顺序共注射成型工艺参数对iPP制品柱晶生成的影响

采用偏光显微镜观察共注射成型制备的等规聚丙烯夹芯制品不同位置处的微观形貌,特别是不同成型工艺条件下复杂温度场和剪切场形成的柱状晶体结构。研究了芯层注射速度、芯层注射温度和延迟时间对选定位置(迟滞线位置处,芯层熔体流动前沿处)柱晶生成数量的影响。结果表明,芯层注射温度为190℃和延迟时间为5 s有利于柱晶的生成,芯层注射速度为20 mm/s时,迟滞线位置处柱晶的数量最多,而芯层熔体流动前沿位置处柱晶数量最少。     

振动注射实现聚丙烯试样自增强自增韧形态研究

利用自行研制的振动注射实验装置，实现振动注射成型和常规注射成型。和常规注射成型相比，随着振动频率的增加，振动注射成型的聚丙烯哑铃试样拉伸强度增加的同时，韧性也得到了一定程度的提高。SEM显示振动注射实现芯层晶粒的细化，剪切层球晶取向程度明显；DSC测试表明振动注射成型有利于试样结晶度的提高，结晶度由常规注射成型的37．04％提高到48．53％；WAXD分析说明试样韧性的改善是由于振动注射成型生成了部分的β晶型。     

低频振动场对HDPE性能的影响

利用低频熔体振动注射成型技术获得自增强高密度聚乙烯。实验结果表明,采用振动注射成型工艺,试样屈服拉伸强度由26.5MPa提高到36.1MPa;试样的芯层中可获取沿流动方向生成的串晶或行式排列的片晶结构;压力振动注射有利于分子在(110)晶面择优取向,使结晶更加完善;振动注射提高了试样的结晶度,芯层结晶度最大提高了10.2%。     

熔体剪切变稀特性对聚合物水辅共注射成型过程的影响

通过建立的全三维非稳态非等温水辅共注射成型过程有限元数值模拟算法与技术,系统研究了芯层熔体剪切变稀特性对水辅共注射成型中水与芯层熔体的穿透过程和前沿界面运动稳定性的影响规律,并揭示了其机理。结果表明,随着芯层熔体剪切变稀特性增加,水辅共注射成型水和芯层穿的透深度增大,这有利于细长制品的水辅共注射成型。然而芯层熔体剪切变稀特性的增加会使水与芯层熔体前沿移动界面流动趋于不稳定,严重影响制品内表面成型品质。     

聚合物流变性能对共注射成型的影响

在共注射成型多相分层流动充模成型机理的基础上，揭示了芯壳层熔体对共注射成型的分层界面形貌和芯层熔体前沿突破的影响，并模拟了芯壳层熔体粘度比对共注射成型的影响，建立了芯壳层熔体粘度与分层界面和前沿移动界面菜貌的关系。本文的模拟研究结果与一些文献的实验结果相吻合。     

夹芯注塑成型过程的计算机可视化模拟分析--材料粘度与工艺参数对芯层分布及均匀性的影响

为了了解夹芯注塑的成型过程、探悉其成型机理,采用Moldflow公司MPI软件中的Co-injection分析模块,对夹芯注塑成型过程进行动态模拟分析,揭示材料粘度以及工艺参数对夹芯注塑成型过程中芯层分布均匀性的影响规律。结果表明,芯层物料分布均匀性随芯／壳层熔体粘度比R值的减小而提高,这主要与芯层和壳层熔体的相对流动能力有关。此外,在工艺参数中,改变熔体注射速度对芯层物料分布均匀性的影响较为突出,而模温和熔体温度对芯层物料分布均匀性的影响却相对较弱。     

长支链聚丙烯微注射成型的研究

研究了长支链聚丙烯微注射试样的形态结构、结晶形态和力学性能,探讨了微注射试样的结构与性能之间的关系。结果表明,长支链聚丙烯微注射试样的皮层区域为串晶结构,芯层区域为球晶结构,长支链结构引入使得芯层区域球晶数量增加,晶粒细化;当单体三羟甲基丙烷三丙烯酸酯(TMPTA)含量超过0.7 mL时,长支链聚丙烯微注射皮芯结构消失,层与层之间的界面模糊,原因在于支链结构导致了熔体松弛时间增加,最终成型微制品芯层分子延流动方向进行取向;通过力学性能分析,发现长支链聚丙烯微注射试样的拉伸强度增至41.22~41.32 MPa,增长幅度为14.27%。     

