二丙烯酸酯参与的反应挤出制备长链支化PP

研究了二丙烯酸酯参与的反应挤出制备长链支化聚丙烯过程,重点考察了二丙烯酸酯双键间链段长度以及单体用量对长链支化程度的影响。结果表明,1,4-丁二醇二丙烯酸酯(BDDA)在聚丙烯分子链上具有较强接枝能力;在接枝率相当的情况下,悬垂双键参与偶合扩链的能力会随双键间链段长度增加而下降。单体接枝率增加以及悬垂双键反应能力增强均会使长链支化程度增大。随着二丙烯酸酯用量增加,长链支化程度增加;单体过量会使大分子自由基偶合扩链程度加重,导致局部交联形成凝胶。     

长链支化聚丙烯的拉伸流变行为研究

采用不同的拉伸流变测量技术研究了长链支化聚丙烯(PP)的拉伸流变行为。结果显示,在瞬态拉伸流变试验中,线型PP不表现出应变硬化,而长链支化PP及线型和长链支化PP的共混物则表现出明显的应变硬化行为,且应变硬化程度随长链支化PP含量的增加而增加。用熔融纺丝(Rheotens)法得到了长链支化对熔体强度和可拉伸性的影响,比较了长链支化和线型PP拉伸流变性能的温度敏感性,给出了拉伸应变速率对长链支化PP拉伸黏度的影响。     

长链支化聚丙烯的反应挤出制备及其流变和热力学性能研究

在过氧化引发剂和季戊四醇三丙烯酸酯(PETA)存在下,采用反应挤出法制备了长链支化聚丙烯（LCB-PP）。用旋转流变仪和差示扫描热法系统研究了纯的和改性PP的流变性能和热力学性能,并考察了不同过氧化引发剂对改性PP的性能和支化情况的影响。研究发现,单纯使用过氧化引发剂改性时,PP以降解为主;加入多功能单体PETA后,PP以接枝反应为主。流变行为研究发现,过氧化引发剂/PETA改性的PP,其流变性能呈现如低频处储能模量增大,剪切变稀行为明显,损耗角随频率变化出现平台区,零剪切黏度增大等特点,证明改性PP存在长链支化结构,通过公式计算发现改性PP的支化度较高。差士扫描量热分析表明,过氧化引发剂/PETA改性PP的结晶温度高于纯PP,这也说明改性PP存在长链支化结构。同时发现过氧化引发剂/PETA改性PP时,过氧化引发剂结构对改性PP的流变性能、热力学性能和支化度影响较小。     

长链支化制备高熔体强度PP的研究

通过长链支化来改性PP，从而得到高熔体强度的PP。实验以丙烯酸酯类单体为接枝单体，过氧化物为引发剂，对PP进行了熔融接枝，重点考察了二官能团单体的改性情况。实验结果表明，二三官能团单体的改性效果较为明显；熔体流动速率随单体加入量增加而降低，随过氧化物浓度增加而升高；拉伸粘度谱图显示有明显的应变硬化现象；改性后产物的熔体强度变化明显；纯化后的产物经工外，差示扫描量热分析表明接枝反应的发生；索氏萃取法没有检测到凝胶的生成。     

用负载型钛系催化剂制备的乙丙共聚物链结构的影响因素

以负载型钛系催化剂为主催化剂,采用常压淤浆聚合工艺进行乙烯与丙烯共聚合,考察聚合条件对共聚合行为和产物结构的影响。以三乙基铝/三异丁基铝(TiBA)混合物为助催化剂时,随着TiBA用量增加,共聚物中聚丙烯(PP)链段越来越长,且长PP链段数量越来越多,而长聚乙烯(PE)链段数量逐渐减少;空间位阻大的外给电子体虽然可以提高PP的规整度,但不利于形成长PP链段;适当降低聚合温度更有利于形成长PP链段;产物中嵌段共聚物的含量随TiBA用量的增加而提高。所以,改变助催化剂的组成、使用不同的外给电子体或调节聚合温度都可以调控乙烯-丙烯共聚物的链结构及其分布。     

长链支化聚丙烯的流变性能研究

利用反应挤出法制备了长链支化聚丙烯,采用旋转流变仪和毛细管流变仪对纯聚丙烯及其改性聚丙烯进行测试,用流变学理论进行表征。结果表明,聚丙烯加入支化剂后,产生了长支链,分子量增大,分子量分布变宽;在一定范围内,随着支化剂量的增大,其支化程度增加;在低频处,能模量G'比损耗模量G″对长支链的出现及量变更敏感;加入支化剂后熔体强度明显增大,且支化的程度越高熔体强度越大,可拉伸性变小,能有效地改善材料的加工性能。     

PP-g-(DAP-co-GMA)的制备及PP/PET相容性研究

以邻苯二甲酸二烯丙酯(DAP)为共单体,将甲基丙烯酸缩水甘油酯(GMA)接枝到聚丙烯(PP)上,通过红外分析(FTIR)、差示扫描量热(DSC)分析、电子显微镜(SEM)观察、力学性能测试,研究了该接枝物对PP/聚对苯二甲酸乙二醇酯(PET)体系的增容作用。结果表明:DAP,GMA可共接枝到PP分子链上生成PP-g-(DAP-co-GMA);该接枝物可与PET反应生成PP-g-PET;由于该接枝物的生成,使得增容共混物中PP和PET的结晶温度及熔点降低,体系黏度增加,力学性能提高,分散相分布均匀。     

