水辅助注塑制品水穿透长度和残留壁厚的研究

介绍了自主研发的水辅助注塑设备以及一款经过大量实验后得到的新型喷嘴,并通过单因素实验法研究了短射法成型聚丙烯弯管时工艺参数对制品水穿透长度和沿水道的残留壁厚的影响。结果表明,熔体注射量对水穿透长度影响最大,当其增加13．5％时水穿透长度减小了153mm；沿水道上制品注水后充填部分比注水前充填部分的残留壁厚减小约0．5～1．0 mm；提高注水压力与增加注水延迟时间时注水后填充部分的残留壁厚略有减小。     

方管短玻纤增强聚合物水辅注射成型穿透模拟及实验

制件的穿透过程一直是水辅助注塑成型(WAIM)研究的热点。基于描述聚合物复合材料的黏弹性方程White-Metzner及流体动力学三大控制方程,采用有限体积法(FVM)开发的软件对由直线构成的方形截面管材短玻璃纤维增强聚合物水辅注射成型的穿透行为进行了数值模拟分析,并通过实验进行验证。分析中主要考虑工艺参数(熔体温度、注水压力、熔体注射量、纤维含量和注水延迟时间)及不同成型方法对制件性能的影响规律。结果表明,熔体温度和注水压力的增加会使制件的中空率增大,而随着延迟时间和注射量的增大,中空率减小;其他工艺参数不变,玻璃纤维含量越高中空率越小,这些现象进一步印证了前人的实验结果。溢流法成型制件的穿透截面形状趋于圆形,玻纤含量越高,圆率越大;短射法成型制件的穿透截面形状趋于型腔截面,且注射量和玻纤含量越高,穿透截面形状越偏离型腔截面;实验结果与模拟相符。     

成型温度对PP和ABS试样表面颜色和光泽度的影响

以K31皮纹为例,研究了成型温度对聚丙烯(PP)和丙烯腈-丁二烯-苯乙烯塑料(ABS)试样表面颜色和光泽度的影响。结果表明,随着模具温度和熔体温度的升高,无论是PP还是ABS,其试样颜色的L值均呈增加趋势而光泽度均呈降低趋势,且ABS试样的光泽度降低程度比PP试样高。注塑温度和模具温度升高,材料的流动性提高,冷却时间延长,试样复制模具皮纹的能力提高,使得PP和ABS试样表面皮纹深度均有所增加,从而使试样的光泽度降低、同时L值升高。与PP结晶型材料不同,ABS作为非结晶型材料,其流动性受温度影响更为显著,随着成型温度的升高,使得ABS试样的光泽度降低的程度更大。     

不同水针口径下的水辅助注射成型数值模拟

使用流体力学软件,对使用溢流法的三维120 °~150 °弯曲圆管件进行了水辅助注射成型可视化研究。分别改变水针口径尺寸、注水延迟时间、注水压力与熔体温度,分析其对制件内部水穿透行为的影响。结果表明,水针口直径为7 mm时,能显著增加制件的内部穿透长度并得到残余壁厚更薄的制件;受水针结构影响,注水延迟时间为1 s、注水压力为8 MPa、熔体温度为250 ℃时,水穿透长度最优能增长400 %,壁厚减少20 %;在注水延迟时间为1 s、注水压力为10 MPa、熔体温度为230 ℃时,穿透长度最大达到298 mm;注水延迟时间为1 s、注水压力为8 MPa、熔体温度为250 ℃时,比熔体温度为210 ℃和230 ℃的实验组受水针影响严重;缩短注水延迟时间、增加注水压力、升高熔体温度都能有效增大制件的中空率,成型出更薄的管件,但是水针对水辅助注射成型的影响不容忽视,其微小变化能极大地改变成型制件的内部型腔,有效提高水穿透行为的效率。     

水辅助注射成型中水穿透行为的可视化研究

基于自主研发的注水系统,利用具有矩形变截面和弯道模腔的水辅助注塑可视化模具,采用聚苯乙烯(PS)材料,对不同水压下的水辅助熔体流动充模的过程进行了观察,着重研究了水的穿透行为。研究发现：注水喷嘴的冷却使其周围熔体黏度增大,水穿透高黏度熔体区后产生紊动射流,射流穿透长度随注水压力的增大而增长。注水压力较低时,水的穿透方向容易发生改变,注水压力越高,水道越光滑。水在弯道入口和收敛过渡区的穿透过程中前缘逐渐缩小,在弯道出口和扩散过渡区的穿透过程中前缘逐渐扩宽。     

