气体辅助注射成型聚丙烯的多层次结构

用扫描电镜(SEM)观察了气体辅助注射成型(GAIM)和常规注射成型(CIM)等规聚丙烯(iPP)在不同部位的结晶形态。发现CIM试样的"皮-芯"结构不明显,而GAIM试样在不同部位则形成了包括球晶、串晶和取向片晶,进而表现出明显的多层次结构。在结晶形态分析的基础上,初步探讨了GAIM制品多层次结构的形成机理。     

玻纤增强HDPE气体辅助注射成型制品的形态

采用气体辅助注射成型(GAIM)和普通注射成型(CIM)制备了玻纤(GF)增强高密度聚乙烯(HDPE)复合材料。通过扫描电镜对复合材料中的玻纤取向进行了研究,发现CIM试样的玻纤仅在表层有轻微取向,而GAIM试样在整个横截面上玻纤均发生了明显的取向,且在次表层处取向强烈,排列十分规整。在此前研究工作的基础上,进一步探讨了玻纤取向结构的形成机理。     

气体辅助注射成型聚苯乙烯制品的双折射

利用偏光显微镜结合补偿器方法测定了气体辅助注射(GAIM)聚苯乙烯制品中双折射分量Δn和nθθ-nrr的径向分布。结果表明,Δn与nθθ-nrr在模壁附近均具有最大值并下降,当降低到一定值时Δn值朝向气道方向变化较小,而nθθ-nrr值在气道附近呈上升趋势。通过与常规注射成型(CIM)对比,初步探讨了GAIM特殊的流场和保压行为对制品双折射分布的影响。     

气体辅助注射成型PC/PE共混物的形态

通过扫描电镜(SEM)对气体辅助注射成型(GA IM)PC/PE共混物制品相形态的观察,发现作为分散相PC的形变规律与在常规注射成型(C IM)制品中的情况有很大差异。在形态分析的基础上,探讨了气体穿透对气体辅助注射成型制品形态的形成和形态分布影响的机理。     

传统注射成型中流动诱导HDPE/UHMWPE共混物的取向结晶

通过熔融共混将少量超高分子量聚乙烯(UHMWPE)引入到高密度聚乙烯(HDPE)中,采用高温熔融和再次剪切对共混物进行处理后,使用传统注射成型方法进行成型。采用偏光显微镜、扫描电子显微镜和二维小角X射线散射对注射成型制品中晶体的形态结构进行了研究。发现传统注射成型(CIM)的流场可以诱导共混物形成明显的多层次晶体结构形态,在次表层存在大量的shish-kebab及互锁shish-kebab晶体结构,具有取向片晶结构的过渡层范围显著增大,而具有球晶结构的芯层范围明显缩小。表明在传统注射成型的流场下也能诱导形成丰富的取向片晶和shish-kebab结构,为注射成型制备自增强材料提供了一条新途径。     

气辅成型过程气体穿透行为的MPI三维模拟及实验

采用MPI/GAS-3D模块分析了不同延迟时间和气体压力条件下的气体穿透效果,并与该工艺条件下实验测定的高密度聚乙烯(HDPE)气体辅助注射成型(GAIM)制品的气体穿透长度(GPL)及残余壁厚(RWT)进行比较,探讨了气辅成型中延迟时间和气体压力等关键工艺参数对制品气体穿透长度和残余壁厚的影响,利用实验数据分析了气体穿透长度与残余壁厚之间的定性关系。     