提高嵌段共聚PP冲击强度的措施探讨

介绍了生产嵌段共聚聚丙烯(PP)的工艺和改善冲击强度的机理,分析了影响嵌段共聚PP冲击强度的主要因素：二聚物的含量、结构及其特性粘数;提出了3条提高嵌段共聚PP冲击强度的措施：提高嵌段共聚PP的键合乙烯量、降低气相比以及控制二聚物特性粘数在适当的范围。     

长链支化聚丙烯的制备及其熔体流变性能的研究

在过氧化物引发剂和季戊四醇三丙烯酸酯存在下,利用反应挤出法制备了长链支化聚丙烯(LCB-PP)。采用熔体流动速率(MFR)仪、旋转流变仪和熔体强度测试仪对纯聚丙烯(PP)及其改性PP进行测试与表征。讨论了不同的过氧化物引发剂对改性PP流变性能的影响。结果表明,采用过氧化苯甲酰时,改性PP具有较高的熔体强度、较低的MFR,并且在低频处储能模量增大。同时发现,随温度的升高,改性PP的熔体强度逐渐降低,但升高到一定温度后,熔体强度的变化不明显。     

长链支化聚对苯二甲酸乙二醇酯的制备及其超临界CO2挤出发泡性能研究

以具有支化结构的多元醇原位聚合改性聚对苯二甲酸乙二醇酯(MPET)为原料，均苯四甲酸二酐(PMDA)为扩链剂，通过反应挤出改性可控制备了不同长链支化程度的聚对苯二甲酸乙二醇酯(PET)。流变测试结果表明长链支化改性MPET熔体黏弹性得到大幅度提升，应变硬化因子也随长链支化程度的增加而增强。在超临界CO₂(scCO₂)挤出发泡过程中，长链支化改性MPET具有优异的挤出可发泡性。采用0.3%(质量分数，下同)PMDA制备得到的MPET-P3具有最佳的挤出发泡性能。当熔体温度为265℃时，其发泡倍率可达14.0倍，泡孔密度为4.81×106个/cm³，平均泡孔直径为153.9μm。     

笼状磷酸酯微胶囊/聚磷酸铵阻燃聚丙烯

将笼状磷酸酯微胶囊(ET)与聚磷酸铵(APP)复配用于阻燃聚丙烯(PP)。采用氧指数和UL 94评价了阻燃PP的阻燃性能,采用热重分析、扫描电子显微镜照片、傅里叶变换红外光谱及X射线电子能谱研究了阻燃剂的协同效应和阻燃机理。结果表明:ET与APP有较好的复配协同效应,ET/APP的阻燃性能随m(ET)/m(APP)的不同而变化。当m(ET)/m(APP)为1∶2时,阻燃效果最好。w(ET/APP)为30%时,氧指数达29.7%,且达到UL 94 V-0级。     

PP Z30S生产波动原因及对策

利用环管法工艺聚丙烯装置生产高熔体流动速率产品Z30S时需要加入大量H2,而H2会提高催化剂活性,因此环管反应器中反应比较剧烈,生产初期会出现产品密度等质量波动。针对这些波动,优化控制比例度、积分时间、微分时间等,改善操作方法,使装置运行趋于平稳状态,产品质量稳定。     

薄壁注塑透明聚丙烯专用料的结构与性能分析

对市场上常见的4种薄壁注塑透明聚丙烯专用料的熔融结晶性能、光学性能、分子量分布、力学性能、毛细管流变性能、热收缩性能等进行对比分析。结果表明，K4860H与其他3种透明聚丙烯专用料相比分子量分布最窄；K4860H相对于其他3种透明聚丙烯专用料具有更好的韧性和透明性；相对其他2种透明聚丙烯，K4860H和MT45S具有更高的结晶温度和更快的结晶速率，表明其具有更为优良的结晶能力；4种透明聚丙烯样品的黏度随剪切速率的变化规律相同，表明其具有相同的加工流变性能；K4860H和500B 2个方向的模塑收缩率接近，说明其具有良好的尺寸稳定性；基于以上对比分析可知K4860H主要性能指标优于对比的3种聚丙烯专用料。     

Crystallization behaviors of polypropylene and functional polypropylene

The crystallization behaviors of polypropylene (PP) homopolymer and its blends with 0–15% functional polypropylene (FPP), the backbones of which were grafted with guanidine and diamide polymer chains, were investigated with differential scanning calorimetry and wide‐angle X‐ray scattering. The crystallization kinetics were studied with spectral depolarization. The results revealed that the presence of FPP reduced the crystallinity and crystallite size of PP. Meanwhile, FPP increased the crystallization rate. Compared with that of the PP homopolymer, the crystallization temperature of PP/FPP blends was increased by more than 10°C. During isothermal crystallization, the relative crystallinity, developed as a function of time, was described by the Avrami equation. The half‐time of crystallization for PP/FPP blends was much shorter than that for the PP homopolymer. The half‐time of crystallization of PP/FPP blends depended much less on the crystallization temperature than that of the PP homopolymer. Therefore, FPP accelerated the crystallization rate of PP in a manner similar to that of a nucleator. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 872–877, 2003     

