动态注射成型聚丙烯制品的热氧老化性能EI

利用电磁动态注射机注射成型聚丙烯试样制品,并用热老化试验箱人工加速其试样的老化降解。对比分析了稳态注射和动态注射成型的聚丙烯试样制品热氧老化期间力学性能的变化规律,用红外光谱(FT-IR)分析了聚丙烯试样制品老化前后羰基含量的变化情况。研究结果表明,采用动态注射成型技术,不但可以提高聚丙烯制品的力学性能,而且还能有效提高制品的抗热氧老化性能。制品在热氧老化过程中,其力学性能保持率高于稳态注射成型的聚丙烯制品。采用振频为8 Hz、振幅为0.10 mm的动态注射成型的聚丙烯试样制品的抗热氧老化性能最好。     

动态注射成型聚丙烯制品的湿热老化性能研究

通过对动态注射成型聚丙烯制品进行人工加速老化,对其老化性能进行测试研究,探讨了聚丙烯制品的抗湿热老化机制.利用动态注射成型机注射成型聚丙烯制品,采用DSC等测试手段分析了稳态注射和动态注射成型的聚丙烯制品的性能特征,通过湿热老化试验(90℃,湿度为95%),对比分析了稳态注射和动态注射成型的聚丙烯制品老化期间力学性能的...     

紫外光辐照对注射成型聚碳酸酯制品光学性能和拉伸性能的影响

本文研究了紫外光辐照对注射成型聚碳酸酯制品的光学性能和拉伸性能的影响。结果表明,紫外老化240h后,制品表面发生了光-弗里斯重排和光氧化反应,生成了有色基团,制品颜色变黄,紫外吸光率增加;拉伸强度和韧性降低。热氧老化对照实验表明,在60℃下,紫外光辐照对注射成型聚碳酸酯制品性能降低起主要作用。     

热氧老化对阻燃型长玻纤增强尼龙6静动态力学及降解动力学的影响

研究了160℃不同热氧老化时间对阻燃型长玻纤增强尼龙6(FR/PA6/LGF)复合材料的静、动态力学性能及降解行为的影响。热与氧对FR/PA6/LGF复合材料的影响通过差示量热分析、动态力学性能分析、扫描电镜及力学性能表征。结果表明,虽然由动态力学性能分析可知热氧老化使得树脂基体分子链的刚性增加,但最终基体分子链断裂、降解导致老化试样表面出现的凹坑、微裂纹和脱粘在老化进程中占据了主导地位。利用Ozawa法求出了不同老化时间处理后FR/PA6/LGF热氧降解反应的活化能,结果表明热氧老化降低了阻燃材料的热稳定性,影响了其在不同燃烧区的阻燃效率。     

不同热氧环境对T800碳纤维/环氧树脂复合材料力学性能的影响EI北大核心CSCD

不同热氧环境(70,130,190℃)对碳纤维复合材料的性能有着重要的影响。分析了不同热氧环境下T800碳纤维/环氧树脂复合材料的失重特性,并对比了老化前后的表面形貌、红外光谱、动态力学性能和层间剪切性能。结果表明:在热氧老化初始阶段,质损率急速上升,老化温度越高质量损失越快;试样表面形貌随热氧温度的升高其破坏程度逐渐加剧,在190℃老化后,纤维表面树脂脱落严重,纤维与纤维之间出现裂缝空隙,无树脂填充,在此老化温度下,试样发生了不可逆化学变化;试样的玻璃化转变温度会随老化温度的升高而变大,但内耗呈现先降低后增大再降低的趋势,在70,130,190℃热氧老化后试样剪切强度分别提高6.0%,13.7%和2.1%。相关实验结果和实验现象可为后续研究新型国产T800碳纤维/环氧复合材料提供数据参考。     

