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81.
A series of polyurethane microcapsules containing a phase change material (PCM) of n‐octadecane was successfully synthesized by an interfacial polymerization in aqueous styrene‐maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene‐2,4‐diisocyanate (TDI). The average diameter of microPCMs is in the range of 5–10 μm under the stirring speed of 3000–4000 rpm. Optical and SEM morphologies of microPCMs had ensured that the shell was regularly fabricated with the influence of SMA. FTIR results confirmed that the shell material was polyurethane and the SMA chains associated on core material reacted with TDI forming a part of shell material. The shell thickness was decreasing in the range of 0.31–0.55 μm with the molar ratio of DETA/TDI from 0.84 to 1.35 and the weight of core material increasing from 40 to 80% (wt %). By controlling the weight ratio of PCM as 40, 50, 60, 70, and 80% in microPCMs, it was found using DSC that the Tm and Tc of microPCMs were in the range of 29.8–31.0oC and 21.1–22.0°C and an obvious phase change had been achieved nearly the same temperature range of that of PCM. The results from release curves of microPCM samples prepared by 1.4, 1.7, and 2.0 g of SMA indicated the release properties were affected by the amount of the dispersant, which attributed to the emulsion effect and shell polymerization structure. The above results suggest that the shell structure of microPCMs can be controlled and the properties of microPCMs determined by shell will perform proper practical usage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4996–5006, 2006 相似文献
82.
Nelly RahmanApriyanti Isanasari Ririn AnggraeniSuharto Honggokusumo Masatoshi Iguchi Toru MasukoKohji Tashiro 《Polymer》2003,44(1):283-288
To investigate the mechanism of high elongation of natural rubber attained by the ‘racking method’, a strip of smoked-sheet was elongated up to 150 times in length, by stretching rapidly at room temperature and forcing to shrink at 75-80 °C repeatedly. On X-ray diffraction, a typical fibre pattern with an amorphous ring appeared already at ×10 (stretch ratio=10). The degree of crystallinity increased to the level of 17-18% at ×20 and turned to decrease after ×60, but the degree of crystallite orientation reached at a high level already at ×10 and did not change significantly and the half-height width of reflection profiles stayed almost at a constant level, while the Young's modulus increased up to ca. 300 MPa at ×100 and then fell rather discontinuously. It was assumed that some fractions of chain segments between entanglements were gradually broken in each step of stretching operation, rather than disentangled and slipped. 相似文献
83.
A series of short fibre reinforced styrene butadiene rubber (SBR) composites were prepared by incorporating sisal fibres of
different lengths and different concentrations. The vulcanization behaviour and the properties of the vulcanizates were measured
by the relevant ASTM procedures. The processing characteristics such as green strength and mill shrinkage were improved by
the addition of fibres. The properties like tensile strength, tear strength, moduli at 10% and 20% elongations were found
to be maximum for composites containing longitudinally oriented fibres of length 6 mm. Mixes containing 35 phr loading of
fibres and bonding agent showed better mechanical performance than others. The failure behaviour of tensile and tear specimens
have been analysed by scanning electron microscopy techniques.
Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995 相似文献
84.
This paper is the first part of a work devoted to the setting-up of a methodology for the mechanical behaviour characterization of rubber-like materials, using a digital speckle extensometer. We present here the experimental approach, specific to large strain measurements. The proposed method is based on in-plane kinematics measurements using an optical extensometer. The whole two-dimensional field of in-plane displacements is obtained by a digital image processing. We discuss then the correlation calculations and how to achieve the optimal subset matching. Next, we specify how to derive the principal stretch ratios, and the accuracy on these components, issued from a subsequent numerical calibration.Finally, we present experimental data dealing with a carbon black, filled natural rubber, issued from uniaxial traction tests, pure shear tests, and tensile tests performed on double-edge notched tensile specimens. 相似文献
85.
