尺寸稳定的多孔聚四氟乙烯复合材料

用拉伸工艺方法加工得到的多孔聚四氟乙烯（PTFE）是优良的绝缘材料。但是,这种材料在使用中存在较大的尺寸不稳定性。在拉伸方向上容易收缩。稍受压缩应力影响时即产生形变。在导体间产生精度难以控制的位移。从而影响到信号传输性能。消除或减小拉伸多孔PTFE的收缩及形变使之保持良好的尺寸稳定性成了一项实际课题。多孔PTFE的尺寸不稳定性主要来自它在拉伸时残留的应力。使用中该应力释放,产生了收缩。另一方面拉伸处理后使PTFE的密度降低,有了微孔,材料的介电常数降低。这对信号传输有益。但这种微孔结构在尺寸的变化方面有…     

电致形状记忆聚己内酯／炭黑复合导电高分子材料的研究

制备了具有电致形状记忆特性的聚己内酯/炭黑(PCL/CB)复合导电高分子材料,研究了其电致形状记忆特性。结果表明,以交联聚酯作为聚合物基体、导电炭黑作为导电填料的复合导电高分子材料具有良好的电致形状记忆特性。拉伸2倍的CB300-25试样在200V电压作用下的形变回复率可达100%,响应时间140s。炭黑质量含量为25%的试样与炭黑含量为20%的试样相比,其响应时间较短,形变回复率也较高。随着电压的提高,试样的响应时间缩短,形变回复率提高。     

熔融沉积成型聚醚醚酮力学性能多尺度分析

对挤出成型(EM)聚醚醚酮(PEEK)和熔融沉积成型(FDM) PEEK试样进行单轴拉伸试验。结果表明,与EM试样相比,FDM试样屈服强度为98.30 MPa,提高4.3%,拉伸模量无明显变化,断裂应变为22.6%,下降87.1%。FDM试样拉伸断口微观形貌显示,试样以脆性断裂为主,伴有部分韧性断裂,试样内部存在大量规则孔洞,显著降低材料的韧性。针对PEEK材料的拉伸过程,通过建立PEEK材料的Johnson-Cook模型,模拟了材料的拉伸断裂过程,vonM ises应力最大偏差为5.8%,与试验较符合;从细观尺度模拟研究FDM不同搭接微孔洞对材料力学性能的影响,结果表明,与三尖瓣状微孔洞相比,星形线状微孔洞下制件承受的拉应力下降27.4%,丝材并行搭接将会降低材料的拉伸强度。     

梯度结构三元乙丙橡胶发泡材料的制备及性能

采用叠层法制备了发泡密度沿厚度方向呈梯度变化的三元乙丙橡胶(EPDM)发泡材料,研究了梯度结构对EPDM发泡材料的泡孔微观形态、力学性能、压缩应力-应变性能、能量吸收特性及动态力学性能的影响。结果表明,在叠层厚度不变的情况下,随着中间层发泡剂用量的减少,试样的邵尔C硬度、拉伸强度和扯断伸长率逐渐增大,100%和300%定伸应力在最内层发泡剂用量达到7份(质量)后不再增加,转而呈下降趋势。在较高的应力下,梯度EPDM发泡材料比传统均质橡胶发泡材料具有更强的吸能效果,而玻璃化转变温度和阻尼因子基本不变。     

聚乙烯管材残余应力的定性和定量评价

研究了冷却速度、挤出速度和拉伸比等不同挤出工艺对管材物理性能及残余应力的影响，结果表明，随着冷却和挤出速度的增加，PE管材纵向回缩率增大，静液压和SCG破坏时间逐渐降低。通过盲孔应变法研究了不同挤出工艺对管材内外层的释放应变和残余应力分布的影响，研究表明，采用理想化的均匀分布模型不适用于残余应力的定量评价，采用非均匀应力分布模型计算得到的管材外层的残余应力随着冷却和挤出速度的增加而增大，而管材内层的残余应力变化较小，由于管材沿壁厚方向冷却速度的不均匀，内外层残余应力分布存在差异。最终，通过对管材内中外层分别进行拉伸、密度和结晶度等物理性能试验，进一步证明了盲孔法定量评价残余应力的有效性。同时试验发现，当挤出拉伸比太高时，分子链取向严重，管材纵向回缩率增大，静液压和耐SCG性能下降，管材外层残余应力的最大值为14.6 MPa,与材料拉伸屈服强度相比，提高了50%。     

