含氟乳液聚合反应稳定性的研究

具有很大发展潜力的高性能自交联含氟乳液,由于C-F基团和自交联剂的引入使其聚合反应的稳定性受到极大的影响。本文在制备自交联含氟乳液的基础上,对影响自交联含氟乳液聚合反应稳定性的主要因素,如乳化剂、引发剂、聚合温度、自交联剂的用量及pH值等进行探讨,提出了确保含氟乳液聚合反应稳定的主要控制参数。     

无皂乳液聚合制备PUA乳液的稳定性研究

采用无皂乳液聚合法制备丙烯酸酯一聚氨酯复合乳液（PUA）。HEMA作为交联剂引入到聚氨酯主链上,利用核壳交联制得复合乳液。研究了不同的合成工艺、丙烯酸酯单体、DMPA及HEMA含量,引发剂种类等对乳液稳定性的影响。研究发现,将丙烯酸酯单体溶胀于水性聚氨酯乳液中再进行聚合可大大提高乳液的稳定性;采用1．0％～12％的AIBN为引发剂、DMPA质量分数为4．5％、HEMA质量分数为4．0％～4．5％、丙烯酸酯单体质量分数为30％时,可制得外观及稳定性良好的PUA复合乳液。     

无皂乳液聚合制备AANa-VAc-TFEMA纳米含氟乳液

以丙烯酸钠(AANa)、乙酸乙烯酯(VAc)和甲基丙烯酸三氟乙酯(TFEMA)为单体进行无皂乳液聚合,合成了P(AANa-VAc-TFEMA)纳米含氟乳液,考察了反应温度、引发剂用量、单体配比对聚合的影响,并着重对聚合物乳液的粒径进行了研究。结果表明:该聚合单体的转化率可达到97.00%以上,聚合得到的无皂乳液稳定性好、粒径分布均匀。通过控制单体配比中AANa的含量及VAc与TFEMA的比例,可以得到纳米含氟乳液。     

聚丙烯酸酯乳液型压敏胶的聚合方法研究

采用三种乳液聚合方式：间歇乳液聚合法、半连续乳液聚合法、种子乳液聚合法,根据实验结果和三种聚合工艺的特点,选出最适合的丙烯酸酯聚合方式;探讨了聚合温度、搅拌强度、软硬单体配比、功能单体、引发剂等因素对聚合反应及压敏胶性能的影响。研究结果表明：种子乳液聚合法最佳;当体系聚合温度为80℃,聚合反应6h,搅拌速率为200f／min时可得到综合性能较好的压敏胶;当软硬单体的比例大约为3：1时,压敏胶可达到最大剥离强度;引发剂的适宜用量为单体总量的0．5％。     

丙烯酸乳液胶粘剂的研究

采用半连续乳液聚合工艺,以MMA、BA、AA等为主要单体,加入乳化剂、引发剂、交联剂,经共聚反应,合成自交联型丙烯酸酯乳液胶粘剂。讨论了聚合机理,考查了固含量、离子稳定性、离心稳定性、剥离强度、拉伸强度、粒径、黏度等多项性能;根据综合的性能测试,分析了单体种类及配比、共聚物的玻璃化温度、丙烯酸用量、乳化剂用量及配比、引发剂用量、温度等因素对乳液型胶粘剂性能的影响,得出了最适宜的反应条件和胶粘剂最佳配方。通过性能对比,表明自交联型丙烯酸酯乳液胶黏剂性能更为优异。     

TMPTMA交联改性聚丙烯酸酯乳液的合成与性能

以三羟甲基丙烷三甲基丙烯酸酯（ TMPTMA ）为内交联单体,苯乙烯（ St ）、甲基丙烯酸甲酯（ MMA）、丙烯酸丁酯（ BA）和甲基丙烯酸（ MAA）为共聚单体,采用半连续核壳乳液聚合工艺合成了自交联聚丙烯酸酯乳液（ T-PAE）。考查了TMPTMA添加量与添加方式对乳液聚合稳定性以及涂膜性能的影响。研究发现：随着TMPTMA含量的增加,T-PAE乳液聚合的稳定性降低,聚合凝胶率增大,乳胶粒的平均粒径下降；涂膜的耐介质性能和交联密度相应提高,合适的TMPTMA加入量为总单体质量的0．5%~1．0%。     

自交联含氟丙烯酸酯共聚物乳液的制备

以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)等为主要单体,甲基丙烯酸六氟丁酯(HFMA)为含氟单体,N-羟甲基丙烯酰胺(NMA)为交联单体,采用种子乳液聚合法制备了自交联含氟丙烯酸酯共聚物乳液。研究了HFMA、NMA、复合乳化剂(SDS OP-10)、引发剂(KPS)用量、聚合温度、聚合时间和搅拌速度等因素对聚合反应最终转化率和乳液稳定性的影响,结果表明在m(MMA)∶m(BA)=1∶1及搅拌速率210 r/min条件下,HFMA、NMA、SDS OP-10和KPS加入量分别为总单体量的7%、3%、3%和0.5%(均为质量分数),以及聚合温度75℃、反应时间4 h时,制备得到的乳液单体总转化率高,乳液凝聚率低,聚合反应稳定,涂膜的综合性能优良。此外,含氟乳胶膜的FT-IR及TG-DSC分析结果表明,HFMA有效地参与了共聚反应,提高了涂膜的耐热性。     

环氧改性苯丙乳液的制备与性能研究

采用半连续种子乳液聚合法制得环氧改性苯丙乳液。研究了环氧树脂、功能单体、引发剂、乳化剂用量对乳液性能的影响。结果表明：环氧树脂用量为单体总量的9％,丙烯酸用量为单体总量2％,硅烷偶联剂A151用量为单体总量的1．5％,引发剂用量为单体总量的0．5％,乳化剂用量为单体总量4％的时得到的乳液具有优良的综合性能。     

模塑级聚偏氟乙烯乳液聚合工艺的研究

研究了乳液聚合工艺对模塑级聚偏氟乙烯(PVDF)树脂性能的影响。结果表明：将乳化剂全氟辛酸和乳液稳定剂石蜡复合使用，可得到粒径分布窄、稳定性良好的PVDF乳液，聚合用石蜡可循环使用，聚合残留的偏氟乙烯(VDF)单体经气液分离、干燥后可用于聚合反应；确定了在100L卧式釜中乳液聚合制备模塑级PVDF的工艺条件为：搅拌转速60r／min、过硫酸铵用量0．035％、链转移剂用量0．6％、全氟辛酸用量0．13％、石蜡用量0．2％，所制得的PVDF的性能可达到国外同类产品的水平。     

顺-苯(M-S)型自交联乳液胶黏剂的研制

以顺丁烯二酸二丁酯 (马来酸双丁酯 )与苯乙烯为主单体 ,引入交联单体 ,采用核壳乳液聚合研制了自交联乳液胶黏剂 ,讨论了组成对胶黏剂性能的影响。     

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.