注射成型工艺参数对塑料制品翘曲变形的影响研究

以方形塑料板注射成型工艺为例,以翘曲变形为评价指标,采用Taguchi方法、极差和方差分析方法,优化了模具温度、熔体温度、保压压力和保压时间,获得了最佳工艺参数组合。进行了单因素变动实验和工艺参数交互作用实验,研究了单工艺参数和交互作用对塑料板翘曲变形的影响。结果表明,翘曲变形量随模具温度的增大而增大,随熔体温度、保压压力和保压时间的增大而减小;模具温度和熔体温度、模具温度和保压压力、熔体温度和保压时间的交互作用对翘曲变形影响显著,模具温度和保压时间、熔体温度和保压压力、保压压力和保压时间的交互作用对翘曲变形影响不显著。     

玻璃纤维增强聚丙烯制品翘曲变形的研究

针对玻璃纤维增强聚丙烯(PP/GF)注射成型制品存在的翘曲变形缺陷,研究了注射工艺参数如模具温度、喷嘴温度、注射速率、保压压力和保压时间对制品成型收缩率及翘曲的影响。结果表明,随着模具温度、喷嘴温度和保压压力的降低,制品的翘曲减小;适当提高注射速率和减少保压时间也可减小制品翘曲。     

带金属嵌件的手机外壳注塑成型翘曲变形分析

在Moldflow模拟分析的基础上,通过正交试验研究了熔体温度、模具温度、注射时间、保压压力、保压时闻和冷却时间等工艺参数对带金属嵌件的手机外壳注塑成型翘曲变形的影响,并优化了成型工艺.结果表明,保压时间和保压压力对翘曲变形的影响最大,最佳工艺组合为:熔体温度310℃,模具温度120℃,注射时间0.3 s,保压压力14...     

注塑成型工艺参数对壳盖注塑件翘曲变形的影响

以降低注塑件翘曲值为目标,采用正交试验法,得到注塑成型工艺参数对翘曲值的影响程度由强到弱依次为保压压力、熔体温度、注射时间、保压时间和冷却时间。对单个注塑成型工艺参数变动和多注塑成型工艺参数交互作用进行了分析。结果表明:延长注射时间或升高熔体温度,均可使翘曲值先增大后减小;增大保压压力或延长保压时间均可使翘曲值逐步缩小;延长冷却时间,翘曲值则先减小后增大;翘曲值在保压压力与熔体温度、注射时间与熔体温度的交互作用下发生显著变化,而保压时间与保压压力、保压时间与熔体温度的交互作用则对翘曲值的影响不明显。     

基于MPI和灰色关联异型出风罩注塑参数优化

针对某异型出风罩注塑成型工艺,以聚碳酸酯/丙烯腈-丁二烯-苯乙烯共聚物(PC/ABS)工程塑料合金为填料,运用Moldflow软件对其注塑过程进行模流分析,通过田口实验设计研究了熔体温度、保压时间、保压压力、注射时间和模具温度对塑件收缩率和翘曲变形量的影响,得到它们对塑件收缩率的影响次序为:保压时间>熔体温度>保压压力>注射时间>模具温度,对翘曲变形量的影响次序为:保压压力>注射时间>熔体温度>保压时间>模具温度。基于灰色关联分析,获得了最优组合工艺参数,即:熔体温度280℃、模具温度为65℃、注塑时间2.1 s、保压时间11 s、保压压力21 MPa。优化后的仿真结果表明,塑件的体积收缩率为6.523%、翘曲变形量为0.80 mm,比灰色关联次序中位组合的样本数据分别降低6.9%和15.8%,并获得最大注射压力为20.34 MPa、最大锁模力为3.25×10^5 N,为后期模具的设计和注塑参数设定提供了有力的参考,缩短了模具开发周期。     

基于正交试验的翼子板成型工艺优化

基于正交试验设计了4因素4水平实验方案，以翘曲变形量为评价指标，研究了模具温度、注塑温度、保压时间和保压压力对汽车翼子板翘曲变形量的影响。结果表明：基于均值和极差值的比较，对翘曲变形量的影响由大到小依次为注塑温度、保压压力、保压时间、模具温度。最佳成型工艺组合为模具温度55℃，注塑温度230℃，保压时间15 s，保压压力95 MPa，此条件下获得的翼子板翘曲变形量为3.967 mm。     