等规聚丙烯微注塑制品的力学性能

采用等规聚丙烯材料,选取弹性模量和屈服强度作为微制品力学性能的指标,基于正交实验设计进行微注塑成型实验以成型微拉伸试样,采用直观分析、信噪比分析及方差分析对微试样的拉伸实验结果进行分析,研究工艺参数对厚度1.0 mm,0.5 mm和0.2 mm的微注塑制品力学性能的影响规律及重要性,并分析尺度效应对微制品力学性能的影响。实验结果表明,不同尺度下,各个工艺参数对微制品力学性能的影响规律和重要性均不同,且随着尺寸的减小,微注塑制品的拉伸屈服强度增大,弹性模量增大。     

3,5-二叔丁基-4-羟基苯甲酸十二硫酯的合成及其对聚丙烯抗氧化性能研究

以3,5-二叔丁基-4-羟基苯甲酸和十二硫醇为原料,采用酯化反应,合成了抗氧剂3,5-二叔丁基-4-羟基苯甲酸十二硫酯(DMB)分子内复合抗氧剂,并通过红外光谱和核磁共振谱对其进行结构表征.同时,制备了抗氧剂DMB和聚丙烯的共混体系,通过差热扫描量热法和烘箱老化试验评价了DMB对聚丙烯树脂的热氧化降解行为.差热扫描量热法结果表明DMB能明显提高PP的耐热氧老化性能.烘箱老化研究显示,PP-DMB试样的拉伸强度和冲击强度在老化5～6d内保持率很好,6d后,迅速下降.熔体流动速率研究表明,PP-DMB试样在烘箱老化5d后,其熔体流动速率开始上升.     

咪唑基离子液体修饰蒙脱土/聚丙烯复合材料的耐热老化性能

研究了1-十八烷基-3-甲基氯化咪唑修饰的蒙脱土/聚丙烯复合材料耐热老化性能。结果表明,热老化前改性蒙脱土/聚丙烯复合材料的拉伸性能、弯曲性能与聚丙烯相比均有所改善,分别提高了7.3%和17.5%,冲击性能提高达54%。经以5d为一老化周期的热老化,研究了4个老化周期中改性蒙脱土/聚丙烯复合材料的力学性能保持率,质量变化率,以及颜色变化的情况。研究发现,在热老化过程中,复合材料的力学性能有很高的保持率,部分性能甚至得到改善,复合材料的质量变化很小,颜色无明显加深,说明该离子液体修饰的蒙脱土/聚丙烯纳米复合材料不仅有很好的力学性能,而且耐热老化性能优越。     

环氧胶粘剂及其胶接界面热氧老化机理研究

采用红外光谱、X射线光电子能谱和扫描电镜对环氧胶粘剂的热氧老化机理进行了研究。同时,对环氧胶接结构进行了力学性能分析,研究了热氧环境对其力学性能退化的影响。结果表明,环氧胶粘剂在热氧加速老化中发生的化学反应主要有后固化反应和氧化反应。热氧老化过程中,环氧胶中的羟基被氧化为醛基化合物,亚甲基被氧化为酰胺。热氧加速老化后的力学性能表明,环氧胶材料本体的耐老化性能好,界面粘接强度具有较好的稳定性。     

成型方法对氢氧化镁/乙烯-乙酸乙烯酯共聚物/线性低密度聚乙烯复合材料结构和热稳定性的影响

分别研究了采用压制成型和挤出成型的氢氧化镁(MDH)/乙烯-乙酸乙烯酯共聚物(EVA)/线性低密度聚乙烯(LLDPE)复合材料的力学性能和热稳定性能。用差示扫描量热分析(DSC)和扫描电镜(SEM)表征了两种成型方法所得试样的不同结构特征,分析了影响试样性能差异的结构因素。结果表明,挤出成型赋予复合材料多层次的取向结构,具有明显的取向增强效应和弹性记忆效应。热老化时明显的热松弛回缩、分子重排、填料脱粘和附聚,是导致材料热老化稳定性劣化的主要原因。     

