聚吡咯/凹凸棒石纳米复合材料的制备及导电性能

以三氯化铁(FeCl_3)为氧化剂,十二烷基磺酸钠(sodium dodecylsulfonate,DSNa)为掺杂剂,使吡咯单体(pyrrole,Py)在凹凸棒石(attapulgite,ATP)的表面发生原位聚合反应,制备出聚吡咯/凹凸棒石(polypyrrole/attapulgite,PPy/ATP)纳米导电复合材料.研究了毗咯用量、聚合温度、聚合时间、FeCl_3用量以及DSNa用量对纳米导电复合材料体积电阻率的影响,确定了制备纳米导电复合材料的工艺条件.通过X射线衍射、热重-差热分析、Fourier红外光谱、Raman光谱和透射电子显微镜对纳米复合材料进行表征,结果表明:当吡咯用量(以ATP的质量计)为30%,FeCl_3与Py的摩尔比为2.3,DSNa的浓度为0.02g/mL时,20℃反应3h得到的PPy/ATP复合材料的体积电阻率可达7Ω·cm,聚吡咯以非晶态形式存在于凹凸棒石表面,两者之间的作用为物理作用.     

聚吡咯/凹凸棒土纳米复合材料的制备及结构表征

以十二烷基磺酸钠为掺杂剂,FeCl3·6H2O为氧化剂,引发吡咯单体（Py）发生化学氧化聚合,制备出聚吡咯/凹凸棒土纳米复合材料（PPy/ATP）,并通过XRD、TG-DTA、FTIR和TEM等技术手段对所得的复合材料进行了表征。体积电阻率测量表明,随着Py用量的增大,纳米复合材料的体积电阻率逐渐变小,当Py/ATP的质量比≥0.25时体积电阻率变化不大。XRD和TEM显示,聚吡咯以非晶态形式包覆在凹凸棒土单晶的表面,形成核-壳棒状纳米结构,包覆层厚度约为2 nm。TG-DTA表明凹凸棒土纳米复合材料的耐热性能与纯聚吡咯相比明显提高。FTIR表明纳米复合材料中聚吡咯与凹凸棒土之间存在物理作用。     

硒掺杂对碳纤维/环氧树脂复合材料导电性能及机敏性的影响

以锗硒玻璃(GeSe_4)作为硒源制备一维硒纳米纤维(SeF),将其与碳纤维(CF)按一定体积比混杂,制备硒/碳共混环氧树脂(SeF/CF/EP)复合材料。测量SeF掺杂前后复合材料的体积电阻率变化,分析SeF/CF混杂比对材料导电机敏性的影响。结果表明,SeF掺杂前,碳纤维/环氧树脂复合材料(CF/EP)体积电阻率随纤维长度的增大而降低,随CF含量的增加呈阶段性减小趋势,2、4和6 mm长度的CF/EP复合材料的渗滤阈值分别为0.9%、0.3%和0.05%,随温度的升高,CF/EP复合材料先后呈现正温度效应(PTC)和负温度效应(NTC),无明显光敏特性;SeF掺杂后,复合材料导电性能显著提高,当SeF/CF体积比为3.06时,材料体积电阻率较掺杂前下降91%,随温度的升高,SeF/CF/EP复合材料的体积电阻率始终保持PTC效应,光敏特性显著增强。     

聚吡咯层对碳纤维/环氧树脂复合材料界面粘结性能的影响

以三氯化铁为氧化剂,采用吡咯液相沉积聚合方法制备聚吡咯-碳纤维(PPy-CF),然后与环氧树脂(EP)复合,制得PPy-CF/EP复合材料,并对其进行拉伸性能测试,研究了聚合温度对PPy-CF/EP复合材料界面剪切强度(IFSS)的影响。结果表明:在CF表面吡咯沉积聚合最佳工艺条件为聚合温度70℃,时间30min,经过吡咯沉积聚合改性后,得到的PPy-CF/EP复合材料的IFSS有所提高;最佳条件下制得的PPy-CF/EP复合材料的IFSS是CF/EP复合材料的1.24倍;在PPy-CF中,PPy与CF之间无化学键作用,PPy-CF/EP复合材料的IFSS与PPy-CF表面含氧基团和粗糙度有关;吡咯化学沉积聚合改性是一种提高纤维与树脂界面粘结性能的有效方法。     

碳纤维/乙烯基酯树脂复合材料的温阻特性分析

为了研究温度对处在"渗滤"区的导电复合材料导电行为的影响,以乙烯基酯树脂为基体,用短切碳纤维(CF)为填料,制备了导电复合材料,研究了温度和CF体积分数的变化对复合材料体积电阻率的影响.结果表明,温度对处于"渗滤"区的导电复合材料的电学性能影响显著.当温度从20℃升到100℃时,CF体积分数为2.00%和3.04%的复合材料其体积电阻率降低了28.01%和37.38%,CF体积分数为4.03%和5.63%的复合材料其体积电阻率分别升高了3.00%和9.87%.     

