动态填充注塑成型PP/nano-SiO2复合材料的力学性能与形貌分析

采用动态填充注塑成型(DFIM)制备了聚丙烯/二氧化硅(PP/nano-SiO2)复合材料。结果表明:与传统的注塑成型技术相比,采用DFIM法制备的PP/nano-SiO2复合材料的拉伸强度和冲击强度比纯PP材料和常规注射制备的复合材料有了较大提高;nano-SiO2通过DPIM技术可以更好地分散在PP基质中,形成的团聚较少。DFIM法制备的PP/nano-SiO2复合材料力学性能的提高,主要归因于nano-SiO2颗粒的均匀分布,使球晶的数量急剧增加,球晶的尺寸明显减小,小晶体有助于形成材料裂纹,从而进一步提高材料的力学性能。     

注塑成型导电高分子复合材料研究进展

综述了注塑成型导电高分子复合材料(CPCs)的典型微观结构,总结了提高注塑成型CPCs力学性能和电性能的方法,提出了优化工艺并进行复合材料微观结构设计是拓宽注塑成型CPCs应用领域的关键。     

聚丙烯/纳米碳纤维复合材料微孔注射成型加工与性能研究

将聚丙烯(PP)和纳米碳纤维(CNF)共混后,通过双螺杆挤出制备成不同组份的复合粒料,采用注射成型加工制备实体和发泡试样,研究不同CNF含量对PP基体复合材料性能的影响。结果表明,随着CNF含量的增加,微孔样品中的孔径显著的减小同时泡孔密度增加;注射成型的样品中,添加CNF后的模量和拉伸强度略微降低,但微孔注塑的PP/CNF复合材料的性能呈现出相反的效果。     

碳纤维增强环氧树脂复合材料的液体成型及其性能研究

本文研究了不同温度下RIM145树脂的粘度和适用期,分析了不同温度下RIM145树脂和碳纤维单丝之间的浸润性;并以碳纤维单向布为增强材料,采用真空辅助灌注成型工艺制备了碳纤维增强环氧树脂(CF/EP)复合材料,研究了复合材料的力学性能,对层间剪切试样剖断面形貌进行了SEM分析,并研究了使用VAP单向透气膜辅助真空灌注成型工艺对CF/EP复合材料厚制件灌注质量的影响。研究结果表明,RIM145树脂基体在50~70℃粘度低、适用期长且树脂与碳纤维单丝之间的浸润性良好,适用于CF/EP复合材料的真空辅助灌注成型工艺;灌注的CF/EP具有良好的力学性能,树脂和纤维具有中等粘结强度界面,采用VAP单向透气膜辅助真空辅助灌注成型工艺可降低CF/EP复合材料的孔隙率。     

短切CF增强TPEE热塑性复合材料的注射成型及力学性能研究

以热塑性聚酯弹性体(TPEE)为基体材料,8 mm短切碳纤维(CF)为增强材料,制备CF/TPEE复合材料。材料通过双螺杆挤出系统混合塑化、挤出造粒后,再经过注塑成型制备成标准拉伸试样,通过力学性能测试及微观结构观察,系统研究了碳纤维含量和等离子表面处理对CF/TPEE复合材料拉伸性能的影响。结果表明,当碳纤维含量为20%时,CF/TPEE复合材料的拉伸强度最大,为39.08 MPa;相比于纯TPEE,其拉伸强度提高了217%;经过等离子表面处理后,拉伸强度进一步提高了5%。结合拉伸后断面的SEM图发现,注塑试样表层碳纤维取向度高,而近中区和中心层取向度相对较低,这是注射CF/TPEE复合材料拉伸性能提高效应不明显的主要原因。     

