GO/SiO_2/PP复合材料的制备与性能研究

采用溶液复合法制备了氧化石墨烯(GO)/二氧化硅(SiO2)杂化材料(HGS),再与聚丙烯(PP)熔融共混制备了HGS/PP复合材料。分别采用X-射线衍射(XRD)分析、微分扫描量热仪(DSC)、扫描电子显微镜(SEM)、热失重分析(TGA)、拉伸及冲击测试等手段对HGS/PP复合材料的结构和性能进行了表征。结果表明,固定HGS中GO与SiO2的质量比为1∶1,当填料HGS的质量分数为0.1%时,HGS/PP复合材料的拉伸强度和冲击强度分别为37.7MPa和4.4kJ/m2,与基体PP相比分别提高了17%和5.8%。DSC测试表明,HGS/PP复合材料中PP的熔融温度和结晶温度分别为167.2℃和112.7℃,与纯PP相比分别提高了5.2℃和4.7℃。TGA测试表明,复合材料的起始分解温度和最大分解温度分别比PP提高了9.5℃和15.7℃。SEM观察表明,当加入少量的HGS时,填料能均匀地分散在基体中,但HGS过多时,则容易形成团聚。     

GO表面原位生长CNTs改善聚丙烯导热复合材料分散与界面形态

二维结构氧化石墨烯(GO)纳米片在高分子导热复合材料领域有良好应用前景,但常受限于片层间相互作用过大导致的局部团聚,不利于力学性能和导热性能的提高。借助GO纳米片表面和边缘提供的大量活性位点以吸附铁基催化剂,进而通过微波辅助合成方法在GO表面原位生长碳纳米管(CNTs)的策略,在数分钟内合成具有三维多层次结构的纳米杂化体(GO-CNT)。通过常规熔融共混方法,可获得GO-CNT在聚丙烯(PP)基体中良好剥离与均匀分散形态,明显不同于GO/PP复合体系中严重的局部团聚现象。均匀分散的GO-CNT对PP复合材料的力学性能和导热性能提升效果显著：在3%(质量分数)含量下,复合材料的屈服强度和热导率分别达到了38.0 MPa和0.76 W/(m·K),较纯PP增幅分别为20%和230%,明显优于传统GO改性复合材料。本研究为解决纳米片状填料在导热复合材料中的应用瓶颈提供了可行的结构设计策略和复合材料制备方法。     

原位制备GO/PET复合材料的结构与性能

采用溶剂置换法制备了分散均匀的氧化石墨烯(GO)/乙二醇(EG)溶液,进而通过原位聚合法制备了氧化石墨烯/聚对苯二甲酸乙二醇酯(GO/PET)复合材料,探讨了溶剂置换法对GO在溶剂中分散性能的影响,并研究了GO含量对PET基复合材料结构与性能的影响。结果表明,通过溶剂置换法预处理,再经原位聚合制备的GO/PET复合材料中的GO分散均匀,无明显团聚现象。随着GO含量的增加,复合材料的熔融温度和拉伸强度明显降低,但结晶温度与弹性模量明显提高。当GO含量为0. 01%时,拉伸强度最大,为52. 9 MPa,与纯PET相比,提高了12%;当GO含量为0. 5%时,弹性模量最大,为2 297. 2 MPa,比纯PET相比提高了16%。     

聚丙烯/氧化石墨烯(PP/GO)复合材料的制备及性能

通过原位聚合法制备了聚丙烯/氧化石墨烯(PP/GO)复合材料,并以此为母料与聚丙烯溶液共混,制备了不同氧化石墨烯含量的PP/GO复合材料,研究了GO对复合材料力学性能、电性能及热性能的影响。力学性能测试发现,石墨烯能显著提高复合材料的刚性,同时,使其韧性降低。当GO的含量为2. 5%时,复合材料的弹性模量和拉伸强度分别提高了700%和82%,而断裂伸长率降低了93%。电性能测试结果发现,PP/GO的渗流阈值为1. 5%,在此含量条件下,复合材料的电导能达到10-2S/m,与PP相比,提高了11个数量级;同时,PP/GO的快速降解温度也提高了250℃。     

PP/OBC/EPDM-g-MAH复合材料的制备及性能

以聚丙烯(PP)为基体材料,乙烯-辛烯嵌段共聚物(OBC)为增韧材料,三元乙丙橡胶接枝马来酸酐共聚物(EPDM-g-MAH)为相容剂,制备了PP/OBC/EPDM-g-MAH复合材料。用DSC、SEM、转矩流变仪分析了OBC及EPDM-g-MAH对PP结晶性能、断面相结构、流变性能的影响,测试了复合材料的力学性能。结果表明:加入15%OBC,PP/OBC复合材料的熔融温度升高了1.63℃,结晶度降低了5.4%,断裂伸长率及缺口冲击强度明显提高,弯曲强度和拉伸强度有所下降;含4%EPDM-g-MAH的PP/OBC/EPDM-g-MAH复合材料,OBC粒子均匀分散在PP基体中,粒径明显细化,熔融塑化扭矩值降低,结晶速率加快;与纯PP相比,断裂伸长率和缺口冲击强度分别提高了128.57%和107.96%,柔韧性有较大幅度提高。     