Crystalline morphology of polypropylene and rubber-modified polypropylene

The crystalline morphology of injection-molded polypropylene (PP), its relationship with crazing, and the effects of various impact modifiers on the morphology, crystallization, and fusion of PP have been studied. The highly oriented skin layer of an injection-molded tensile bar after deformation was found to be free from crazing in contrast to the heavy craze density in the randomly oriented spherulitic core zone. Reasons for the difficulty in craze nucleation in a preoriented zone are given in light of Argon's theory of craze initiation. Addition of a rubbery phase results in an irregular texture of spherulite, smaller spherulitic diameter, and decrease in the degree of undercooling, but no appreciable change in heats of fusion and crystallization other than a trivial volume effect. The rubbery phase is not pushed by the melt–solid interface to relocate to the interspherulitic boundaries. Rather, it is engulfed by the growing melt–solid interface, leaving behind a random spatial distribution of rubber particles in the PP matrix.     

丙纶纤维自增强聚丙烯树脂的研究

以丙纶纤维为增强体,聚丙烯树脂为基体,采用热压成型的方法制备丙纶纤维/PP复合材料板材.研究了不同热压温度、不同纤度的丙纶纤维用量对复合材料力学性能的影响.结果表明:本实验最佳热压温度为195℃,在此温度下,随着纤维用量的增加,复合材料的拉伸强度呈先升后降的趋势,在用量为15%时达到最高点,纤度为240D的丙纶纤维/P...     

Interfacial tension of polypropylene/polystyrene: Degradation of polypropylene

The coefficient of the decrease of the interfacial tension of polypropylene/polystyrene with temperature is considerably higher than the value of other polymer pairs. This coefficient can be estimated by considering the change of the interaction parameters with temperature, but this approach fails for polypropylene/polystyrene, and other mechanisms are expected to play a role. In this paper it is shown that polypropylene starts to degrade at higher temperatures, leading to smaller polymer chains, which decrease the interfacial tension. Besides the change of the interaction parameters with temperature, these smaller molecules also contribute to the temperature coefficient, leading to an apparently high coefficient. The smaller molecules, however, lead to a permanent lower interfacial tension, e.g. the interfacial tension of polypropylene/polystyrene at 200°C is 4.9, 3.9, and 3.0 mN/m, if the polypropylene is first processed at 200, 250, and 300°C, respectively.     

高熔体流动速率薄壁注塑聚丙烯专用料的结构与性能分析

采用多种分析测试方法，对3类高熔体流动速率薄壁注塑聚丙烯（PP）专用料的熔融结晶性能、光学性能、分子量分布、力学性能、毛细管流变性能、热收缩性能进行了分析研究。结果表明，K1860与2种市售主流PP1、PP2各项性能相当，其中K1860分子量分布相对PP1、PP2较窄，弯曲性能、拉伸性能更优，可满足大型薄壁注塑制品的生产要求。     

Stabilization of polypropylene

Antioxidants and UV absorbers are vital to the commercialization of polypropylene because of their influence on this polymer's light stability, heat or oxidative stability, processing stability, and gas fading due to nitrogen oxides. The effects of these stabilizers are measured in terms of polypropylene's initial color, color retention, and retention of physical properties when the polymer is exposed to direct weathering and to elevated temperatures. The relative washfastness or resistance to extraction by aqueous systems under various laundering conditions is another important, measurable property of UV absorbers and antioxidants in polypropylene. Such measurements are usually made using stabilized polypropylene molded plaques and monofilaments containing UV absorbers, antioxidants and, often, combinations of the two.     

Crystallization behavior of polypropylene in polypropylene/nylon 6 blend

This article describes the crystallization behavior of polypropylene (PP) in the presence of a crystallizable polymer, namely, nylon 6, in the binary blend of PP/nylon 6 in the composition range from 0 to 30 wt % of nylon 6 content in the blend. The crystallization behavior was studied through variation of the crystallinity with the blend composition and changes in the crystallization exotherms were recorded by differential scanning calorimetry (DSC) and the spherulite morphology was observed via polarized light microscopy (PLM). Comparison of the crystallization exotherms and melting endotherms revealed some differences which are attributed to the role of a sufficiently high thermal energy of the nylon 6 crystals on the melting of PP. The crystallinity of PP decreased in the presence of nylon 6, whereas the crystallinity of nylon 6 increased considerably in the presence of PP. The rate of nucleation of PP on addition of nylon 6 decreased rapidly in the region 0–10 wt % nylon 6 content, and, thereafter, at a higher nylon 6 content, decrease of the nucleation rate was relatively slow. PLM observation revealed the presence of composite spherulites with PP spherulites grown on the surface of the already‐formed nylon 6 spherulites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1153–1161, 1999