添加Y_2O_3的ZrO_2-Al_2O_3复相陶瓷力学性能的研究

采用工业ZrO2,Al2O3原料,以Y2O3作为稳定剂,通过适当的工艺制备出ZrO2 Al2O3复相陶瓷。研究结果表明,Y2O3添加量为3.5%(摩尔分数)的ZrO2基陶瓷中加入Al2O3可有效地抑制ZrO2晶粒的生长,有利于使ZrO2晶粒以亚稳四方相存在,从而提高材料的强度与断裂韧性。Al2O3含量为20%(质量分数)时,复相陶瓷的抗弯强度、断裂韧性分别为676.7和10MPa·m1 2,其值接近湿化学法制备的复相陶瓷的力学性能。相变增韧与颗粒弥散增韧作用相互叠加提高了复相陶瓷材料的力学性能。     

TPU共混增韧POM的研究

通过机械共混的方法制备了聚甲醛(POM)和热塑性聚氨酯弹性体(TPU)复合材料.考察了不同硬度TPU及其含量对共混材料韧性的影响.结果表明,TPU硬度的变化对共混材料的力学性能起着非常重要的作用,硬度为65HA的TPU对POM的增韧效果较好,对POM的相形态和结晶性能影响更为显著.     

Ce-TZP和Ce-TZP/Al_2O_3层状复合材料受载裂尖的相变特性

用云纹干涉法研究了带直通切口的Ｃｅ ＴＺＰ（Ｔｅｔｒａｇｏｎａｌ ＺｉｒｃｏｎｉａＰｏｌｙｃｒｙｓｔａｌ）和Ｃｅ ＴＺＰ／Ａｌ２Ｏ３层状复合材料三点弯曲梁的相变过程．实验发现１６００°Ｃ／３ｈ烧结１２％ｍｏｌＣｅＯ２稳定的Ｃｅ ＴＺＰ在室温下就具有强烈的自催化效应，直通切口前缘的相变区呈树枝状，Ｃｅ ＴＺＰ／Ａｌ２Ｏ３层状复合材料的自催化相变被Ａｌ２Ｏ３层抑制，切口前缘的相变区变短，且相变区的覆盖面积减小．文中最后对Ａｌ２Ｏ３层改变Ｃｅ ＴＺＰ相变区及力学性能的原因进行了讨论．     

Crack tip superblunting: experiment,theory and numerical simulation

Experimental revelation ofsuperblunting along plane strain predominant crack tip segment is reported here for modified polyproplene. As elucidated by a heuristic model of progressive circumferential cold-draw, the formation of superblunting crack tip depends critically on the ratio between the cold-draw propagation speed and the loading speed, and contributes significantly to the material toughening, especially for the improvement in impact toughness. Detailed numerical calculations are conducted based on a hyperelastic-viscoplastic and anisotropic damage constitutive model at finite deformation. The simulated results recapitulate the essential features of crack tip superblunting. The project supported by the National Natural Science Foundation of China     

The effect of T-stress on crack–inclusion interaction under mode I loading

A closed-form solution has been developed to predict the effect of T-stress on the crack–inclusion interaction. As validated by several numerical examples, the approximate solution has satisfactory accuracy for different inclusion shapes and modulus ratios between inclusion and matrix under different T-stress levels. Thus the role of T-stress in crack–inclusion interaction can be predicted quantitatively.     

Reactive Core-Shell Bottlebrush Copolymer as Highly Effective Additive for Epoxy Toughening

