炭黑用量对过氧化物硫化三元乙丙橡胶性能的影响

以双叔丁基过氧化异丙基苯为硫化剂,通过无转子硫化仪、毛细管流变仪及橡胶加工分析仪考察了炭黑用量对乙烯含量不同的2种三元乙丙橡胶(EPDM)混炼胶硫化特性、流变行为、动态黏弹性能及硫化胶拉伸性能的影响。结果表明,随着炭黑用量的增加,2种EPDM混炼胶的焦烧时间(ts1)均缩短,正硫化时间均变化不大,门尼黏度均逐渐增大,混炼胶黏-切依赖性增大; 在相同炭黑用量下,乙烯含量高的混炼胶的ts1较短,硫化程度和硫化速率提高,2种EPDM混炼胶均表现出剪切变稀行为,乙烯含量高的EPDM混炼胶的剪切弹性模量明显高于乙烯含量低的EPDM混炼胶; 随着炭黑用量的增加,2种EPDM硫化胶的拉伸强度和100%定伸应力均不断提高,且高乙烯含量有助于提高EPDM硫化胶的拉伸性能。     

GMA原位改性炭黑对EPDM胶料性能的影响

探讨甲基丙烯酸缩水甘油酯(GMA)原位改性炭黑对EPDM胶料硫化特性和硫化胶性能的影响。结果表明，GMA起连接炭黑与橡胶的作用．对胶料的硫化特性影响显．提高了硫化胶的物理性能、粘合性能和常温(30～60℃)下的减震阻尼性能；GMA用量为5份时，EPDM胶料的硫化速度较快，硫化胶的表观交联密度较大，物理性能和粘合性能较好。     

不饱和羟基脂肪酸原位改性炭黑补强三元乙丙橡胶的性能

本文研究了不饱和羟基脂肪酸原位改性炭黑补强三元乙丙橡胶(EPDM)的硫化特性、加工性能和物理机械性能，测试了硫化胶的热氧老化性能和屈挠疲劳性能：结果表明：随着不饱和羟基脂肪酸用量的增加，硫化胶的300％定伸强度略有下降，拉伸强度和撕裂强度上升，扯断伸长率先上升然后趋于平缓，动态疲劳性能显著改善。同时硫化胶具有较好的加工性能和热氧老化性能。     

原位改性三元乙丙橡胶炭黑混炼胶与天然橡胶共混胶的性能

研究了三元乙丙橡胶(EPDM)炭黑混炼胶经偶联剂Si-69原位改性前后与天然橡胶(NR)共混胶的性能.结果表明,在EPDM炭黑混炼胶的原位改性过程中,Si-69在与炭黑表面作用的同时会与EPDM发生活性反应.这不仅增大了EPDM与炭黑间的亲和力,而且使EPDM的硫化反应活性增强,从而改善了共混硫化胶的物理机械性能.动态力学性能测试和扫描电子显微镜观察结果均表明,改性后的EPDM炭黑混炼胶与NR的硫化相客性增强.     

炭黑混炼胶和白炭黑混炼胶的结合橡胶及Payne效应研究

研究天然橡胶(NR)/炭黑、NR/白炭黑、异戊橡胶(IR)/白炭黑混炼胶的结合橡胶含量和Payne效应。结果表明:随着二段混炼胶停放时间延长,炭黑混炼胶的结合橡胶含量增大,Payne效应增强,硫化胶应力应变性能和动态性能等变化不明显;白炭黑混炼胶的结合橡胶含量增大,Payne效应基本不变,硫化胶定伸应力明显提高,动态性能有一定程度改善;白炭黑混炼胶的结合橡胶含量明显大于炭黑混炼胶。     

炭黑对IIR1751性能影响的研究

考察了不同炭黑对IIR1751橡胶硫化特性、交联密度、力学性能及动态力学性能的影响,并分析了炭黑在相应胶料中的分散状况。结果表明,随着炭黑比表面积的增大,IIR1751混炼胶门尼粘度增大,炭黑N375填充的胶料焦烧时间最长;粒径太小或结构度太高的炭黑均不利于在其混炼胶中分散,但炭黑N330在其混炼胶中分散性最好;炭黑N220填充的胶料交联密度最大;不同炭黑填充的IIR1751硫化胶tanδ峰值,ΔG′,G″有明显差别;炭黑N220,炭黑N347和炭黑N375填充的硫化胶永久变形较大,炭黑N330填充的胶料各项力学性能比较均衡。     

氯化炭黑在EPDM胶料中的应用

研究氯化炭黑在EPDM胶料中的应用。加入氯化炭黑后，EPDM混炼胶呈现假塑性流体特征，并有延迟硫化的作用;硫化胶的物理性能和炭黑的分散性提高，氯化炭黑中氯质量分数的最佳范围为0．001～0.002加入氯化炭黑还可提高胶料与帘线的粘合强度。     

填充油用量对硫黄硫化EPDM的影响

采用橡胶加工分析仪,研究了填充油用量对硫黄硫化EPDM硫化特性和硫化胶交联网络结构的影响。结果表明,当填充油用量一定时,EPDM硫化胶的总交联密度与硫黄用量呈线性关系;当硫黄用量一定时,随着填充油用量的增加,EPDM混炼胶的最低扭矩和硫化程度不断降低,硫化速率减慢;EPDM硫化胶的物理缠结密度随填充油用量的增加而线性下降,填充油用量较大时,填充油对胶料的稀释作用在硫黄硫化EPDM总交联密度的降低中占主导地位。     

偶联剂Si-69对白炭黑填充EPDM硫化胶网络结构和物理性能的影响

本工作通过溶胀法测定了白炭黑填充的三元乙丙橡胶(EPDM)硫化胶的表观交联密度1/Q和橡胶-填料间的相互作用程度。考察了硅烷偶联剂(Si-69)对白炭黑填充 EPDM硫化胶网络结构和物理机械性能的影响。试验结果表明,Si-69可使EPDM胶料的门尼粘降低,焦烧时间延长,1/Q提高,并增强橡胶-填料间的相互作用,从而改善了胶料的加工性能和某些物理机械性能。     

硫化对炭黑填充SBR体系中多重相互作用的影响

本工作综合运用MDR,RPA以及DMA等表征手段,考察了硫化对炭黑填充SBR体系中多重相互作用的影响。结果表明,炭黑聚集体的絮凝在硫化初期完成。当炭黑含量达到一定值时,炭黑对混炼胶的增强效果优于相应的硫化胶,且应变扫描对混炼胶的增强效果影响较大。Payne效应与炭黑的体积含量间存在一定的对应关系。混炼胶的玻璃化转变温度随炭黑含量的增多升高的幅度大于硫化胶。未填充体系硫化前后的玻璃化转变温度之差大于填充体系。玻璃化转变温度及结合橡胶含量均随炭黑含量的增多而线性增大。     

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.     

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.     

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.