聚对苯二甲酸乙二醇酯／蒙脱土复合物的制备与表征

分别采用蒙脱土与对苯二甲酸乙二醇酯(BHET)和与乙二醇(EG)混合的方法，通过原位插层聚合制备聚对苯二甲酸乙二醇酯／蒙脱土(PET／MMT)复合材料，研究了MMT含量对PET粘均相对分子质量、复合材料微观结构及热和结晶性能的影响。结果表明，随有机化MMT的加入量增加，PET的粘均相对分子质量降低；将有机化MMT分散在乙二醇中再聚合所得复合物中MMT分散更为均匀；MMT的加入使PET的玻璃化温度、冷结晶温度和维卡软化温度降低，BHET法的PET结晶度和热结晶温度增加，而EG法的PET结晶度和热结晶温度下降。     

低模温玻纤增强PET复合材料的制备与表征

采用差示扫描量热法研究了聚对苯二甲酸丁二醇酯(PBT)、乙烯-醋酸乙烯酯共聚物(EVA)、乙烯-正丁基丙烯酸酯-甲基丙烯酸缩水甘油酯共聚物(PTW)对聚对苯二甲酸乙二酯(PET)冷结晶峰温的影响,发现随着PBT含量的增大,PET的冷结晶峰温;当PBT的添加量为50份时,冷结晶峰基本消失;同时加入20份PBT和15份EVA亦可使冷结晶峰消失;PBT、PTW和EVA在降低冷结晶峰温的同时还有助于提高玻纤增强PET复合材料的冲击强度;在PET/PBT体系中,加入适量的无机填料硫酸钡和滑石粉可使热变形温度达到220℃以上。     

聚羟基丁酸己酸酯对聚羟基丁酸戊酸酯结晶性能的影响

采用溶液浇铸法制备了生物可降解聚羟基丁酸戊酸酯（PHBV）和聚羟基丁酸己酸酯（PHBHHx）共混物,用差示扫描量热仪和偏光显微镜研究了PHBHHx对PHBV热性能与结晶性能的影响。结果表明,PHBV和PHBHHx之间存在一定的相互作用,PHBV的冷结晶温度随PHBHHx含量的增加向高温方向移动;PHBV/PHBHHx共混物的结晶呈环带球晶现象,随PHBHHx含量的提高,环带球晶逐渐变得规整、清晰,且带宽逐渐减小。     

不同温度熔融条件下聚对苯二甲酸乙二醇酯的结晶与熔融行为

分别采用低黏度和高黏度的聚对苯二甲酸乙二醇酯(PET)树脂切片,利用差示扫描量热分析(DSC)的方法研究不同的熔融温度条件对PET结晶行为和熔融行为的影响。结果表明:和高黏度PET相比,低黏度PET的结晶过程对熔融温度的变化极其敏感,不同熔融温度将对它的结晶行为与熔融行为产生显著的影响;在同等条件下,低黏度PET结晶速率快且易生成稳定的结晶结构,其稳定结晶的熔融温度要比高黏度PET高数度;总体上,采用较低的熔融温度有利于提高PET结晶温度和结晶速率,而采用较高的熔融温度有利于提高PET结晶的稳定性。     

PET/PCTG比例对共混材料热性能影响

聚对苯二甲酸乙二醇/环已烷二甲醇酯(PCTG)由于其具有较高的玻璃化温度且与PET具有结构上的相似性,PET与PCTG共混有助提高材料的耐热性能。研究PET与PCTG共混材料的热性能可为共混材料成型加工提供理论基础。文章对不同比例PET/PCTG共混材料进行升温和降温差示扫描量热分析(DSC),研究了不同比例PET/PCTG共混材料的冷、热结晶性能。研究结果表明:不同比例的PET/PCTG共混材料的冷、热结晶峰值温度不相同,当PET/PCTG比例为7:3时,其冷结晶峰值温度最低,结晶熔融峰值温度和热结晶峰值温度最高。     