夹芯注射成型研究进展

为了了解夹芯注射的成型过程及内部结构、探悉其成型机理,研究者主要对芯层熔体前缘的冲破现象、芯壳层物料的分布情况以及夹芯注塑件的力学性能进行了研究。文献显示,物料的性能尤其是粘度、加工工艺参数如注射速度、模温、熔融温度等以及模具尺寸对夹芯注射的充模过程及其制品最终的性能影响最为突出。     

中等分子量PP在动态保压单向流动场中的结构与性能研究

利用自行研制的能够方便改变工艺条件的新型动态保压注射成型(DPIM)装置,研究了中等分子量聚丙烯(PP)注射成型试样的结构与性能.研究表明:所得中等分子量PP试样的结构与性能与注射成型过程中的工艺条件有密切关系,如:振动压力、熔体温度等.振动压力、熔体温度对试样性能的影响呈二次曲线关系,拉伸强度随着振动压力的升高先提高而后减小,有一个最大值.拉伸强度同样也随着熔体温度的升高先提高后减小,有一个最大值.DSC曲线表明:动态试样熔融呈现明显的脊纤维晶和片晶两个熔融峰,而静态试样呈现明显的片晶熔融单峰.SEM照片显示静态试样剪切层结晶形态主要为球晶结构,动态试样剪切层产生明显的高度取向串晶结构.所有的测试结果表明:中等分子量PP在动态保压单向流动场中所得试样内部结晶由静态试样中的球晶转变成了串晶,且性能明显提高.     

夹芯注塑成型过程的计算机可视化模拟分析--材料粘度与工艺参数对芯层熔体穿透深度的影响

采用Moldflow公司MPI软件中的Co-injection分析模块,对夹芯注塑成型过程进行动态模拟分析;以揭示材料粘度以及工艺参数对夹芯注塑成型过程中芯层熔体穿透深度的影响规律。结果发现,芯层熔体穿透深度值随芯／壳层熔体粘度比R值的减小而增大,这主要与芯层和壳层熔体的相对流动能力有关;此外,在工艺参数中,改变熔体注射速度对芯层熔体穿透深度的影响较为突出,而模温和熔体温度对芯层熔体穿透深度的影响相对较弱。     

Morphology evolution including formation of cylindrulite in isotactic polypropylene derived from periodical shear field

It has been well established that periodical shear stress can improve the mechanical performance of isotactic polypropylene during injection molding. In the current study, Polarized Light Microscopy (PLM), two-dimensional Wide-Angle X-ray Diffraction (2D-WAXD), Scanning Electron Microscopy (SEM) were employed to investigate the morphology evolution of vibration sample. Compared with static sample, the morphology of vibration one, which is derived from periodical shear field, exhibits different hierarchy structure: there is an additional fiber layer containing cylindrulites between the shear layer and the core layer, and the orientation is enhanced obviously. Through etching technique, it is found that there exists non-crystalline component in the fibril (core) of cylindrulite, and it may induce the growth of β crystals directly regardless of its non-crystalline nature. Based on the investigated results, a model of formation of cylindrulite is proposed.     

Shish-kebab-like cylindrulite structures resulted from periodical shear-induced crystallization of isotactic polypropylene

