固化工艺规范对复合材料固化残余应力影响的实验研究

单束纤维拉伸法是以简单的单束纤维聚合物基复合材料结构为研究对象,研究固化工艺过程中树脂体积变化与纤维上残余应力之间的关系.同时固化过程中树脂体积是随工艺温度变化而产生变化的,经理论分析及计算得到了固化工艺温度历程对纤维上固化残余应力的影响规律.     

浅析同条件养护试件留置、养护与评定

着重阐述新修订的国家标准《混凝土结构施工质量验收规范》GB50204-2002中同条件养护试件的留置、养护与评定.     

Polymerization shrinkage and porosity profile of dual cure dental resin cements with different adhesion to dentin mechanisms

This research aims to probe the porosity profile and polymerization shrinkage of two different dual cure resin cements with different dentin bonding systems. The self‐adhesive resin cement RelyX U200 (named RU) and the conventional Allcem Core (named AC) were analyzed by x‐ray microtomography (μCT) and Scanning Electron Microscopy (SEM). Each cement was divided into two groups (n = 5): dual‐cured (RUD and ACD) and self‐cured (RUC and ACC). μCT demonstrated that the method of polymerization does not influence the porosity profile but the polymerization shrinkage. Fewer concentration of pores was observed for the conventional resin cement (AC), independently the method used for curing the sample. In addition, SEM showed that AC has more uniform surface and smaller particle size. The method of polymerization influenced the polymerization shrinkage, since no contraction for both RUC and ACC was observed, in contrast with results from dual‐cured samples. For RUD and ACD the polymerization shrinkage was greater in the lower third of the sample and minor in the upper third. This mechanical behavior is attributed to the polymerization toward the light. µCT showed to be a reliable technique to probe porosity and contraction due to polymerization of dental cements.     

固化度与固化收缩对非对称复合材料层合板固化变形的影响

采用三维有限元方法研究复合材料非对称层合板在热载荷和固化收缩载荷下的固化变形情况, 建立了材料力学特性、 固化体积收缩量和温度与固化度之间的函数关系, 考察了层合板变形曲率与温度和固化度之间的关系。数值计算结果表明: 非对称层合板变形曲率与固化终止时固化度有密切关系; 固化变形主要发生在降温阶段; 固化收缩对层合板变形曲率影响很小, 主要发生在第二个保温平台的前半段。      

特厚煤层综放开采瓦斯综合防治技术分析

为了防治厚煤层综放开采时工作面瓦斯超限问题,保证高产高效矿井建设顺利进行,根据开滦唐山矿业分公司厚煤层综放开采瓦斯涌出情况,研究分析了瓦斯来源及涌出规律,采取了有针对性的综合防治技术措施,如优化巷道布置,合理配风,打钻泄放瓦斯,综合瓦斯抽放,瓦斯监测系统等,取得了明显的治理效果．     

论西部大开发中的荒漠化防治

分析了西部环境脆弱的表现之一是土地荒漠化，其面积占全国荒漠化总面积的72.79%，且其治理速度远小于扩展速度。荒漠化主要是诸如五滥行为等人类非理性活动的必然结果。它破坏生产力、基础设施和生态平衡，给人们造成严重的生命财产损失。必须在西部大开发中，正确处理开发与荒漠化防治的关系，其防治要做到制度化、法制化、市场化和科学化。     

Failure analysis of anticorrosion plastic alloy composite pipe used for oilfield gathering and transportation

Incident involving failures of anticorrosion plastic alloy composite pipe which was used for oilfield gathering and transportation had caused serious burst after several years of usage. Investigations were performed to identify the most probable causes of the pipe failures. The study was conducted by reviewing the background of the incident, inspecting visual physical morphology of the failed pipe, analyzing FTIR spectra and TG–DSC curves of inner plastic alloy and outer GRP resin. Results revealed that additives in damaged plastic alloy may not be stirred enough before extrusion or the content of additives may exceed their normal range. The lower degree of cure for resin of GRP layer leads to decrease of glass transition temperature as well as its thermal stability, which will make the outer GRP structural layer have a relatively lower mechanical property, thus giving rise to final failure of the composite pipe under the long time service conditions.     

In Situ Forming Hydrogel Based on Chondroitin Sulfate–Hydroxyapatite for Bone Tissue Engineering

In this research, tissue engineered hydrogels consist of chondroitin sulfate and hydroxyapatite capable of light curing and cell encapsulation were prepared. Chemical and physical characteristics were analyzed by FTIR spectroscopy, compressive strength and water uptake measurements. Observations with fluorescence microscopy as well as MTT viability assay revealed no toxicity for encapsulated cells. Moreover, alkaline phosphatase activity, calcium deposition, and gene expression analysis were determined to prove the osteogenic potential of the prepared hydrogel. In conclusion, this in situ forming hydrogel can be utilized as filler for bone deficiencies as well as carrier for cell encapsulation and osteogenic differentiation.     

CURE OF PREPOLYMER BASED ON METHYL METHACRYLATE/STYRENE AND OPTICAL PROPERTY AND HYDROTHRMAL STABILITY OF TRANSPARENT FIBRE—REINFORCED THERMOPLASTIC COPOLYMER COMPOSITES

Copolymers used for transparent.fibre glass-reinforcedthermoplastic composite were prepared from methyl methacrylate(MMA)and styrene (St).Composites containing 20～25 wt% glassfibre and 0.7 mm in thickness had an overall optical transmission of 88～90%.The gel time and cure time of the prepolyners from MMAand St decreased markdly with addition of the two linear unsaturatedpolyesters(LUPE)and curing process of composite laminate becamecontrolling easily,The effect of the concentration of LUPE on thermalstability of copolymers.the optical properties and the hydrothermal sta-bility of composites was investigated by comparing with those of trans-parent unsaturated composites.     

氯化丁基橡胶和三元乙丙橡胶共交联的研究

本工作对氯化丁基橡胶(CIIR)和三元乙丙橡胶(EPDM)并用胶的共交联问题作了初步的探讨。重点进行了并用胶硫化体系的选择,试验结果表明在 CIIR/EPDM 并用胶的树脂硫化体系中,加入适量的硫黄和促进剂 TMTD可使并用胶的交联密度提高,物理—机械性能明显改善。通过中心合成设计试验法考察了树脂、硫黄和 TMTD 对并用胶料物理性能的影响。采用差示溶剂法和交联密度法测试了并用胶的共交联程度,结果表明 CIIR/EPDM 并用,选择适当的硫化体系可以实现共交联。