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《工程塑料应用》2020,(5)
以热塑性聚氨酯为原料,超临界CO_2为发泡剂,通过喷动床发泡技术制备了热塑性聚氨酯发泡珠粒,考察了CO_2流速、饱和温度、饱和压力、泄压速率对珠粒发泡行为的影响。结果表明,珠粒发泡均匀性先随着CO_2流速上升而上升,之后基本不变,表明形成稳定喷动后流速的提升对珠粒发泡均匀性无改善作用。珠粒发泡倍率随着饱和温度和饱和压力的提高先上升后下降,随着泄压速率的提高而提高。饱和温度的提高使泡孔密度下降,泡孔直径增大,饱和压力和泄压速率的提高使泡孔密度上升,泡孔直径下降。当CO_2流速为0.012 m/s、饱和温度为150℃、饱和压力为10 MPa、泄压速率为20 MPa/s时,珠粒发泡倍率最大,达到9倍,泡孔密度为1.13×10~7个/cm~3,平均泡孔直径为82.3 μm。 相似文献
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以偶氮二甲酰胺(AC发泡剂)、Zn O和Na HCO3复合体系作为发泡剂,采用模压发泡的方法制备高填充粉煤灰聚氯乙烯(PVC)复合发泡板材,确定复合发泡剂的最优配比及其在复合发泡板材中的最佳用量,并对其性能进行了研究。采用发气量测定、热重/差示扫描量热(TG/DSC)分析对AC发泡剂进行了改性研究,选出分解温度满足加工条件的复合发泡剂。添加不同份数的复合发泡剂制备PVC复合发泡板材,用扫描电子显微镜(SEM)分析其断面,测试板材的冲击强度及弯曲强度。实验结果表明,当AC发泡剂、Zn O和Na HCO3的配比为2∶1∶1.5时,最大发气量为213 m L/g,分解温度区间为165~177℃,满足PVC发泡板材加工。当复合发泡剂添加量为6份时,力学性能达到最佳,弯曲强度为17.63 MPa,冲击强度为21.88 k J/m2,达到国家硬质聚氯乙烯低发泡板材的标准;粉煤灰填充量高达61.16%。 相似文献
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在种子乳液聚合中加入发泡剂偶氮二甲酰胺(AC),制备了可发气核壳结构复合微球。探讨了AC用量对以聚苯乙烯(PSt)微凝胶为种子,St或甲基丙烯酸甲酯(MMA)为壳层单体的2种体系稳定性及转化率和反应速率的影响。结果表明,以MMA为壳层单体的聚合体系是较理想体系。当AC用量从1g增加到8g时,以St为壳层单体体系的最终转化率从96.2%下降到74.2%,以MMA为壳层单体体系的最终转化率基本不变,保持在96%左右。但AC的加入使以MMA为壳层单体体系的反应速度最大值的出现时间推后了10min,且其值仅为未加入AC体系的1/2左右。 相似文献
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以水蒸气作为物理发泡剂,对高熔体强度聚丙烯(HMS-PP)进行挤出发泡。在实验中,通过改变水蒸气压力以及卸压速率研究泡孔的结构和分布,分析压力、卸压速率对发泡体结构和性能的影响。实验结果表明:当水蒸气压力为1.5 MPa,卸压速率为77.8 MPa/s时,可以获得发泡均匀、泡孔密度大、表观密度小的PP发泡制品。得到的泡孔平均直径为0.48 mm,发泡倍率约为12。 相似文献
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采用注射成型工艺制备了热塑性弹性体(TPEE)发泡材料。研究了发泡剂用量、发泡温度以及注射压力对TPEE发泡材料性能的影响。采用万能力学试验机和扫描电子显微镜(SEM)分别测试和观察了TPEE发泡材料的力学性能和泡孔结构,并测试了TPEE发泡材料的表观密度。试验结果表明:TPEE发泡材料的材料性能与发泡剂用量之间的关系为非线性关系;一定的发泡温度可以影响发泡材料的表观密度,进而影响材料的力学性能;注射压力在一定程度上影响发泡剂的发泡倍率,对发泡材料的性能以及外观产生一定的影响。在发泡剂用量为4.5份、注射温度185℃、合模时间200 s、注射压力40 MPa、注射速度30 g/s的条件下,能够得到综合性能比较理想的发泡材料。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
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. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
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. 相似文献
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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. 相似文献
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Peter A. Edwards Grant Striemer Dean C. Webster 《Journal of Coatings Technology and Research》2005,2(7):517-527
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. 相似文献
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Dongjiang Yang Yao Xu Lei Zhang Shangru Zhai Dong Wu Yuhan Sun 《Journal of Coatings Technology and Research》2006,3(2):127-131
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. 相似文献