LDPE熔融接枝纳米SiO2协同增韧PPS的研究

采用熔融接枝共混法制备PPS基纳米复合材料。熔融接枝改性的纳米S iO2粒子在PPS中形成界面粘接较好的S iO2-LDPE核壳包覆结构以及微纤网络结构,使PPS结晶温度显著提高、晶粒细化、结晶度降低。包覆结构、微纤网络结构的形成和结晶特性的变化对PPS的增韧效果显著,使复合材料冲击强度高达85.1 kJ/m2(纯PPS的3.7倍)。     

Modern advances in bismaleimide resin technology: A 21st century perspective on the chemistry of addition polyimides

The chemistry of bismaleimides (BMIs), their blends and copolymers is reviewed critically with particular emphasis placed on the development of the field after 1990, which was marked by several comprehensive review articles. A general introduction to the structure property relationships of BMIs is presented, outlining the development of the preparative chemistry, and the early strategies adopted to address the inherent brittleness of the cured ‘first generation’ BMI polymers. ‘Second generation’, diallylbisphenol-toughened BMIs, form the basis of the benchmark commercial systems, and the polymerization mechanism is discussed. The current review is placed in context, addressing the issues of cost, processing and precursor toxicity, the major barriers to wider acceptance of BMIs. The main body of the review evaluates a number of observations made by Dr Horst Stenzenberger in 1990, for the future development of BMI technology. Hence, the synthesis of novel bismaleimide building blocks, incorporation of new thermoplastics and additives, and blending with new thermosetting comonomers are all discussed in detail. The aforementioned review had been written before the concept of nanocomposites or smart polymers had been explored with BMIs, but the fields have since grown (especially in the case of the former topic) and are reviewed herein. The application of BMIs to continuous fibre composites is one of the proposed fields of commercial development. The topic falls a little beyond the scope of the present review of BMI chemistry, and is the subject of another publication, but a brief discussion of the most recent developments is presented. The review is concluded with some thoughts about the future outlook for BMI chemistry.     

硫化胶粉／PP共混材料的研究

研究了硫化胶粉／PP共混体系的力学性能，流动性能和热变形温度等。结果表明，利用硫化胶粉可以明显改善PP的冲击性能，而且胶粉粒径越小，改善的效果越显著，但共混体系的拉伸强度有所下降。胶粉含量在5％－15％时，共混体系的综合性能较好。     

核壳结构PMMA纳米微球增韧R-PVC/CPE

研究了核壳结构聚甲基丙烯酸甲酯（PMMA）纳米微球对硬质聚氯乙烯/氯化聚乙烯（R-PVC/CPE）体系的增韧和增强作用及其对加工流变性的影响。研究发现，核壳结构PMMA纳米微球与R-PVC/CPE基体在适当配比下共混，在显著提高基体的冲击强度的同时，拉伸强度、伸长率和加工流变性也有改善。     

Pseudoplastic deformation pits on polished ceramics due to cavitation erosion

In a previous study, pseudoplastic deformation pits created by cavitation exposure were reported in silicon nitride and zirconia. In this research, further comparison of the size and number of pits between several silicon nitride and zirconia materials is carried out. The pits are larger and much more numerous in silicon nitride than in zirconia although silicon nitride is harder than zirconia. An explanation of this phenomenon is given. Also, in the previous study it was reported that apparently a partially stabilized zirconia with yttria oxide developed a delay in the phase transformation from tetragonal to monoclinic after being exposed to cavitation. In this research, further experiments related with this phase transformation delay are carried out. Also, the phase transformation is verified with X-ray diffraction analysis. It is concluded that the “activation” of the partial stabilized zirconia happens regardless of the oxide used to stabilize it.     