In this study, isotactic polypropylene (iPP) samples were prepared by conventional injection molding (CIM) and pressure vibration injection molding (PVIM), in which a periodical shear field was imposed on the iPP melt during the cooling solidification. The distribution of supermolecular structures of samples was investigated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM). Results show that the through-the thickness-morphology of sample prepared by CIM features a typical skin-core structure, as a result of general shear-induced crystallization. This structure can be divided into three layers, including a skin layer in which the shish-kebab structure was found, a transition region with deformed spherulite structure and a core layer with spherulitic structure. However, the morphology of the sample prepared by PVIM, as a result of periodical shear-induced crystallization, features a richer and fascinating supermolecular structure and can not be roughly divided into three layers. A region full of shish-kebab-like cylindrulite structures was found between the transition region and the core layer, which is rare to be seen in conventional injection molding. Based on their various core structures, two kinds of shish-kebab-like cylindrulites were defined: one is multi-fibril-core cylindrulite of which core is an assembly of multiple fibrils, and the other is single-fibril-core cylindrulite of which the core just contains a single fibril. Based on the investigated results, a schematic illustration is proposed to depict the through-the thickness-distribution of supermolecular structure of iPP sample prepared by PVIM. The mechanism of the formation of the two kinds of shish-kebab-like cylindrulite structures is also depicted by a schematic illustration, and it was discussed in terms of periodical shear-induced crystallization.     

两种羧酸盐成核剂的制备及其对聚丙烯的成核效果研究

合成了两种具有相似化学结构的聚丙烯（iPP）α晶型成核剂二环［2.2.1］庚⁃5⁃烯⁃2,3⁃二羧酸钠（NA₁）和二环［2.2.1］庚烷⁃2,3⁃二羧酸钠（NA₂）,研究了其在iPP中的成核效果。首先,利用差示扫描量热仪（DSC）和偏光显微镜（PLM）分别考察了两种成核剂对iPP结晶行为的影响。结果表明,当NA₁和NA₂的含量为0.3 %（质量分数,下同）时,iPP的结晶峰值温度分别提升了14.5 ℃和16.0 ℃。同时,两种成核剂都能够明显细化iPP球晶尺寸。其次,利用广角X射线衍射仪（WXAD）对成核iPP进行了表征,两种成核剂都诱导iPP产生了α晶型,说明均为α晶型成核剂。然后,对成核iPP的力学性能进行了表征。结果表明,随着两种成核剂用量的增加,iPP的拉伸强度和弯曲模量呈现先升高后平稳的趋势。当NA₁和NA₂含量为0.05 %时,成核iPP的拉伸强度较纯iPP分别提升了4.6 %和8.6 %,弯曲模量分别提升了8.2 %和21.7 %;冲击强度基本保持不变。     

Comparison of structure development in injection molding of isotactic and syndiotactic polypropylenes

A comparative study of the crystallization and orientation development in injection molding isotactic and syndiotactic polypropylenes was made. The injection molded samples were characterized using wide angle X‐ray diffraction (WAXD) techniques and birefringence. The injection molded isotactic polypropylene samples formed well‐defined sublayers (skin, shear and core zones) and exhibited polymorphic crystal structures of the monoclinic α‐form and the hexagonal β‐form. Considerable amounts of β‐form crystal were formed in the shear and core zones, depending on the injection pressure or on the packing pressure. The isotactic polypropylene samples had relatively high frozen‐in orientations in the skin layer and the shear zone. The injection molded syndiotactic polypropylene exhibited the disordered Form I structure, but it did not appear to crystallize during the mold‐filling stage because of its slow crystallization rate and to develop a distinct shear zone. The core zone orientation was greatly increased by application of high packing pressure. The isotactic polypropylene samples exhibited much higher birefringence than the syndiotactic polypropylene samples at the skin and shear layers, whereas both materials exhibited similar levels of crystalline orientation in these layers.     

Shear‐induced migration of conductive fillers in injection molding

The effect of shear‐induced conductive filler migration on surface and volume conductivity of injection molded articles of polystyrene and polypropylene with carbon black was investigated. It was found that the loss of conductivity was most significant when the mean particle concentration was at or slightly above the percolation threshold. The compounds with mean particle concentration well above the percolation threshold showed no loss at all. The conductivity decreased with the increase of shear rate used in molding. The removal of surface layers by excimer laser led to restoration of the conductivity to the value of well‐mixed, compression‐molded specimens. The thickness of surface layer removed before conductivity was restored was found to be a strong function of the shear rate and the nature of polymer used. Polym. Eng. Sci. 44:2101–2109, 2004. © 2004 Society of Plastics Engineers.     

