Research progress of polymethylsilane

聚甲基硅烷是SiC陶瓷前体的一种,该前体含有大量的活性Si—H键,易于低温固化交联,因此受到了越来越多的关注。本文介绍了聚甲基硅烷主要合成方法,包括Wurtz耦合聚合法、超声合成法、脱氢耦合法和电化学合成法;讨论了聚甲基硅烷的改性方法如热交联改性或化学改性,对改性聚甲基硅烷的性能作了比较,并对今后的研究方向作了展望。     

氯铂酸催化剂在聚碳硅烷与二乙烯基苯交联中的应甩

为了提高聚碳硅烷与二乙烯基苯(polycarbosilane/divinylbenzene,PCS/DVB)硅氢化交联反应程度,采用改性氯铂酸催化的方法对PCS/DVB交联进行了研究。研究表明:氯铂酸催化性能与其用量、交联温度、以及PCS相对分子量有关。当固体PCS相对分子量低于1500,该反应中氯铂酸催化剂的用量为12.5×10-6,低分子量PCS中Si—H含量较高,且分子链支化程度低,易发生硅氢化反应;高分子量PCS中Si—H含量较低,且分子链自身支化程度高,活性基团被包裹于大分子链中,其Si—H键参加反应空间位阻大。氯铂酸催化剂在低温下催化作用不明显,催化交联的反应温度在150℃以上。     

聚碳硅烷的高温高压生成机理研究II蒸馏产物的结构分析

以液态聚硅烷(LPS)在450℃反应得到的聚碳硅烷(PCS)粗产品为原料,经溶解、过滤、热处理后减压蒸馏,收集蒸馏馏分并进行表征,由此推出不同摩尔质量的PCS的典型结构,进而推测出LPS转化为PCS分子的机理是:随着温度的升高,LPS中的Si—Si键发生断裂、重排,转化为Si—C键,生成低分子碳硅烷;随着温度的继续升高,碳硅烷分子间发生脱氢、脱甲烷缩合反应,摩尔质量逐渐长大,生成PCS。     

聚碳硅烷的高温高压生成机理研究Ⅱ蒸馏产物的结构分析

以液态聚硅烷（LPS）在450℃反应得到的聚碳硅烷（PCS）粗产品为原料,经溶解、过滤、热处理后减压蒸馏,收集蒸馏馏分并进行表征,由此推出不同摩尔质量的PCS的典型结构,进而推测出LPS转化为PCS分子的机理是：随着温度的升高,LPS中的Si—Si键发生断裂、重排,转化为Si—C键,生成低分子碳硅烷;随着温度的继续升高,碳硅烷分子间发生脱氢、脱甲烷缩合反应,摩尔质量逐渐长大,生成PCS。     

先驱体转化法原位制备TiO_2膜层SiO_2纤维

用聚碳硅烷与钛酸四正丁酯(titanium tetrabutoxide,TBT)在200℃氮气气氛中反应5h得到含过量TBT的聚钛碳硅烷(polytitanocarbosilane,TPTC)先驱体。将先驱体TPTC于160℃熔融纺丝制得原纤维后,经空气中100℃熟化处理20h,200℃交联处理20h及1200℃烧结可原位制得TiO2/SiO2纤维。利用红外光谱、核磁共振(13C,29Si)、X射线衍射、扫描电镜和能量散射X射线光谱分析表征发现:随着TBT量的增加,TPTC中的Si—H键含量减少,Si—O键增多;纤维由无定形SiO2和锐钛矿TiO2组成,表面光滑致密无明显缺陷,纤维表面为TiO2富集。     

低电阻率碳化硅纤维先驱体的熔融纺丝与不熔化处理

为了制备低电阻率SiC纤维，在聚碳硅烷合成时引入了聚氯乙烯。研究了引入聚氯乙烯制得的聚碳硅烷PC—P的熔融纺丝与PC—P至维的不熔化处理。研究表明：PC—P具有良好的纺丝性，PC—P的纺丝温度高出其熔点60～90℃。PC—P纤维不熔化处理最高温度高出其熔点15～30℃，PC—P纤维需要的不熔化程度是：质量增加率2％～6％，Si—H键反应程度25％～50％，凝胶含量0～75％，均比普通聚碳硅烷(PCS)纤维低。     

红外光谱法定量研究硅烷自然交联聚乙烯的结构演变

为了利用傅立叶变换红外光谱(FTIR)定量分析硅烷自然交联聚乙烯分子结构的演变,提出了一种通过热压成型制备FTIR测试用薄膜试样的方法,采用热延伸装置和索氏提取法及FTIR对一步法硅烷自然交联聚乙烯的交联结构和性能进行了分析和考察。结果表明,采用的薄膜试样制备方法操作简单,效果明显;一步法硅烷自然交联聚乙烯在湿度75%以上、温度1~15℃的自然条件下交联4 d后其热延伸率、永久变形率以及凝胶率等性能均可满足JB/T 10437–2004的相关要求;相应的FTIR谱图中Si—O—Si基团对应1 080 cm-1处的峰强度在交联第4天时为0.27,可作为快速判断一步法硅烷自然交联聚乙烯交联性能是否达标的一种参考方法。     

二丁基二月桂酸锡固化聚甲基苯基硅氧烷研究

以二丁基二月桂酸锡(DBTDL)为固化剂固化聚甲基苯基硅氧烷(GZ-1),通过凝胶化时间和拉伸强度测试,红外光谱和热重分析研究其固化机理及相关性能。结果表明,随DBTDL用量增加或温度升高,凝胶时间缩短。DBTDL中易水解的酯键与空气中的水进行水解,反应生成的—OH与聚硅氧烷中的—OCH3发生脱醇反应,生成Sn—O—Si键,最后交联固化。体系拉伸强度随DBTDL用量增加而降低。固化物具有良好的耐高温性能。     

硅酸乙酯在熔模铸造上的应用

一、前言硅酸酯与通常所见的硅有机化合物不同,后者分子中至少含有一个Si—C键,前者的有机基团是通过氧原子与硅连接Si—O—C,因此它在有机化合物内形成了一个独立的分支。硅酸酯分子中Si—OR键水解时会发生断裂。与Si—X(卤素)键相比,这种键的共价特性较为明显,因此它对水解的感受性要低得多。烷氧基硅烷用酸或碱水解,实际上包含着     

密封材料

9805495可室温固化的有机聚硅氰烷密封剂组合物及其制备:JP97一176490【日本专利公开)/日本:Shin一Etsu Chemieal Industry Co.,Ltd.(Kimura,Tsuneo等),一1997.7.8一5页一95/351413(1995.12.26);IPCC()8L83/06 该密封剂组合物含有粘度25一1 X 106est、带)2个与Si键合的OH基的二有机聚硅氧烷、触变剂、二氧化硅粉、带)2个与Si键合的酮肘基的有机硅烷和/或其部分水解物、固化催化剂和氨基硅烷偶合剂。例如,一种密封剂组合物含有二甲基聚硅氧烷二醇100份、三乙二醇1份、疏水气相法二氧化硅10份、甲基三丁酮肪硅烷6份、二辛酸二丁基锡0…     

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.     

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.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。