聚丙烯结构发泡注塑成型研究进展

介绍了聚丙烯(PP)结构发泡注塑成型工艺及相应的PP树脂的改性方法,对PP结构发泡注塑成型的发展前景进行了展望。     

注塑成型工艺对透明PP光学性能的影响

采用不同的工艺条件注塑成型无规共聚透明聚丙烯(PP),测试透光率、雾度和表面光泽度,分析了成型工艺参数对制品光学性能的影响。所选透明PP的最佳注塑工艺为:加工温度220～230℃,模具温度40～60℃。在保证制品顺利成型的情况下应尽量采用较小的注塑压力。注塑速率和注塑时间对制品的光学性能影响较小。     

聚丙烯/亚麻纤维复合材料的成型工艺及力学性能研究

选取聚丙烯(PP)纤维为基体材料,亚麻纤维为增强材料。运用正交设计法,探讨了PP/亚麻纤维复合材料的模压成型工艺。研究分析了两种纤维的质量比、模压温度、热压保温时间对复合材料力学性能的影响。结果表明,两种纤维的质量比为50:50、模压温度为180℃、热压保温时间为60min时,PP/亚麻纤维复合材料的力学性能最佳。     

成型工艺对碳纤维增强热塑性聚酰亚胺复合材料性能的影响

采用双螺杆挤出共混的方法,制备了热塑性聚酰亚胺(TPI)/碳纤维(CF)复合材料,考察了注射和热模压两种成型工艺对 TPI/CF 复合材料力学性能、应力-应变曲线、线性膨胀系数以及摩擦磨损性能的影响。结果表明,注射成型试样的各项力学性能均比模压成型的高,达到1.5～2.0倍;相比模压成型,注射成型试样具有较高的断裂强度和断裂伸长率,其应力-应变曲线斜率也较大;由于纤维在注射流动方向上高度取向,注射成型试样具有最佳的高温尺寸稳定性;注射成型试样的摩擦系数和磨损率为模压成型的1.7倍和1.5倍;扫描电镜分析表明,纤维在注射流动方向上高度取向,模压成型试样呈现黏着磨损,注射成型试样以磨粒磨损为主。     

微发泡PP/GF复合材料力学性能研究

采用化学发泡注塑成型的方法制备了微发泡聚丙烯/玻璃纤维(PP/GF)复合材料;结合成核理论和玻纤增强机理,研究了发泡质量对微发泡PP/GF复合材料力学性能的影响。结果表明:在PP/GF复合材料中添加5.0%纳米SiO2后,纳米SiO2对PP与GF的相容性并无太大影响,微孔发泡PP/GF复合材料的拉伸强度和冲击强度得到较大提高。     

提高注塑件性能的熔体振荡技术

目前有一种新开发的注射熔体振荡技术,无需添加填料和助剂,就可提高注塑部件的机械特性。这项技术还可转移、隐藏或减少部件表面的注射熔接痕,并纠正制件取向应力等缺陷。     

注塑成型模拟技术在注塑工艺中的应用

注塑成型工艺已经发展成为塑料工业最重要的加工手段,注射模塑过程中需要选择和控制的压力包括塑化压力、注射压力和保压压力,它们直接影响塑料的塑化和塑件质量。通过对注塑过程中所涉及的工艺条件如何影响塑料制品的质量作了探讨,借助注塑工程分析软件对塑料制品的成型过程进行模拟,合理确定这些工艺参数,并分析了一个应用CAE技术优化工艺参数的实例,提出了比较切合实际并容易提高产品质量的注塑工艺方案。     

橡胶注射成型机注射装置结构分析研究

主要介绍了橡胶注射成型机及其注射装置的发展情况,阐述了橡胶注射成型的特点以及注射装置设计要求,并对三种常用的注射装置的结构特点及应用作系统的分析比较.     

Predicting molding forces during sheet molding compounds (SMC) compression molding. II: Effect of SMC composition

One of the fastest‐growing applications of SMC compression molding is the manufacture of truck body panels. Because of their large size, the molding forces required are substantial and have a major influence on the molding cycle. Also, as SMC moves towards parts requiring higher strength, the fiber length and percentage by weight of fibers must increase. This will also contribute to larger molding forces. In this paper, a procedure is presented to evaluate the SMC rheological parameters needed to predict molding forces. In addition, the effect of SMC composition on the molding forces is investigated. In particular, we evaluate the effect of reinforcement type (glass versus carbon) and level, filler level and thickener level. It was found that the factors most affecting molding forces are the reinforcement length and level; and the filler level. In addition, it was discovered that for SMC thickened with magnesium oxide, the level of thickener does not affect the molding force.     