基于Moldflow的注塑件残余内应力的研究

通过对注塑件残余内应力的影响因素的分析,发现熔体温度和模具温度对残余内应力的产生较大的影响,注射速率、保压时间和保压压力相对影响较小,通过对注塑工艺参数的优化,可以降低残余内应力;工业静液压测试验证了数值模拟的结果,且发现熔体温度和模具温度对残余内应力的产生较大的影响,注射速率、保压时间和保压压力相对影响较小。     

基于Moldflow变直径管工艺参数优化与模具设计

建立变径管模型,并利用Moldflow对变直径管进行充填、保压、冷却、翘曲模拟分析得出最佳浇口位置与数量,结合正交实验分析了模具温度、熔体温度、充填时间、保压压力、保压时间等工艺参数对变直径管翘曲变形的影响并得到最佳参数组合;利用Moldflow验证最佳参数组合,并在此基础上设计出模具,使得生产的产品品质得到提高。     

工艺参数对沉降斑影响的实验研究

采用实验方法考察工艺参数对沉降斑的影响。基于一个带凸台的平板模具,采用L27(313)正交矩阵进行实验,研究了几何尺寸、熔体温度、注射时间、保压压力及保压时间对厚度突变处沉降斑形成的影响,同时还考虑了熔体温度和注射时间以及保压压力和注射时间之间的交互作用影响;通过性噪比分析和F检验优化成型工艺条件并对工艺参数的影响进行显著性分析。结果表明,对于厚度突变的平板制品,厚度突变的程度对其沉降斑形成的影响最大,其次为熔体温度,保压压力,保压时间等;采取减小厚度变化,降低熔体温度或增加保压压力和保压时间等措施,可以减小厚度突变处沉降斑,从而减少其对外观质量的影响;因素之间的交互作用对制品沉降斑的形成有一定的影响,熔体温度B和注射时间C之间的交互作用影响较为明显,而保压压力D和注射时间C之间的交互作用对该质量指标的影响最小,可以并入误差。     

基于制品体收缩率的多型腔注塑模工艺参数优化

选用L27(313)正交表设计实验,研究模具温度、熔体温度、充填时间、保压压力和保压时间以及三个两因素交互作用对多型腔模具PP塑料制品每个型腔体收缩率的影响程度。对于所选参数,模具温度和保压时间对体收缩率的影响是高度显著的,熔体温度和保压压力对体收缩率的影响是显著的。在优化工艺组合下体收缩率降低了21.46％。     

微流道中聚合物熔体的弹性特性研究

采用双机筒毛细管流变仪,以直径1.5 mm的口模作为宏观流道、直径0.5 mm的口模作为微观流道、直径1.0 mm的口模作为临界参考,通过毛细管入口压力降和聚合物熔体应力松弛时间研究了微尺度下聚甲基丙烯酸甲脂（PMMA）、聚苯乙烯（PS）、高密度聚乙烯（PE-HD）及聚丙烯（PP）4种聚合物熔体的弹性特性,并讨论了在口模直径为0.5 mm条件下温度对入口压力降和应力松弛时间的影响。结果表明,微流道中4种聚合物熔体的入口压力降与应力松弛时间与宏观流道相比均有增大的趋势,且流道尺寸越小,增大趋势越明显;随着剪切速率的增大,4种聚合物熔体的入口压力降增大,但在高剪切速率下,增大趋势变缓;微流道中,随着温度的提高,4种聚合物熔体的入口压力降降低,应力松弛时间变短。     

