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总结了高分子材料加工的发展趋势及发展历程,并指出过去很多加工新技术的出现都得益于从自然现象及其他材料行业中获得很好的借鉴,如从蜘蛛吐丝发展出溶液纺丝成型、从玻璃吹制发展出吹塑成型、从金属锻造发展出压延成型及固相拉拔成型等;随后针对生物基可生物降解的立构复合型聚乳酸难以采用传统熔融加工方法成型的问题,借鉴金属粉末冶金加工的思路,提出了一种通过低温烧结制备高性能立构复合型聚乳酸制品的新方法.通过这种加工方法不仅可以有效解决立构复合型聚乳酸在熔融加工过程中熔体稳定性差、易降解的问题,而且可以制得耐热性好、光学透明度高、耐水解降解性佳、综合力学性能优异的高性能聚乳酸制品. 相似文献
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明胶/聚乳酸复合纤维膜的制备、表征及作为角膜细胞载体的评价 总被引:1,自引:0,他引:1
利用静电纺丝技术制备了明胶与聚乳酸的复合纤维膜, 研究了组分配比对复合膜的表面性能、孔隙结构和力学性能的影响, 并以复合膜为组织工程支架进行兔角膜上皮细胞的体外培养. 采用扫描电子显微镜、免疫荧光染色和噻唑蓝四氮唑溴化物(MTT)比色法综合评价了细胞在支架表面的黏附与增殖能力. 结果表明, 纺丝溶液的组分对纤维的直径分布和表面亲水性有显著影响, 不同组分配比的复合纤维膜均具有高孔隙率的通孔结构; 以明胶为基材可维持复合膜的细胞黏附性; 与聚乳酸复合可以明显提高复合膜的力学性能. 相似文献
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采用毛细管流变仪研究低于表观熔点的过冷聚丙烯熔体的流变学行为.过冷聚丙烯熔体先经过一段诱导期后,熔体发生凝胶化,剪切黏度在短时间内大幅度升高,最终固化结晶.在诱导期中,过冷聚丙烯熔体的流变行为与高于聚丙烯熔点的常规熔体的流变行为相仿.诱导期的长度与温度有关.在160℃下,诱导期的长度足够长,于是使用过冷聚丙烯熔体进行纺丝加工成为可能.实验结果表明,由过冷熔体制备的初生纤维各项性能与由高温熔体制备的初生纤维亦相似,因此,通过降低喷丝头温度的方法发展一种节能降耗的聚丙烯纤维制造技术有潜在的可能性. 相似文献
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热塑性塑料熔体质量流动速率测量不确定度的评定 总被引:1,自引:0,他引:1
以聚乙烯为例讨论了热塑性塑料熔体质量流动速率测量不确定度的来源,依据JJF 1059-1999对熔体流动速率测试过程中的测量不确定度分量进行了分析和评定。7149型聚乙烯熔体质量流动速率测量结果的扩展不确定度为0.096 g/(10 m in)。 相似文献
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聚乳酸/羧基化聚丙烯共混物的形态与热性能研究 总被引:1,自引:0,他引:1
以扫描电子显微镜、热重分析仪、差示扫描量热仪、热台偏光显微镜分别研究了聚乳酸/羧基化聚丙烯共混体系的相形态、热性能和结晶形态.结果显示,共混物熔体冷却时,聚乳酸和羧基化聚丙烯均形成球晶,但羧基化聚丙烯球晶较大而十字消光较暗,聚乳酸球晶尺寸较小而十字消光较亮,且聚乳酸球晶产生规则的、不连续的同心环线——裂纹,裂纹厚度约为1~2μm,且裂纹内部有微纤存在.当聚乳酸含量≤50%时,由于聚丙烯上羧基的存在而使共混体系具有较好的相容性.共混物的热分解过程分为三个阶段,热分解温度的变化是聚丙烯上的羧基、聚乳酸和聚丙烯骨架分解三种机制共同作用的结果,少量聚乳酸能够明显提高共混物中聚丙烯上羧基的热稳定性.共混物中的羧基化聚丙烯组分可以发挥稀释剂的作用,大幅度降低了聚乳酸的冷结晶温度.聚乳酸含量≥50%时,共混熔体降温时DSC谱图中聚乳酸和羧基化聚丙烯分别结晶,而聚乳酸含量<50%时,只观察到羧基化聚丙烯的结晶行为. 相似文献
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对比研究了熔体旋淬和常规熔铸Ml(NiCoMnAl) 5 贮氢合金的组织结构和电化学特性。SEM和XRD分析表明 :熔体旋淬合金为细小的柱状晶粒组成 ,随着旋淬速度的增加 ,晶粒越来越细小 ,成分越来越均匀 ;它们的晶体结构和铸态一样 ,都为CaCu5 型六方晶体结构 ;随着旋淬速度的增加 ,晶粒主要按 (111) [111]择优取向生长。电化学测试表明 :旋淬态合金电极初始容量都大于 2 10mAh·g - 1 ,活化性能好 ,经两次充放电循环 ,就可达到最大放电容量。旋淬速度 10m·s- 1 的合金电极的最大放电容量 (2 94mAh·g- 1 )与铸态合金电极的最大容量相当 ,所有旋淬速度的合金电极充放电循环稳定性优于铸态合金电极。在 6 0 0mA·g- 1 电流密度下 ,旋淬速度 10m·s- 1 的合金电极充电 45min就能达到其最大容量的 6 5 %左右 ,具有较好的高倍率充放电能力 ,但随着循环次数的增加 ,它的容量稳定性稍次于旋淬速度 40m·s- 1 的合金电极。 相似文献
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P. L. Carr R. Jakeways J. L. Klein I. M. Ward 《Journal of Polymer Science.Polymer Physics》1997,35(15):2465-2481
The concept of the drawing of a molecular network has been employed to derive a total network draw ratio from the combination of the two deformations occurring in the production of poly(butylene terephthalate), PBT, fibers by the consecutive processes of melt spinning and cold drawing. The mechanical properties of PBT can then be more readily explained in terms of increases in this total network draw ratio. However, the preorientation and crystallization that occurs in the melt-spinning process can occur at different strain rates and temperatures, depending on the wind up speed employed, on the extensional viscosity of the polymer, and on the variation of the extensional viscosity with temperature. Therefore, for polymers such as poly(butylene terephthalate), which can exist in two crystalline forms, the morphology of the final drawn fiber might be expected to depend on the first melt-spinning stage of the process as well as on the total network draw ratio. In this work, density, birefringence, mechanical measurements, and WAXD measurements, which have been made on the melt-spun fibers and on the drawn fibers, are described. Small differences in some of the drawn yarn mechanical properties at the same overall network draw ratio are related to the crystallinity and in particular to differences in the proportion of the α and β phases present in the drawn yarn. These in turn are related to differences in the temperature and stress during melt spinning and drawing. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2465–2481, 1997 相似文献