聚酰胺酯结晶行为研究

利用差式扫描量热法对聚酰胺酯进行结晶行为分析。结果表明:与常规PET相比,聚酰胺酯玻璃化温度、冷结晶温度、熔点、熔融结晶温度均较低,同时其熔融结晶速率也较慢;且随着共聚酯中聚酰胺成分的增加,玻璃化温度、熔点、熔融结晶温度逐渐降低并呈现一定的变化关系;在相同结晶温度下,聚酰胺成分增加,共聚酯半结晶周期t_(1/2)增加,结晶随之变慢。     

聚萘二甲酸乙二醇酯工业丝的制备及性能研究

采用酯交换法合成聚萘二甲酸乙二醇酯（PEN）,通过聚合纺丝、捻线、织布、浸胶制备浸胶帘布．并对其性能进行研究。结果表明：PEN T业丝是一种高强高模低缩纤维,其模量是聚对苯二甲酸乙二醇酯（PET）的2倍,收缩率是PET的1/2;PEN的热稳定性、尺寸稳定性和化学稳定性好,玻璃化温度比PET高40-50℃,比水的沸点高15-20℃。     

勃姆石改性PET复合材料的阻燃和增强机理研究

采用勃姆石（BM）作为阻燃和增强材料,利用熔融共混法制备了BM阻燃和增强改性的聚对苯二甲酸乙二醇酯（PET）/BM复合材料。分别测试了BM用量对于PET复合材料的力学性能、结晶性能、热性能、阻燃性能的影响。结果表明,随着BM用量的增加,PET/BM复合材料的刚性逐渐增加,韧性逐渐降低;PET/BM复合材料的热结晶温度（Tc）和冷结晶温度（Tcc）分别随着BM用量的增加逐渐升高和降低,且ΔT(Tc-Tcc)逐渐增加,BM具有异相成核作用,提高了复合材料的结晶速率和相对结晶度（Xc）;而复合材料的熔融温度则随着BM用量的增加而逐渐降低;BM对PET具有良好的阻燃作用,BM能够使PET/BM复合材料的残炭量增加,使复合材料的分解温度降低,增加了材料燃烧时的热稳定性。     

聚乳酸/聚丁二酸丁二醇酯嵌段共聚物的合成与表征

以丁二酸和1,4-丁二醇为原料,采用熔融缩聚法合成了聚丁二酸丁二醇酯(PBS)预聚物,再与L-丙交酯(L-LA)开环共聚,合成聚乳酸/聚丁二酸丁二醇酯嵌段共聚物(PLLA-co-PBS)。研究了共聚物的结构、热性能、结晶性能和亲水性。结果表明,PBS与L-LA开环共聚生成了PLLA-co-PBS嵌段共聚物;PLLA-co-PBS嵌段共聚物经两个阶段的热分解,且PBS链段的引入提高了聚合物的热稳定性;随着PBS引入量的增加,聚合物的结晶性能,亲水性能都有一定的提高。     

有机硅磷酸酯对PBT/PET酯交换反应的影响

采用两次循环扫描方法研究了有机硅磷酸酯对聚对苯二甲酸丁二醇酯/聚对苯二甲酸乙二醇酯（PBT/PET）酯交换反应的影响,测定了PBT/PET合金的结晶性能、热变形温度、力学性能和相对黏度,并与常规的抑制剂亚磷酸三苯酯进行了比较。结果发现：加入有机硅磷酸酯后PBT/PET合金的结晶温度提高了4.5 ℃,相对黏度提高了0.1 dL/g,热变形温度提高了7.0 ℃。而加入亚磷酸三苯酯后PBT/PET合金的结晶温度降低了1.5 ℃。说明有机硅磷酸酯可有效控制PBT/PET合金中端羟基的含量,从而可有效抑制PBT和PET之间的酯交换反应。亚磷酸三苯酯和有机硅磷酸酯的加入对PBT/PET体系的力学性能影响不大。     

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.     

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.     

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.