1-丁基-3-甲基咪唑磷酸二丁酯+水/醇蒸气压的测量和关联

合成了离子液体1-丁基-3-甲基咪唑磷酸二丁酯(［BMIM］［DBP］),用静态法测量了［BMIM］［DBP］与H₂O/CH₃OH/C₂H₅OH 所形成的3个二元体系的汽液平衡数据,并用NRTL模型对活度因子进行关联。实验结果表明,［BMIM］［DBP］+H₂O/CH₃OH/C₂H₅OH二元体系汽液平衡数据对Roualt定律呈负偏差,说明3个体系均可作为吸收式热泵的潜在工质。3个体系的关联结果与实验数据的平均相对误差分别为2.37%、2.51%和1.89%。     

Dependence of microstructure and properties of polypropylene/bromo-isobutylene-isoprene rubber thermoplastic vulcanizates on the molding process

To explore the dependence of the microstructure and properties of thermoplastic vulcanizates (TPVs) on the molding process. The polypropylene/bromo-isobutylene-isoprene rubber thermoplastic vulcanizates (PP/BIIR-TPVs) are molded by high rate shear injection and compression molding, and the phase morphology and physical-mechanical properties of PP/BIIR-TPVs specimens are investigated. Detailed small-angle X-ray scattering, scanning electron microscopy and atomic force microscopy investigations demonstrate that the high rate shear of injection molding not only decreases the size of BIIR particles but also induces the orientation of the PP matrix and further increases its crystallinity. Subsequently, the PP/BIIR-TPVs molded by injection molding have higher tensile strength and Young's modulus, while the compression molding benefits to higher elongation at break. The mechanism regarding the effects of high rate shear during injection molding on phase morphology development of PP/BIIR-TPVs is discussed. This study guides the preparation of TPVs products with desired properties.     

羟丙基封端聚硅氧烷的合成及性质

用羟丙基封端剂[1，3-二（3-羟丙基）-1，3-二甲基-1，3-二乙基二硅氧烷]和八甲基环四硅氧烷制备了一系列不同摩尔质量的α，ω-二羟丙基聚硅氧烷，用定量分析、红外光谱及核磁共振谱对其进行了确证和表征，用端基分析法测定了其数均摩尔质量Mn，用乌氏粘度计测定了其特性粘数[η]，研究了α，ω-二羟丙基聚硅氧烷的Mn与[η]的关系，得到了在不同摩尔质量范围内的关系式，结果表明，在聚硅氧烷中引入羟丙基后，相对于聚二甲基硅氧烷，其物理、化学性质有了较大的变化。     

酸性离子液体催化合成三醋酸甘油酯

合成了［HSO₃-pmim］Cl、［HSO₃-pmim］［H₂PO₄］、［HSO₃-pmim］［BF₄］和［HSO₃-pmim］ ［HSO₄］离子液体，用1H-NMR和FT-IR对离子液体的结构进行了确定。将几种酸功能化离子液体应用于三醋酸甘油酯的合成反应中，筛选出了一种催化效果好又可以重复使用的离子液体［HSO₃-pmim］［HSO₄］。考察了催化剂用量、原料配比和反应时间对反应的影响，得到了较佳反应条件：n(甘油)∶n（醋酸）=1∶8，催化剂用量为醇酸总质量的5.8%，反应时间6 h，反应温度(80~90) ℃。对该功能化离子液体的重复使用性进行了考察，重复使用10次后，三醋酸甘油酯的收率仍大于90%。     

Residual stresses and aging in injection molded polypropylene

The residual stresses in injection molded bars of polypropylene have been examined using a stress relaxation method and by the layer removal technique. A positive value for the internal stress parameter was obtained with newly molded specimens and was found to be retained by specimens stored at liquid nitrogen temperature. The stress relaxation parameter reduced to zero both for specimens aged at room temperature and also for those aged at ?40°C. Nevertheless the relaxation behavior of specimens aged at all three temperatures was quite distinct. The layer removal technique showed that the stresses near to the surface were compressive and those in the interior tensile, in apparent contradiction to the interpretation of Kubat and Rigdahl for the meaning of a positive internal stress parameter. A marked reduction in stress levels on aging at room temperature was confirmed, however. The relevance of the relaxation spectrum of polypropylene to these observations is discussed.