注塑成型长玻璃纤维/聚丙烯复合材料的冲击韧性

利用自行研制的连续纤维/热塑性树脂浸渍装置,制备了注塑成型用长玻璃纤维增强聚丙烯粒料。利用Charpy冲击试验,研究了界面相容剂(接枝马来酸酐聚丙烯)的用量、粒料长度等对注塑试样冲击韧性的影响。试验发现,随着接枝聚丙烯含量的增加,试样的冲击韧性显著提高。但当接枝聚丙烯含量达到一定程度时,冲击韧性反而下降。注塑试样的冲击韧性随长纤维粒料的长度增加和冲击试样模具的浇口尺寸变大而升高。对于平板材料,冲击试样所处的位置不同,其韧性也有较大的变化。试验还发现,退火处理可以有效地提高注塑试样的冲击韧性。      

变模温与型腔气体反压辅助微孔发泡注塑技术及其产品内外泡孔结构演变

建立了一种变模温和型腔气体反压协同控制的微孔发泡注塑技术,研制了相应的变模温控制系统与型腔气体反压控制系统,构建了变模温与型腔气体反压辅助微孔发泡注塑试验线,并对变模温与型腔气体反压作用下的产品内外泡孔结构演变进行了研究。结果表明,变模温与型腔气体反压辅助工艺单独施加于微孔发泡注塑技术时,对其产品内外泡孔结构均具有双重影响:变模温可以改善产品大部分的表面形貌,但其对填充过程中的熔体发泡影响不大;型腔气体反压可以基本抑制填充过程中的熔体发泡,但却对产品内部泡孔密度有比较明显的降低影响。通过变模温与型腔气体反压的协同控制,可以实现微孔发泡注塑产品表面气泡形貌和内部泡孔结构的良好调控。     

Effect of reinforced fiber length on the joint performance of thermoplastic leaf spring

Joint strength plays a significant role in the performance of leaf spring suspension system. Current work reported the influence of reinforced fiber length on the performance of injection molded thermoplastic leaf spring joint. Leaf springs were molded using 20% short, long glass fiber reinforced polypropylene as well as unreinforced polypropylene and evaluated for the joint strength. Servo hydraulic test facility with suitable fixture is utilized to evaluate the leaf spring joint performance under static and dynamic conditions. Test joints were subjected to completely reversed fatigue loads, wherein long fiber reinforced leaf spring joint exhibited superior performance at high cycle fatigue conditions than that of short fiber reinforced and unreinforced polypropylene leaf spring joints. However, at low cycle fatigue loading conditions, unreinforced and short glass fiber reinforced leaf spring exhibited superior performance than that of long glass fiber reinforced leaf spring joint. High notch sensitivity characteristics of the long glass fiber reinforced polypropylene material contributed to this inferior performance. Load–deflection hysteresis plot of the long glass fiber reinforced leaf spring joint under fatigue loading conditions exhibited a lesser amount of hole elongation compared to that of short glass fiber and unreinforced leaf spring joint. Failure morphology of tested joint under fatigue condition exhibited net-tension and shear-out failures besides bearing damages.     

Mechanical property and hydrothermal aging of injection molded jute/polypropylene composites

This study discussed the effects of jute fiber content and hot water immersion on the tensile properties of jute fiber reinforced polypropylene (PP) composites. The jute/PP composite with different fiber contents was molded by injection molding by dry-blending of jute/PP and neat PP pellets in various mix ratios. Firstly, the quasi-static tensile test was performed. Then the specimens were aged in hot distilled water at 80 °C. After the fixed periods of aging, the changed weight and the tensile properties were investigated. It is found that with the increase of the jute fiber content, the tensile modulus is increased lineally. However, referring to the tensile strength, it is increased firstly followed by a decreased when the jute weight percent is over 30. Additionally, it is found that the weight gain by water absorption was significantly affected by the fiber content. The specimens with the jute fiber content of or over 30 wt% absorbed water easily and significant material loss by aging was also occurred. The tensile strength after aging decreased remarkably in these specimens with the jute fiber content of or over 30 wt%, and all the jute/PP composites showed the lower strength than neat PP after the aging of 1000 h. It is considered that the hydrophilic property of natural fiber decreases the resistance of the composite in humidity environment.     