气辅新增参数对气辅注塑成型质量的影响

气辅注塑成型新增气辅参数(注气时间、注气压力、延迟时长)直接影响了其成型质量.采用气辅注塑成型全三维数值模拟、成型实验以及正交设计法,研究各新增气辅参数与气辅注塑成型质量之间的关系.结果 表明,较长的注气时间能提高气体穿透深度,减少表面缺陷,降低内应力和翘曲变形,但是会使气指缺陷的程度增大.当注气时间过长时,会导致气辅...     

水辅助注塑技术研究进展

水辅助注塑是在气体辅助注塑基础上发展起来的一种成型中空制品的新技术,综述了水辅助注塑中熔体的流动行为、工艺参数对制品残留壁厚及穿透长度的影响、制品微观形态及力学性能和数值模拟技术的最新进展,最后对水辅助注塑技术研究前景进行展望。     

方管短玻璃纤维增强聚丙烯高压水穿透行为研究

采用方形截面管件,以短玻璃纤维增强聚丙烯为原料,通过溢流法水辅助注射成型实验探究了熔体注射温度、注水延迟时间和注水压力等工艺参数对制件宏观现象的影响机理,并分析了高压水在方形管道中的穿透行为。结果表明,当熔体温度升高时,方管的直角边和斜边残余壁厚都呈减小趋势,但温度过高时会出现管件收缩现象,管件截面中空面积增大且截面形状与高压水的穿透前沿形状一致,偏圆形,但截面的圆率逐渐减小;当注水压力增加时,管件残余壁厚减小,截面中空面积增大,其截面形状随着注水压力的增加逐渐与型腔结构一致,偏方形;当注水延迟时间增加时,管件残余壁厚增大,中空截面减小且管件截面形状也与高压水前穿透前沿一致,偏圆形,但相较另外两个参数,注水延迟时间对方管件的影响程度更小,因而对截面的圆率影响不大。     

镀镍碳纤维/镀镍石墨粉填充PC/ABS材料导电性能的研究

在PC/ABS材料中填充镀镍碳纤维（NiCF）和镀镍石墨粉,制备一种新型填充型导电复合材料,分析了NiCF与镀镍石墨粉的填充量及NiCF长度对复合材料导电性能的影响。结果表明,随着NiCF和镀镍石墨粉填充量的增加,复合材料的体积导电率会下降,即导电性能得到提高。与镀镍石墨粉相比,NiCF对复合材料导电性的影响更显著。NiCF/镀镍石墨粉/PC/ABS复合材料存在渗滤效应,当NiCF含量在10%~15%范围内时,材料的体积导电率急剧下降,导电性能迅速提高。当复合材料颗粒长度为10mm左右时,注塑成型的材料导电性能最佳。     

短玻纤增强PP溢流法水辅注塑水穿透行为影响分析

通过对短玻纤增强聚丙烯溢流法水辅注塑过程进行数值模拟,研究了注水压力、型腔截面形状,以及玻纤含量对水穿透行为的影响。结果表明,注水压力为4 MPa时,各个型腔截面形状的水穿透形状都趋于圆形;随着注水压力升高,边残余壁厚及角残余壁厚则随之减小,且角残余壁厚减小量更大,水穿透率随之增大,但水穿透率增值会呈现减小趋势;当注水压力增大至10 MPa时,水穿透形状都趋于型腔截面形状;水穿透率随型腔截面形状的圆率减小而减小;在注水压力较低(4,6 MPa)时,水穿透率随玻纤含量升高而降低,而在注水压力较高(8,10 MPa)时,趋势相反,此外,随着短玻纤含量的增加,水穿透率受水压的影响越大。这些发现可为实际生产的工艺调节提供参考。     

Non-Isothermal Crystallization of High-Impact Polystyrene/Poly(Phenylene Sulfide) Blends

The morphology of isothermally crystallized poly(phenylene sulfide) (PPS) and a blend combining it with high-impact polystyrene (HIPS) were observed through a polarized optical microscope equipped with a CSS450 hot-stage. The crystalline superstructure of PPS is mainly spherulite, and it was found that the presence of HIPS has little influence on the morphology of PPS, but decreases the nucleation rate of PPS. The effect of HIPS on the non-isothermal crystallization of PPS was investigated by differential scanning calorimetry (DSC). The maximum and onset crystallization temperatures for the HIPS/PPS blend were about 10°C lower than those of neat PPS, which indicates that the crystallization of PPS was retarded by HIPS. The Ozawa model was used to analyze the non-isothermal crystallization kinetics of PPS and its blends. The Avrami exponent values of neat PPS were higher than those of its blend, which shows that the presence of HIPS changed both the nucleation rate and the crystallization rate of PPS.     