PAN/GO包覆改性C/MnO_2合成锂离子电池负极材料及性能研究

本文以碳基二氧化锰(C/MnO_2)为前驱体,用聚丙烯腈(PAN)/氧化石墨烯(GO)包覆改性前驱体合成锂离子电池负极材料。通过XRD、XPS、SEM对材料进行结构形貌表征。结果显示,复合材料为氮、碳基锰氧化物,随包覆物PAN和GO含量减少,复合材料由颗粒嵌入平整膜转变为褶皱纱状覆盖颗粒物;在PAN/GO与C/MnO_2包覆比例为3:3时,碳化改性制备的复合材料电极有最优充放电性能,在200 A g~(-1)电流密度条件下,经过100次循环后放电比容量为447 m Ahg~(-1)。     

聚吡咯/二氧化硅复合材料的制备及导电性的研究

以三氯化铁(FeCl3)为氧化剂,对甲苯磺酸钠(TSANa)为掺杂剂,在水中使吡咯(Py)单体在二氧化硅(SiO2)粒子表面发生化学氧化聚合反应,制备了具有良好导电性的聚吡咯/二氧化硅(PPy/SiO2)复合材料。结果表明:当FeCl3与Py的摩尔比为2 5,Py与SiO2的质量比为0 3,TSANa的浓度为0 020g·ml-1,在10℃下反应4h,得到的复合材料具有最高电导率12 6S·cm-1。FT-IR结果表明:在形成复合材料过程中PPy与SiO2发生了一定的物理和化学作用。     

聚(吡咯/二苯胺磺酸)/石墨烯复合材料的制备及其抗静电性能研究

采用化学氧化聚合法,以石墨烯(RGO)为掺杂剂,吡咯(Py)和二苯胺磺酸(SD)共聚制备导电复合材料。通过正交实验和分散性实验确定最佳合成条件为:以Fe Cl3·6H2O为氧化剂,n(氧化剂)∶n(单体)=1∶1,n(Py)∶n(SD)=7∶3(总量为0.01 mol),m(RGO)=0.05 g;在此条件下制备的复合材料电导率为12.05 S/cm,且具有良好的水分散性。用傅里叶变换红外(FTIR)光谱和X射线衍射(XRD)对其结构进行了表征,并使用热重分析仪(TGA)对复合材料的热稳定性进行了测试。结果表明,SD结构单元成功嵌入聚吡咯(PPy)的分子链中,RGO的掺杂使复合材料电导率和热稳定性都有了明显提升。将复合材料作为导电填料加入到水性聚氨酯中,考察了涂层的抗静电性能和机械性能,在添加量为4%时,涂层的综合性能较好,涂层表面电阻率可达8.65×107Ω。     

聚吡咯/海泡石一维纳米复合材料的制备及表征

以三氯化铁（FeCl3）为氧化剂,十二烷基磺酸钠（SDS）为掺杂剂,通过原位聚合的方法制备了聚吡咯/海泡石（PPy/SEP）纳米复合材料。研究了吡咯（Py）用量、聚合时间、氧化剂用量以及掺杂剂用量对复合材料电导率的影响,确定了制备导电复合材料的工艺条件。结果表明,在Py用量（以SEP质量计）为25 %,聚合温度为0 ℃,聚合时间为12 h,FeCl3/Py摩尔比为2.3/1,SDS/Py摩尔比为1/5的条件下制备的PPy/SEP复合材料电导率为2.15 S/cm。采用透射电镜、红外光谱、X射线衍射及热分析表征纳米复合材料的形貌与结构。结果表明,制备的PPy/SEP纳米复合材料为具有核壳结构的一维纳米复合材料,且PPy以非晶态的形式存在于SEP表面。     

染料掺杂聚吡咯复合材料的研究进展

介绍了聚吡咯制备方法及掺杂剂种类,主要综述了使用不同染料作为掺杂剂制备聚吡咯对其形貌和性能的影响,指出了目前染料掺杂聚吡咯复合材料的研究现状,并对其发展进行了展望。     

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.