Fe_2O_3/石墨烯纳米材料填充聚合物基复合材料介电性能研究

随着电子设备向多功能化和小型化方面的迅速发展,电子工业领域迫切的需要具有优异介电性能的材料,从而可以提高电子设备的散热能力并且减小电子电容器的体积,研究具有高介电性能的聚合物基复合材料具有非常重要的意义。本实验分别选用Fe2O3作为填料,以PVDF为聚合物基体,采用热压工艺制备了不同组分的Fe2O3/PVDF复合材料,分析对比了影响复合材料的介电性能的因素,得到了如下的结论:(1)Fe2O3/PVDF复合材料的电导率及介电性能与频率的曲线图表明,该体系复合材料的电导率随频率的增大而增大,复合材料的介电常数随频率的增大而逐渐减小,复合材料的介电损耗随频率的增大先减小后增大。(2)Fe2O3/PVDF复合材料的电导率及介电性能与Fe2O3体积含量的关系显示,随着Fe2O3体积分数的增大,该体系复合材料的电导率、介电常数和介电损耗整体均为逐渐增大。     

QW220/5284RTM复合材料的介电性能研究

采用RTM工艺制备了四种不同纤维体积含量的石英纤维增强环氧树脂基复合材料层板。研究了温度、吸湿、频率、纤维体积分数和后固化等因素对该复合材料体系介电性能的影响。结果表明,在30~150℃温度范围内,QW220/5284RTM复合材料的介电常数和介电损耗均随温度升高而增大;纤维体积分数为53%时,该复合材料体系的饱和吸湿率较低,约为0.44%,吸水后,介电常数和介电损耗都有一定程度的增加;室温下,7~18GHz频率范围内,该复合材料体系的介电常数和介电损耗随频率改变没有表现出明显和规律的变化;该复合材料体系的介电常数和介电损耗随着纤维体积分数的提高而分别增大和减小;后固化使该复合材料体系的介电常数和介电损耗均减小。QW220/5284RTM复合材料具有良好的介电性能,且介电性能具有较好的耐环境特性,可用于飞机透波结构。     

聚酰胺6/碳纳米管复合材料的电学性能研究

对碳纳米管(CNTs)进行有机化处理之后,采用原位聚合法制备了聚酰胺（PA）6/ CNTs复合材料。研究了CNTs含量、温度、频率等因素对复合材料电学性能、介电性能和电磁屏蔽性能的影响。结果表明,随着CNTs含量的增加,复合材料的体积电阻率和表面电阻率均下降,最显著情况分别下降了2、3个数量级;随着温度的升高复合材料的介电常数增大,增大趋势随CNTs含量的增加而急剧减小;复合材料的介电常数和介电损耗随着频率的升高变化幅度增大,频率在105.5～109 Hz范围内复合材料有一定的电磁屏蔽效能,随着频率的增大电磁屏蔽效果急剧减小,109 Hz以上几乎没有电磁屏蔽效果。     

硅烷偶联剂改性SiC晶须/PVDF复合薄膜的制备及其介电性能研究

设计填料为半导体纳米晶须、基体为高分子聚合物是制备具有良好介电性能和力学性能材料的基本要求.首先利用化学改性法将不同硅烷偶联剂修饰在碳化硅晶须(SiCw)表面,再利用溶液流延法制备改性SiCw/聚偏氟乙烯(PVDF)复合薄膜.采用直接观察、FT-IR和热重分析对SiCw的改性效果进行评价,通过SEM观察SiCw在PVDF中的分布情况,并测试了该复合薄膜的介电性能随温度的变化情况.结果表明:利用本文的试验方法可成功将硅烷偶联剂引入到SiCw表面;SEM结果显示,利用化学改性法可有效改善SiCw的团聚问题,使其均匀分布在PVDF基体内;TGA结果表明,添加SiCw作为填料可有效改善复合材料的热稳定性能,且当采用KH792型硅烷偶联剂时修饰率为6.37％.室温介电性能测试结果表明:添加改性SiCw可提高复合材料的介电常数,相对纯PVDF提高了近8倍;在0.1wt％KH792-SiCw/PVDF的介电性能测试中,当f=100 Hz时介电常数εr达到最大值33,介电损耗tanδ达到最小值0.07,且随频率的增加介电常数逐渐减小,介电损耗先减小后又增加;随着温度的增加,介电常数和介电损耗逐渐增加,当f=500 Hz,T=150℃时,εr最大为110,对应tanδ也最大为1.76.     