The effects of γ irradiation on toughening mechanisms in rubber-modified polymers

High-impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) have been subject to γ irradiation in doses up to 20 and 12.5 Mrad, respectively. During tensile testing, both longitudinal extension and lateral contraction were simultaneously measured, allowing determination of volume strain, and from this to identify the relative contributions of crazing and shear yielding to the tensile deformation process. Both materials show a dose-related increase in the strain at which crazing commences, though the relative change with dose in HIPS is much greater than in ABS. However, the contribution of crazing to total deformation remains high in HIPS when compared with ABS. Shear yielding is an important deformation process in ABS and the results indicate that this is relatively unaffected by irradiation, whereas the ability to craze is severely limited. The reduced ability to craze observed in both materials is considered to be the result of crosslinking in the rubbery phase. The notched impact strength of ABS is particularly sensitive to irradiation and again reflects the reduced ability to craze observed in the tensile testing. ABS fracture surfaces examined by scanning electron microscopy display reduced ductility in the irradiated material. © 1993 John Wiley & Sons, Inc.     

Morphology and thermal properties in the binary blends of poly(propylene-co-ethylene) copolymer and isotactic polypropylene with polyethylene

The morphology and thermal properties of isothermal crystallized binary blends of poly(propylene-co-ethylene) copolymer (PP-co-PE) and isotactic polypropylene (iPP) with low molecular weight polyethylene (PE) were studied with differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). In PP-co-PE/PE binary blends, however, the connected PE acted as a phase separating agent to promote phase separation for PP-co-PE/PE binary blends during crystallization. Therefore, the thermal properties of PP-co-PE/PE presented double melting peaks of PE and a single melting temperature of PP during melting trace; on the other hand, at cooling trace, the connected PE promoted crystallization rate because of enhanced segmental mobility of PP-co-PE during crystallization. At isothermal crystallization temperature between the melting points of iPP and PE, the binary blend was a crystalline/amorphous system resulting in persistent remarkable molten PE separated domains in the broken iPP spherulite. And then, when temperature was quenched to room temperature, the melted PE separated domains were crystallized that presented a crystalline/crystalline system and formed the intra-spherulite segregation morphology: these PE separated domains/droplet crystals contained mixed diluent PE with connected PE components. On the other hand, in the iPP/PE binary blends, the thermal properties showed only single melting peaks for both PE and iPP. Moreover, the glass transition temperature of iPP shifted to lower temperature with increasing PE content, implying that the diluent PE molecules were miscible with iPP to form two interfibrillar segregation morphologies: iPP-rich and PE-rich spherulites. In this work, therefore, we considered that the connected PE in PP-co-PE functioned as an effective phase separating agent for PP and diluent PE may be due to the miscibility between connected PE and diluent PE larger than that between PP and dispersed PE.     

ABS/HIPS共混材料的改性研究

研究了(丙烯腈/丁二烯/苯乙烯)共聚物(ABS)与高抗冲聚苯乙烯(HIPS)质量比对ABS/HIPS共混材料力学性能和加工流动性的影响,并着重对质量比分别为80/20和70/30的两种ABS/HIPS共混材料进行了改性研究。结果表明,氯化聚乙烯(PE-C)、(苯乙烯/丁二烯/苯乙烯)嵌段共聚物(SBS)和K树脂对ABS/HIPS共混材料有不同程度的增容增韧改性作用。如采用9份PE-C与3份SBS并用改性的ABS/HIPS(70/30)共混材料的拉伸强度为27.04MPa,冲击强度为32.60kJ/m2,比改性前约提高2.7倍。转矩流变仪分析表明,PE-C、SBS和K树脂改性的ABS/HIPS共混材料加工流动性和稳定性良好。维卡软化温度测试表明,改性后ABS/HIPS共混材料的耐热性能略有降低,但影响不大。扫描电子显微镜照片清晰反映出改性后ABS与HIPS两相的相容性得到了改善。     

