碳纳米管在PA 6/PP共混体系中的选择分散性

采用熔融共混法制备了聚酰胺（PA）6／聚丙烯（PP）／碳纳米管（CNTs）三元复合材料。研究了相容剂的结构、CNTs的表面性质对复合体系微观分散性的影响。结果表明,在相容剂增容条件下,PP可以在PA6基体中均匀分散,呈明显的“海-岛”结构;CNTs的表面有机基团决定了其在不同相中的分散,强酸处理的CNTs1^#表面氧化生成的羧基与PA6的胺基反应,在不同相容剂增容的PA6与PP共混体系中CNTs1^#均分散在PA6相中;而氧化后与己内酰胺原位聚合的CNTs2^#表面生成低聚合度的PA6,表面引入了一定的胺基,与双羧基相容剂（衣康酸与苯乙烯共聚接枝聚丙烯）反应,可使CNTs2^#进入PP相中。     

纳米无机粒子选择性分布与迁移对聚合物共混物形态与性能的影响

综述了纳米无机粒子在聚合物合金中选择性分布的影响因素及纳米无机粒子在聚合物中分散的重要性,重点从相行为、相形态、力学性能、电学性能、流变行为、结晶和熔融行为以及光学性能等方面总结了近年来纳米无机粒子在聚合物共混物中的选择性分布与迁移对以聚合物共混物为基体的纳米复合材料的形态和性能的影响。特别强调了如何利用热力学和动力学因素调控纳米无机粒子在聚合物合金中的分布。     

碳纳米管/HDPE复合材料的制备及性能研究

将酸化处理以后的碳纳米管（CNTs）与高密度聚乙烯（HDPE）复合,采用机械共混法制备了定向CNTs／HDPE复合材料,并对其力学性能、相态结构、流变性能及热性能进行了研究。结果表明：CNTs的加入,提高了复合材料的屈服强度和拉伸模量,但同时却降低了材料的断裂强度和断裂伸长率;CNTs在HDPE基体中有了较好的分散性和相容性;CNTs的加入对复合材料流变性能产生了较大的影响,加入少量的CNTs可以使复合材料体系的表观粘度降低,有利于HDPE加工性能的改善;CNTs加入后,HDPE的熔融温度和结晶熔融焓均有所下降。     

改性碳纳米管增强热塑性聚氨酯复合材料的性能研究

以碳纳米管（CNTs）和热塑性聚氨酯（TPU）为原料,通过硫酸（H₂SO₄）/硝酸（HNO₃）混合溶液处理碳纳米管颗粒表面以达到改性的效果,使用改性过后的碳纳米管熔融共混制备出TPU/CNTs复合材料。研究了不同含量的CNTs对TPU基体的流变、力学、耐磨性以及热性能的影响。结果表明, 改性过后的CNTs在TPU基体中形成了良好的分散性和相容性;TPU/CNTs复合材料在高频剪切下保留了复合材料的加工流动性,并且复合材料的拉伸强度以及耐磨性相较于TPU有明显的增强,其中在改性碳纳米管含量较低时,复合材料的力学性能改善较为明显;改性CNTs的加入提高了TPU基体的熔融温度和结晶度;改性CNTs的加入提高了复合材料的热降解温度,提高了TPU基体的热稳定性。     

超支化聚合物共价修饰碳纳米管的制备及应用研究

碳纳米管(CNTs)具有很多优良性能,但由于在聚合物基体分散性差,限制了其广泛应用。超支化聚合物是高度支化的大分子,具有低黏度、高溶解性及含有大量末端基团等特点。利用超支化聚合物共价修饰CNTs,不仅可以提高CNTs在聚合物基体中的分散性,还能使CNTs拥有新的功能。介绍了超支化聚合物共价修饰CNTs的方法,探讨了其在生物医学、纳米材料等方面的应用前景,最后对超支化聚合物共价修饰CNTs的发展提出了建议。     