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Suong-Hyu Hyon Fengzhe Jin Khosrow Jamshidi Sadami Tsutsumi Tetsuo Kanamoto 《Macromolecular Symposia》2003,197(1):355-368
The hydrostatic molecular orientation technique was used to explore the highest mechanical improvements achievable for poly-L-lactide (PLLA). The mechanical attributes of these materials designed for bone fracture fixation devices, i.e. bending strength and modulus were measured and compared with those prepared by stretching method. The starting samples were prepared by conventional melt extrusion at 200 °C followed by hydrostatic extrusion at 140 °C using glycerin filled extruder. Uniaxially stretched rods were prepared by drawing in silicon oil at 120 °C. The physical properties of these rods are inadequate as mechanical supports in the dynamic healing process of the bone. Moreover, they underwent a marked strength deterioration when immersed in aqueous buffered solution for 90 days. On the other hand, the hydrostatic extrusion technique produced rods with progressively higher bending strength that showed only a small drop after 90 days hydrolytic degradation. Micrographs suggested a superior molecular orientation and packing, which could be associated with the improved performance. The hydrostatic extrusion technique proved to be a safe and effective approach for strengthening biodegradable polymeric materials for dynamic mechanical support in orthopedic medical devices. 相似文献
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Waleed E. Mahmoud 《European Polymer Journal》2011,47(8):1534-1540
Organic–inorganic hybrids are artificially created structures presenting novel properties not exhibited by either of the component materials alone. In this contribution one addresses processing, morphology and properties of polymer nanocomposites reinforced graphene. First, synthesis routes to graphite oxide (GO) and foliated graphene sheets (FGS) are illustrated. Physical characterization of these graphene sheets were conducted using atomic force microscopy and X-ray diffraction techniques. Processing, structure and properties of graphene/poly(ethylene oxide) (PEO) nanocomposites are discussed. FGS was dispersed into PEO via two different composite manufacturing techniques: melt compounding and solvent mixing. Morphology of dispersed graphene and properties from different blending routes are compared. TEM showed that graphene distributed parallel to the composite surface using solvent method, while distributed randomly in melt blended method. Optical measurements indicated that the transparency of PEO/graphene prepared by solvent method is higher than that of melt blended method in the visible region. Electrical conductivity measurements are employed to evaluate threshold concentration for rigidity and connectivity percolation. The percolation concentration of the composites prepared by solvent method is less than those of melt blended method. The mechanical performance of the composites prepared by solvent method is higher than melt blended. Halpin–Tsai model has been used to confirm the distribution of the graphene into PEO by the two different processing techniques. 相似文献
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We report a melt-spinning spark-plasma-sintering synthesis process of the polycrystalline p-type material composed of AgSbTe2 coarse grains and evenly formed 5-10 nm pores that occur primarily on the surface of matrix grains. The formation mechanism of nanopores and their influences on the thermoelectric properties have been studied and correlated. Microstructure analysis shows that the as-prepared sample can be regarded as a nanocomposite of matrix and in situ generated nanopores evenly coated on matrix grains. For the single-phase component and the possible energy-filter effect caused by the nanopores, the electrical transport properties are improved. Moreover, the thermal conductivity is significantly reduced by strong phonon scattering effect resulted from the nanopores. The thermoelectric performance of the as prepared sample enhances greatly and a ZT of 1.65 at 570 K is achieved, increasing∼200% compared with the sample prepared by traditional melt and slow-cooling method. 相似文献
