利用溶胶-凝胶法制备连续莫来石纤维

利用溶胶-凝胶法以氢氧化铝、羧酸、硅溶胶为原料、结合干法纺丝制备了连续莫来石陶瓷纤维。通过TEM、TG-DSC、FT-IR、XRD、SEM等方法对纺丝溶胶的微观结构、纤维晶型以及纤维表面和内部结构进行了研究,利用流变仪对溶胶的流变性能进行了研究。结果表明：通过溶胶-凝胶法制备的前驱体溶胶可纺性优异,性能稳定;采用干法纺丝得到的连续莫来石凝胶纤维表面光滑、直径均匀;经陶瓷化处理后获得连续莫来石纤维,纤维直径11～13μm,单丝拉伸强度可达1.9GPa,1200℃煅烧后主晶相为莫来石相。     

不同硅源对溶胶凝胶法制备莫来石纤维可纺性和结构的影响

采用铝粉和结晶氯化铝作为铝源,分别加入硅溶胶、硅溶胶与纳米氧化硅(7 nm、15 nm)的混合物作为硅源,采用溶胶-凝胶法,制备莫来石纤维。研究了不同硅源对莫来石前驱体溶胶纺丝性能、并对纤维晶化温度和结构的影响。结果表明加入纳米氧化硅后,溶胶纺丝性能下降;全部加硅溶胶制备的溶胶,纺丝性能最好,凝胶纤维长度大于500 cm。不同硅源凝胶纤维,在1200℃煅烧后主要物相为莫来石。加入纳米氧化硅(7 nm和15 nm)的试样,在1600℃煅烧后,有硅线石生成。加入纳米二氧化硅为硅源,纤维致密度明显增高,晶粒得到细化,孔隙率降低。     

莫来石纤维前驱体溶胶-凝胶化转变的研究

以水为分散介质,硝酸铝、异丙醇铝、正硅酸乙酯为原料,聚乙烯吡咯烷酮为纺丝助剂,采用溶胶-凝胶法合成了莫来石纤维前驱溶胶,通过对流变、粘度以及折光指数的测试,研究了不同条件下莫来石纤维溶胶的凝胶化过程。根据Chambon-Winter(CW)法则确定了不同体系的凝胶化时间,探讨了溶胶-凝胶化转变过程中体系粘度的变化以及温度、添加剂对体系凝胶化时间的影响,为连续莫来石纤维干法纺丝工艺提供了一定的理论依据。     

莫来石纺丝溶胶的流变特性及可纺性研究

本文以氢氧化铝为铝源,以硅溶胶为硅源,采用溶胶-凝胶技术制备了莫来石纺丝溶胶,采用稳态及动态两种测试模式,研究了纺丝溶胶的粘度及流变性能,并采用干法纺丝制备连续莫来石凝胶纤维,评价了溶胶的可纺性。结果表明,温度对溶胶的非牛顿指数及结构粘度指数影响不大,这将有利于纺丝工艺的调节;高固含量有利于莫来石凝胶纤维的纺丝成纤,制备的凝胶纤维更细,纺丝稳定性更好。     

纺丝液参数对静电纺丝制备莫来石纳米纤维的影响

为了获得静电纺丝制备莫来石纳米纤维的最优工艺参数,以无水氯化铝、正硅酸乙酯、异丙醚和二氯甲烷为原料,采用非水解溶胶-凝胶法制备莫来石前驱体凝胶,再以聚乙烯吡咯烷酮(PVP)为助纺剂,无水乙醇和N,N-二甲基甲酰胺(DMF)为溶剂制备纺丝溶液,利用静电纺丝技术获得莫来石前驱体凝胶-PVP纤维,经1 000℃煅烧合成莫来石纤维。研究了凝胶化温度(未凝胶、100和110℃)、凝胶用量(0.031、0.041和0.052 mol·L~(-1))和PVP用量(0.025、0.042和0.058 g·mL~(-1))等纺丝液参数对莫来石纤维相组成及显微结构的影响,并测试了最优工艺参数下制备的莫来石纤维在50℃下的热导率。结果表明:凝胶化温度对莫来石纤维物相组成影响较大,未凝胶化时纤维中仅有少量的γ-Al_2O_3相,凝胶化温度为100和110℃时则为莫来石相,但凝胶用量和PVP用量对莫来石纤维物相组成影响不大;纤维直径随着凝胶用量的增加而增大;当凝胶化温度为100℃,凝胶用量为0.041 mol·L~(-1),PVP用量为0.042 g·mL~(-1)时,纤维表面连续光滑,粗细较均匀,直径主要分布在150~300 nm,平均直径为213 nm,50℃下的热导率为0.053 W·m~(-1)·K~(-1)。     