硬弹性材料拉伸成孔机理及PVDF多孔膜的制备

对硬弹性材料结构特征和拉伸成孔机理进行了总结，重点介绍了聚偏氟乙烯（PVDF）硬弹性材料及多孔膜的研究发展现状。结果表明，硬弹性材料是一类经特殊加工的具有排状片晶结构的合成聚合物材料，截然不同于普通弹性材料，具有高弹、高模等特性，并且低温弹性优异，特别是在拉伸时可以形成微孔，该特性已被用于多孔膜的制备。同时指出，目前熔...     

温度对PE燃气管热熔焊接接头性能的影响

主要研究了聚乙烯(PE)燃气管热熔焊接接头在不同温度下的力学性能,通过不同温度下PE材料的拉伸破坏实验,根据不同温度下PE燃气管道焊接接头拉伸应力及拉伸应变,利用数值拟合的方法建立了PE材料接头的最大应力和断裂伸长率与温度的函数关系。其中卷边的存在容易产生应力集中使管道断裂,无卷边试样断裂伸长率总体高于有卷边试样且温度越高越明显,去除卷边对拉伸强度影响较小,可提高试样的断裂伸长率。温度对PE材料的拉伸强度、断裂伸长率影响较大,温度升高,PE材料的拉伸强度降低,断裂伸长率增加。     

发泡杜仲胶/高密度聚乙烯形状记忆材料的制备与性能

通过物理共混的方式制备了发泡杜仲胶(EUG)/高密度聚乙烯(HDPE)形状记忆材料,探讨了共混比对其硫化特性、物理机械性能、发泡程度、结晶熔融行为和形状记忆性能的影响。结果表明,随着HDPE用量的增加,EUG/HDPE形状记忆材料的交联程度降低,100%定伸应力、300%定伸应力增大,但拉伸强度及扯断伸长率降低,物理机械性能与材料的交联结构、晶区、泡孔等微观结构密切相关;HDPE的加入使材料的发泡程度增大,EUG相的熔融温度及相对结晶度随着HDPE用量的增加而降低,HDPE的相对结晶度增大而熔融温度基本无变化;随着HDPE用量的增加,材料的热刺激响应温度Tr升高,形变回复速率Vr减小,热致形变回复率Rf无明显变化。     

流延聚丙烯的高温应力-应变行为

研究了流延聚丙烯高温下的应力-应变行为，在特定的实验条件下捕捉到了应力波动，即应力随应变的增大而发生复杂波动的现象，通过试样拉伸前后结构的DSC和WAXD表征，发现拉伸后试样的熔融行为和结晶结构都发生较大的变化，因此认为应力波动主要与高温条件下拉伸过程引起的试样的应力诱导结晶有关，为了避免应力波动，提高拉伸速率时，应使其聚物的序列分布均匀，即乙烯链能均匀地插入丙烯主链中，打乱丙烯链段的边疆性。以降低结晶速率和结晶度，实现高速稳态拉伸。     

塑料土工格栅拉伸过程的试验研究

通过试验研究了塑料土工格栅的拉伸过程,总结了结晶聚合物土工格栅试样拉伸的一般规律,根据聚合物拉伸理论解释了试验现象,并探讨了塑料土工格栅连续稳定拉伸的条件。试验表明,塑料土工格栅试样的各成肋部分沿纵向被依次拉伸伸长是连续生产的基础;可由材料的应力-应变关系初步判定塑料土工格栅试样拉伸的连续性,这对新型塑料土工格栅材料、工艺的研发,缩短试验周期是有利的。     

Determination of Mechanical Properties of Thermoplastics Suitable for Micro Systems

