纳米 TiO2包覆改性研究及其对 PVC 性能影响

利用硅烷偶联剂 KH–570对纳米 TiO2进行改性,探讨了改性工艺,通过正交试验得出改性的最佳工艺条件：分散液 pH=7.5,偶联剂加入量为7 mL,超声时间40 min,沉降实验和粒度分析结果表明,改性纳米 TiO2表面亲油性能显著提高,粒子间的团聚也得到改善。将改性及未改性纳米 TiO2加入 PVC 基体中,制得 PVC／纳米 TiO2复合材料,并对其进行紫外屏蔽性能测试和拉力测试。结果表明,添加改性纳米 TiO2的 PVC 复合材料紫外屏蔽性能和力学性能均显著高于添加未改性纳米 TiO2的材料,且当改性纳米 TiO2质量分数为3%时,PVC／改性纳米 TiO2材料的紫外屏蔽性能和力学性能最佳。     

新型纳米光触媒剂二氧化钛改性聚丙烯的研究

采用一种新型的纳米光触媒剂二氧化钛(TiO2)来改性聚丙烯(PP)，将无机纳米粒子通过熔融共混方法与PP复合制备了纳米TiO2／PP复合材料，利用透射电子显微镜(TEM)观察纳米粒子在聚丙烯基体中的分散效果，研究了纳米TiO2／PP复合材料的力学性能和抗菌性能。实验结果表明，填充量较少时纳米TiO2在PP基体中能够实现良好的分散。力学性能测试结果表明，填加质量分数为1％的纳米TiO2可以明显提高PP材料的抗冲击性能；纳米粒子质量分数在0～1％范围内对复合材料的拉伸强度几乎没有影响；而随着纳米光触媒剂TiO2的加入，PP具有良好的杀菌作用，并且随着TiO2含量的增加，复合材料的抗菌性能呈明显提高趋势。     

PET/纳米TiO2抗紫外纤维的制备及性能研究

将金红石型TiO2添加至聚合反应体系中进行原位聚合,得到PET／纳米TiO2复合材料,通过透射 电镜(TEM)、扫描探针显微镜(SPM)研究了纳米TiO2在PET基体中的分散情况。将复合材料纺制成纤维, 并进行了力学性能、抗紫外性能等测试。结果表明,金红石型TiO2在基体中分散较均匀,TiO2质量分数为 1％时,基本呈纳米尺寸分散;PET／纳米TiO2纤维中含1％TiO2时,断裂强度较纯PET纤维下降6％左右,断 裂伸长率、结晶度也有所下降。织物对UVA,UVB波段的紫外线具有优异的屏蔽效果,抗紫外因子(UPF 值)可达50以上。     

纳米SiO2/TiO2复合粉体的制备及表征

以Na2SiO3为原料,采用非均匀成核法在纳米TiO2基体上制备了SiO2表面保护膜层,通过红外光谱、X射线光电子能谱、扫描电镜、粒径测量、BET比表面积测量分析,证实纳米TiO2颗粒表面包覆了一层均匀致密的SiO2纳米膜,而且两者是以化学键合方式结合在一起。分散性能测试表明:纳米SiO2/TiO2复合粉体的分散性能明显提高。     

纳米SiO2包覆SiC填充改性UHMWPE的热性能

采用纳米粒子表面包覆处理技术制备了纳米碳化硅/超高摩尔质量聚乙烯(SiC/UHMWPE)复合材料,并用傅立叶红外光谱(FTIR)、扫描电镜(SEM)、透射电镜(TEM)、热重分析(TG)和差示扫描量热(DSC)进行了测试表征。结果表明:纳米SiC经包覆处理后表面有一层均匀致密的SiO2,包覆处理能改善SiC在UHMWPE基体中的分散效果。当SiC质量分数为5%时,UHMWPE/SiC复合材料具有较高的耐热性能和热导率,这是由于纳米粒子包覆改性纳米SiC与UHMWPE基体均匀分散并形成良好的结合界面,增加了填料对UHMWPE的成核作用,提高其结晶度和耐热性能。     

PP/纳米SiO2复合材料的研究

采用傅立叶红外光谱仪(FT-IR)表征了改性前后纳米SiO2粉体的性能特征;通过熔融共混法制备了PP/纳米SiO2复合材料。研究了纳米SiO2用量对PP基体性能的影响。通过力学性能测试、DSC热分析和SEM照片观测,对PP/纳米SiO2复合材料的结构和性能进行了系统的研究。结果表明:当纳米SiO2含量为2%时,PP/纳米SiO2复合材料的综合力学性能最好。DSC表明,纳米SiO2对PP基体有异相成核作用。SEM电镜分析得出,经表面改性的纳米SiO2均匀地分散于PP基体中,从而起到良好的改性作用。     

纳米SiO_2改性环氧树脂胶粘剂的研究

选择纳米 SiO_2 作为增强材料改性环氧树脂基体, 以物理分散法将纳米 SiO_2 分散在环氧树脂中。通过力学性能测试和热稳定性能测试, 研究了不同含量的纳米 SiO_2 对改性环氧树脂胶粘剂的热性能、拉伸性能和冲击性能的影响; 通过 NOL环测试和扫描电子显微镜(SEM) 分析, 研究了不同含量的纳米 SiO_2 对国产芳纶纤维/改性环氧复合材料的界面性能和层间剪切强度的影响。实验结果表明, 基体树脂中当 w( 纳米SiO_2)=3%时, 改性环氧树脂胶粘剂的拉伸强度和冲击强度分别提高了 28.8%和 22.6%, 复合材料的层间剪切强度(ILSS) 达到最大值, 比未改性胶粘剂提高约 56.8%。     

纳米TiO_2表面改性及在PUA复合涂层中的应用

以硬脂酸和钛酸酯偶联剂为复合改性剂对纳米TiO2进行表面改性,并通过原位分散和光固化方法制备了改性纳米TiO2/聚氨酯丙烯酸酯(PUA)复合涂层。讨论了纳米TiO2的改性条件及改性效果,并通过SEM、DSC和力学性能测试等手段考察了改性纳米TiO2对PUA性能的影响。结果表明,当钛酸酯为0.00234 mol/L、硬脂酸为0.0352 mol/L、温度45℃、时间1.5 h时,纳米TiO2的表面改性效果较好;改性后的纳米TiO2在PUA中的分散稳定性得到提高,且改性纳米TiO2/PUA复合涂层的力学性能,尤其是耐冲击力和拉伸强度得到了提高。     

分子筛改性NEPE推进剂丁羟包覆层研究

通过机械共混法制备了分子筛改性NEPE推进剂丁羟包覆层,该包覆层具有良好的力学性能。研究了填料变化对包覆层力学性能的影响,讨论了分子筛改性机理,并优化了包覆层中填料含量。结果表明,丁羟包覆层中分子筛和二氧化钛质量分数均为20％时,包覆层的力学性能最好,其拉伸强度为3．96MPa,断裂延伸率为629．91％,且抗硝化甘油迁移性能良好。     

抗紫外聚酯纤维的制备和性能

将经过表面无机包覆改性和表面有机包覆改性的金红石型纳米级TiO2粉体分散于乙二醇（EG）中,再经研磨设备循环研磨数次,配制成一定浓度的均匀浆料。按一定的比例与PTA、EG配料参加原位缩聚反应,从而制得具备永久抗紫外功能的聚酯切片。同时还研究了含纳米TiO2材料的抗紫外聚酯切片的纺丝、后加工工艺,并测试了所制备样的抗紫外性能。     

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.