Herein,we designed a core-shell structured bottlebrush copolymer (BBP),which is composed of rubbery poly(butyl acrylate) (PBA)core and an epoxy miscible/reactive poly(glycidyl methacrylate) (PGMA) shell,as an epoxy toughening agent.The PGMA shell allows BBP to be uniformly dispersed within the epoxy matrix and to react with the epoxy groups,while the rubbery PBA block simultaneously induced nanocavitation effect,leading to improvement of mechanical properties of the epoxy resin.The mechanical properties were measured by the adhesion performance test,and the tensile and fracture test using universal testing machine.When BBP additives were added to the epoxy resin,a significant improvement in the adhesion strength (2-fold increase) and fracture toughness (2-fold increase in Klc and 5-fold increase in Glc)compared to the neat epoxy was observed.In contrast,linear additives exhibited a decrease in adhesion strength and no improvement of fracture toughness over the neat epoxy.Such a difference in mechanical performance was investigated by comparing the morphologies and fracture surfaces of the epoxy resins containing linear and BBP additives,confirming that the nanocavitation effect and void formation play a key role in strengthening the BBP-modified epoxy resins.     

ABS树脂研究进展

聚(丙烯腈-丁二烯-苯乙烯)三元共聚物即ABS树脂具有优异的机械性能、热稳定性能、耐化学性能、美学性能和加工性能等因而被广泛应用。本文综述了国内外ABS树脂的生产工艺和制备方法,指出了连续本体聚合法具有优势,但仍要与乳液聚合法长期竞争、共存,并重点阐述了ABS树脂的增韧改性用橡胶品种及其增韧机理,最后讨论了仪器化冲击试验机在高分子材料尤其是在ABS领域中的应用状况及前景,指出将显微技术与仪器化冲击手段结合可深层次地评价树脂材料的动态断裂过程与机理。     

Polyethylene‐poly(L‐lactide) diblock copolymers: Synthesis and compatibilization of poly(L‐lactide)/polyethylene blends

A model polyethylene‐poly(L ‐lactide) diblock copolymer (PE‐b‐PLLA) was synthesized using hydroxyl‐terminated PE (PE‐OH) as a macroinitiator for the ring‐opening polymerization of L ‐lactide. Binary blends, which contained poly(L ‐lactide) (PLLA) and very low‐density polyethylene (LDPE), and ternary blends, which contained PLLA, LDPE, and PE‐b‐PLLA, were prepared by solution blending followed by precipitation and compression molding. Particle size analysis and scanning electron microscopy results showed that the particle size and distribution of the LDPE dispersed in the PLLA matrix was sharply decreased upon the addition of PE‐b‐PLLA. The tensile and Izod impact testing results on the ternary blends showed significantly improved toughness as compared to the PLLA homopolymer or the corresponding PLLA/LDPE binary blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2755–2766, 2001     

Toughened polypropylene with balanced rigidity (I): preparation and chemical structure of toughening master batch

The title toughening master batch (TMB) was synthesized in a low‐viscosity reaction system by using dynamic vulcanization technique starting from polypropylene (PP) as the matrix resin and ethylene–propylene or butadiene–styrene elastomer as the toughening agent through a polymer–bridge conjunction derived from a monomer containing a carbonate group in the presence of a free radical initiator. The chemical structure of the TMBs and the effects of technological conditions on structural parameters were investigated using fractional extraction and infrared spectroscopy. The prepared TMBs consisted of unreacted PP, unreacted elastomers, graft copolymer of PP and/or elastomers containing branched chains formed by bridging agent, and crosslinked copolymer of PP and/or elastomers in conjunction with polymer bridge chains derived from bridging agent. Results showed that the PP existed in graft and crosslinked forms was in the range of 3–21 wt% and that of the elastomer toughening agent was in the range of 50–70 wt%, grafting and bridging efficiency of bridging agent was in the range of 62–88 wt%, graft copolymer content in the total TMB was in the range of 0.18–3.65 wt% and crosslinked copolymer content was in the range of 22–42 wt%. Copyright © 2000 John Wiley & Sons, Ltd.     

超高分子量聚乙烯／聚丙烯共混体系流变行为及形态的研究

超高分子量聚乙烯／聚丙烯共混体系流变行为及形态的研究汪晓东,励杭泉,金日光（北京化工大学高分子系,北京,１０００２９）关键词共混合金,线性互穿网络,双连续相,网络增韧机理通常聚合物的增韧机理是在树脂中引人柔性链段［１］形成复合物（如橡塑共混物）,这些...