热拉伸过程中PE–UHMW/PE–HD共混纤维的晶体结构演变

将超高分子量聚乙烯(PE–UHMW)与高密度聚乙烯(PE–HD)按照质量比为6︰4进行共混熔融纺丝,并对初生丝进行高倍热拉伸制得PE–UHMW/PE–HD共混纤维。利用广角X射线衍射、差示扫描量热、声速取向试验等方法研究了PE–UHMW/PE–HD共混纤维在热拉伸过程中的晶体结构演变过程。研究显示,随着热拉伸过程的进行,纤维的分子链沿纤维的轴向取向度逐渐增加,熔融峰温度逐渐升高,结晶度逐渐增加;沿径向的晶粒尺寸逐渐减小,而沿轴向的晶粒尺寸逐渐增加,即形成了更细长的晶粒;晶体的取向度逐渐增加。当拉伸倍数由1增大至6时,上述现象变化显著,当拉伸倍数由9增至15时,上述现象变化缓慢。与PE–HD共混后的纤维结晶度、晶体取向度和分子链取向度更高,晶粒更加细长。     

Deformation,yield and fracture of polymers at high pressure

The effects of hydrostatic pressure on the shear, compressive, and tensile stress-strain behavior of both amorphous and crystalline polymers are reviewed and illustrated. For polymers with T_g near to but below ambient temperature, there is a steep increase of modulus with pressure and, above some critical pressure, there is a lower rate of increase. The critical pressure is a linear function of the test temperature and, from its slope, one can deduce the pressure coefficient of T_g. For many other polymers, there is a linear increase, over a wide pressure range, of elastic and shear moduli with pressure, and this is in accord, to a first approximation, with predictions of finite strain theory. Most all polymers investigated show a strong pressure coefficient of yield stress and in many cases this variation is linear over a wide pressure range, in accord with several pressure dependent yield criteria. To a considerable extent, the yield stress rise with pressure parallels that of the modulus, and this behavior is predicted by some yield theories. The effects of pressure on fracture stress and fracture strain are discussed. The results obtained depend on the polymer composition and structure and on the pressure medium. Consideration is also given to the effects of pressure on crazing and stress-whitening.     

Hydrostatic extrusion rate relaxation in polyethylene,polyoxymethylene, and their blends. The relaxation of viscosity and compressibility in polymeric solids

It is reported on precision measurements of the hydrostatic extrusion rate of polyethylene, polyoxymethylene, and their blends in dependence on pressure and temperature. It turns out that the extrusion rate change after a sudden pressure change consists of an immediate response and a second one which relaxes toward its new equilibrium value with a time constant of several minutes. Both relaxation components have different sign. Increasing pressure causes a decrease of the extrusion rate by the slow relaxation step. Relaxation strength and inverse time constant of this relaxation component exhibit a maximum at a certain pressure. The overall relaxation behaviour is assumed to be caused by a superposition of the competing effects of free volume relaxation in the amorphous parts in these semicrystalline polymers, of compressibility relaxation, of volume recovery in the extruded strands, and of viscosity changes in the sample materials during the pressure induced plastic deformation of both the amorphous and the crystalline phases.     

曲率对PE管材环向拉伸强度的影响

选用环向拉伸试验的方法对高密度聚乙烯（PE-HD）管材环向拉伸的强度进行检测,主要研究拉伸试样在试验进行过程之中曲率的改变对环向拉伸强度的影响,整个试验过程采取多个平行试样进行试验,用以取得准确的试验数据来确定试验结果,并就曲率对PE-HD管材环向拉伸强度影响的变化规律进行研究探讨。结果表明,同一外径的PE-HD管材,随着环向拉伸试样在试验中曲率的减小,环向拉伸强度数值减少可达10 %。     

高密度聚乙烯振动注射试样的结构与性能

为了研究高密度聚乙烯振动注射试样的晶体结构与性能．研制并采用压力振动装置进行振动注射实验一通过振动，高密度聚乙烯由常规注射试样的典型球晶结构转变为明显取向的片晶结构，在不同的振动条件下，片晶的尺寸和取向度都不同。振动试样的拉伸强度随振动频率和振动压力的提高而提高，最大增幅为41.0％。断裂伸长率随振动压力的增高而下降，随振动频率的增高开始时下降，然后开始回升。     

A stochastic analysis of the effect of hydrostatic pressure on the pit corrosion of Fe-20Cr alloy