超声功率对导电炭黑填充PA 66/PPO共混物性能的影响

在熔融挤出过程中,对导电炭黑填充聚酰胺(PA)66/聚苯醚(PPO)共混物施加一定超声,研究了超声功率对PA 66/PPO共混物力学性能、结晶性能、导电性能及微观形貌的影响。结果表明:超声作用下,共混物的拉伸强度、弯曲强度、弯曲模量和悬臂梁缺口冲击强度分别提高13.0%,10.4%,7.0%,11.8%;超声作用利于导电炭黑在聚合物基体中的分散;导电炭黑的分散性提高,结晶成核作用增强,PA 66的结晶温度提高;导电炭黑分散性提高有利于使共混物的导电性能提高,表面电阻率和体积电阻率分别提高了92.9%和96.3%。     

聚合物共混体系／黏土纳米复合材料多相形态的研究进展

论述了聚合物共混体系/黏土纳米复合材料内部多相结构形态研究的最新进展；从共混聚合物基体对黏土的分散形态以及黏土对不相容共混基体相结构的影响两方面总结了多相形态的影响因素；探讨了相形态改善、反转的机理。     

同向旋转双螺杆挤出机中的聚合物共混胶(下)

鉴于聚合物组合的形态结构可使聚合物共混胶的性能测定达到准确无误的程度，为此，挤出机设计需要采用模型，以能计算熔体输送段中挤出机螺杆长度上的估算形态发展。由于观测到的最明显的形态变化出现于熔融段，本文就着重描述了挤出机这一段中的共混胶熔融过程中形态的形成和发展。文中对PP和PA6共混胶的熔融流变性、界面张力、熔融形态进行了描述，并对熔融过程中开始时的固体含量、固体温度平均熔体温度及溶体温度的发展熔融过程的模拟、熔融度、粘度比、单位挤出恒定时的速度影响、挤出机规格影响、螺杆顶部的熔融度、挤出量恒定时螺杆速度的影响、恒速下挤出量的影响、粘度比的影响、微滴分散与聚结等作了较为详尽的计算与讨论。从而为研究熔融过程、形态发展以及为理论模型和形态发展对比提供了数据基础。     

同向旋转双螺杆挤出机中的聚合物共混胶(上)

鉴于聚合物组合的形态结构可使聚合物共混胶的性能测定达到准确无误的程度，为此，挤出机设计需要采用模型，以能计算熔体输送段中挤出机螺杆长度上的估算形态发展，由于观测到的最明显的形态变化出现于熔融段，本文就着重描述了挤出机这一段中的共混胶熔融过程中形态的形成和发展。文中对PP和PA6共混胶的熔融流变性、界面张力、熔融形态进行了描述，并对熔融过程中开始时的固体含量、固体温度平均熔体温度及熔体温度的发展熔融过程的模拟、熔融度、粘度比、单位挤出量恒定时的速度影响、挤出机规格影响、螺杆顶部的熔融度、挤出量恒定时螺杆速度的影响、恒速下挤出量的影响、粘度比的影响、微滴分散与聚结等作了较为详尽的计算与讨论，从而为研究熔融过程、形态发展以及为理论模型和形态发展对比提供了数据基础。     

制样方法对SiO2/PA6复合材料基体PA6结晶熔融行为的影响

采用差示扫描量热法(DSC)研究了原位聚合法和熔融共混法制样方法对纳米SiO2/PA6纳米复合材料结晶熔融行为的影响,结果表明:通过阴离子原位聚合法制备的纳米复合材料,由于采用超声波分散技术,纳米粒子在基体的分散性好。随着纳米粒子含量的升高,纳米粒子的诱导成核能力增强;熔融共混法制得复合材料中,SiO2在机械力的剪切作用下,很难均匀地分散,多以团聚体的形式存在,在PA6基体结晶时,结晶成核的条件相匹配,有较强的成核效应,纳米粒子的含量影响不大。     

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.