快速拉挤用环氧树脂体系TTT图构建及应用

拉挤成型复合材料由于其质量轻、强度高、生产成本低等优点被广泛应用。拉挤成型用树脂基体是影响复合材料工艺和性能的关键因素，掌握其在成型固化过程中的凝胶化和玻璃化行为对工艺制定和提高复合材料性能具有重要意义。文中制备了快速拉挤成型环氧树脂基体，采用动态差示扫描量热仪(DSC)和半经验的唯象模型研究了树脂固化度和固化时间、温度之间的关系，绘制了等固化度曲线；采用恒温DSC得到了基于DiBenedetto经验方程的玻璃化转变曲线；通过测试树脂的凝胶点，研究了凝胶时间和温度的关系。综合上述工作绘制了拉挤树脂体系的TTT(Time-Temperature-Transition)图，由TTT图确定了拉挤速度及模具温度设置。依据确定的工艺参数制备了拉挤板材，经超声扫描和DSC测试，复合材料内部无空隙，玻璃化转变温度达到了树脂完全固化水平。     

风电叶片用碳纤维拉挤板材国产化树脂性能的研究

随着风电叶片长度的增加,对增强材料的刚度和强度等性能提出了新的要求,使用碳纤维增强已经成为一种发展趋势。选取了国产化的拉挤树脂,对树脂黏度、凝胶时间以及浇筑体性能进行了研究。研究发现:国产化的拉挤树脂具有良好的流动性和浸润性,树脂凝胶时间较长,固化时间较短,非常适于拉挤工艺对树脂的要求;拉挤树脂固化浇筑体的拉伸和弯曲性能均满足拉挤风电复合材料的性能要求。     

拉挤成型用树脂配方体系的研究

通过对拉挤成型用树脂配方体系的研究,为拉挤用树脂配方的设计与改进提供思路与方向,从而满足拉挤生产中的不同需求。通过FTIR和GC-MS研究了树脂配方的成分,该配方主要由环氧/酸酐体系加上叔胺类促进剂以及添加剂组成;通过树脂凝胶试验仪和DSC研究了该树脂配方体系的固化反应行为,发现其在140℃时具有最短的凝胶时间(121.0 s)和固化时间(184.5 s),同时在升温速率为5℃/min时的最佳固化反应温度为136℃;对该树脂配方体系和环氧/酸酐体系固化物的力学性能、热变形温度进行了对比研究,发现该树脂配方体系在韧性较好的同时其热变形温度没有受到影响,进一步通过SEM研究发现拉挤用树脂配方体系为韧性断裂而环氧/酸酐树脂体系为脆性断裂。     

基于DSC法的混杂纤维增强树脂基复合材料拉挤工艺研究

为提高碳纤维/玻璃纤维混杂增强树脂基复合材料(以下简称混杂纤维复合材料)拉挤型材的固化质量和力学性能,通过差示扫描量热分析(DSC)法,得出了相同配方条件下复合材料的4种不同升温速率下的固化DSC曲线,运用T–β外推法初步确定了三段式加热拉挤成型方法的温度工艺参数范围。在此基础上,选择直径为10 mm的混杂纤维棒材作为研究对象,变化不同的拉挤温度和速度制备型材,并对其分别进行力学性能试验,研究拉挤工艺参数对复合材料力学性能的影响,从而根据力学性能表征进一步明确适合于本配方的生产工艺参数。结果表明,通过以上方法所得到的混杂纤维复合材料拉挤工艺参数能够满足制备混杂纤维复合材料型材的要求;与传统的经验方法相比,采用该方法更为高效和准确。     

酚醛型氰酸酯的性能

表征了采用"改进的卤化氰-酚法"合成得到的酚醛型氰酸酯未固化树脂的粘度、反应性和凝胶特性,固化树脂及其复合材料的力学性能、耐热性、耐烧蚀性能等。结果表明,固化气氛对酚醛型氰酸酯的反应活性有着显著的影响,在空气气氛中的凝胶时间远小于惰性气氛的凝胶时间。固化树脂及其复合材料具有优异的耐热性和烧蚀残留率,力学性能优于酚醛树脂。     

耐高温拉挤环氧树脂及其复合材料性能研究

本文研究了改性多元缩水甘油胺型耐高温环氧树脂的固化动力学,分析了该树脂体系的浇注体性能,制备了碳纤维拉挤复合材料,并通过热机械分析(DMTA)考察了树脂浇注体及其复合材料的动态热机械性能.结果表明,树脂体系的凝胶化温度与固化温度相差较小,固化反应放热集中,适合于快速拉挤成型;其复合材料具有优良的耐高温性能,玻璃化温度(Tg)达到210℃以上.     

环氧—甲基丙烯酸树脂的固化特性研究

本文研究了EAM树脂的凝胶特性,用DSC、IR研究了树脂的固化特性。结果表明,BPO含量增加或升温,可使凝胶时间缩短;Tgel约100℃,Ttreat约120℃;并制定了该树脂的固化工艺。     

环氧—甲基丙烯酸酯树脂的固化特性研究

本文研究了EAM树脂的凝胶特性 ,用DSC、IR研究了树脂的固化特性。结果表明 ,BPO含量增加或升温 ,可使凝胶时间缩短 ;Tgel约 10 0℃ ,Tcure约 110℃ ,Ttreat约 12 0℃ ;并制定了该树脂的固化工艺。     

烯丙基酚醛改性双马来酰亚胺树脂的制备与性能

合成并表征了烯丙基酚醛树脂,再将其与双马来酰亚胺共聚制备了烯丙基酚醛改性双马树脂。通过DSC和FTIR分析了该树脂的固化行为,研究了其工艺性,利用TGA和DMA评价了其固化物的耐热性。结果表明,烯丙基酚醛树脂改性双马树脂可用于RTM等成型工艺,其固化物Tg约为330℃,初始热分解温度约400℃,5%失重温度达410℃,10%失重温度423℃。该树脂耐热性优异,可用作耐高温先进复合材料的基体树脂。     

生物质基酚醛树脂的合成及其复合材料性能

用苯酚在酸性条件下对杉木木粉进行常压、高温液化制备液化油,以中和后的生物液化油和改性剂尿素进行氨基甲酸酯提质,并与多聚甲醛缩聚得到生物基热固性树脂;以生物基热固性树脂作为复合材料基体,制备了石英布层压板复合材料。采用凝胶渗透色谱法(GPC)、差热扫描量热法(DSC)、傅立叶红外光谱(FT-IR)、流变测量和热失重分析(TGA)等表征了生物热固性树脂及其固化物的性能,采用扫描电镜(SEM)、三点弯曲力学性能测试和动态热机械分析(DMA)等技术对复合材料的断面形貌和力学性能进行了评价。结果表明:生物基热固性树脂的固化存在2个固化放热峰(185和220℃);生物基热固性树脂的树脂残炭率约为45%~48%;生物树脂基层压板复合材料的室温弯曲强度为357 MPa、弯曲模量为17 GPa;生物树脂基复合材料的玻璃化温度大于270℃(远高于酚醛树脂复合材料的玻璃化温度215℃)。生物质酚醛树脂是一种可以替代纯酚醛树脂的绿色低成本热固性复合材料基体。     

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.