近熔点状态下聚乙烯在收敛流道模具连续挤出自增强

采用楔形收敛流道挤出口模，通过控制挤出成型工艺获得了聚乙烯自增强片材，研究了制品结构性能之间的关系，结果表明：聚乙烯自增强片材连续挤出成型存在成型温度窗口，在此成型温度窗口内，聚乙烯自增强连续挤出片材在平行于拉伸方向可以形成大量排列有序，取向程度很高的微纤结构，这些微纤结构成为片材的增强相，赋予片材以极高的纵向强度。     

在复合外场中形成HDPE双向拉伸自增强片材

采用具有复合外场的双向拉伸口模，实现了聚乙烯片材双向拉伸自增强，并对其片材的拉伸强度、结晶形态进行了研究。结果表明：HDPE双向拉伸自增强片材纵向和横向拉伸强度均有明显的增加，其内部结晶形态为平行串晶结构，正是由于生成了大量的平行串品结构，导致了双向拉伸自增强片材的强度的提高。揭示了材料的结构与性能之间的关系。     

临界状态下温度对挤出自增强PP片材结构性能的影响

采用楔形收敛流道挤出口模，临界挤出状态下获得了聚丙烯自增强片材。研究结果表明：PP自增强片材在此状态下挤出成型其纵、横向拉伸强度均有明显上升，其结晶形态为串晶互锁结构，而结晶的晶型与常规成型的PP片材相比则没有变化。     

聚乙烯在复合应力场中临界状态挤出成型的研究

采用具有复合应力场的双向拉伸挤出口模，在临界状态下成功制备了聚乙烯双向自增强片材。研究表明，制备的增强片材的纵横向力学性能均有明显提高，维卡软化点提高了21℃。微观测试表明，其晶态结构为串晶，正是由于片材内部生成了大量的串晶结构，才赋予了增强片材比较好的力学性能。     

计及界面损伤的纤维片材加固砼梁的弯曲破坏分析

对四点弯曲荷载作用下含微裂缝的纤维片材加固钢筋砼梁,建立一种计及梁中裂缝和纤雏片材与梁跨中界面发生损伤的分层剪滞模型,并采用复合材料力学中的细观统计破坏理论,研究了纤维片材断裂模式下的纤维应力重新分布和极限承载力,定量获得了纤维应力集中、纤维片材与砼梁之间的界面损伤区长度和极限承载力与界面剪切强度的关系.结果表明,应力集中随界面剪切强度的增加而增加;界面损伤区长度随界面剪切强度的增加而减小;极限承载力随界面剪切强度的增加是先增大后减小;适宜的界面黏结,极限承载力最高.     

复合拉伸力场挤出HDPE片材的力学性能

利用收敛-发散口模挤出制备了高密度聚乙烯(HDPE)片材,研究了挤出温度对片材力学性能的影响.结果表明:在复合拉伸力场作用下,熔态挤出(140℃)片材的纵、横向屈服拉伸强度分别为28.3,27.0MPa,固态挤出(112℃)片材的纵、横向屈服拉伸强度分别为181.4,51.3 MPa,纵、横向屈服拉伸强度分别增加了540%和90%.与固态挤出相比,熔态挤出片材纵、横向断裂伸长率分别增加了760%和124%.扫描电子显微镜显示,熔态挤出HDPE片材由球晶结构构成;固态挤出片材由大量垂直于挤出方向规整排列的片晶组成,并有少量的串晶生成,片晶厚度增加,这种结构有利于改善制品的双向力学性能.     

新型PVC片材的力学性能和阻隔性能的研究

采用微层挤出技术制备了微层PVC片材,采用涂覆法制备了多层PVC/PVA复合片材,对其力学性能和阻隔性能进行了研究。结果表明:①多层结构有利于提高PVC/PVA复合片材的阻隔性能,涂覆PVA溶液增大了片材的拉伸强度。②微层PVC片材的分子链发生取向,沿挤出方向的拉伸强度明显高于垂直挤出方向;微层PVC片材的层数越多,取向作用越强,越有利于阻隔性能的提高。     

PET聚酯非纤应用及进展

PET聚酯材料主要用于纤维生产，但它在非纤领域的应用越来越多，用量也不断增长。详述了PET聚酯瓶、聚酯薄膜、工程塑料以及PET片材等的主要应用情况，并介绍了聚酯非纤应用的最新研究和开发进展。     

玻纤增强PP热塑性片材的制备及力学性能研究

采用熔融浸渍法制备了玻璃纤维毡增强聚丙烯（PP）热塑性复合片材；通过在PP中加入复合改性PP改善了基体与增强纤维间的相容性；考察了相容剂、PP种类及玻纤毡种类对复合片材的影响。结果表明，相容剂的加入可使复合片材的拉伸强度提高29％、拉伸模量提高23％、弯曲强度提高42％、弯曲模量提高25％；高熔体质量流动速率PP可使片材的弯曲与冲击性能进一步改善。连续玻纤毡和长玻纤毡增强PP复合片材，前者综合力学性能良好，而后者则冲击强度较弱、弯曲性能加强。     