Aircraft and aerospace industry as well as medical and automotive engineering continuously develop smaller and lighter system components. Therefore it is not only important to be able to produce micro parts but also to provide properties for dimensioning and design. This paper explains to what extent mechanical properties from the macro‐range are also valid for micro structures. Thereby the modulus of elasticity as well as stress and strain at the yield point are regarded as relevant properties for the part dimensioning. Systematic investigations with tensile bars of different size show that the geometry‐dependent property changes are obviously not specific for the material classes of amorphous or semi‐crystalline thermoplastics, respectively. That is why a single material testing of micro samples is necessary to determine valid properties for this range. On the other hand the determination known from the classic materials science of plastics that lower temperatures as well as higher loading rates lead to a stiffer material behaviour, is also appropriate for the micro range. The measurements prove that the influence of temperature is much higher than the one of deformation rate. The influence of the production conditions on the mechanical behaviour of test specimen made of semi‐crystalline thermoplastics is demonstrated by using a varied cooling process. The correlation between the resulting different morphological structures and the changes in the mechanical properties is pointed up on the basis of microscopic views.

Micro tensile testing machine at the IKV.     

Effects of incorporating technique and silver colloid content on antibacterial performance for thermoplastic films

Antibacterial efficacies of various thermoplastics, such as medium‐density polyethylene (MDPE), polystyrene (PS), polyethylene terephthalate (PET) and polyvinyl chloride (PVC) containing nano‐silver colloids were studied under a wide range of testing conditions. The effects of nano‐silver colloid content and the silver‐polymer contact time were of our main interests and quantitatively assessed by shake flask method coupled with a plate‐count‐agar (PCA) technique using Escherichia coli as testing bacteria. Two different methods were used for incorporating the nano‐silver colloids into the thermoplastics, these being spray‐coating and melt‐blending techniques. The experimental results suggested that all neat thermoplastics alone could not generally inhibit the E. coli growth, suggesting that all thermoplastics exhibited nonbactericidal behavior. However, neat PVC appeared to show a retarding effect for the E. coli growth. In addition, coating silver colloid onto all types of thermoplastic substrates could inhibit the E. coli growth up to 99.9% at the optimum silver content of 50 ppm for PS, PET and PVC and of 75 ppm for MDPE. The optimum contact time for all thermoplastics was 150 min. Among the thermoplastics used, PVC exhibited the highest % E. coli reduction, and this was confirmed by the higher silver content via Atomic Absorption Spectrometry (AAS) technique. For a given silver content, the spray‐coating technique could give better dispersion level of silver throughout the thermoplastic films and this led to more effective antibacterial performance as compared with the dry‐blending technique. In PVC sample, the contact angle value appeared to increase with the addition of silver content for both incorporating techniques. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

聚氨酯增韧聚甲醛的研究

采用机械共混的方法，制备了聚甲醛(POM)／热塑性聚氨酯弹性体(TPU)复合材料；研究了缺口曲率半径对纯POM以及TPU增韧体系冲击韧性的影响；并对其形态结构进行了测试分析。结果表明，纯POM的冲击韧性受缺口尖锐程度影响大，TPU能减小POM结晶度，缩小球晶尺寸，显著降低POM的缺口敏感性；POM／TPU形成双连续结构时成为超韧体系。     

热塑性树脂／植物纤维复合材料的纤维改性方法

简述了纤维增强热塑性树脂的研究状况,介绍了植物纤维／热塑性树脂在共混过程中存在的问题。重点讨论了植物纤维预处理的物理、化学改性方法来提高两者之间相容性。     

环氧树脂与热塑性树脂的共混研究进展

综述了国内外有关环氧树脂与热塑性树脂共混研究的最新进展。介绍了热塑性树脂增韧环氧树脂体系相态结构的控制，环氧树脂改性热塑性树脂，以降低难加工聚合物加工温度、改进某些热塑性树脂(如PVC，PET)的力学性能，以及利用环氧基团的活性改善不相容热塑性树脂共混体系的相容性的研究进展。     

Predicting toughness of impact thermoplastics from high-speed tensile data

A photographic procedure is presented for evaluating uniaxial true stress-true strain tensile behavior of thermoplastics at strain rates typical of impact situations. The advantage of combining this information with observed macroscopic material changes which occur during tensile deformation is discussed in terms of establishing parameters which define end use abuse resistance of impact thermoplastics. In particular, test parameters are evaluated which provide a direct correlation with measured bottle drop failure resistance for selected materials. These test parameters are obtained by measuring the area under true stress-true strain curves obtained at impact strain rates. Area is measured up to the point of ultimate uniaxile tensile strain. Ultimate uniaxial tensile strain corresponds to either (a) strain at onset of necking in materials which produce necking during deformation, or (b) strain at fracture in materials which deform without necking. Measured test parameters are discussed in terms of modern theories of strength of materials. Pitfalls associated with quantitatively defining the abuse resistance of thermoplastics based on total energy for breaking, i.e., conventional numeric criterion of impact strength, it also discussed.     