利用差示扫描量热仪、傅里叶红外光谱仪、广角X射线衍射仪研究了一种新型的以聚乙二醇为软段的聚氨酯相变储能材料。结果表明,当软段含量低于90%(质量分数,下同)时,即使温度高于聚乙二醇的熔点,此类材料仍不会熔化成液体,而表现出一种固-固相变行为。该聚氨酯储能材料相变焓较大,相变温度适中,且随着软段含量的减少,材料相变焓和相变温度呈递减趋势。其相变过程实质是聚氨酯软段聚乙二醇由结晶固态转变为无定形固态的过程。 相似文献
86.
87.
硅橡胶机械强度改进方法的研究 总被引:3,自引:0,他引:3
使用以硅橡胶为绝缘材料的新一代高压复合绝缘子是解决输变电线路污闪问题行之有效的方法,针对复合绝缘子用硅橡胶生产和运行中存在的主要问题,从添加补强材料白炭黑(最佳用量在35份左右)和改变硫化时间(最佳硫化时间8min)两方面入手进行试验,研究如何改善硅橡胶的机械强度尤其是抗撕裂强度。 相似文献
88.
影响喷气燃料与橡胶相容性的因素 总被引:5,自引:0,他引:5
采用几种具有不同初始物理性能及不同丙烯腈含量、不同硫化剂和硫化程度的丁腈橡胶,考察了其配方和物理性能对采用不同工艺条件生产的喷气燃料的相容性。结果表明,喷气燃料与橡胶的相容性不仅与喷气燃料的加工工艺有关,而且与橡胶的组成及其制备工艺有关。采用非加氢工艺生产的喷气燃料与橡胶的相容性好于采用加氢工艺(特别是加氢裂化工艺)生产的喷气燃料。橡胶材料的初始力学性能的好坏并不完全决定其与喷气燃料相容性的好坏,橡胶材料的耐过氧化物侵蚀能力才是影响相容性好坏的主要因素。橡胶的组成和其制备工艺决定了橡胶在喷气燃料中萃取物的数量和组成,不同萃取物的综合作用给相容性带来不同程度的影响。用硫作硫化剂的橡胶虽然原始强度低于用过氧化物作硫化剂的橡胶,但前者与喷气燃料的相容性却远好于后者。 相似文献
89.
A series of polyesters was prepared to evaluate hydrolytic stability as a function of cyclohexyl dibasic acid content. The
three cyclohexyl dibasic acids: 1,2; 1,3; and 1,4 were formulated into polyesters with two glycols. The proportion of cis
and trans isomers was evaluated via 1H NMR. The hydrolytic stability of short chain polyesters was evaluated in an acetone/water mixture which solubilized the
polyesters to mimic oligoester behavior within a thermosetting polyester coating environment. The rate of hydrolysis was monitored
by acid titration and corroborated by GPC. Surprisingly, 1,2-cylohexyl diacid-based polyesters were robust, and 1,3-cyclohexyl
diacid-based polyesters were the most susceptible to hydrolysis. Evidently, a 1,2-anchimeric effect for cyclohexyl dibasic
acid polyesters was not an important consideration, while the 1,3-cyclohexyl ester interaction was. Consequently, an anomeric
effect was proposed.
Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia,
PA. 相似文献
90.
A series of novel block polymers of polyurethane (PU) and chitosan have been prepared in two steps. The first step is the preparation of PU prepolymer, obtained from polytetramethylene oxide glycol (PTMO, Mn = 1000), isophrone diisocyanate (IPDI), and 2,2′-dimethylol propionic acid (DMPA), followed by ionizing PU prepolymer with triethylamine (TEA). The second step involves PU chain-extended by water-soluble chitosan of low molecular weight (Mn = 5000) by self-emulsion polymerization method. The sizes of the latex particles, morphology, and copolymer architecture have been characterized by dynamic light scattering (DLS), general tensile test, infrared spectroscopy (IR), surface contact angle measurement, and transmission electron microscopy (TEM). Furthermore, it shows that the addition of chitosan remarkably increases anticoagulative property of PU elastomers confirmed by the recalcification time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献