全同聚丁烯-1注塑成型参数对力学性能和结晶形态的影响

全同立构聚丁烯-1(i PB)根据加工条件的不同,在冷却结晶时会形成复杂的多晶结构和形貌。在注射成型加工过程中,i PB的结晶过程是在高的注射压力下进行的非等温流动诱导结晶。文中研究了注射成型的模具温度、注射压力及保压压力对i PB力学性能的影响,并通过差示扫描量热测试和偏振光学显微镜观察i PB的结晶行为。结果表明,低的模具温度可以提高制品的初始密度和室温放置4 d后的成型密度,30～40℃时制品最终密度和体积收缩率最低。成型温度提高有利于改善制品的弯曲性能,但冲击强度显著降低。随着模具温度升高,制品的结晶度和熔点升高。注射成型中的流动诱导结晶可以改变i PB的晶体形态,制品表面形成微晶组成的取向层,内部较大的球晶显示出随注射流动方向取向的椭球形。     

熔体温度对注塑成型iPP制品结晶形态的影响

注塑成型聚丙烯制品的内部结晶形态对制品的最终性能起着至关重要的作用,而结晶形态的形成对成型条件(尤其是熔体温度)有一定依赖性。文中利用偏光显微镜、小角X射线散射和广角X射线衍射等实验方法,详细研究了熔体温度对注塑成型iPP制品结晶形态的影响。研究结果表明,在实验温度范围内,制品厚度方向形态呈现五层皮芯结构,即冷冻层、过渡层、剪切层、β晶层、α球晶层。随着熔体温度提高,皮层厚度减小;结晶度提高,取向度极大值并无明显变化。     

注塑成型二亚苄基山梨糖醇/茂金属等规聚丙烯的结晶结构及力学性能

利用普通注塑(CIM)和振动剪切注塑(OSIM)方法制备了二亚苄基山梨糖醇(DBS)不同质量含量的茂金属等规聚丙烯(m-iPP)试样,并研究了制品的结晶结构和性能。对试样的X射线衍射和差示扫描量热分析表明,DBS的加入使γ晶相对含量(fγ)减少,这是由于DBS生成网络结构增强了成型过程中α和γ晶的取向生成,进而抑制了试样中的γ晶含量。对试样的力学性能研究发现,添加0.5%DBS且经过OSIM成型的m-iPP试样具有最高的拉伸强度为45.2 MPa。     

振动剪切诱导茂金属全同立构聚丙烯生长γ晶

采用普通注射成型(CIM)和振动保压注射成型(OPIM)两种方法制备茂金属全同立构聚丙烯(m-iPP)试样。利用二维广角X射线衍射(2D-WAXD)和差示扫描量热法(DSC)分别表征试样从表层到芯层的晶体结构和热行为。结果表明:(1)γ晶的相对含量是温度场控制和剪切场诱导共同作用的结果。慢的冷却速率有利于γ晶形成,剪切取向一定程度抑制分子链的折叠有利于γ晶形成;(2)DSC与2D-WAXD的试验结果有很好的一致性。     

The role of gas penetration on morphological formation of polycarbonate/polyethylene blend molded by gas-assisted injection molding

Polycarbonate (PC)/polyethylene (PE) blend was molded respectively by short shot (SS) and gas-assisted injection molding (GAIM). In order to investigate the origin of the “skin-core” structure during GAIM process, the morphology of the two parts molded by SS and GAIM, far from skin, was studied. The results indicate that the structure of the SS part (SSP) is similar to that molded by conventional injection molding (CIM), while the structure of the GAIM part (GAIMP) shows an unusual gradient structure. Many coarse, short PC fibrils arise in sub skin, while such fibrils become more well-defined and reduce in number towards core layer. And the PC phase at the non-gate end, experiences more severe deformation than that at the gate end, which is also different from that in CIM parts. In addition, Moldflow 5.1, a commercial simulation package, was employed to determine the flow behaviors during SS and gas penetration processes. The experimental and simulated results indicate that shear rate and cooling rate are significant for the gradient structure formation during GAIM.     

