响因素。研究表明试样的剪切流动基本上服从牛顿流体流动定律,熔体剪切粘度对温度的敏感性相当同。     

无规共聚聚丙烯(PP-R)结晶与流变性能的研究

研究了无规共聚聚丙烯的结构与加工性能,利用DSC研究了PP R的结晶速率与结晶动力学,通过改造的聚合物流变在线测量装置和毛细管流变仪研究了无规共聚聚丙烯(PP R)的熔体表观粘度与剪切应力的关系,熔体粘度与加工温度的关系以及挤出胀大现象。     

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。     

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.