ABS树脂拉伸性能及形变机理的研究

研究了丙烯腈丁二烯苯乙烯共聚物（ABS）树脂在不同温度和不同拉伸速率时的拉伸行为以及物理老化对其拉伸行为的影响。结果表明,屈服强度随测试温度的升高而下降,断裂伸长率并不随着测试温度的升高而提高,直到测试温度升高到接近ABS树脂塑料相的玻璃化转变温度时,断裂伸长率才显著提高;断裂伸长率随拉伸速率的增加而降低,在不同的拉伸速率下,ABS的形变区内均可观察到银纹现象;在较高的拉伸速率下,形成的银纹数量较多,但银纹较短,银纹的扩展得到了有效抑制;ABS树脂经物理老化后断裂伸长率明显降低,银纹数量增加并出现了空洞成串现象。     

Weld line improvement of short fiber reinforced thermoplastics with a movable flow obstacle

Short fiber reinforced (SFR) thermoplastics are ideal materials from which to manufacture complex technical parts in high volumes with low energy expenditure. The orientation of the fibers, and hence their reinforcing effect, depends strongly on the nature of the cavity and on the injection molding process. One disadvantage of SFR thermoplastics is a significant decrease in mechanical properties in the areas of the weld lines, due to subopt imal fiber orientation as the melt streams reunite at these points. Common mold‐based and process‐based optimization techniques alter the fiber orientation after the formation of the weld line. The mold‐based approach presented here, on the other hand, operates at the time the weld line is formed: by redirecting the melt streams, it moves the weld line and improves the fiber orientation. A prototype mold is described, and samples produced from it with both standard and modified weld lines are compared with flawless specimens. The new technique yields a large rise in flexural strength and a smaller but significant improvement in tensile properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42025.     

微孔注射成型技术的应用

论述热塑性塑料微孔注射成型技术在电视机外壳上的应用，针对微孔注射成型的技术难点，如制品易出现的缺料、拉白、拉裂、表面凹凸不平，烧焦等问题，从产品设计，模具设计，工艺技术等方面提出了综合解决措施，以提高产品合格率，降低生产成本。     

Adhesion between ethylene-propylene-diene monomer and thermoplastics in two-component injection molding: Effect of dicumylperoxide as curing agent

Strong adhesion at the interface is an important aspect in two-component (2K) injection molding. It was therefore investigated whether dicumylperoxide (DCP) as curing agent in ethylene-propylene-diene monomer (EPDM) could stimulate interdiffusion and/or induce chemical bonding with thermoplastics. EPDM mixtures containing DCP concentrations between 2 to 8 parts per hundred rubber (phr) were combined with polar and non-polar thermoplastics. Changes in EPDM physico-mechanical bulk properties were analyzed, and the adhesion was evaluated by high temperature contact angle measurements and tensile testing. Results showed that DCP concentration did not influence EPDM-thermoplastic compatibility. However, EPDM adhesion with polyethylene (PE) did improve when using up to 6 phr DCP (57% adhesion) as crosslinking is promoted. While with polypropylene (PP), adhesion linearly decreased (from 55% to 35% adhesion) with higher DCP concentrations due to prevailing scission reactions. Adhesion through chemical bonding with acrylonitrile-butadiene-styrene (ABS) caused better adhesion at 4 phr (43% adhesion) compared to polycarbonate (PC) at 4 phr (13% adhesion) where only limited interdiffusion occurs. Thus, selecting the optimal DCP concentration is highly important to boost adhesion between EPDM and thermoplastics. Furthermore, at these optimal DCP concentrations, physico-mechanical properties require consideration as these properties were significantly affected.