静电纺丝结合碳热还原法制备碳化硅纤维研究

以TEOS为硅源,乙醇为溶剂,PVP为助纺剂制备出前驱体溶液,采取静电纺丝制备SiO_2/PVP前驱体纤维,经碳热还原后得到SiC纤维。采用XRD和SEM研究了纺丝电压、纺丝流速等对SiC纤维物相及显微结构的影响。结果表明,当纺丝电压为25 k V,纺丝流速为4.0 m L/h时,经1450℃碳热还原2 h后制备出SiC纤维,纤维物相较纯,β-SiC的特征衍射峰明显,纤维表面光滑,平均直径为1μm。     

纳米纤维增韧碳纤维树脂基复合材料的制备方法

一种纳米纤维增韧碳纤维树脂基复合材料的制备方法,属于复合材料领域。其特征为采用热塑性工程塑料的纳米纤维毡或膜作为增韧部分。其制备方法是:将碳纤维的预成型体作为静电纺丝的负极接收器,直接将热塑性工程塑料纳米纤维毡或膜纺丝于预成型体上,所纺纳米纤维毡或膜相对于碳纤维预成型体的树脂基体具有质量比例;将含有纳米纤维毡或膜的碳纤维的预成型体铺层,制备含纳米纤维夹芯结构的碳纤维预成型     

聚丙烯腈基超细碳纤维毡的制备及其表征

采用静电纺丝法制备了不同黏均分子质量(Mη)的聚丙烯腈(PAN)超细纤维毡,并通过280℃预氧化和900℃碳化进一步制备超细碳纤维毡。讨论了Mη对纤维制备的影响,发现PAN的Mη大于3×105则不利于静电纺丝,小于5×104则纤维毡发脆,无法进一步加工处理成碳纤维毡。用场发射扫描电镜、红外光谱、X-射线衍射对纤维毡进行表征,结果表明:随着PAN相对分子质量的升高,碳纤维的直径和得率增大。此外,抗拉强度测试表明:随着相对分子质量的增大,超细碳纤维毡的抗拉强度增加。     

不同模板取样方式及烧结工艺低温制备SiC木材陶瓷

以废弃枫木为原材料,分别取轴向和径向的木材制成生物模板,以聚碳硅烷(PCS)为陶瓷前驱体,采用直接烧结法和分步炭化烧结法,在惰性气氛下1000℃低温热解制备了SiC木材陶瓷。分别对不同模板取样方式和不同烧结工艺下烧成产物的微观形貌、线收缩率、体积密度、力学性能和物相组成等特征变化进行了讨论分析。结果表明:以PCS为陶瓷先驱体,在1000℃低温下可以烧结制备出具有原木材模板结构特征的SiC木材陶瓷。预处理可以防止木材热解过程中的翘曲问题。轴向木材模板制备的SiC木材陶瓷在相同PCS含量下,线收缩率更低,开裂的几率更小,体积密度更大,抗弯强度更好,更适合用于承压情况。分步炭化烧结法制成的SiC木材陶瓷在相同模板取样方式和相同PCS含量下,壁厚更厚,线收缩率更低,体积密度更高,力学性能更好。     

热解碳对先驱体浸渍裂解3D-C_f/SiC复合材料性能影响

以三维编织T300碳纤维为预制体,通过控制化学气相渗积(CVI)沉积时间制备厚度不同的热解碳界面相,采用先驱体浸渍裂解(PIP)工艺增密制备3D-C_f/SiC复合材料,研究界面相对先驱体浸渍裂解3D-C_f/SiC复合材料性能影响。结果表明:3D-C/SiC复合材料在合适的界面相厚度下能够获得更好的增韧效果。热解碳厚度为220±20 nm时,3D-C_f/SiC复合材料弯曲强度为388.8 MPa,弯曲断口处纤维呈台阶式拔出,拔出面参齐不齐,弯曲强度最大,增韧效果最佳。     

