成核PP注塑样品的非等温结晶行为与熔融特性

用DSC研究了两种成核剂成核PP的非等温结晶行为与熔融特性,致命伤中成核剂均使PP的降温结构温度提高,结晶峰半高宽变窄,结晶度与熔点略有提高,但结晶峰对称性变差,熔融峰半高宽加大,成核样品的结晶温度对冷却速率的依赖性较纯PP的小,根据过冷度和成核PP与纯PP的结晶温度之差,成核剂成核作用大小顺序为：A＞D。     

有机硅/可膨胀石墨复合阻燃PP/TPU共混物的研究

为分析有机硅(Si)/可膨胀石墨(EG)对聚丙烯/热塑性聚氨酯/(PP/TPU)共混物性能的影响,通过差示扫描量热(DSC)、扫描电镜(SEM)、热重分析(TGA)、锥形量热仪(CONE)等表征方法对复合材料体系的结晶行为、热稳定性能、燃烧行为及残炭形貌特征进行了研究.结果表明:EG是一种有效的阻燃剂,能显著提高材料的阻燃性能;Si的存在对PP/TPU/EG复合材料有促进结晶作用,熔点增加,耐热性能得以提高,但Si的添加对复合材料体系的阻燃性能有一定的抑制作用,表明Si与EG复配在阻燃PP/TPU共混物时在阻燃效果上具有反协同效应.     

可膨胀石墨的功能化改性及其在阻燃聚丙烯中的应用

研究了1种有机协效阻燃剂(OSF)表面功能化可膨胀石墨(EG)及其在阻燃聚丙烯(PP)中的应用。通过红外光谱(FT-IR)、扫描电镜(SEM)、极限氧指数(LOI)、UL-94垂直燃烧、热失重分析(TG)和差示扫描量热(DSC)等表征方法对EG的功能化效果、阻燃PP复合材料的阻燃性能、热稳定性、结晶行为与力学性能进行了研究。结果表明OSF成功地接枝到了EG表面。改性后的EG是1种有效的阻燃剂,能显著提高PP的阻燃性能,其阻燃性能达UL-94V0级。改性EG的加入,PP的热稳定性得到改善,高温时的残炭量增加。改性EG对PP有异相成核作用,PP结晶温度向高温方向偏移。阻燃剂的加入劣化了PP的力学性能,且随着其含量的增加而逐渐降低。     

增容剂对PP/PA6共混体系结晶行为的影响

研究了在PP/PA6体系中,不同种类增容剂及其含量对PP、PA6的结晶行为的影响,探讨了结构与结晶行为之间的关系。研究结果表明,在PP/PA6体系中,随着增容剂含量的增加,抑制了PA6结晶,PA6出现分级结晶现象,PP的结晶也受到抑制,PA6分散相变小对PP异相成核有促进作用,Tc上升,分散过细,Tc则会下降。在PAM体系中,PP除165℃的熔融峰外,在较低温度出现较小的熔融峰,这是处在界面相的PP-g-PA6共聚物结晶时受限所致。     

母料制备纳米CaCO3/PP复合材料的结晶性能

本文用溶液法制备的不同单体改性PP包覆纳米CaCO3母料制备纳米CaCO3/PP复合材料,用DSC和POM研究了复合材料中PP的结晶与熔融行为及结晶形态.研究结果表明改性复合材料中PP的结晶温度与单体类型和用量有关.单体的极性增加,异相成核作用越强.除马来酸酐外,反应单体改性对PP熔融温度影响不大,但峰形不同.丙烯酸甲酯、丙烯酸丁酯、甲基丙烯酸甲酯、马来酸酐和苯乙烯改性更有利于形成β晶,β晶熔融峰的强度与单体类型有关;但丙烯酸改性无β晶形成.改性复合材料的球晶明显变小.     