熔体温度对水穿透行为影响的可视化研究

利用水辅助注塑可视化模具和自主研发的注水系统,以聚苯乙烯(PS)为原料,对不同熔体温度下的水辅助熔体流动充模的过程进行了观察,并研究了水的穿透行为。结果表明：熔体温度低,水前缘熔体的惯性力增大,产生"折线"水道,水在后半模腔熔体的穿透中,水前缘速度与水前缘熔体速度相近;熔体黏度高,水前缘速度大于水前缘熔体速度;熔体温度越高,射流穿透的时间越长,水在前半模腔穿透用时越少。     

Crystallization behavior of PBT/ABS polymer blends

Poly(butylene terephthalate) (PBT) crystallization behavior is modified by blending it with acrylonitrile‐butadiene‐styrene copolymers (ABS). The effects of ABS on melting and crystallization of PBT/ABS blends have been examined. Most ABS copolymers of different rubber content and styrene/acrylonitrile ratios studied showed little effect on the melting behavior of PBT crystalline phase. However, ABS copolymer with high acrylonitrile content had a significant effect on the crystallization behavior of the PBT/ABS blends. The nucleation rate of the PBT crystalline phase decreased due to the presence of the high acrylonitrile content ABS, whereas the spherulitic growth rate increased significantly. These phenomena are attributed to changes in nucleation and growth mechanisms of PBT crystalline phase promoted by ABS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 423–430, 1999     

Effect of HIPS on polymorphism,melting, and crystallization behavior of sPS crystallized dynamically from melting state

Syndiotactic polystyrene/highly‐impact polystyrene (sPS/HIPS) blends were prepared with a twin‐screw extruder. Differential scanning calorimetry and wide angle X‐ray diffractometry were used to investigate the effect of the maximal melting temperature, the content of HIPS and cooling rates on the melting and crystallization behavior and crystal forms of sPS. The experimental results indicated that the addition of low content of HIPS induced the formation of more α‐crystal, whereas the addition of high content of HIPS favored the formation of β‐crystal for sPS/HIPS blends crystallized dynamically from low melting temperature. Both sPS and its blends produced only β‐crystal as crystallized from high melting temperature. The crystallization temperatures of sPS and its blends decreased as the melting temperature increased, favoring the formation of β‐crystal. Higher temperature of sPS crystallization favored the formation of more content of α‐crystal while lower temperature of sPS crystallization produced more content of β‐crystal. Cooling rates showed no significant effect on the crystal form of sPS and its blends, but influenced the melting behavior of both sPS and its bends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3353–3361, 2007     

Solid-state C NMR analyses of the structures of crystallized and quenched poly(lactide)s: Effects of crystallinity, water absorption, hydrolytic degradation, and tacticity

The effects of crystallinity, water absorption, hydrolytic degradation, and tacticity on the solid structure and chain mobility of poly(lactide)s were investigated by solid-state ¹³C NMR spectroscopy. The following results were obtained from the line shapes of the carbonyl and methine carbons in ¹³C NMR spectra and their spin-lattice relaxation behavior. The crystallized poly(l-lactide) (PLLA) specimens in the dried, hydrated, and hydrolyzed states had two components, rigid and mobile components which can be, respectively, assigned to the crystalline and non-crystalline components. Upon water absorption, the chain mobility in the non-crystalline component of PLLA-C remained unvaried, reflecting a very small effect of the incorporated water molecules at room temperature. In contrast, the elevated chain mobility in the crystalline component and unclear splitting of carbonyl carbon strongly suggest that the water molecules are incorporated in the crystalline lattice. Upon removal of the non-crystalline components by hydrolytic degradation of crystallized PLLA, the chain mobility was slightly elevated in both crystalline and non-crystalline components by the lowered crystalline thickness and shortened non-crystalline chains. The non-crystalline specimens, PLLA (PLLA-Q) and poly(dl-lactide) (PDLLA), could be analyzed to contain two components, rigid and soft components, with the similar conformation but different restricted states of chains which cause high and low chain mobility. The insignificant difference in the spectral shapes and T_1C values between PLLA-Q and PDLLA strongly suggests that the effects of difference in the chain regularity and interaction on the spectral shapes and T_1C values are very low.