Centering molding assemblies

Methods are surveyed for centering molding assemblies as used to mold large ceramic blanks from aqueous slip. Existing and promising future methods of centering are examined, with emphasis on their advantages and shortcomings. The analysis shows that video centering is the most promising method.     

Predicting molding forces during sheet molding compound (SMC) compression molding. I: Model development

Because of its high strength‐to‐weight ratio, corrosion resistance, and low cost, Sheet Molding Compound (SMC) production offers great potential for growth in the automotive and trucking industry. Much attention is now being given to improving the economy of SMC compression molding by reducing the cycle time required to produce acceptable parts in steady production. One of the fastest‐growing applications of Sheet Molding Compound (SMC) compression molding panels is the manufacture of truck body panels. Owing to their large size, the molding forces developed are substantial and have a major influence in the molding cycle. The relevant process models for SMC flow are reviewed and a procedure is developed that can be used to obtain the closing force and calculate the needed material parameters. Experiments were done using commercially made SMC to verify the validity of this model and the compression force was predicted and compared to experimental values for commercially made automotive hoods.     

MuCell微发泡注塑成型技术应用

MuCell微发泡注塑成型技术的使用日趋普及,其制品主要集中在品质要求较高、材料较贵的产品上。近年来,选用微发泡注塑成型技术的中国企业数目快速增长,其应用领域也正在扩大。     

滚塑成型新论

滚塑成型最大的优点之一是模具成本相对较低。由于在制造过程中不存在任伺压力,模具不需要象其它工艺要求的那样成本高、结构复杂。所用材料可以产生只有滚塑成型才有的效果,能生产出一些表观极好的制品,一种制品可以,日用一种聚合物制造,这对回收工艺是理想的。     

Principles of rotational molding

Rotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This paper is devoted to the theoretical understanding of the process of rotational molding. There are seven sections: The Art, wherein we describe the process, discuss previous attempts at understanding the process, and mention processes that are similar in principle to rotational molding. Transient Heating of Mold Surface, wherein we show that the criterion for selection of mold materials is the ratio of the thermal diffusivity to the thermal conductivity, and present the heating curve for a mold in a rotational mold machine. Melting of Plastic Powder in a Rotating System, wherein we discuss in detail those physical powder characteristics that are necessary for good flow within the mold cavity. Fluid Flow During Rotational Molding, wherein we discuss the velocity profiles within the melt film, point out that there is very little bulk polymer flow possible within the mold cavity under normal processing conditions, and consider capillary flow forces and surface wetting. Sinter-Melting, wherein we compare the Kuczynski-Neuville empirical sintering model with the Lontz viscoelastic model, conclude that the latter is correct for the sintering of materials such as ABS, and apply the Frenkel glass densification theory to the prediction of void disappearance in sinter-melt polymers. Degradation, wherein we compare our experimental tensile strengths of polystyrene, obtained at varying oven cycle times and oven set point temperatures, with values obtained from degradation models given in the literature. Laboratory Simulation of Rotational Molding, wherein we propose two series of experiments, the first series being carried out without using rotational molding equipment, and the second using rotational molding equipment with molds having relatively simple geometries.     

High-temperature molding of pyrrones

The cross-linked, ladderlike structure of cured pyrrones is not susceptible to forming at ordinary temperatures and pressures. At unusually high processing temperatures, of the order of 500°C, these intractable materials are observed to undergo transient flow sufficient to allow molding of the material. This observation, supported by analytical information, suggests that the flow occurs because of the breakage of covalent organic bonds and subsequent structural rearrangement of the cross-linked polymer network. This is in accord with a number of isolated reports of the pyrolytic behavior of several polymers.