The effect of hydrostatic pressure on the pit corrosion behavior of Fe-20Cr alloy was investigated in 3.5% NaCl solution by means of potentiodynamic polarization and potentiostatic technology, and the experiment data was analyzed based on stochastic theory. With the increase of hydrostatic pressure, the pit corrosion resistance of Fe-20Cr alloy was deteriorated, which was distinguished by the decrease of critical pit potential (E_cirt) and the increase of passive current density. The results also demonstrated that there exist two effects of hydrostatic pressure on the corrosion behavior of Fe-20Cr alloy: (1) the pit generation rate was evidently increased compared to that under lower hydrostatic pressure, and the metastable pits become faster and larger. However, it seemed that pit generation mechanism shows no hydrostatic pressure dependence; (2) the probability of pit growth increased with the increase of hydrostatic pressure, which implied that the metastable pit on Fe-20Cr alloy exhibited higher probability to become larger pit cavity during shorter time interval than that under lower hydrostatic pressure.     

Polymerization kinetics of 10,12-pentacosadiynoic acid monolayer and possible acceleration effect of visible light

The molecular area change of 10,12-pentacosadiynoic acid (PDA) monolayer was recorded and large molecular area expansion was observed during UV-polymerization. The expansion speed experienced a quick increase to maximum and then a steady decrease to zero and finally the area change was converted into a slow contraction. The rate of molecular area change depended on the reaction temperature. Turning off the UV-light during the experiments resulted in area contraction. The contraction speed was described with a kinetic equation, which suggested an accompanied area relaxation during the polymerization. A model for the reaction kinetics (both based on the polymerization and the area relaxation) was proposed and well corresponded to the experimental data. By using this model, the ‘activation area’ was calculated to be 0.127 nm² which was little dependence of the reaction temperature. The positive activation area during the monolayer polymerization indicated that there was an increase in area when the activated complex was formed. The rate constant decreased upon elevated surface pressure. The possible effect of visible-light on the monolayer UV-polymerization was investigated in detail by periodically switching on and off the visible light while keeping the UV-light on. An acceleration phenomenon of the visible light on the monolayer UV-polymerization was observed. The acceleration effect was illustrated by the polymerization mechanism and the electronic state of the polymerization intermediates.     

RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FLUIDS WITH A NOVEL VISCOMETER

A hydrostatic head viscometer and its novel viscosity equation were developed to determine flow characteristics of Newtonian and non-Newtonian fluids. The objective of this research is to test capabilities of the hydrostatic head viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of well-known polyethylene oxide aqueous solutions as non-Newtonian fluids with 60 wt.% sucrose aqueous solution as a reference/calibration fluid. Non-Newtonian characteristics of 0.3–0.7 wt.% polyethylene oxide aqueous solutions were extensively investigated with the hydrostatic head viscometer and its non-Newtonian viscosity equation over a 294–306 K temperature range, a 0.14–40 Reynolds number range, and a 55–784 s^?1 shear rate range at atmospheric pressure. Dynamic viscosity values of 60 wt.% sucrose aqueous solution were determined with the calibrated hydrostatic head viscometer and its Newtonian viscosity equation over a 3–5 Reynolds number range at 299.15 K and atmospheric pressure and compared with the literature dynamic viscosity value.     

RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FLUIDS WITH A NOVEL VISCOMETER

A hydrostatic head viscometer and its novel viscosity equation were developed to determine flow characteristics of Newtonian and non-Newtonian fluids. The objective of this research is to test capabilities of the hydrostatic head viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of well-known polyethylene oxide aqueous solutions as non-Newtonian fluids with 60 wt.% sucrose aqueous solution as a reference/calibration fluid. Non-Newtonian characteristics of 0.3-0.7 wt.% polyethylene oxide aqueous solutions were extensively investigated with the hydrostatic head viscometer and its non-Newtonian viscosity equation over a 294-306 K temperature range, a 0.14-40 Reynolds number range, and a 55-784 s^-1 shear rate range at atmospheric pressure. Dynamic viscosity values of 60 wt.% sucrose aqueous solution were determined with the calibrated hydrostatic head viscometer and its Newtonian viscosity equation over a 3-5 Reynolds number range at 299.15 K and atmospheric pressure and compared with the literature dynamic viscosity value.