PLA/PBAT原位微纤复合材料的制备与性能研究

采用自制的多级挤出拉伸装置实现了聚乳酸(PLA)在聚对苯二甲酸-己二酸-丁二醇酯(PBAT)中原位成纤,并对PLA/PBAT原位微纤复合材料的微观形貌、力学性能、流变性能进行了研究。结果表明,PLA在PBAT基体中形成了微纤,随着PLA含量的增加,PLA微纤的平均直径增大;纯PBAT经多级挤出拉伸装置制得的片材的拉伸强度为50.1 MPa,随着PLA微纤含量的增加,复合材料的拉伸强度逐渐下降,断裂应变及拉伸模量逐渐增大;随着PLA微纤含量的增加,体系的G′逐渐升高,在低频区复合材料的G′对频率的敏感性降低,当PLA微纤含量为20%,复合材料的弹性性质更加明显。     

超高分子量聚乙烯的固态挤出研究

用柱塞式挤出机进行超高分子量聚乙烯(UHMWPE)的固态挤出,所得制品光滑、透明、密度较大,拉伸强度超过110MPa,拉伸弹性模量高达85GPa。差示扫描量热分析和扫描电子显微镜观察表明,制品内部产生大量的微纤结构,坯料固态挤出前的退火处理和固态挤出的强变形致使制品结晶度提高,分子链取向增强,其拉伸强度和拉伸弹性模量得到极大提高,其熔点、熔融焓、熔融熵也有所提高。     

木粉对PVC木塑复合材料力学性能影响

采用电镜扫描观察了3种木粉的纤维细胞尺寸及其木粉微观形态。研究了木粉粒度、微观特性以及木粉添加量对了聚氯乙烯（PVC）木塑复合材料力学性能的影响。结果表明，木粉表面裸露的微细纤维增加和粒度减小，有助于提高木塑复合材料力学强度；加入少量木粉使木塑复合材料力学性能降低，但随着木粉添加量的增大，木塑复合材料的抗弯性能和拉伸强度上升；木塑复合材料的冲击强度随木粉含量增加而下降。     

超高相对分子质量聚乙烯固相挤出过程研究

采用一种新型超高相对分子质量聚乙烯成型技术—固相挤出成型。采用扫描电子显微镜观察了制品成型前后内部微观结构变化;采用差示扫描量热分析,研究了不同挤出温度与口模拉伸比对挤出制品热性能的影响。结果表明,相对熔融挤出成型,固相挤出成型制品光滑、透明、密度较大;制品内部产生大量的微纤结构,结晶度提高,分子链取向增强,拉伸强度提高了2.7～4.5倍,拉伸弹性模量提高了42倍;另外,熔点上升了3～5 ℃、熔融焓及结晶度分别提高了8~10个百分点。     

聚酰胺酸的化学环化与微纤的成形

采用化学环化方法制备不同酰亚胺化程度的聚酰胺酸-聚酰亚胺(PAA-PI),通过红外光谱、热失重分析对其结构和性能进行了表征,发现产物的环化程度与理论值相符合。PAA-PI液滴在非溶剂中经过牵伸、变形、取向、凝固,沉析出不同环化程度的PAA-PI微纤,通过宏观照片和扫描电子显微镜(SEM)研究了聚合物的环化程度与微纤成形的相互关系,结果表明:相对于没有环化的纯PAA,经过化学环化的PAA-PI制备出的微纤微观上具有更规则的形貌,表面光洁,手感柔软。     

热处理时间对磷石膏基复合胶凝材料劈裂抗拉性能的影响

通过恒温烘箱对磷石膏(PG)进行热处理,复掺灰钙粉、普通硅酸盐水泥、缓凝剂及减水剂制备磷石膏基复合胶凝材料(PGCM),研究热处理时间对PGCM的劈裂抗拉强度、轴心抗压强度与劈裂抗拉强度折减系数、破坏形态、劈裂抗拉应力-应变曲线的影响规律。结果表明:PGCM的劈裂抗拉强度随热处理时间的延长先增加后减小,当热处理时间为90 min时,PGCM的劈裂抗拉强度最大达到1.68 MPa;轴心抗压强度与劈裂抗拉强度折减系数随热处理时间的延长几乎都减小,PGCM的劈裂抗拉强度为轴心抗压强度的4.2%~9.2%;PGCM的破坏形态主要有中心开裂破坏、局部破坏和次要裂缝破坏;PGCM的劈裂抗拉应力-应变曲线先逐渐上升后呈直线下降。结合试验数据,得到PGCM的轴心抗压强度与劈裂抗拉强度的换算关系以及劈裂抗拉应力-应变上升段曲线方程,拟合结果与试验数据较吻合。     