气辅助成型聚丙烯制品的结晶聚集态

用偏光显微镜和X射线衍射对气体辅助成型聚丙烯制件的结晶形态分布和β晶分布进行了分析研究,并与传统注射成型聚丙烯制件的结晶形态分布进行了对比。结果表明,气辅助成型制件在厚度上呈现取向层-过渡层-大球晶层非对称分布;取向层厚度与延气时间呈"V"字形关系,而随着延气时间的延长,过渡层变厚;过渡层的β晶含量比取向层和大球晶层要高。基于上述现象,提出高压气体延时充入引起二次剪切,并主要集中在过渡层,其次是取向层,气熔界面没有剪切发生,使得该处的晶体形态为大球晶。     

Flow-induced fiber orientation in gas-assisted injection molded part

Polyamide 66 with 33 wt.% glass fiber (DuPont, Zytel 70G33) was molded by gas-assisted injection molding (GAIM). Scanning electron microscope (SEM) micrographs indicated that fibers orientated notably in the core layer and slightly in the region near the mold wall, but aligned disorderly in the region near the gas channel. However, fibers orientated remarkably in the center of the thickness of the GAIM part, which was greatly different from the fiber orientation behavior in the samples molded by the conventional injection molding (CIM) and the water-assisted injection molding (WAIM) as reported in the literatures. Combining with a previous simulation dealing with gas penetration, the mechanisms for fiber orientation in the GAIM part are also discussed.     

气辅注射成型中气体穿透下的聚合物熔体壁厚的形成

针对气辅注射成型模壁表层熔体形成的复杂过程，对薄壁气辅注塑件在气体沿圆形截面气道进行气体穿透推进的充模过程进行了研究分析，通过引入合理的简化和假设，建立了描述气体穿透下模壁表层熔体厚度比β计算的数学模型和近似计算公式。在此基础上，进一步提出了三维薄壁气辅注塑件在气辅注射成型中气体穿透并推动熔体向前充模流动发展变化的熔体／气体前沿处理的程序算法，并用实例进行了数值模拟。研究结果表明，当气体前沿与熔体前沿的压力梯度之比值m在1．0—1．3范围内时，其β的计算结果为0．20—0．43，接近国外学者的实验到定值0．23—0．40，也比较符合实际的气辅注射成型工艺结果。     

Morphological comparison of isotactic polypropylene molded by water-assisted and conventional injection molding

It is well known that water-assisted injection molding (WAIM) process can be fulfilled based on the melt filling stage of conventional injection molding (CIM) process. However, due to the different physical fields involved during WAIM and CIM processes, WAIM part should exhibit unique morphological features compared with the CIM one. In this study, isotactic polypropylene (iPP) parts were prepared by WAIM and CIM, respectively, and their comparative study on morphology were therefore carried out by means of polarized optical microscopy (POM) and two-dimensional (2D) wide-angle X-ray diffraction (WAXD). POM observations illustrated that the WAIM part exhibits a “skin–core–water channel” structure, while the CIM part shows a typical “skin–core” structure. 2D-WAXD results showed obvious arclike reflections in each position along thickness direction of the WAIM part, indicating a pronounced molecular orientation. Furthermore, a parent–daughter model (or branched shish-kebab structure) appears at 0 and 100 μm for both the parts, and the fraction of daughter lamellae for WAIM part is lower than that of CIM part. As for the 1D-WAXD curves, it is noticed that there is a very tiny (300) reflection of β-form in the CIM part, while it is invisible in all positions of the WAIM part. In addition, the crystallinity and crystalline size L of CIM part are found to be higher than that of WAIM part. Those results demonstrate that water penetration and rapid cooling rate have a significant effect on the morphological features of WAIM part.     

气体辅助注塑成型制件开发工艺研究

对塑料家俱制件进行了气辅注塑工艺开发与研究,考察了塑料转奇扶手的气辅加工中气嘴位置,熔体注入量,熔体注射温度,延迟时间、气休注射压力等对充模过程的影响,应用气辅注射模拟软件Ｃ－Ｍｏｌｄ对该制件的气辅助才不同工艺条件对气辅制件的影响做了模拟,并和生产实际进行了比较。