改性聚丙烯反应挤出可控降解研究

利用反应挤出技术，研究了聚丙烯（PP）、PP及改性剂和无规共聚聚丙烯（PPR）在过氧化物作用下在反应挤出机中进行可控降解的规律。试验发现，产物的熔体流动速率（MFR）随过氧化二异丙苯引发剂（DCP）用量的增加而呈成倍增长趋势；封闭反应挤出机排气口更利于可控降解反应；可控降解产物在满足材料力学性能需要的前提下其外观质感得到了显著提高；加入改性剂EVA（乙烯／醋酸乙烯共聚物）或POE（乙烯／辛烯共聚物）后有利于提高产物的韧性和表观质量；PPR在反应挤出机中表现出与纯PP相同的降解规律，但产物的性能在降解后得到了提高。     

无规共聚聚丙烯高速挤出流变性能

采用恒速型双毛细管流变仪对比研究了无规共聚聚丙烯PPR-4220,PPR-2400的高速挤出流动规律及挤出特征;通过动力学分析(DMA)探究了无规共聚聚丙烯分子结构特点.结果表明:无规共聚聚丙烯挤出压力基本保持稳定;其零长口模挤出物出现周期性螺纹,相应地,长口模挤出物出现规则状扭曲;随挤出速率升高或熔体温度降低,螺纹周期变长,螺槽深度加深.DMA结果表明,与均聚聚丙烯相比,无规共聚聚丙烯损耗因子较大,从损耗峰的宽度来看,其宽度也较大,其玻璃化转变温度也较早出现.     

聚丙烯高速挤出的螺纹畸变行为的研究

采用恒速型双毛细管流变仪研究聚丙烯熔体在高速流场中的流变特性.结果表明,高速挤出时挤出物出现螺旋状挤出外观,这种不稳定现象是由熔体在人口区存在扰动造成的.螺旋挤出畸变与剪切速率、温度、材料种类、口模长径比以及材料黏弹性有关.     

异型材挤出口模内的流动模拟

本文根据挤出机理，对口模内的流动行为进行适当的简化和假定，建立了挤出口模内流动分析的数学模型，并采用横截面／假想区域法实现了复杂异型材挤出口模内的数值模拟，数值分析结果与三维有限元解和解析解的对比，取得了满意的效果。     

高速挤出模设计

目前,应用于管材生产的挤出模可归结为三种:支架型挤出模、篮式挤出模和螺旋式挤出模。高速挤出成型是一个系统工程,模具是影响生产效率的重要因素。由本文第三章对比分析,要实现挤出模的高速挤出应尽量保证料流在机头内最大限度的形成稳定流动[1]。     

利用反应挤出的聚丙烯熔融接枝改性

系统简介了聚丙烯熔融接枝体系的组成、机理及实现熔融接枝的反应挤出技术。介绍了聚丙烯接枝物的表征和应用状况，并指出了熔融接枝体系中存在的问题。     

通过反应挤出提高聚丙烯的熔体强度

利用反应挤出技术研究了不同反应物对聚丙烯(PP)熔体强度的影响。考察了不同用量的低密度聚乙烯(LDPE)、乙烯-乙酸乙烯酯共聚物(EVA)、季戊四醇三丙烯酸酯(PETA)、二乙烯基苯(DVB)以及上述物质的混合物在过氧化二异丙苯的引发下对PP熔体强度、熔体流动速率、熔垂的影响。结果表明,LDPE、EVA的加入对产物熔体强度的影响有限,PFTA也只能使其提高1倍左右;而DVB的加入可使产物的熔体强度显著提高,仅加入1％就可使熔体强度提高20倍,熔垂实验也证明了这一点;几种反应物混合使用效果不如单独使用好。     

反应挤出法制备含氟改性聚丙烯

接枝过程以线型等规聚丙烯（iPP）为原料,分别采用甲基丙烯酸三氟乙酯（FA-3F）、甲基丙烯酸十二氟庚酯（FA-12F）和甲基丙烯酸十七氟癸酯（FA-17F）为接枝单体,过氧化二异丙苯（DCP）为引发剂,通过反应挤出过程制备含氟改性聚丙烯。结果表明,长链含氟单体在接枝过程中更具优势,这可能与其较高的沸点有关;含氟单体的接枝度随单体加入量和引发剂加入量的增加均呈现出先迅速增加而后增加速度变缓的趋势,接枝效率则呈现明显的先增加后减少的现象;改性后聚丙烯的分子量大幅度下降,其中长链含氟单体在获得较高接枝度的同时尚保持较高的分子量,且其分布略窄。     

硅藻土含量和粒径对聚丙烯／硅藻土复合材料挤出膨胀行为的影响

应用熔体流动速率仪测定了3种粒径硅藻土填充聚丙烯复合材料的口模膨胀比，考察了硅藻土含量和粒径对复合材料口模膨胀行为的影响。结果表明：当载荷和温度一定时，复合材料的口模膨胀比随着硅藻土体积分数的增加而非线性减小，随着硅藻土垃径的增加而非线性提高，两者之间成二次函数关系。     

反应挤出微交联聚丙烯的熔体和力学性能研究

以过氧化二异丙苯(DCP)为引发剂、二乙烯基苯(DVB)为交联剂,通过反应挤出对聚丙烯(PP)进行微交联改性,并考察了改性效果。结果表明:DCP是最佳的PP微交联引发剂,当其加入量仅为0.04%时,即能使DVB(用量0.5%)与PP发生微交联反应,生成0.51%的凝胶,使产物的熔体强度比原料提高4倍,结晶度和维卡软化温度也有一定程度的提升,同时,产物中有少量β晶生成,使其力学性能有所改善。     

