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排序方式: 共有59条查询结果,搜索用时 31 毫秒
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Char-forming property of PU rigid foams, which can be assessed by char residue (%) when PU is burned at certain temperature, was studied by TG and DTG. The results showed that pure PU rigid foam had low char residue of only 17%, while 33% of char residue was achieved when PU rigid foam was modified by adding 8 wt% of 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2,2,2] octane (PEPA), which is a caged bicyclic phosphate. The experiment results of FTIR and XPS showed that the PEPA modified PU rigid foam could be dehydrogenated and dehydrated at temperature between 380 and 450 °C, resulting in the increase of char residue of PU rigid foam. Further study also revealed that the addition of CaCO3 nanoparticles could enhance the char stability when the PEPA modified PU rigid foam was being burned. The mechanism was investigated and it was found that the enhanced char stability could be attributed to the limited permeation of oxygen caused by the formation of calcium phosphate and calcium pyrophosphate by the reaction of PEPA and CaCO3 at high temperature, which were covered on or buried in the char layer. 相似文献
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This study was focused on evaluating the suitability of a wide range of lignins, a natural polymer isolated from different plant sources and chemical extractions, in replacing 20 wt.% of petroleum-based polyol in the formulation of PU flexible foams. The main goal was to investigate the effect of unmodified lignin incorporation on the foam’s structural, mechanical, and thermal properties. The hydroxyl contents of the commercial lignins were measured using phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, molar mass distributions with gel permeation chromatography (GPC), and thermal properties with differential scanning calorimetry (DSC) techniques. The results showed that incorporating 20 wt.% lignin increased tensile, compression, tear propagation strengths, thermal stability, and the support factor of the developed PU flexible foams. Additionally, statistical analysis of the results showed that foam properties such as density and compression force deflection were positively correlated with lignin’s total hydroxyl content. Studying correlations between lignin properties and the performance of the developed lignin-based PU foams showed that lignins with low hydroxyl content, high flexibility (low Tg), and high solubility in the co-polyol are better candidates for partially substituting petroleum-based polyols in the formulation of flexible PU foams intended for the automotive applications. 相似文献
4.
Excimer laser polymer ablation: twenty years on 总被引:7,自引:0,他引:7
P.E. Dyer 《Applied Physics A: Materials Science & Processing》2003,77(2):167-173
Research and development in excimer laser polymer ablation has been actively pursued for some twenty years, driven by interest
in the basic science as well as by numerous applications that have emerged for this high-resolution technique for material
removal. This paper reviews some of the basic mechanistic aspects of the UV laser–polymer interaction as a prelude to dealing
with practical matters related to polymer processing by ablation. Applications in micro-machining and potential areas for
future research are briefly covered.
Received: 7 October 2002 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1482/465-606, E-mail: p.e.dyer@hull.ac.uk 相似文献
5.
Zhiqin Peng Yoichiro Yoshida Sachiko Sukigara 《Journal of Polymer Science.Polymer Physics》2010,48(1):1-14
A novel macro/nano blended nonwoven with excellent physical properties was prepared by electrospinning polyurethane (PU) nanofibers onto the surface of ramie webs under different weight ratios of N,N‐dimethylacetamide (DMAc)/acetone cosolvents. The ratio of cosolvents has a significant influence on the morphology, tensile properties, resilience, and thermal properties of the resultant samples. Bead‐free and fine interconnected nanofibers were obtained with an increase of acetone content up to 60 wt%. The total physical properties of the blended nonwovens were optimal for a DMAc/acetone ratio of 40/60, in which the tensile load at break, extension at break and Young's modulus were 441, 54, and 256% higher than that of pure ramie web, respectively. The resilience of the blended nonwovens was ~20% higher than that of nonblended ramie web. The significant improvement of physical properties may be due to the good connection between PU nanofiber membranes and ramie webs and the molecular chain structure differences, interconnected structural differences, and high extensibility of PU nanofibers, according to the results of crystallization by differential scanning calorimetry (DSC) and morphological observation by scanning electronic microscopy (SEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1–14, 2010 相似文献
6.
Antibacterial thermoplastic polyurethane(TPU) electrospun fiber mats were prepared by adsorption of Ag nanoparticles(Ag NPs) onto TPU/3-aminopropyltriethoxysilane(APS) co-electrospun fiber mats from silver sol. The use of APS can functionalize TPU fibers with amino groups, facilitating the adsorption of Ag NPs. The effects of p H of silver sol and APS content on Ag NP adsorption and antibacterial activity were investigated. Ag NP adsorption was evidenced by TEM, XPS and TGA. Significant Ag NP adsorption occurred at p H = 3-5. The main driving force for Ag NP adsorption is electrostatic interaction between ―NH3~+ of the fibers and ―COO-derived from the ―COOH group capped on the surfaces of Ag NPs. The antibacterial activity of the Ag NP-decorated TPU/APS fiber mats was investigated using both gram-negative Escherichia coli and gram-positive Bacillus subtilis. The antibacterial rate increases with increasing APS content up to 5% where the antibacterial rates against both types of bacteria are over 99.9%. 相似文献
7.
Synthesis and Characterization of Polyurethane/Poly (Urethane Modified Bismaleimide-Bismaleimide) IPNs 总被引:1,自引:0,他引:1
Themethodofblendingbyinterpenetratingpolymernetworks(IPNs)isoftenusedtoobtainelastomerswithpropertiesinexcessofthoseexhibitedbytraditionalblendingways'.Inthispaper,aseriesofnovelpolyurethane/poly(urethanemodifiedbismaleimide-bismaleimide)(PU/P(UBMI-BMI))IPNsweresynthesizedandcharacterizedby'HNMR,FTIR,TEM,andTGAanaIysis.BMIwassynthesizedasfollowsfUBMlwasintroducedtomodifythecompatibilityofthetwonetworks,whichwassynthesizedasfollows:Where(l)ishydroxyl-terminatedpoly(diethyleneadipa… 相似文献
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10.
聚氨酯与铁电陶瓷粉复合物的电致感应性能研究 总被引:4,自引:0,他引:4
利用双辊制备了一系列热塑性弹性体聚氨酯(PU)和铁电钛酸锆酸铅盐(PZT)的电感应PZT/PU复合物。X-衍射和SE镜结果显示,复合物中,在铁电相中PZT陶瓷粉呈现结晶态并且均匀分布在PU基体中,复合物的弹性模量和相对电容率随着复合物中PZT体积分数增加而升高,在高压电场下,低PZT含量的复合物呈现负的电致伸缩应力,当PZT体积分数增加到6%以上时,在某个临界电场下,复合物呈现出电致伸缩应力反转的特性,即电致伸缩应力从负转变为正,并且发生应力反转的临界电场随着复合物中PZT体积分数的增加而降低,PU的电致伸缩特性与PZT在高电场下极化反转效应结合,导致了PZT/PU复合物这种有趣的性能,因此PZT/PU复合物将在高电压场方面作为传感器开关材料得到广泛应用。 相似文献