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<正>Syndiotactic polypropylene(sPP) as-spun fiber(sPP1) and drawn fiber(sPP2) were prepared by melt-spinning and melt-spinning/hot-drawing,respectively.The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy(FTIR),wide-angle X-ray diffraction(WAXD) and tensile testing.The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature (40℃).With increasing the annealing temperature,the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension.Upon removing the tension,a small amount of mesophase and trans-planar conformation will be regained.The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature. 相似文献
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In this work, a new kind of aliphatic polyesteramide (PEA) copolymer based on -caprolactone and 6-aminocaproic acid was synthesized by the melt polycondensation method. Biodegradable PEA fibers were processed by the melt-spinning method. 1H-NMR, FTIR, SEM, and tensile testing were used to characterize the degradation of PEA fibers in concentrated alkaline solution. The PEA fiber undergoes surface erosion in such concentrated alkaline solutions. 相似文献
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A study on thermoplastic polyurethanes (TPU) is described. The investigation focuses on morphology of TPU parts depending on processing conditions and its relation with mechanical and thermal properties. It was found that TPU materials present different crystalline structures depending on chemical composition and melt processing conditions during part manufacturing. Due to that fact, strong variations in mechanical and tribological properties are expected. 相似文献
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Zuzana Jakubíková Marek Liška Alfonz Plško Jana Pagáčová 《Journal of Thermal Analysis and Calorimetry》2012,108(2):493-496
The filter dust from the container glass production was studied by the X-Ray powder diffraction, differential thermal analysis (DTA), X-Ray fluorescent spectroscopy, and Raman spectroscopy. The analysis of the elemental composition indicated that the major portion (≈96 wt%) of filter dust is comprised of sulfates. Predominant abundance of sodium sulfate was confirmed by comparative DTA of investigated filter dust. The characteristic redox property (COD—Chemical Oxygen Demand) was determined. The raw materials used in manufacturing of container glass in Vetropack Nem?ová with 0, 25, 50, 75 or 100 wt% of filter dust as a substitution of sulfate raw material were used for the preparation of samples of glass batch. Thermal properties of prepared samples were characterized by means of DTA. The substitution of sulfate raw material by filter dust does not significantly affect the thermal properties of the examined glass batches and consequently the course of the glass melting. 相似文献
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N-羧丙酰壳聚糖钠增强改性壳聚糖棒材 总被引:2,自引:0,他引:2
采用原位沉析法制备N-羧丙酰壳聚糖钠增强改性的三维壳聚糖复合棒材, 并用傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、热重(TG)分析、扫描电镜(SEM)以及力学性能测试等方法研究复合棒材结构与性能之间的关系. FTIR分析表明, 壳聚糖分子中的氨基官能团和乙酰氨基官能团均与N-羧丙酰壳聚糖钠分子中的羧酸盐官能团发生强烈的静电相互作用. 加入N-羧丙酰壳聚糖钠后: 两种分子间产生强烈的静电相互作用, 限制了大分子链的运动, 使得大分子链趋于刚性, 同时复合棒材的层状叠加结构变得更加紧密, 提高了复合棒材的热稳定性与力学性能; 大分子链的刚性增强, 限制了分子链排入晶格, 从而降低了壳聚糖的结晶度. 当复合棒材中含有15% (w)的N-羧丙酰壳聚糖钠时, 其弯曲强度和弯曲模量可达156.0 MPa、5.3 GPa, 与纯壳聚糖棒材相比, 分别提高了68.8%、29.3%.因此, N-羧丙酰壳聚糖钠可有效地增强改性三维壳聚糖棒材, 该三维复合物棒材有望用作骨折内固定材料. 相似文献