Polypropylene degradation control during reactive extrusion

In this work, a proportional‐integral‐derivative (PID) control scheme with two different tuning methods to control the degree of degradation of polypropylene (PP) during reactive extrusion is proposed. The concentration of dicumyl peroxide is taken as the manipulated variable. The molten viscosity of PP under processing is taken as the controlled variable. The degree of degradation is determined by a viscosity function derived by an off‐line identification. A first‐order‐plus‐time‐delay empirical model is identified to simulate the system plant. Both Ziegler–Nichols tuned PID and internal model control (IMC)‐based PID controllers are implemented on the system. Better performances in settling time and precision can be achieved using the IMC‐based PID controller. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 280–289, 2005     

In situ compatibilization of polypropylene/polystyrene blend by controlled degradation and reactive extrusion

In situ compatibilization of polypropylene (PP) and polystyrene (PS) was achieved by combinative application of tetraethyl thiuram disulfide (TETD) as degradation inhibitor and di‐tert‐butyl peroxide as degradation initiator in the process of reactive extrusion. The PP/PS blends obtained were systematically investigated by rheological measurement, scanning electron microscopy, and differential scanning calorimetry. The results indicate that peroxide‐induced degradation of PP can be effectively depressed by adding TETD, which may favor the formation of PP‐g‐PS copolymer during melt processing. The PP‐g‐PS copolymer formed may act as an in situ compatibilizer for PP/PS blends, and subsequently decreases the size of dispersed PS phase and changes both rheological and thermal properties of the blends. Based on the present experimental results, the mechanisms for the controlled degradation of PP and in situ formation of PP‐g‐PS copolymer in the PP/PS blends have been proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Grafting of maleic anhydride onto polypropylene by reactive extrusion

Maleic anhydride grafting onto polypropylene was conducted in a twin‐screw extruder according to an experimental design in which the maleic anhydride and peroxide concentrations were varied. The modified polypropylene was characterized by FTIR spectroscopy, melt‐flow index measurements, size‐exclusion chromatography, differential scanning calorimetry, and nuclear magnetic resonance. The results showed that only the independent variable peroxide concentration influenced the amount of reacted maleic anhydride, whereas the two variables studied influenced the molecular weight of the grafted polypropylene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2706–2717, 2002     

Rheology and thermal behavior of long branching polypropylene prepared by reactive extrusion

Long‐chain branching polypropylene (LCB‐PP) was achieved by reactive extrusion in the presence of bifunctional monomer [1,6‐hexanediol diarylate (HDDA)] and peroxide of dicumyl peroxide (DCP). Influences of HDDA and DCP concentrations on the branching efficiency were comparatively evaluated. Fourier transformed infrared spectroscopy (FTIR) results indicated that the grafting reaction took place, and HDDA has been grafted on PP skeleton. In comparison with initial PP, some modified samples showed lower melt flow index because of a large number of LCB in their skeleton. Several rheology plots were used to investigate the rheological properties of the initial PP and modified PPs, and the rheological characteristics confirmed the LCB in modified PPs skeleton. DSC results showed that the crystallization temperatures of modified PPs were higher than those of initial PP and degraded PP, suggesting that the modified PPs had long‐chain branched structure. The contrastive investigation in the rheology of modified PPs suggested that proper concentrations of HDDA and DCP were more beneficial to producing LCB during reactive extrusion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

反应挤出马来酸酐接枝聚丙烯的结构与性能

选择最佳的配方和工艺条件,制备了每100g试样总酐基含量为8．1mmol的马来酸酐接枝聚丙烯(PP-g-MAH)产品、通过化学分离和红外光谱分析,发现PP-g-MAH产品的纯度很高,几乎没有游离态的MAH。广角X射线衍射实验发现,PP经过接枝处理后,晶型没有改变,但040晶面明显增大;晶胞在a和c轴上变化不大．在b轴上减小;结品度略有上升：通过分析接枝物的流变性能,发现接枝物与PP一样．仍属于非牛顿型假塑性流体。实验证明,PP-g-MAH产品具有良好的可注塑性。     

POE/PP体系的反应挤出接枝马来酸酐研究

通过研究辛烯-乙烯共聚物/聚丙烯（POE/PP）比例。第二反应单体的选择，马来酸酐（MAH）单体和过氧化二异丙苯（DCP）用量变化以及反应温度，螺杆转速，真空度对接枝产品性能的影响情况，找出了适合于工业生产的最佳配方和工艺条件，即POE/PP为60：40，MAH为1.5%，DCP为0.04%，提纯苯乙烯为1.5%。螺杆转速为45r/min，真空度为-0.10MPa，螺筒各段温度为160，190（反应段），190（除杂段），150（机头）℃。     

反应性挤出制备PP-g-PEGA调温纤维的研究

以过氧化二异丙苯(DCP)为引发剂,通过反应性挤出的方法将相变材料丙烯酸聚乙二醇酯(PE-GA)接枝到聚丙烯(PP)基体上,利用熔融纺丝的方法制备PP-g-PEGA调温纤维。通过红外光谱法和溶剂萃取法表征了PEGA在PP上的接枝情况;通过差示扫描量热仪、纤维强力仪和扫描电镜分别表征了PP-g-PE-GA调温纤维的储热性能、力学性能和外观形态。结果表明:PEGA与PP发生了化学接枝,PP-g-PEGA纤维的接枝率达3.2%;当PEGA的质量分数为8.0%,引发剂DCP质量分数为0.6%时,相变焓达6.93 J/g;PP-g-PEGA调温纤维的断裂强度随着PEGA含量的增加呈先增大后减小的趋势;PP与PEGA相容性良好,纤维的外观光滑均匀。