溶胶-凝胶工艺对不锈钢涂覆莫来石涂层的影响

以九水合硝酸铝(Al(NO3)3·9H2O)和正硅酸乙酯(TEOS)为主要原料,氧化硼(B2O3)为助熔剂,采用溶胶-凝胶法和提拉浸渍法在不锈钢基片上制备莫来石涂层.分别研究了溶胶加热时间、溶胶浓度、热处理的升温速率、灼烧温度对涂层的影响.通过FT-IR和TG-DSC分析了莫来石前驱体的结构和热处理过程的成分变化,利用体视显微镜观察涂层形貌.实验结果表明:利用溶胶-凝胶法,当溶胶加热时间为7 h,溶胶浓度0.094×10-3 mol/mL和0.117×10-3 mol/mL之间,3 ℃/min升温速率下可得到完好、致密、无裂纹的莫来石前驱体陶瓷膜的涂层,热震性实验表明在950 ℃灼烧的涂层与基体结合强度较好.     

莫来石纤维制备方法综述

莫来石纤维是一种重要的陶瓷材料,被广泛用作高温隔热材料、金属基或陶瓷基复合材料的增强体等.本文主要综述了莫来石纤维的多种制备方法,特别是重点介绍了溶胶-凝胶法制备多晶莫来石纤维的研究现状.在溶胶-凝胶法制备莫来石纤维的过程中,原材料的选择、单相和双相溶胶的制备以及各种因素都会影响水解和浓缩过程,并决定莫来石纤维的最终性能.最后对制备莫来石纤维的发展方向进行了展望.     

溶胶-凝胶法制备可纺莫来石溶胶的特性研究

以水作为分散剂,以异丙醇铝、氯化铝和正硅酸乙酯为原料,盐酸和醋酸做复合催化剂,聚乙烯醇为纺丝助剂,采用溶胶-凝胶法合成了可纺莫来石溶胶,并分析了获得适宜拉丝性的原料的较佳配比、不同水解时间对后续热处理的影响及溶胶粘度与温度的关系,为制取连续莫来石纤维提供必要借鉴.采用DTA-TG,IR,XRD及旋转粘度计分析测试了胶体各方面的性能.     

溶胶-凝胶法制备多晶氧化铝纤维的研究

本文探讨了溶胶-凝胶法制备多晶氧化铝过程中影响胶体性能的因素,成纤方法与工艺参数,热处理工艺制度及晶相转化关系等一系列问题.实验得到了以莫来石为主晶相长期使用温度超过1500℃的多晶氧化铝纤维.     

PVA作纺丝助剂制备莫来石-氧化铝长纤维

用氯化铝和铝粉为原料制备了铝溶胶,再向铝溶胶加入硅溶胶、封端剂和聚乙烯醇（PVA）纺丝助剂,制得莫来石-氧化铝溶胶,研究了纺丝助剂加入量对溶胶纺丝性能的影响。研究发现,溶胶在浓缩时,胶粒间发生缩合反应,形成线性或非线性的分子链,生成可纺的黏性溶胶;在溶胶中加入纺丝助剂,铝/硅离子或胶粒与纺丝助剂的活性基团发生缩聚反应,生成有机-无机的杂化分子链,提高了溶胶的纺丝性能;在加入封端剂的同时,加入质量分数为1%的PVA,凝胶纤维的最大长度可达100 cm。凝胶纤维在1 200 ℃下烧结1 h后,得到的陶瓷纤维的物相为γ-Al₂O₃和莫来石相,纤维表面光滑、直径均匀。     

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.     

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。     

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.