纳米CaCO3／PP／PS复合材料的结晶与熔融行为

熔融方法制备了纳米CaCO3／PP／PS复合材料，DSC研究了PP／PS、增容PP／PS共混物及其纳米CaCO3填充共混物的结晶与熔融行为。研究结果表明加入PS对PP结晶行为影响不大，但导致PP熔点下降，熔融峰从单峰变为双峰。纳米CaCO3和增容剂对PP／PS共混物中PP结晶存在异相成核作用，提高PP结晶温度和熔点，PP—g—MA和PP—g—AA的异相成核作用比CaCO3的大。PP—g—MA增容的PP／PS共混物和CaCO3填充共混物有利于PP形成β晶，但CaCO3填充共混物、PP—g—AA的增容PP／PS共混物和CaCO3填充共混物无β晶形成。     

马来酸酐混合单体改性PP/PS共混物的结晶与动态力学性能

用熔融法制备了马来酸酐（MAH）及其与苯乙烯（St）混合单体改性PP／PS共混物,以及MAH、St改性聚丙烯（原住形成PP／PS共混物）。用DSC、DMA和FT—IR研究了改性共混物的结晶与熔融行为、动态力学性能和接枝产物。结果表明,MAH加入对PP／PS共混物中PP的结晶温度影响不大,但其与St混合单体对共混物中PP的结晶温度影响明显,原位生成PP／PS的结晶温度也有较大提高。改性对共混物中PP的熔融温度影响不大,但熔融峰形变化明显。改性PP／PS共混物具有高的E′和E″强度。     

表面改性对可膨胀石墨填充PP/TPU复合材料的结晶行为、燃烧与力学性能的影响

研究了钛酸酯偶联剂对可膨胀石墨(EG)填充聚丙烯(PP)/热塑性聚氨酯(TPU)复合材料性能的影响。通过差示扫描量热(DSC)、热重分析(DTA)、锥形量热仪(CONE)和扫描电镜(SEM)表征方法对PP/PUT/EG复合体系的结晶行为、燃烧与力学性能进行了研究。结果表明,EG是一种有效的阻燃剂,能显著提高材料的阻燃性能。未改性的EG对PP/TPU基体有促进成核结晶作用;而偶联剂的添加削弱EG粒子对基体的这种作用。偶联剂的加入可以改善PP/PUT/EG复合材料的力学性能,当加入20phr的EG时,复合材料的拉伸强度和断裂伸长率分别由改性前的5.3MPa和17.6%提高到经改性后的5.6MPa和18.3%。     

热塑性聚氨酯/尼龙612共混体系的相互作用及结晶行为

采用溶液共沉淀法制备了热塑性聚氨酯(TPU)/尼龙(PA)612共混物,通过变温红外光谱仪和差示扫描量热仪(DSC)研究了共混体系中 TPU与PA612分子间的相互作用及其对结晶行为的影响.DSC结果表明,随着共混体系中TPU含量的增加,PA612的结晶峰温度明显降低,结晶峰宽明显变宽;相对于纯TPU,共混体系中TPU...     

液晶聚合物对尼龙1010/聚丙烯共混合金的结晶行为和力学性能的影响

用DSC研究了液晶聚合物（LCP）的含量对PA1010／聚丙烯（PP）共混合金结晶和熔融行为的影响：用TGA研究了共混合金的热稳定性：用拉伸试验检测共混材料的力学性能。结果表明：PA1010／PP共混合金中加入0．6％－0．8％（质量）LCP时能起微纤增强和异相成核剂作用,提高合金结晶温度和结晶度,使结晶完善程度略有增加,结晶速率略受影响,并且共混材料的拉伸强度明显增强,但对其热稳定性影响不大。当LCP含量增加到5％时,将作为独立组分在共混合金中起作用,使PA1010和PP的结晶峰均出现明显分峰现象,共混材料的力学性能和热稳定性显著下降。     

Effect of liquid additives on morphology and properties of thermoplastic elastomers prepared from phase-modified EPDM elastomer and isotactic polypropylene blends

Thermoplastic elastomers (TPEs) were prepared from ternary blends of ethylene propylene diene poly methylene rubber (EPDM), isotactic polypropylene (PP), and low loadings (5–10 phr) of different types of interfacial phase modifiers (like maleated EPDM, styrene-ethylene-co-butylene-styrene block copolymer, and maleated PP). These showed much improved physico-mechanical properties compared to the binary blend of EPDM-PP. The effects of non-polar paraffin oil and polar di-octyl phthalate liquid additives (5–20 phr) were investigated in these phase-modified ternary and binary EPDM-PP blends. Only 5 phr of liquid additives provided synergistic improvement in physical properties (maximum stress, modulus, and elongation at break) and generated improved finer morphology of the ternary blends as revealed from scanning electron and atomic force microscopy studies. Enhanced physical properties and dynamic mechanical properties of these blends were explained with the help of better phase morphology and enhanced crystallinity of the blends.     

