机械力引发官能化POE及其增韧尼龙66的研究

采用在熔融挤出过程中提高双螺杆挤出机螺杆转速的方法,研究了机械力引发马来酸酐(MAH)熔融接枝弹性体POE的接枝反应。化学滴定法和红外光谱法分析的结果表明,随着螺杆转速的增加,接枝产物的接枝率出现先下降后增大的变化趋势,接枝产物的熔体流动速率(MFR)在螺杆转速≥400r/min时出现显著增大,随着接枝反应温度的增加,产物接枝率和熔体流动速率均明显增大;一定条件下,可控制制得具有较高接枝率(接枝率≥0 39%)、较好熔体流动速率(MFR=0 05～0 4g/min)和较低凝胶质量分数(≤0 3%)的接枝产物(POE-g-MAH)。材料力学性能测试和试样断面SEM分析结果表明,此接枝产物POE-g-MAH对尼龙66具有良好的增韧作用,可使PA66/POE-g-MAH共混材料的缺口冲击强度达到原未改性材料的12倍左右。     

挤出机螺杆转速对马来酸酐官能化EVA性能的影响及其增韧研究

采用添加引发剂过氧化二异丙苯（DCP）和提高熔融挤出过程中双螺杆挤出机螺杆转速的机械力引发方法研究了马来酸酐（MAH）官能化乙烯一醋酸乙烯酯共聚物（EVA）的熔融挤出反应.研究了引发剂用量和螺杆转速对产物的接枝率和熔体流动速率的影响.结果表明,随着DCP用量的增加,产物接枝率出现峰值,而随着螺杆转速的增加,产物接枝率出现先下降后增大的变化,接枝产物的熔体质量流动速率（MFR）在螺杆转速达到300r/min时出现显著增大,在一定的配方条件下,通过改变螺杆转速,可以抑制EVA在接枝过程中的交联副反应,控制制得具有较高接枝率（0.29%～0.8%）和较好熔体质量流动速率（0.7～1.2g/10 min）的接枝产物（EVA-g-MAH）.力学性能测试表明,此复合引发接枝产物对尼龙66具有较好的增韧效果.     

苯乙烯在POE接枝GMA中的作用及其对增韧PBT效果的影响

采用苯乙烯(St)为辅助接枝单体,在聚烯烃弹性体(POE)上熔融接枝甲基丙烯酸缩水甘油酯(GMA),制备了POE-g-GMA,通过红外光谱表征证实了接枝反应的发生,考察了St的引入对POE-g-GMA接枝率、熔体流动速率以及POE-g-GMA增韧聚对苯二甲酸丁二醇酯(PBT)的影响。结果表明,在m(St)/m(GMA)为1时POE-g-GMA接枝率达到最大值,为1.057%;随着St用量的增加,接枝物的熔体流动速率持续降低;St的引入使POE相区尺寸明显减小,POE分散相与PBT基体间的相容性明显改善,共混物的冲击强度显著提高,PBT得到有效增韧。     

POE熔融接枝甲基丙烯酸缩水甘油酯的研究

采用同向双螺杆挤出机熔融法制备乙烯-1-辛烯共聚物接枝甲基丙烯酸缩水甘油酯（POE-g-GMA），利用红外光谱法和化学滴定法对接枝物进行表征及接枝率的测定。考察了GMA／St（苯乙烯）、St、引发剂用量以及反应温度和螺杆转速对接枝率的影响。结果表明。随着GMA／St用量、引发剂用量的增加。POE-g-GMA的接枝率随之增大。而熔体流动速率下降；St的加入有效地提高了GMA的接枝率；随着反应温度提高接枝率提高；螺杆转速提高接枝率下降。     

高剪切应力诱导引发乙丙橡胶与马来酸酐官能化反应的研究

采用在熔融挤出过程中提高双螺杆挤出机螺杆转速的高剪切应力诱导引发方法和采用添加引发剂与提高螺杆转速的应力诱导复合引发方法,研究了乙丙橡胶(EPR)与马来酸酐(MAH)的官能化反应;采用化学分析、熔体流动速率测定、FT IR、SEM观测和材料力学性能测试等方法考察了官能化产物(EPR-g-MAH)性能及其对PA66/EPR-g-MAH共混材料力学性能的影响。结果表明:双螺杆挤出机的螺杆转速和官能化反应温度对产物的接枝(嵌段)率和熔体流动速率具有重要影响;与热引发方法相比较,270℃条件下螺杆转速由80 r/m in提高至800 r/m in时,产物的接枝(嵌段)率由0.26%提高至0.47%;与引发剂引发方法相比较,产物熔体流动速率由每10 m in约0.07 g提高至1.80 g,抑制或避免了官能化过程中的交联副反应;所得产物的接枝(嵌段)率和熔体流动速率易于控制,对于PA66的增韧作用,存在最佳接枝(嵌段)率(约0.66%)和最佳熔体流动速率(每10 m in约2.0 g)。     