CE/BMI/GO复合材料的制备与性能

以双马来酰亚胺树脂(BMI)预聚体改性氰酸酯树脂(CE)(CE/BMI)作为基体树脂,以氧化石墨烯(GO)作为增强体,通过浇铸成型工艺制备了CE/BMI/GO复合材料。研究了GO的质量分数对CE/BMI/GO复合材料力学和摩擦学性能的影响。结果表明,GO的加入有益于复合材料力学性能和摩擦学性能的提高。GO的质量分数为0.8%时复合材料获得最好的韧性和耐磨性。对比基体树脂,CE/BMI/GO复合材料的冲击强度和弯曲强度分别提高了33.6%和27.6%;摩擦系数和磨损率分别降低了22.5%和77.6%。     

SIVO408改性硅灰石在聚丙烯树脂中的应用研究

文章采用低聚短链烷基硅烷SIVO408对硅灰石进行表面改性,然后与聚丙烯树脂(PP)熔融共混制备PP树脂基复合材料,研究了改性硅灰石的填充份数对PP树脂基复合材料的密度、熔体流动速率、热变形温度、拉伸强度、弯曲强度和弯曲模量等性能的影响。结果表明：改性硅灰石的加入增大了PP树脂基复合材料的密度,与纯PP树脂相比,填充30份改性硅灰石的PP树脂基复合材料的密度从0.898 g/cm³增大到1.049 g/cm³;显著改善了PP树脂基复合材料的热性能,硅灰石添加份数为20份时其热变形温度达到最高值82.5℃,升高了9.9℃(13.6%)。重要的是,改性硅灰石在高填充量的情况下基本不会影响PP树脂基复合材料的加工流动性和拉伸强度,明显提高了PP树脂基复合材料的弯曲强度和弯曲模量,硅灰石添加份数为25份时PP树脂基复合材料的弯曲强度达到最大值35.890 MPa,增加了3.5410 MPa(10.9%),硅灰石添加份数为30份时PP树脂基复合材料的弯曲模量最大为1 709.50 MPa,增加了435.40 MPa(34.2%)。     

石墨烯/聚丙烯纳米复合材料性能的研究

采用水合肼还原氧化石墨烯(GO)制备石墨烯(GE),通过熔融共混法制备GE/聚丙烯(PP)纳米复合材料,研究了GE的用量对PP结晶性能、力学性能以及热稳定性的影响。结果表明:GE能在PP基体中良好地分散。添加2.0份GE时,与纯的PP相比,纳米复合材料的结晶温度提高2.9℃,拉伸强度提高13.4 MPa,最大热分解温度上升了48.9℃。     

排水管道中玻纤增强聚丙烯防腐材料性能研究

本研究制备了玻璃纤维增强聚丙烯(PP/GF)复合材料,并研究了玻璃纤维(GF)添加的用量对PP/GF复合材料的力学性能和耐腐蚀性的影响。采用SEM、热失重和强度测试对PP/GF复合材料的形貌和力学性能进行分析。结果表明:GF作为增强体可以在PP材料中呈现出良好的分散状态,GF在PP材料的均匀分散能够提高其作为工程塑料的力学性能、阻燃特性和耐腐蚀性。通过拉伸强度和弯曲强度测试发现,当GF在PP/GF复合材料中的加入量为15%时,复合材料具有最佳的力学性能。     

原位聚合法制备酚醛树脂/氧化石墨烯复合材料

以自制的氧化石墨烯(GO)为改性填料,采用原位聚合法制备了酚醛树脂(PF)/GO复合材料,通过X射线衍射仪、红外光谱、扫描电镜、热重分析及力学性能测试研究了产物结构,GO在PF中的分散以及GO含量对PF/GO复合材料性能的影响。结果表明,GO在PF基体中的分散度可达到微米级,且未与PF发生化学反应。适量引入GO,可有效提高PF的力学性能和热稳定性,当GO的质量分数为1.0%时,PF/GO的冲击强度和弯曲模量达到最大值7.15 kJ/m~2和19.57 GPa,分别比纯PF提高了14.04%和17.96%,当GO质量分数为1.5%时,PF/GO热稳定性最好,T_(5%)、T_(max)和800℃残炭率分别比纯PF提高58.3℃,8.2℃和2%。     

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.