聚苯乙烯制品熔接线区域的双折射行为分析

基于双折射实验原理,利用偏光显微镜,运用"楔形法",测定了聚苯乙烯注塑制品熔接线区域厚度面上双折射行为分布。结果表明:距离嵌件的不同位置处,由于流动行为的差异导致了完全不同的双折射行为,根据应力-光学定律,这种行为也体现了塑料制品的分子取向、残余应力的分布情形。     

聚碳酸酯注射成型分子取向分布的双折射实验研究

运用楔块法研究了聚碳酸酯(PC)注塑平板不同位置处厚度方向上的双折射和分子取向分布,同时考察了注射成型工艺和退火处理对制品双折射分布的影响。结果表明,在制品侧壁处出现沿厚度方向上双折射非对称分布的现象;在靠近冷模壁侧,次表层出现双折射峰值或不连续分布;熔体温度和保压压力对厚度方向双折射影响较大;退火处理几乎不影响双折射和分子取向分布。     

注射成型聚苯乙烯制品双折射的光弹测试与分析

分析了无定形聚合物注射成型双折射行为及其产生机理,利用光弹法测试了不同工艺条件下聚苯乙烯(PS)平面内双折射分布,考察了熔体温度和保压压力变化对制品双折射和流动残余应力的影响。结果表明,PS制品残余双折射值在流动方向上从浇口附近至流动末端逐渐降低,并且最大双折射值随保压压力增加和熔体温度降低而升高;保压压力对浇口附近双折射分布影响明显。根据双折射的光弹测试结果分析了P制品分子取向和流动残余应力的分布趋势。     

消除熔接线提高注塑件的质量

塑料制件上的熔接线使制件的机械强度降低。本文介绍熔接线产生的原因,减少或削弱、消除熔接线所采取的有效措施。     

注塑成型熔接线缺陷

熔接线是注塑制品常见缺陷之一,研究熔接线的形成机理及影响因素,并找出相应的解决办法,对于改善注塑制品外观质量、提高力学性能有很大的实际意义.对熔接线已有大量的系统研究,研究熔接线的方法和手段也不断发展进步.论述注塑成型中熔接线缺陷的主要研究方法,对开展熔接线的研究将会有一定的帮助.     

注射成型参数对透明制品双折射影响仿真研究

以透明塑料制品的平均双折射为质量目标,利用Moldflow分析计算了不同工艺条件下的制品平均双折射。采用正交实验分析法找出了最佳的成型工艺条件,然后采用单因素分析法仿真研究了显著因素对制品平均双折射的影响规律。实验结果表明,保压时间和熔体温度对制品平均双折射影响最为显著,但二者对平均双折射的影响机理却不一样, 保压时间仅对近浇口区域的双折射值影响显著,熔体温度则对制品整个区域的双折射值有较大影响。     

注射成型中的熔体温度均匀性研究

注射成型中的熔体温度均匀性直接影响注射制品的最终质量，熔体温度均匀性的大小与螺杆设计，加工工艺条件关系密切，对不同工艺条件和螺杆几何参数时的轴向温差进行了测量，并讨论了轴向温差的形成机理及其与加工工艺条件和螺杆参数之间的关系。     

注塑成型熔接线截面熔接过程数值模拟

在多浇口和带嵌件注塑制品的成型过程中必然存在熔体的熔接过程,从而形成熔接线。熔接线沿厚度方向的熔接过程是影响该区域的力学强度以及纤维取向等制品性能的重要因素。本文采用有限元法针对注塑制品的典型截面建立数学模型,采用T6P3单元(速度二次插值,压力线性插值),数值模拟了注塑制品熔接线的截面熔接过程。通过等厚度截面和非等厚度截面两个算例,给出了两股熔体熔接过程中的截面速度场和压力场分布。讨论了熔接线区域的壁厚均匀程度对熔接过程的影响。该计算结果可以为制品力学性能以及纤维取向等数值模拟提供数据支持。     

可熔型芯在注射成型中的应用

以低熔点合金为可熔型芯材料,注射成型形状复杂的30%玻纤增强尼龙66中空塑料件。介绍可熔型芯材料的组成及配制方法、可熔型芯的成型、塑料件注射成型过程,以及可熔型芯的熔出。结果表明,用低熔点合金制作可熔型芯材料并用于塑料件注射成型技术可行,工艺控制可靠,但塑料件制作成本高,只能用于附加值较高的塑料件上。     

纤维增强注塑熔接线强度预测模型与实验研究

熔接线是影响注塑制品强度的关键因素之一,而目前以汇合角预测熔接线强度的力学模型并没有体现注塑工艺的影响。为了科学定量地认识熔接线区域强度的变化规律,准确预测熔接线力学性能,首先对带扇形孔的制品进行注塑模拟分析,研究了注塑温度、注射速率以及保压压力对熔接线汇合角的影响,结果显示注塑温度、保压压力不是通过改变熔体前沿汇合角来影响熔接线强度。基于此,为全面体现注塑工艺、汇合角对熔接线强度的影响,在现有模型基础上通过引入注塑工艺影响因子重新构造了体现注塑工艺、汇合角对熔接线区域强度影响的预测模型。设计并制造了用于成型扇形孔制品的注射模具,开展了不同工艺条件下30%长玻纤增强聚丙烯扇形孔制品注塑实验,根据实验结果推导出了体现注塑温度和保压压力影响的注塑工艺影响因子数学表达式,利用实验数据拟合确定了模型中的相关参数,并对模型进行了回归分析。结果表明,新构建的强度预测模型可以准确计算不同注塑温度、保压压力下熔接线不同位置的强度。     