PVP/PLA乳液静电纺丝成形及纤维毡亲水性能研究

利用乳液静电纺丝可制备一定复合结构的共混纤维,且可通过调控乳液的组成而实现聚合物溶液在低浓度下的静电纺丝成形。以聚乙烯基吡咯烷酮(PVP)水溶液为分散相,聚乳酸(PLA)氯仿溶液为基体相,制备不同水相比例的PVP/PLA乳液,研究了PVP/PLA乳液静电纺丝成形及其纤维毡的亲水性能。结果表明:乳液体系中PVP水相的加入可使PLA乳液在远低于其单独可纺溶液浓度下纺丝成形,所得纳米纤维随着PVP水相比例的提高而表现出纤维直径增加,并发生纤维集结成束,PVP大部分分布在复合纤维毡的表层,纤维毡呈现明显的透水性能;PVP的加入可有效改善PLA纳米纤维毡的亲水性能。     

静电纺丝纳米纤维的制备工艺及其应用

简述了静电纺丝制备纳米纤维的原理;探讨了静电纺丝电压、流速、接收距离、溶剂浓度等工艺条件;介绍了同轴静电纺丝制备皮芯结构的超细纤维及中空纤维技术以及静电纺丝纳米纤维毡在生物医药方面的应用。指出静电纺丝纳米纤维材料在生物医用方面具有广阔的应用前景,进一步实现低压纺丝、开发无毒溶剂,控制同轴静电纺丝纳米纤维的释放性能是今后静电纺丝的研发方向。     

超细碳纤维毡的制备及其形貌研究

采用静电纺丝法制备了聚酰胺酸（PAA）无纺布纤维毡,通过亚胺化工艺得到聚酰亚胺（PI）纤维毡,再以PI纤维毡为前驱体经高温碳化工艺制备PI基超细碳纤维毡,并对制得的PI基超细碳纤维毡进行了扫描电镜（SEM）形貌分析和元素分析。经SEM分析得知,随着碳化温度的升高碳纤维毡中纤维的直径逐渐减小,其分布略变窄,主要分布在200-300nm之间,当碳化温度达到1000℃时,PI基超细碳纤维毡中纤维的碳含量为96.16％。     

静电纺丝法制备聚酰亚胺/碳化硅复合纳米纤维

利用聚酰胺酸(PAA)溶液和纳米碳化硅(SiC)混合物作为纺丝液,通过静电纺丝法制备聚酰胺酸/碳化硅(PAA/SiC)复合纳米纤维,PAA/SiC复合纳米纤维亚胺化后得到聚酰亚胺/碳化硅(PI/SiC)复合纳米纤维。研究了PAA溶液中PAA含量、纺丝电压、纺丝距离及SiC含量对PAA/SiC复合纳米纤维形貌的影响,利用热重法分析了PI/SiC复合纳米纤维的热稳定性。结果表明,使用固含量为15%的PAA溶液作为基体材料,再将纳米SiC以6%的含量均匀分散于基体材料中制备出纺丝液,在纺丝电压为10～18kV左右、纺丝距离为15cm时,可制备出直径250nm左右、光滑、连续、SiC分布均匀的PAA/SiC复合纳米纤维。PI/SiC复合纳米纤维热稳定性优异,氮气气氛中热分解温度为550℃。     

PSA纳米纤维毡的制备和性能（英文）

以聚砜酰胺(PSA)无纺布为支撑层,采用静电纺丝法制备了PSA纳米纤维毡,并用于高温高效空气过滤领域;研究了环境湿度对PSA纤维成形的影响规律,探讨了纺丝时间、纺丝电压、接收距离对纳米纤维毡形貌、孔径、纤维直径及其力学性能的影响,以及纳米纤维毡面密度对滤材过滤效率和压阻的影响。结果表明:当环境相对湿度达到30%时,纳米纤维成形良好;当纺丝电压为22 kV,纺丝时间23 h,接收距离为16 cm时,制备的纳米纤维毡面密度为6.78 g·m~(-2),滤材过滤效率达到99.93%,过滤压阻为754 Pa,纳米纤维毡质量因子为9.63×10~(-3);PSA纳米纤维毡达到了PM2.5过滤的要求,有望在高温过滤领域得到广泛应用。     

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。