聚偏氟乙烯/钛酸钡高介电复合材料的制备与研究

受功能梯度材料设计理念的启发,采用聚合物微纳层叠共挤装置,提出了交替多层介电复合材料的假设,设计了(聚偏氟乙烯/钛酸钡)(PVDF/BaTiO3)/PVDF交替多层介电复合材料,研究了复合材料的结构和性能。结果表明,复合材料中PVDF以α、β两种晶型共存;随着BaTiO3含量的增加,体系的结晶度逐渐降低;介电常数先增大后减小,在BaTiO3质量分数为7.5%时,介电常数达到最大61.43 F/m(25℃,1 MHz);介电损耗因数先减小后增大,但介电损耗因数都小于0.1。因此,利用微纳多层共挤技术,设计的交替多层介电复合材料满足要求。     

聚苯胺改性PVDF薄膜的结构与介电性能研究

本文通过溶液共混方法制备了聚苯胺改性PVDF薄膜,运用XRD、SEM和DSC技术分析了复合材料结构,并探讨了聚苯胺含量和频率对复合薄膜介电性能的影响。结果表明:适量PANI的加入能够诱导PVDF结晶,提高其结晶程度。随着聚苯胺含量的增大,复合材料薄膜的介电常数、介电损耗迅速升高。     

氮化硼/碳纤维复合填料对聚氨酯介电性能的影响

采用绝缘性氮化硼(BN)与导电性碳纤维(CF)为复合填料,以聚氨酯(PU)为基体,制备得到BNCF/PU复合材料。加入BN填料或CF填料制备得到BN/PU复合材料及CF/PU复合材料,并对BN-CF/PU复合材料的介电常数、介电损耗和电导率进行了对比研究。结果表明,当BN的质量分数为1%及CF的质量分数为14%时,BN-CF/PU复合材料具有高介电低损耗的特性。此时,在BN与CF复合填料的协同效应下,能使BN-CF/PU复合材料的介电常数提高至16. 73 [在频率为1 k Hz处,其介电常数是BN(15%)/PU复合材料介电常数的2. 14倍,是CF(15%)/PU复合材料介电常数的1. 12倍]。而且,在频率为107Hz处,BN-CF/PU复合材料的介电损耗(低于0. 125)和电导率(低于5. 82×10~(-4)S/cm)均得到了有效的控制。     

改性纳米氧化锆对甲基苯基硅橡胶性能的影响

以甲基苯基硅橡胶(MPQ)为基体,硅烷偶联剂改性纳米氧化锆(ZrO_2)为填料,采用机械混合法制备了纳米ZrO_2/MPQ复合材料,研究了纳米ZrO_2质量分数对复合材料光学性能、电性能及热性能的影响。结果表明,随着纳米ZrO_2质量分数的增加,纳米ZrO_2/MPQ复合材料的透光率逐渐降低,体积电阻率先增加后减小,介电常数先降低后增加,介电损耗变化不大,热导率先增加后减小。当纳米ZrO_2质量分数为0.06%时,纳米ZrO_2/MPQ复合材料具有较好的透光率,体积电阻率为1.08×10~(12)Ω·cm,热导率达到0.399 W/(m·K),同时具有低的介电常数与介电损耗。     

低温烧结玻璃/陶瓷复合材料的微结构及性能

借助钙长石陶瓷和硼酸盐玻璃良好的介电和热膨胀性能,制备了一系列玻璃/陶瓷复合材料,并对这些复合材料进行了X射线衍射分析、扫描电镜观察和性能测试.结果表明:复合材料的介电常数、热膨胀系数和显微硬度随着陶瓷含量的增加而增加,其介电损耗则随陶瓷含量的增加而减小.陶瓷含量(质量分数≥60%)高的复合材料在高于850℃烧结时析出一定量的α-石英和方石英,这增加了材料的热膨胀系数,但对其介电常数影响不大.所制备的复合材料具有高的相对密度(≥96.5%)、低的介电常数(5～6)、低的介电损耗(0.10%～0.42%)、低的热膨胀系数(4.6×10-6～6.5×10-6/℃)和低的烧结温度(≤900℃),有望用作介电材料和基板材料.     

钛酸钡-环氧树脂复合材料厚膜的制备及性能研究

通过棒式涂布的方法得到了厚度均匀的钛酸钡-环氧树脂复合厚膜.研究了环氧树脂的热固化性质及钛酸钡含量对复合材料的微观结构、剥离强度及介电性能的影响.结果表明:随着BaTiO2/BT)含量的增加,复合材料中的气孔不断增加,导致剥离强度在BT含量为40 vol%时达到最高值后急剧下降.复合材料的介电常数及介电损耗随着BT含量的增加而不断增加.在BT含量一定时,复合厚膜的介电常数和介电损耗分别随着频率的增加而减小和增加.     

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。