一种通用型厌氧胶的制备及性能研究

采用复合厌氧单体,加入增韧剂制备了一种通用型多功能厌氧胶,研究了单体和增韧剂对厌氧胶性能的影响,考察了该胶的固化性能、粘接性能、耐介质性能和耐热老化性能。研究表明制备的通用型厌氧胶对多种金属材质以及油面试件具有良好的粘接性能,耐环境老化性能优异,并在150℃下长期使用,可满足螺纹锁固、圆柱固持和平面粘接等多种用途的需要。     

甲基苯基硅树脂的制备工艺优化及阻燃性能

以苯基甲氧基硅烷和甲基甲氧基硅烷为原料,用水解缩合法制备硅树脂阻燃剂,通过对反应时间、反应温度、催化剂量和封端时间等因素的正交实验分析,优化硅树脂阻燃剂制备条件.结果表明：硅树脂具有良好的热稳定性,在800℃、N₂气氛下,热失重低于39%,其热稳定性越好,对聚碳酸酯（PC）的阻燃效果越佳.在PC中添加5 %（质量）优化条件制得的硅树脂就能使其氧指数（OI）从26.0提高到34.0.     

有机硅改性酚醛环氧树脂耐高温胶粘剂的研制

采用甲基苯基硅树脂对酚醛环氧树脂进行改性,硼酚醛树脂与自制固化促进剂作为固化剂,辅以纳米蒙脱土、绢云母粉作为填料,制备出一种能在300℃条件下长期使用的耐高温胶粘剂。在不同的配方及固化工艺条件下測定了有机硅改性酚醛环氧树脂体系的剪切强度,分析了甲基苯基硅树脂／酚醛环氧树脂比例关系、硼酚醛树脂与自制固化促进剂比例关系、固化剂用量、固化工艺条件、纳米蒙脱土的加入量对体系的影响。     

新型耐高温PI胶粘剂用单体的合成及表征

为了提高聚酰亚胺(PI)胶粘剂的耐热性能,将碳硼烷引入PI分子链中,首次合成出一种新型含碳硼烷的PI单体,并采用红外光谱(FT-IR)法对其结构进行了表征。结果表明:含碳硼烷的PI单体在400～500℃升温过程中可交联固化;以此作为PI胶粘剂的基体,可赋予PI胶粘剂极佳的热稳定性能(500～1 300℃时热失重变化不大),从而为制备耐高温胶粘剂提供了新的途径和新的方法。     

甲基苯基硅树脂改性丙烯酸酯厌氧胶的性能研究

以马来酸酐、丁二酸二乙二醇酯、甲基丙烯酸甘油酯为原料合成丙烯酸酯厌氧胶,再通过铂催化剂和交联剂将甲基苯基硅树脂对厌氧胶进行改性。对改性后的厌氧胶进行贮存稳定性、热老化强度及吸水率测试,并对厌氧胶进行~(29)Si-NMR表征。研究结果表明:甲基苯基硅树脂与丙烯酸酯厌氧胶成功交联;甲基苯基硅树脂对厌氧胶的热老化强度提升有所帮助,铂催化剂用量增大会对厌氧胶的贮存稳定性产生不利影响,三乙醇胺会加快厌氧胶的固化速度,而胶膜的吸水率对比则发现甲基苯基硅树脂能增大厌氧胶的憎水性能。     

甲基苯基硅树脂的表征与性能研究

合成了一种适用于耐高温防腐涂层的硅树脂,并对其进行了表征和性能研究.红外光谱(FT-IR)和核磁共振(29Si NMR)分析表明,合成的硅树脂是含有Si一0H的甲基苯基硅树脂.热重(TG)分析表明,在氮气氛中,硅树脂320 ℃开始失质量,400℃失质量不到2.0%,具有良好的耐热性.机械性能测试及恒温热失质量表明,硅树脂的清漆涂层在300 ℃下长期使用时,附着力、耐冲击性、柔韧性能仍保持良好.电化学阻抗分析(EIS)结果表明,硅树脂的清漆涂层常温同化后和在300℃高温烘烤后都具有优良的耐腐蚀性能.     

聚硼硅氮烷固化氰酸酯基耐高温胶粘剂的制备与性能研究

以氰酸酯为基胶,聚硼硅氮烷前驱体为固化剂,复配相应的填料,制备了氰酸酯基耐高温胶粘剂。研究了聚硼硅氮烷用量对氰酸酯固化特性、固化产物的结构变化及固化物热稳定性的影响。研究结果表明：与传统的氰酸酯胶粘剂相比,聚硼硅氮烷催化氰酸酯的固化温度降低了50～100℃;聚硼硅氮烷可以催化氰酸酯在150℃低温固化,20份聚硼硅氮烷催化氰酸酯固化物T_5%最高达到476.3℃。以此为基础制备的耐高温胶粘剂的室温粘接强度最高为16 MPa,400℃老化3 h后粘接强度仍达到12 MPa,表明该胶粘剂具有较好的粘接性能和耐老化性能。本研究制备的胶粘剂凭借较低的固化温度、良好的粘接性能和耐温性,有望用于航空、航天和电子等行业。     

硅溶胶–有机硅改性聚酯复合涂料的合成及应用

以碱性硅溶胶和有机硅单体合成了硅树脂,然后用其改性聚酯,得到硅溶胶–有机硅改性聚酯复合树脂。以此复合树脂配制成涂料,喷涂在铝合金底材上,并与纯聚酯所制涂膜进行比较。考察了反应温度对硅树脂稳定性的影响,得到最佳反应温度为35~40°C。通过热重分析和测试涂膜机械性能,探讨了硅树脂含量对复合树脂的热稳定性以及涂膜光泽、铅笔硬度、附着力和柔韧性的影响。结果表明,硅树脂的加入使聚酯的热稳定性显著提高,并且硅树脂含量越高,热稳定性越好。然而,加入硅树脂虽然显著提高了涂膜铅笔硬度,且在高温下也能保持较高硬度,但其用量并不是越多越好,因为它会造成涂膜的光泽度和附着力下降。综合考虑,选择硅树脂含量为30%,此时所得涂膜表现出良好的附着力、耐高温性、耐盐水性和耐酸碱性,满足QB/T 2421–1998《铝及铝合金不粘锅》标准的要求。     

MQ硅树脂的制备及热性能研究

以六甲基二硅氧烷(MM)、四甲基二乙烯基二硅氧烷、硅酸乙酯为原料,异丙醇为溶剂,盐酸为催化剂,通过受控水解反应合成了不同乙烯基含量的MQ硅树脂。并表征了产物的性能。结果表明,所合成的MQ硅树脂具有良好的热稳定性,其质量损失率为5%时的热分解温度在276～389℃之间;随着乙烯基含量的增加,MQ硅树脂的热稳定性下降;甲基MQ硅树脂在DSC第一次升温过程中存在熔融峰70.6℃,表明具有一定程度的结晶性。     

固体酸催化合成MQ硅树脂及其性能研究

以MM(六甲基二硅氧烷)和TPOS(正硅酸丙酯)为原料、固体酸为催化剂,采用水解-缩聚法制备了含甲基的MQ硅树脂。考察了m(M)∶m(Q)比例、反应时间和反应温度等对MQ硅树脂产率的影响。研究结果表明:以固体酸作为催化剂能成功制得MQ硅树脂;当m(M)∶m(Q)=0.60∶1、反应时间为3 h和反应温度为85℃时,合成的MQ硅树脂在N_2和空气气氛中的热稳定性较高,并且该MQ硅树脂对硅橡胶的力学补强作用较佳,具有潜在的应用价值。     

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.     

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.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.