复配增塑剂改性聚乙烯醇的热塑加工性能研究

以甘油/二缩三乙二醇(GP)为主增塑剂,N-甲基吡咯烷(NMP)辅助增塑剂,对聚乙烯醇(PVA)进行增塑改性,研究了增塑剂类别和配比对PVA的增塑效果。通过红外光谱分析(FTIR)研究了复配增塑剂与PVA间的相互作用,采用X射线衍射分析(XRD)、差示扫描量热分析(DSC)、热失重分析(TGA)表征了改性PVA的结晶性能和热性能,采用熔融指数仪和转矩流变仪研究了改性后PVA的热塑加工性能。结果表明:复配增塑剂能有效地破坏PVA自身的氢键,降低PVA的熔融温度和结晶度,改善PVA的热塑加工性能,并成功实现了改性PVA的注塑成型。通过注塑成型的PVA具有较好的力学性能,拉伸强度为28.6 MPa,断裂伸长率为534%。     

改性聚乙烯醇的热塑成型性能研究

聚乙烯醇(PVA)是多羟基线型高分子,含有大量氢键。分子结构规整,结晶度高,熔点高达230℃。用复配增塑剂和稳定剂对PVA进行改性,并通过DSC和FTIR测试研究了改性剂对PVA热塑成型性能的影响。结果表明:添加适量改性剂的PVA其热塑成型性能得到明显改善。     

淀粉/三聚氰胺增塑PVA熔融加工膜的制备及性能

以淀粉/三聚氰胺为复配增塑剂,利用熔融加工工艺制备聚乙烯醇(PVA)膜,采用差示扫描量热(DSC)、热失重分析(TG)和力学性能测试等考察了增塑剂含量对PVA膜性能的影响.结果表明,复配增塑剂能有效破坏分子链间氢键,对PVA的增塑作用明显.随增塑剂含量增大,PVA膜的力学性能和熔体质量流动速率呈先增大后减小的趋势,熔点...     

尿素/甲酰胺复配增塑聚乙烯醇薄膜的制备及性能研究

以尿素/甲酰胺为复配增塑剂,采用熔融共混法制备聚乙烯醇（PVA）薄膜。通过傅里叶变换红外光谱、扫描电子显微镜、差示扫描量热仪以及力学测试对PVA薄膜的结构与性能进行表征。结果表明,尿素/甲酰胺复配增塑剂通过破坏PVA分子内与分子间的氢键而影响了PVA分子链的有序结构,在改善PVA加工性能的同时降低了PVA的结晶度,并有效提高了薄膜的韧性。     

聚乙烯醇的熔融加工工艺与性能研究

本文主要研究了聚乙烯醇的熔融加工工艺及其性能。聚乙烯醇是一种生物可降解高分子材料,但是聚乙烯醇分子链中含有大量的羟基,容易在分子内或分子间形成大量的氢键,熔融温度高于分解温度,熔融加工困难。本实验通过甘油和芥酸酰胺复配作为增塑剂,降低聚乙烯醇的熔点,使其能够在适合的加工工艺下熔融加工。并以轻质碳酸钙为填料,对聚乙烯醇进行填充改性。实验表明,在增塑剂为20份,轻质碳酸钙为30份时,拉伸强度得到明显提高。     

聚甘油增塑改性聚乙烯醇复合膜性能研究

以聚甘油(PG)为增塑剂,采用溶液流延法制备了PG增塑改性聚乙烯醇(PVA)复合薄膜。通过红外光谱分析(FTIR)、X射线衍射分析(XRD)、差示扫描量热分析(DSC)、热失重分析(TGA)、拉伸测试等考察了PVA/PG复合膜的氢键作用、结晶性能、热性能、力学性能。结果表明:PG增塑剂能有效破坏PVA自身的氢键,在PVA热分解温度基本保持不变的前提下降低材料的熔融温度和结晶度,从而扩展PVA的热塑加工温度窗口。随着PG用量的增加,PVA/PG复合薄膜的拉伸强度逐渐降低,而断裂伸长率明显提高。     