Effects of processing conditions on birefringence development in injection molded parts. II. Experimental measurement

The birefringence of injection molded parts was measured using a digital photoelasticity system, which combines a digital image analysis technique and the half-fringe photoelasticity (HFP) method The effects of processing conditions, including melt temperature, mold temperature, filling time and packing pressure, on the birefringence development in the molded parts were investigated. It was found that temperature and pressure are the two dominant factors that determine the birefringence development in the parts during the molding process. Frozen-in birefringence of the molded parts decreases with increasing melt temperature, mold temperature and injection speed. Birefringence of the parts also increases with increased packing pressure, especially around the gate area. Numerical simulations using the Leonov viscoelastic fluid model predict similar dependence of birefringence of parts on processing conditions. Simulated results are also consistent with measured values.     

一步法注射成型机

简述了注射成型法与模压成型法相比所具有的诸多优点，同时指出了传统注射成型方法所存在的问题。着重介绍了一步法注射成型技术及其设备的结构特点、工作原理及工作特性。     

纵论注射成型技术

以注射成型技术在橡胶行业的发展现状为依据,从工作原理、生产工艺、产品质量、生产效率等几个方面着手,对模压成型技术和注射成型技术进行了比较,阐述了注射成型技术的优越性。同时,针对推广注射成型技术遇到的困难,提出了注射成型技术在橡胶行业的推广过程中所需要解决的一系列问题。     

注塑工艺参数对制品残余应力和收缩的影响

注塑成型工艺参数对制品的最终残余应力和收缩有着直接的影响。基于线性黏弹性模型模拟计算了注塑成型过程中由温度和压力引起的残余应力和收缩。以无定型材料PS和ABS为例,系统地研究了不同成型工艺条件下平板制件的最终残余应力和收缩,并和实验结果进行对比验证。结果表明：在流动方向上无定型材料的收缩基本保持不变,残余应力沿壁厚分布的形状也基本相同,但流动末端处的应力值稍大于流动入口处;保压压力是影响制品收缩的关键因素,提高保压压力和注射温度可以降低制品的最终收缩,而模具温度对收缩的影响较小。     

Heat transfer in injection molding of crystalline plastics

A theoretical mathematical model is presented to describe the temperature distribution and the rate of phase change in the injection molding process of crystalline plastics. Under some assumptions, an exact closed form is solved with the use of an internal technique. The model was tested by measuring the temperature profile in a slab mold instrumented with thermocouples. Measurements of temperature profiles in the center of the polymer slab compare well to model prediction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2249–2253, 2006     

Multilayer injection molding of high-profile convex lens

The use of injection molding to produce a convex lens of a high thickness and a high proportion of the component thickness requires not only a long cooling time but also results in a low production efficiency and a low yield. In particular, the heat concentration in thick regions can create high shrinkage and create poor surface geometry in these lenses. Multilayer injection molding (MIM) has reduced the cycle time and also improved the geometrical accuracy of thick parts, and thus it has drawn attention in recent years. This study evaluated the feasibility of MIM to produce a convex lens having a high thickness and a high thickness ratio, in which a thick optical lens would be made of a plurality of thin layers. In this study, conventional injection molding (CIM), two-layer IM, and three-layer IM were evaluated empirically to explore the effects of various molding combinations on surface contours accuracy, cycle time, residual stress, and lens transmittance. In the comparison, the three-layer IM significantly reduced the surface profile error to 0.015 mm (CIM was 0.1 mm) and reduced the surface profile error to 30%. Moreover, uniformity of the shrinkage distribution and good surface profile accuracy can be obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48600.     

注射成型薄壁制品收缩与翘曲因素

介绍了薄壁注射成型的充填、保压、冷却和残余应力的数值模型,并将集成的模拟程序对收缩翘曲问题进行定量地模拟分析.采用Taguchi 实验优化设计理论,用L₂₇（3¹³）正交表设计实验并进行了统计分析.研究了因素如熔体温度、模具温度、保压时间、保压压力、浇口尺寸和注射速率对收缩与翘曲的影响的显著性.得出优化工艺参数如熔体温度、模具温度、保压时间和压力能减少残余热应力;保压压力和熔体温度是影响收缩与翘曲的最显著因素.     

Surface morphology alignment of block copolymers induced by injection molding

Block copolymers are of increasing interest because of their nanometer-scale morphologies, which can be utilized in a range of applications, including nanolithography. Orientation of the domains can be controlled by part design and processing conditions in injection molding. In this work the surface morphology and alignment of block copolymers by mechanical flow fields from injection molding was investigated using a styrene-ethylene/butylene-styrene triblock copolymer (SEBS) and compared with the morphology induced by spin coating. Compared with the isotropic morphology found by spin coating and annealing, the surface domains were oriented in the flow direction. Increasing mold temperature and injection velocity enhanced the degree of orientation, whereas melt temperature had little effect. Smaller characteristic lengths were produced with higher mold temperatures and injection velocities.