三氯溴甲烷改性天然胶乳的力学性能与阻燃性分析

对单用三氯溴甲烷改性天然胶乳和并用三氧化二锑改性胶乳的硫化胶膜的力学性能和阻燃性能进行了研究,并采用TG和DTG进行了热性能的分析。结果表明:三氯溴甲烷与三氧化二锑改性天然胶乳比单用三氯溴甲烷改性胶乳的阻燃性要好;三氯溴甲烷用量增加,改性天然胶乳硫化胶膜的阻燃性提高,而力学性能下降;三氯溴甲烷改性胶乳的起始热降解温度提前,改性胶乳热降解为二步反应。     

环保硫化体系对天然胶乳硫化及其性能的影响

以浓缩天然胶乳为原料,采用非亚硝胺型(ZBEC)、低亚硝胺型(ZDBC)传统型(ZDC)硫化促进剂分别加入天然胶乳中制备配合胶乳及硫化胶膜。考察硫化促进剂的种类和用量、氧化锌的用量、硫磺的用量及制品加工温度对天然胶乳的硫化性能与硫化胶膜物理机械性能的影响。试验结果表明:适当增加氧化锌用量,可明显提高天然胶乳硫化胶膜的交联密度和撕裂强度;适当增加硫化促进剂或硫磺的用量,不仅可以加快胶膜的硫化速度,同时也可以有效的增大硫化胶膜的交联密度,从而提高硫化胶膜的物理机械性能;天然胶乳胶膜的硫化温度控制在100℃左右,具有较大的交联密度和较好的物理机械性能;从天然胶乳胶膜的硫化速度和硫化胶膜的物理机械性能方面考虑,采用环保硫化促进剂ZBEC、ZDBC代替传统的硫化促进剂ZDC是可行的。     

补强剂对三氯溴甲烷改性天然胶乳力学性能的研究

对用纳米SiO2和纳米CaCO3补强三氯溴甲烷改性天然胶乳的性能进行了研究。结果表明．纳米SiO2和纳米CaCO3对三氯溴甲烷改性天然胶乳具有一定的补强作用．随补强剂用量的增加．胶膜力学性能呈上升趋势，但当补强剂用量达到一定程度时,随补强荆用量增加补强效果变差。     

溴丙烯改性天然胶乳的制备

采用溴丙烯对天然胶乳进行接枝共聚改性,研究改性工艺条件对改性天然胶乳性能的影响,正交试验结果表明,改性天然胶乳的优化制备工艺条件为:溴丙烯用量 15份,亚硫酸氢钠用量 1.5份.胶乳固形物质量分数0.4,反应时间 3 h,反应温度 35℃.与未改性天然胶乳胶膜相比,改性天然胶乳胶膜的定伸应力和撕裂强度略小,拉伸强度和拉断伸长率略大,阻燃性能提高.     

不同填料对丁苯胶乳硫化特性和力学性能的影响

通过不同种类填料按一定配方与丁苯胶乳配合,考察配合胶乳胶膜的硫化特性、硫化胶膜的物理机械性能.结果表明:填料滑石粉用量越多,胶膜的物理机械性能越差,硫化速度加快;CaCO3作为填料加到丁苯胶乳中时,硫化速度最快,胶膜的物理机械性能最好.     

氯化石蜡共混改性天然胶乳的研究

分别采用氯化石蜡、氯化石蜡／Sb2O3共混改性天然胶乳．考察了改性胶乳硫化胶膜的力学性能及阻燃性能．并进行了TG·DTG和DSC分析。结果表明：改性胶乳的阻燃效果比未改性天然胶乳的高．且氯化石蜡／Sb2O3共混改性天然胶乳可产生协同阻燃效果；随Sb2O3用量的增加．硫化胶膜撕裂强度增加．而拉伸强度下降。氯化石蜡／Sb2O3改性胶乳的热降解过程为二步反应．且起始热降解温度比天然胶乳的低．玻璃化转变温度提高。     

偶联剂对有机硅改性天然胶乳性能的影响

采用接枝共聚改性的方法制备有机硅改性天然胶乳，考察偶联剂、有机硅单体对有机硅改性天然胶乳的胶体性能、胶膜物理机械性能的影响。结果表明，用有机硅VD4比用有机硅D4改性胶乳的性能要好，用A—171作偶联剂制得的改性胶乳胶膜的物理机械性能最好。     

改性纳米粘土/天然胶乳复合材料的制备与性能研究

研究表面改性剂对纳米粘土/天然胶乳复合材料性能的影响。结果表明:烷基表面活性剂对纳米粘土改性后,天然胶乳硫化胶膜老化前后的拉伸强度均明显提高,十六烷基三甲基溴化铵(CTAB)的改性效果最好,当改性纳米粘土用量为2份时,天然胶乳硫化胶膜的拉伸强度最高;CTAB改性纳米粘土能提高天然配合胶乳的保存稳定性、粘度和机械稳定性,并提高天然胶乳硫化胶膜的物理性能和耐热老化性能,补强效果明显。     

氮化硼对天然胶乳硫化胶膜力学性能的影响

研究氮化硼用量、不同改性氮化硼对天然胶乳胶膜力学性能的影响,通过热重分析仪分析其热稳定性。结果表明:随着氮化硼用量的增加,复合胶乳胶膜的力学性能先增加后降低,当氮化硼的用量为20份,天然胶乳胶膜的力学性能最好;使用KH570改性过的氮化硼制得天然胶乳胶膜的性能好,且KH570的最佳用量为2.5份时,复合胶膜的力学性能最好,热失重分析可知,改性的硫化胶膜的热稳定性有所提高。     

偶联剂对木薯淀粉补强天然胶乳硫化胶膜性能的影响

采用偶联剂改性木薯淀粉补强天然胶乳,研究偶联剂种类和用量对木薯淀粉/天然胶乳硫化胶膜物理性能和动态力学性能的影响,并对其微观结构进行观察.结果表明,加入偶联剂Si69的硫化胶膜的物理性能较好,当偶联剂Si69用量为0.6份时,硫化胶膜的综合物理性能达到最佳.动态力学性能分析表明,淀粉经偶联剂改性后,硫化胶膜的损耗因子减小,玻璃化温度向低温方向移动,低温使用性能提高.扫描电子显微镜分析显示,偶联剂的加入可以改善淀粉在天然胶乳中的分散效果,提高淀粉与橡胶的界面结合作用.     

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.     

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.