硅笼改性耐热厌氧胶的制备及其固化动力学

为提高厌氧胶的热性能,用二步法合成了邻甲酚醛环氧丙烯酸酯(o-CFEAR),并以该树脂为单体,不饱和笼型倍半硅氧烷(POSS)为耐高温改性剂,选择合适的氧化还原体系及其它助剂,制成耐高温厌氧胶,测定了相关性能,研究了该胶的固化动力学。结果表明,此厌氧胶剪切强度最高达15.3 MPa,在200℃、96 h时剪切强度保持率为87%左右,耐高温性能良好;固化过程的反应级数为1.084 9,表观活化能为86.86 kJ/mol。     

一种改性厌氧结构胶的研究

用直接水解法制备了七异丁基三硅羟基笼型倍半硅氧烷,以环氧丙烯酸酯为主要单体,七异丁基三硅羟基笼型倍半硅氧烷为改性剂,以异丙苯过氧化氢-糖精-乙酰苯肼为氧化-还原体系,制得一种剪切强度高、耐高温性较好的厌氧结构胶。实验结果表明,厌氧胶的剪切强度和耐高温性得到大幅提高,最大剪切强度达到19.0 Mpa,耐高温达到200℃。     

高性能厌氧胶

由大连瑞华实业有限公司研制开发生产的高性能厌氧胶，它除了具有普通型厌氧胶的通性外，还具备了耐高温的特性，它具有很高的软化点和稳定的化学基团。其生产工艺先进，性能达到了世界同类同用途胶种的水平。在高温时，其力学性能一套压剪切强度，达到了美国乐泰型号产品的标准。该胶不含溶剂，具有单组分，强度高。应用温度范围广，使用方便等优点。高性能厌氧胶，不但有厌氧胶的通性，并且具有高强度，     

乙氧基化双酚A二甲基丙烯酸酯对耐高温厌氧胶性能的影响

研究乙氧基化双酚A二甲基丙烯酸酯(BPA2EODMA)对厌氧胶热稳定性、热强度和其他性能的影响.实验结果表明:随着BPA2EODMA用量的增加,厌氧胶的热稳定性增加,当BPA2EODMA添加量为30％时,厌氧胶的起始分解温度由原来220℃提高到了270℃;200℃烘箱老化96h后,厌氧胶剪切强度保持率仍然在80％以上,...     

填料对耐高温厌氧胶油面黏接性影响研究

以乙氧化双酚A二甲基丙烯酸酯、环氧丙烯酸酯和三羟甲基丙烷三甲基丙烯酸酯为主要原料,分别采用SiO2、nCaCO3、有机膨润土为无机填料制成耐高温厌氧胶,研究了填料对耐高温厌氧胶油面黏接性的影响。结果表明:填料吸油量的大小影响厌氧胶的油面黏接性,当w(SiO2)=4%~6%时,油面黏接强度损失最小,耐高温厌氧胶的油面黏接性较优。     

耐高温型结构厌氧胶黏剂的研究进展

本文综述了耐高温厌氧胶的发展状况，根据其单体的特点将耐高温厌氧胶进行分类，并着重阐述了耐高温结构厌氧胶的单体合成及以该单体配制成厌氧胶的性能特点。     

表面粗糙度对厌氧平面密封胶初固时间和粘接强度的影响

选择应用于平面密封的厌氧胶,测试了在不同表面粗糙度(Ra)剪切试片上的初固时间和剪切强度,得出了不同Ra对厌氧胶初固时间和剪切强度的影响。结果表明,Ra越大,初固时间越长,当达到一定Ra时,初固时间出现明显变慢现象,即存在了一个拐点;但是对剪切强度来说,随着Ra的增大,强度呈现先增大后降低趋势,相对最大强度出现在Ra为3.2左右。     

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。     

耐高温厌氧胶的研制

以甲基丙烯酸单体、耐高温树脂为主体材料，选择合适的氧化-还原体系、稳定体系及其他助剂，研制出可在200℃以上的温度条件下使用的厌氧胶系列产品，并测试了其相关性能。结果表明：耐热系列厌氧胶在200℃条件下，其强度保持率仍在70％以上,可以于200℃以上长期使用。     

影响螺纹锁固厌氧胶性能的因素研究

以BPA2EODMA(乙氧化双酚A二甲基丙烯酸酯)和EA(双酚A环氧丙烯酸酯)为主要原料、异丙苯过氧化氢(CHP)为引发剂、1,4-萘醌为阻聚剂、N,N-二甲基苯胺为促进剂和糖精为助促进剂,采用单因素试验法优选出厌氧胶的最佳配方。结果表明:当m(BPA2EODMA):m(EA)=3:7、w(CHP)=3.0%、w(N,N-二甲基苯胺)=0.8%、w(糖精)=0.5%和w(1,4-萘醌)=0.03%时,厌氧胶的综合性能较好,其剪切强度达到26 MPa,施工性能及储存稳定性能俱佳。     

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.