特种氯丁橡胶热氧老化研究

通过对特种氯丁橡胶在热空气中进行加速老化,比较了其老化前后性能的变化,得出了该橡胶的性能变化与老化时间的函数关系,并建立了100％定伸应力、拉伸强度、断裂伸长率、强韧度、撕裂强度与邵尔A硬度之间的关联关系。结果表明：在整个老化期间,100％定伸应力、硬度逐渐增加;拉伸强度、断裂伸长率、强韧度、撕裂强度逐渐降低;机械性能与硬度呈线性关系。     

Strength Analysis of Yttria-Stabilized Tetragonal Zirconia Polycrystals

Tensile strength of Y₂O₃-stabilized ZrO₂ polycrystals (Y-TZP) was measured by a newly developed tensile testing method with a rectangular bar. The tensile strength of Y-TZP was lower than that of the three-point bend strength, and the shape of the tensile strength distribution was quite different from that of the three-point bend strength distribution. It was difficult to predict the distribution curve of the tensile strength using the data of the three-point bend strength by one-modal Weibull distribution. The distribution of the tensile strength was analyzed by two- or three-model Weibull distribution coupled with an analysis of fracture origins. The distribution curve of the three-point bend strength which was estimated by multimodal Weibull distribution agreed favorably with that of the measured three-point bend strength values. A two-modal Weibull distribution function was formulated approximately from the distributions of the tensile and three-point bend strengths, and the estimated two-modal Weibull distribution function for the four-point bend strength agreed well with the measured four-point bend strength.     

在单方向往复低剪切力场中生成双向自增强HDPE试样的研究——(Ⅰ)试样制备及工艺条件对力学性能的影响

介绍在动态保压注塑成型技术提供的单方向往复低剪切应力场作用下来制备双向自增强试样。作者设计并制造了成型装置，初步研究了其成型原理、成型工艺、探讨了自增强效果与各工艺条件之间的关系。结果表明，采用本文所述的动态保压注塑成型技术显著提高了ＨＤＰＥ试样的力学性能——流动方向和垂直流动方向的拉伸强度均从２５ＭＰａ提高到３６ＭＰａ以上，达到了双向自增强的效果。自增强ＨＤＰＥ试样的拉伸强度强烈依赖于熔体的流动条件：流动方向的拉伸强度随液压站输出压力的提高而提高，垂直流动方向的拉伸强度则有一个对应最大拉伸强度的液压站输出压力；模具温度对拉伸强度的影响与压力对拉伸强度的影响相类似；熔体温度的提高有利于两个方向拉伸强度的提高；保压周期太长或太短均会使拉伸强度下降。     

Relationship Between Bond Strength and Crystallinity of High Polymers-Polyethylene, Polyethyleneterephthalate, and Nylon

The effect of crystallinity of polyethylene on the peel strength of aluminum plate-polyethylene-aluminum foil laminate was investigated. The 180° peel strength increased by rapid cooling with water, ice water, or liquid nitrogen after bonding with hot-melt polyethylene compared with slow cooling with air at room temperature. It was concluded that the increase of peel strength by rapid cooling was due to the decrease of modulus by the microcrystallization of polyethylene.

The tensile bond strength of steel-polyethyleneterephthalate (PET)-steel composite was investigated. The tensile bond strength increased about 10 times by rapid cooling of the composite bonded with hot-melt PET compared with slow cooling. On annealing the rapidly cooled composite over 100°C, the tensile bond strength decreased rapidly. It was concluded that the tensile bond strength decreases with the development of PET spherulite. Also in the case of Nylon 12, the tensile bond strength increased about 2 times by rapid cooling compared with slow cooling. In the case of Nylon 12, however, the tensile bond strengths of the both rapidly and slowly cooled specimens increased by annealing at high temperature.     

Aligned carbon nanotube sheet high efficiency particulate air filters

Aerosol filters, made with conventional micro-fiber fabrics, are designed to efficiently capture small particles from the air. Filters constructed of nano-fiber fabric structures provide even greater filtration efficiency than conventional micro-fiber fabrics due to their higher surface area and smaller pore size. Carbon nanotubes (CNTs) are very small diameter fibers that have the potential to be integrated into filters to further increase particle capture efficiency. In this study, CNT sheets, drawn from millimeter tall CNT arrays, were integrated between traditional micro-fiber fabrics to produce aerosol filters. The filtration performance of the novel filters showed that when the number of CNTs layers increased, the filtration efficiency increased dramatically, while the pressure drop also increased. In order to meet high efficiency particulate air (HEPA) filter requirements with a reasonable pressure drop, CNTs were laid in a cross-plied structure within the filter. The results demonstrated that the three layer cross-ply structure provided 99.98% filtration efficiency at 0.3 μm particle size at a 10 cm/s face velocity, making it a viable method for producing low basis weight HEPA filters utilizing CNTs as the main filtration component.