液压支架密封圈用聚氨酯弹性体的性能

采用不同游离甲苯二异氰酸酯(TDI)含量的预聚体和不同结构的二胺扩链剂3,3'-二氯-4,4'-二氨基二苯基甲烷(MOCA)、3,5-二甲硫基甲苯二胺(E-300)和4,4'-亚甲基双(3-氯-2,6-二乙基苯胺)(MCDEA)制备了一系列用于液压支架密封的聚氨酯(PU)弹性体,考察了游离TDI含量及不同扩链剂对PU弹性体物理机械性能、热性能和动态力学性能的影响。结果表明,采用相同预聚体时,对于不同的扩链剂,当扩链系数为95%时,PU弹性体的综合性能最佳;以MCDEA为扩链剂制得PU弹性体的邵尔A硬度、弹性和定伸应力最高,扯断伸长率最低,低温动态性能最好,而撕裂强度和玻璃化转变温度则以E-300为扩链剂制得的PU弹性体最低,拉伸强度相差较小;以MCDEA和MOCA为扩链剂制得PU弹性体的耐热性优于以E-300为扩链剂制得的PU弹性体;以MOCA为扩链剂制得PU弹性体的高温动态性能最好;采用相同扩链剂时,随着预聚体中游离TDI含量的降低,PU弹性体的弹性、定伸应力、撕裂强度和动态性能提高,扯断伸长率降低和永久变形减小,拉伸强度相差较小。     

扩链剂对IPDI基透明聚氨酯弹性体的影响

采用异佛尔酮二异氰酸酯(IPDI)和不同结构的扩链剂、多元醇合成了透明聚氨酯弹性体，通过DSC、TG、WAXD等研究了聚氨酯弹性体的形态结构和力学性能、热稳定性及光学透明性。结果表明，扩链剂结构对聚氨酯弹性体形态结构和力学性能、热稳定性及光学透明性有很大影响。降低扩链剂长度有利于微晶的长大、微相分离程度及力学性能的提高；增加扩链剂用量，聚氨酯弹性体的微相分离程度、微晶尺寸、力学性能及热稳定性能提高；硬段含量对聚氨酯弹性体光学透明性的影响不明显。     

扩链剂对PPG-1000/MDI体系聚氨酯弹性体阻尼性能的影响

以聚氧化丙烯二醇(PPG-1000)、MDI-50与不同的二醇扩链剂采用二步法合成PPG-1000/MDI体系的聚氨酯(PU)弹性体,并对其阻尼性能进行了测试。结果表明,扩链剂对PPG-1000/MDI体系的聚氨酯弹性体的阻尼性能有明显影响。加入含侧甲基和醚键的扩链剂在不同程度上提高了聚氨酯弹性体的阻尼因子(tanδ),拓宽其阻尼温域。因此选择适宜的扩链剂对调节聚氨酯弹性体的阻尼温域具有一定的意义。     

不同硬段结构的液化改性MDI型HTPB-PU弹性体的合成与研究

用端羟基聚丁二烯为原料、液化改性MDI为交联剂、BD或ED为扩链剂合成不同硬段结构的聚丁二烯聚氨酯弹性体，研究了扩链剂种类、用量等对弹性体性能的影响。用扫描电镜研究弹性体应力断裂的断口形态。     

增韧母料ETMB对PE-HD/ETMB力学性能的影响

以2200J高密度聚乙烯(PE-HD)为基体树脂,乙丙弹性体和丁苯弹性体为增韧剂,加入适量引发剂、阻交联剂等,通过特殊的技术和化学反应研制出不同系列聚乙烯增韧母料(ETMB),将ETMB与2200J PE-HD热机械共混制得PE-HD/ETMB共混物.研究了ETMB中弹性体不同配比、基体树脂和弹性体不同配比、不同阻交联...     

聚氨酯弹性体水解稳定性研究

研究和讨论了不同扩链剂、扩链剂的量以及软段分子量对聚酯型聚氨酯弹性体水解稳定性的影响,并引入了参数Ｑ、Ｗ。     

TODI和MDI并用对浇注型聚氨酯弹性体性能的影响

以聚四氢呋喃(PTMG)为聚合物多元醇,TODI和MDI并用为异氰酸酯,添加一定量的扩链剂,采用预聚法制备了一系列浇注型聚氨酯弹性体;研究了TODI/MDI不同并用比、扩链剂种类以及扩链系数对弹性体工艺性能和力学性能的影响。结果表明,随着TODI用量的增加,可操作时间延长,弹性体的耐热性能提高;当采用PTMG 1000为聚合物多元醇,TODI/MDI并用比为60/40,1,4-BD为扩链剂,且扩链系数为0.95时,聚氨酯弹性体的综合性能最佳。     

MDI体系聚氨酯弹性体的合成及性能

以聚醚多元醇、MDI、1，4-BDO和DMTDA等为主要原料，采用半预聚物法合成了双组分聚氨酯弹性体。考察了不同种类多元醇、半预聚物中-NCO基团百分含量、不同扩链剂及其不同配比、-NCO对活泼氢化合物过量比等对聚氨酯弹性体的影响。结果表明，PTMG／MDI／DMTDA半预聚物体系制备的弹性体具有优良的物理性能及工艺性能。。     

聚氨酯弹性体新型扩链剂的合成及应用

聚氨酯弹性体是一类综合性能优异的高分子合成材料,扩链剂对弹性体有重要的影响,能显著改善其性能.本文简单介绍了聚氨酯弹性体用新型扩链剂的分类,详细论述了一些新型扩链剂的合成和应用,并指出了聚氨酯弹性体扩链剂的发展方向和应用前景.     

PTMG体系聚醚型聚氨酯弹性体的力学性能研究

选用MDI体系,采用半预聚法合成了聚醚型聚氨酯弹性体;研究了组分A和组分B中不同多元醇配用、不同扩链剂配用和扩链系数对弹性体力学性能的影响。结果表明,组分B中多元醇PTMG2000/多元醇330N配比为75/25时,弹性体拉伸强度和硬度均较高;当配比为40/60时,弹性体冲击弹性较好。组分A中多元醇PTMG2000/多元醇330N/多元醇PTMG1000配比为70/15/15时,弹性体拉伸强度、撕裂强度和拉断伸长率均较高,力学性能较好;当多元醇PTMG2000/多元醇330N配比为70/30时,弹性体冲击弹性较高。扩链剂BDO/扩链剂TMP配比为8/1时,弹性体综合力学性能和冲击弹性均较优异。扩链系数为0.95时,弹性体力学强度和冲击弹性均优,定伸应力和硬度相对较低。     

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.     

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.     

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。