环氧化天然橡胶增韧聚氯乙烯力学性能研究

对环氧化度为50％的环氧化天然橡胶（ENR－50）增韧聚氯乙烯（PVC）体系的力学性能进行了研究，并分析了防老剂4010与增塑剂DOP对PVC／ENR增韧体系性能的影响。结果表明：ENR有较好的增韧效果，且对PVC的强度影响不大；DOP既可增塑也可增韧，但DOP的加入将影响ENR对PVC的增韧作用；防老剂4010可阻止ENR的老化，改善PVC／ENR－50共混物的性能。     

Toughening of polyamide 11 via addition of crystallizable polyethylene derivatives

BACKGROUND: Conventional rubber‐like toughening modifiers are soft and amorphous, and when used to toughen polyamide 11 (PA11) they commonly induce a decrease in the tensile strength and modulus. In this study, crystallizable polyethylene (PE) derivatives, i.e. linear low‐density polyethylene (LLDPE) and maleic anhydride‐grafted polyethylene (PE‐g‐MA), were adopted to toughen PA11. RESULTS: Compared to pure PA11, a highest improvement by a factor of eight in the impact toughness was achieved; also, the tensile strength and modulus could be maintained at a relatively high level. PE‐g‐MA acted as a compatibilizer for PA11 and LLDPE, bringing strong interfacial adherence, and especially a domain‐in‐domain morphology observed in PA11/PE‐g‐MA/LLDPE (70/10/20 by weight) blends. The observation that PA11 was toughened by the crystallizable PE derivatives is discussed in depth, based on the combined effect of surface crystallization of LLDPE on pre‐formed PA11 crystallites and interfacial compatiblization between PA11 and PE‐g‐MA. CONCLUSION: The crystallizable PE derivatives LLDPE and PE‐g‐MA were shown to be effective toughening modifiers for the proportions PA11/PE‐g‐MA/LLDPE 70/10/20 (by weight), which is considered to be an optimum composition: special domain‐in‐domain morphology was observed indicating a good dispersion of PE in the PA11 matrix and strong interfacial adherence between PE phase and PA11 phase. The reason why strength and modulus were maintained at a high level in the as‐prepared blends was attributed to the existence of rigid crystalline domains in PE. Copyright © 2009 Society of Chemical Industry     

EFFECT OF HEAT-TREATMENT ON THE MECHANICAL PROPERTIES OF AIN/SICw(Y_2O_3+SiO_2)COMPOSITE

In the paper, the effect of heat-treatment on thestrength and toughness of AlN-SiC whisker composites with Y_2O_3+SiO_2 additives have been studied. When the sample contining 10wt%Y_2O_3+SiO_2(Y_2O_3/SiO_2=1/0. 66) was treated at 1330℃ in air for 140hours,the flexural strength of composites was raised from 481 MPa to784 MPa the toughness was also enhanced slightly. The phase composi-tion microstructure and grain boundary phase structure have been char-acterized by combining XDR, SEM, TEM/EDXA and HREM tech-niques. reinforcenent and toughening mechanism of the composites re-sults from the crystallization of glass phase in the grain boundary atthe high temperature oxidizing atmosphere to form the crossing struc-ture of 2H°sialon fibrous phase and SiC whisker     

某些结构钢科学研究的进展

本文通过作者长期从事的一些特殊用途结构鋼科学研究概况,阐述了这个工程技术体系结构鋼研究发展过程和发展趋势。其中包括建立符合國内資源条件的新鋼种研究,以及通过研制和采用新材料和新技术等多种途径提高鋼的力学性能的研完。这些研究的各方面都不断取得新的进展和成就。     

Al2O3/SiC纳米复相陶瓷断裂韧性的研究

采用平均粒径为20 nm和150 nm的SiC粉作为增强相，基体粉为亚微米的Al₂O₃粉(美国)，在1 550～1 750 ℃无压烧结，制备了Al₂O₃/SiC纳米复相陶瓷并对其显微结构和断裂韧性之间的关系进行了研究.结果表明，当采用20 nm SiC粉作为强化相，加入量为3%时，断裂韧性从3.0 MPa·m^1/2提高到6.67 MPa·m^1/2，增加122.5%，材料的相对密度达到98.7%以上.利用SEM观察其显微组织，发现组织中若干个细小的晶粒组成一个单元体，单元体内各晶粒之间结合牢固，这种微观结构有利于Al₂O₃/SiC纳米复相陶瓷韧性的提高.而细晶增韧是重要增韧机理之一.