腰果壳油改性酚醛树脂的耐热性研究

酚醛树脂(PF)作为重要的摩擦材料用胶粘剂,其热稳定性对摩擦制动材料性能的影响至关重要。为改善传统PF耐热性欠佳的缺点,以腰果壳油、苯酚和甲醛为原料,制备了改性PF预聚体,并对其结构和热稳定性进行了分析。研究结果表明:腰果壳油、苯酚和甲醛三者之间可发生聚合反应,生成腰果壳油改性PF;腰果壳油改性PF的失重过程主要发生在400℃以上,其耐热性明显优于未改性PF;腰果壳油改性PF可用作高温摩擦制动材料的胶粘剂。     

腰果壳油改性摩擦材料用酚醛树脂的研究进展

腰果壳油是天然有机酚化合物,利用其改性摩擦材料用酚醛树脂具有改善材料力学性能和降低成本等优点,本文介绍了腰果壳油的组成及特性,简述了腰果壳油酚醛树脂的制备方法、改性途径及改性树脂用于摩擦材料方面的研究进展,进而展望了该树脂研究的前景。     

酚醛树脂耐热改性的研究

以腰果壳油、苯酚及甲醛为原料制备了改性酚醛树脂,通过红外光谱、DSC及TG分析研究了原料配比对产物性能的影响。结果表明,当甲醛(37%水溶液)用量为97.30g,苯酚用量为56.40g,腰果壳油用量为121.60g,氨水用量为30.00 g时合成的改性酚醛树脂的耐热性最佳,热失重温度在400℃以上,非常适合用作高温摩擦制动材料的胶粘剂。     

复合改性酚醛树脂基摩擦制动材料的制备与表征

酚醛树脂主要用于制造各种塑料、涂料、胶黏剂及合成纤维等。本论文中使用腰果壳酚和环氧树脂对酚醛树脂进行复合改性,并以该复合改性树脂为基体制备了连续纤维增强摩擦材料。并利用TG对复合改性树脂的热性能进行了表征,利用chase摩擦试验机,对摩擦制动材料的摩擦性能进行了表征。TG测试表明,复合改性树脂在400°C才开始失重,但失重速率较大;chase摩擦磨损测试表明,以复合改性树脂为基体制备的摩擦材料其摩擦系数可以稳定在0.45以上。     

腰果壳液的性质及其在摩擦材料工业中的应用

腰果壳液中主要含有腰果酚,利用腰果酚中酚羟基、侧链双键及活泼氢等的化学性质,人们将腰果壳液广泛地应用于材料的各种改性,其中以应用在摩擦材料领域效果最为显著,并主要应用于以下三个方面：1、腰果壳液改性酚醛树脂黏结剂2、腰果树脂黏结剂3、摩擦粉。     

摩擦材料中树脂基体的选用

概述了摩擦材料对树脂基体的性能要求，讨论了硼改性酚醛树脂，三聚氰胺-腰果壳油改性酚醛树脂和开环聚合酚醛树脂的改性方法，并对它们的热性能进行了比较分析，测试了以这三种改性酚醛树脂为基体的摩擦材料的摩擦性能，结果表明，三聚氰胺-腰果壳油改性酚醛树脂为适宜的摩擦材料用基本树脂。     

木质素改性高耐磨酚醛树脂的制备及性能研究

利用酶解木质素(EHL)和腰果壳油(CNSL)改性热塑性酚醛树脂,讨论了不同酚醛摩尔比、CNSL用量和1,4-丁二醇对改性树脂性能的影响。研究表明,木质素及腰果壳油双改性的酚醛树脂耐热性能优于腰果壳油改性的酚醛树脂。改性后酚醛树脂基摩擦材料具有良好的摩擦磨损性能,更适合作为摩擦材料的树脂基体。     

低噪声制动摩擦材料的研制

用粘弹性振动理论分析认为,增加摩擦材料的粘弹性有利于降低或消除车辆制动噪声。研制的腰果壳油和三聚氰胺改性酚醛树脂,使酚醛树脂基石棉摩擦材料的硬度大幅度降低并提高了材料的热稳定性。试验证明,该材料可降低制动噪声,满足车辆制动要求。     

汽车刹车片用改性酚醛树脂的生产

在原有的酚醛树脂生产设备上，用腰果壳油和三聚氰胺对酚醛树脂进行改性，制得的改性树脂具有较好的软化点、聚合速度、挥发度和游离酚等性能；并且热分解温度较普通酚醛树脂大大提高。用它作胶粘剂生产的汽车刹车片，冲击强度增大：磨损率降低、摩擦性能提高、产品成本也大为降低。     

酚醛树脂的耐热改性研究进展

对酚醛树脂的耐热改性研究进行了综述。研究表明,改性后酚醛树脂的耐热性得到了显著的改善。改性的方法包括:硼酸改性、钼改性、双马来酰亚胺改性、聚砜改性、苯并口恶嗪化合物改性、酚三嗪树脂改性、腰果壳油改性及桐油改性。     

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.