高剪切应力诱导引发马来酸酐官能化三元乙丙橡胶

在熔融挤出过程中,采用提高双螺杆挤出机螺杆转速所产生的高剪切应力诱导引发的方法及添加引发剂与提高螺杆转速的复合引发方法,研究了三元乙丙橡胶(EPDM)与马来酸酐(MAH)的官能化反应.结果表明,双螺杆挤出机的高螺杆转速所产生的高剪切应力作用可诱导EPDM的断链反应,引起官能化产物黏均相对分子质量的明显减小及接枝率与熔体流动速率的明显增大;在适量过氧化物类引发剂存在的条件下,此种高剪切应力作用可抑制EPDM官能化过程中的交联副反应,使产物的凝胶含量明显下降,接枝率及熔体流动速率明显增大;此种官能化反应过程易于控制,可制得接枝率0.80%～1.13%、熔体流动速率0.11～0.28 g/min及凝胶质量分数不大于1.0%的MAH官能化EPDM.     

双单体MMA／St熔融接枝POE的研究

利用熔融接枝法制备了甲基丙烯酸甲酯接枝乙烯-辛烯共聚物(POE-g-MMA),探讨了各个因素对POE-g-MMA接枝率和熔体质量流动速率(MFR)的影响.得出了最佳配方为:MMA 2.5%,DCP 0.5%;第二单体St的加入使接枝率有所提高,当St与MAH物质的量比为1/1时,接枝率达到最高;最佳工艺条件为:温度150℃,反应时间10 min,螺杆转速80 r/min.     

POE-g-GMA的制备及其对纳米CaCO_3／PA66的增韧

采用熔融法制备乙烯-1-辛烯共聚物(POE)接枝甲基丙烯酸环氧丙酯(GMA),利用红外光谱对其结构进行表征。考察了GMA和过氧化二异丙苯(DCP)用量以及反应温度和反应时间对接枝率的影响,结果表明,GMA用量增加,接枝宰逐渐增大,熔体流动速率逐渐下降；隨着引发剂用量的增加,接技率也隨之增加；同时隨著反应温度和反应时间的变化,接枝率随之变化。然后采用熔融共混法制备了纳米CaCO_3／POE-g-GMA／PA66复合材科,研究了该体系的力学性能,结果表明,纳米CaCO_3和POE-g-GMA对PA66具有一定的增韧作用。     

LDPE-g-GMA的接枝率和流动性研究

利用熔融接枝法制备了聚甲基丙烯酸缩水甘油酯接枝低密度聚乙烯(LDPE-g-GMA),用红外光谱对接枝产物进行了表征,研究了接枝单体、接枝共单体和引发剂对LDPE-g-GMA接枝率和熔体流动速率(MFR)的影响。结果表明:随着接枝单体用量的增加,LDPE-g-GMA的接枝率提高,MFR下降;随着接枝共单体用量的增加,LDPE-g-GMA的接枝率提高,MFR在小范围内波动,变化不大;随着引发剂用量的增加,LDPE-g-GMA的接枝率先升后降,MFR大幅下降。     

高剪切应力对苯乙烯-乙烯/丁烯-苯乙烯三嵌段聚合物马来酸酐化反应的影响

通过提高双螺杆挤出机螺杆转速的应力引发方法,研究了高剪切应力下马来酸酐(MAH)与苯乙烯-乙烯/丁烯-苯乙烯三嵌段聚合物(SEBS)的官能化反应。结果表明,随着双螺杆挤出机螺杆转速的提高,官能化产物的接枝率和熔体流动速率明显增大。高剪切应力的作用引起大分子链断链,形成大分子自由基,从而引发SEBS的接枝反应。通过提高螺杆转速可有效地抑制交联副反应,制得接枝率较高(质量分数0.79%～0.89%)、熔体流动速率适宜(1.859～4.398 g/min)和凝胶含量较低(质量分数不大于0.32%)的官能化产物。同时,由应力诱导引发所得官能化产物SEBS-g-MAH对尼龙(PA 66)的增韧效果较好,其共混物的悬臂梁缺口冲击强度能达到约94 kJ/m2,较纯PA 66提高30余倍,而其拉伸和弯曲强度的下降并不剧烈。     

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.