水在聚乙烯醇/水体系中的状态及氢键作用

水在聚乙烯醇(PVA)中的状态直接影响PVA的热塑加工.采用DSC和Raman光谱研究了水含量对其在PVA中的状态及氢键作用的影响.结果表明:水在PVA中以3种状态存在,随水含量增加,非冻结合水比例减小,可冻结合水和自由水比例增加.通过高斯分峰可将Raman光谱水的羟基伸缩振动峰分为5种羟基振动峰叠加,分别代表多氢键结合水分子的羟基对称与反对称伸缩振动,双氢键结合水分子羟基伸缩振动,单氢键结合水分子羟基伸缩振动,无氢键或弱氢键相互作用水分子的羟基伸缩振动.水含量增加,单氢键结合与多氢键结合水分子含量增加,而双氢键结合与无氢键结合水分子含量减少.     

PVA/TPU共混材料热塑加工性能及相容性的研究

采用热塑加工方法制备了聚乙烯醇/热塑性聚氨酯(PVA/TPU)共混材料,系统研究了共混材料的热塑加工性能、相容性及力学性能。结果表明:TPU的引入对共混材料的熔点影响不大,但其与PVA间的氢键作用可屏蔽PVA的羟基,较大幅度地提高了PVA初始热分解温度,获得更宽的热塑加工窗口;引入适量的TPU还可降低共混材料的熔体黏度,改善材料的热塑加工性能,另外,还可获得良好的材料相容性;随着TPU用量的增加,共混材料的拉伸强度先增后降,并在TPU用量为50 phr时达到最大值。     

大豆分离蛋白的化学改性和增塑研究

研究了尿素、氢氧化钠和二甲基二氯硅烷对大豆分离蛋白的化学改性以及甘油、聚乙二醇、山梨醇、己内酰胺、乙酰胺对改性蛋白质材料的增塑作用。采用红外光谱对改性蛋白质进行了表征,并测试了改性蛋白质的热性能、力学性能、流变性能及耐水性能。结果表明,强碱可以有效地截断蛋白质分子的长链结构,提高蛋白质分子的加工流动性;尿素和二甲基二氯硅烷与蛋白质分子中的亲水基团发生反应或遮盖了蛋白质分子中的亲水基团,从而提高了大豆分离蛋白的耐水性;聚乙二醇和己内酰胺是效果较好的增塑剂。     

己内酰胺/氯化镁复配增塑聚乙烯醇的性能研究

采用己内酰胺/氯化镁为复配增塑剂,通过流延法制备出了增塑改性的聚乙烯醇(PVA)膜。采用DSC、TGA、XRD分析和力学性能与熔体流动性能测试的方法考察了己内酰胺/氯化镁复配增塑剂对PVA性能的影响。结果表明:氯化镁与己内酰胺复配具有良好的协同增塑效应,其对PVA的增塑效果优于单独使用己内酰胺;复配增塑剂能够有效破坏PVA分子间的氢键,降低PVA的结晶度;加入复配增塑剂后,PVA的熔点降低,热稳定性提高,熔体流动性有所改善,拉伸强度降低,断裂伸长率上升。     

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.     

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.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。     

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.     

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.     

基于ATRP法制备的触角状亲水性羟胺树脂的吸硼性能的研究

以大分子引发剂氯乙酰化聚苯乙烯微球(PS-acyl-Cl)经原子转移自由基聚合(ATRP)法引发丙烯酰胺(AM)和甲基丙烯酸缩水甘油酯(GMA)单体的共聚接枝,制得一种触角状亲水性环氧载体(PS-acyl-g-P(AM-co-GMA)),再经二乙醇胺(DEA)的环氧基开环胺化反应,得到一种含多个-NCH2CH2OH螯合配基的多齿-五元螯合环的触角状亲水性羟胺树脂(PS-acyl-g-P(AM-co-GMA)-DEA)。将此树脂用于硼吸附研究,结果表明,PS-acyl-g-P(AM-co-GMA)-DEA树脂对硼的吸附满足Langmuir方程,为单分子层吸附;饱和吸附量约为37.7 mg·g-1,且树脂5 min即可达到吸附平衡,与其它已报道的吸硼树脂相比,该树脂具有更高的吸附量和吸硼速率。吸附动力学研究表明,树脂吸附硼的过程主要由颗粒扩散过程控制。重复使用5次后该树脂的吸附量基本不变,解吸率均在90%以上,重复使用性能良好。