聚合物注塑内应力和翘曲变形的数值模拟

由聚合物粘弹性理论和注塑成型原理出发,考虑了聚合物玻璃态的非线性粘弹性响应,采用新的四元件粘弹性力学模型模拟计算注塑制品冷却过程中内应力的形成与发展。在此基础上,采用改进的Allman膜单元[1]和离散Kirchhoff板单元[2]组合生成的板壳单元,模拟计算注塑件的翘曲变形,计算结果与实验结果一致,计算精度有所提高。     

注塑成型制品翘曲变形优化建模分析

目的 针对传统建模方法在预测的翘曲变形位置与实际偏差较大的问题,开展基于Moldflow的注塑成型制品翘曲变形优化建模分析研究.方法 通过数据模拟分析预处理、浇注体系模型构建、基于Moldflow的注塑成型制品翘曲变形过程模拟等手段,实现对注塑成型制品曲面参数优化.结果 通过对比实验证明,新的建模方法与传统建模方法相比...     

聚丙烯分子量对其注射成型试样的拉伸和抗冲特性的影响

通过对聚丙烯及其经化学降解后的一系列不同分子量聚丙烯的注射成型样条的密度、结晶度、形态、取向、常温拉伸特性和低温抗冲性等方面的实验,讨论了分子量对这些性能的影响。分子量对密度、结晶度影响不大,但对形态及内外层的取向结构影响较大,而低温抗冲性能随分子量下降较多,常温抗拉特性随分子量变化较复杂,就其综合性能而言,以分子量在某一范围内较好。     

长玻璃纤维/聚丙烯复合材料粒料注塑制品的拉伸强度

利用自行研制的玻璃纤维(GF)增强聚丙烯(PP)预浸装置,制备了长玻纤增强聚丙烯(LGFRP)粒料,并通过普通注塑机注塑成型。研究了界面改性、粒料长度、浸渍程度及退火处理等对注塑试样拉伸强度的影响。试验发现,用接枝马来酸酐PP作为界面相容剂,试样的拉伸强度明显提高。当接枝马来酸酐量占PP量的0.3 %左右时,试样强度达到最大值。长纤维粒料内纤维浸渍度越高,注塑试样的强度越好。15 mm和5 mm长纤维粒料注塑成型试样的拉伸强度均高于10 mm粒料注塑成型的试样。退火处理可较大程度地提高注塑试样的拉伸强度。     

Picosecond Laser Surface Texturing of a Stavax Steel Substrate for Wettability Control

In this investigation, a picosecond laser was employed to fabricate surface textures on a Stavax steel substrate, which is a key material for mold fabrication in the manufacturing of various polymer products. Three main types of surface textures were fabricated on a Stavax steel substrate: periodic ripples, a two-scale hierarchical two-dimensional array of micro-bumps, and a micro-pits array with nano-ripples. The wettability of the laser-textured Stavax steel surface was converted from its original hydrophilicity into hydrophobicity and even super-hydrophobicity after exposure to air. The results clearly show that this super-hydrophobicity is mainly due to the surface textures. The ultrafast laser-induced catalytic effect may play a secondary role in modifying the surface chemistry so as to lower the surface energy. The laser-induced surface textures on the metal mold substrates were then replicated onto polypropylene substrates via the polymer injection molding process. The surface wettability of the molded polypropylene was found to be changed from the original hydrophilicity to super-hydrophobicity. This developed process holds the potential to improve the performance of fabricated plastic products in terms of wettability control and easy cleaning.