Use of Differential Scanning Calorimetry (DSC) in the Characterization of EPDM/PP Blends

New polyolefinic thermoplastic elastomers based on the ethylene–propylene-diene monomer (EPDM) and polypropylene (PP) containing an EPDM elastomer of the last generation (Nordel NDR 47130), obtained by polymerization in the gaseous phase with metallocene catalysis, were prepared and characterized. The melting and crystallization behavior of these blends was investigated by differential scanning calorimetry. It is observed that the melting temperature, crystallization temperature, and crystallinity degree increase with an increase of PP loading. The influence of the blend composition on the physico-mechanical characteristics was discussed using statistical processing of the experimental data. Two compatibilizing procedures were utilized to improve the physico-mechanical characteristics of the samples: an addition method using different compatibilizing agents and dynamical vulcanization with three types of crosslinking systems. Significant improvements of the tensile strength and tear strength were noted by dynamic crosslinking, and the best results were obtained using a crosslinking system based on phenolic resin and tin chloride.     

阻燃型PA6／PP／硅灰石复合材料的制备及阻燃机理研究

采用固相力化学方法制备的聚丙烯接枝羟甲基丙烯酰胺作增容剂，以高效低毒的三聚氰胺三聚氰酸盐（MCA）作阻燃剂制备了阻燃型硅灰石填充尼龙6/聚丙烯复合材料，该复合材料具有很好的力学和阻燃性能，当MCA与聚合物质量比为10%时，该复合材料的极限氧指数达到31，拉抻强度为54.1MPa，悬臂梁缺口冲击强度为59.7J/m。通过TG和FT-IR分析对阻燃机理作了初步的探讨。     

Properties of polyethylene-polypropylene blends

High-density polyethylene (PE)-isotactic polypropylene (PP) blends have been characterized by a number of techniques such as wide-angle X-ray scattering, differential scanning calorimetry, picnometry, swelling in n-hexane and finally stress-strain tensile elongation. All the measurements have been performed on cilindrical shaped specimens, obtained directly by extrusion. The specimens show a complete random orientation of the crystallites of both the components. No co-crystallization phenomenon are observed. The melting point of both PE and PP decreases slightly with increasing concentration of the second component. The fractional crystallinity of PE decreases and that of PP increases with respect to the corresponding homopolymer values with increase in the concentration of the companion polyolefin. Such an effect is related to morphological kinetic effects and to different rates of crystallization of the two components, during the non-isothermal crystallization process following extrusion. Young's modulus, E is proportional to the overall fractional crystallinity. The ultimate properties show a synergistic effect due to the strong interactions between the crystallites and their tie molecules of the two PE and PP distinct phases. Finally, it is to be remarked that the results obtained in this paper, especially with respect to the ultimate properties, are quite different from those reported by other authors. This can be attributed to the different processing conditions used for obtaining the present blend specimens. Such conditions are certainly very important in determining particular blend morphologies which will determine in turn the properties of the analysed samples.     

Investigation into mechanical and microstructural properties of polypropylene manufactured by selective laser sintering in comparison with injection molding counterparts

This work evaluated the processibility of a low-isotacticity polypropylene (PP) powder by selective laser sintering (SLS), and systematically analyzed and compared the melting and crystallization characteristics, crystalline structure, tensile properties and thermo-mechanical properties of the PP specimens fabricated by SLS and injection molding (IM). The results show that the PP powder has a nearly spherical shape, smooth surfaces, appropriate particle sizes, a wide sintering window and a low degree of crystallinity, consequently indicating good SLS processibility. In SLS, the molten PP continues to maintain at a high part bed temperature until the whole manufacturing process finished, thus demonstrating a low cooling rate. This gives rise to a high degree of crystallinity, formation of γ phase and coarse microstructure. On the contrary, in IM, the fully molten PP is rapidly cooled down to room temperature after injection, and thus show a higher cooling rate and rapid crystallization, leading to a lower degree of crystallinity, absence of γ phase and finer microstructure. Owing to these differences in crystallization characteristics and crystalline structure mentioned above, the SLS PP parts exhibit higher tensile strengths, tensile moduli and storage moduli, but lower elongation at break, toughness and glass transition temperatures, compared with the IM counterparts.     

表面改性对聚丙烯/纳米氢氧化镁复合材料性能的影响

研究了表面处理剂(钛酸酯和硅烷偶联剂)对聚丙烯/纳米氢氧化镁(MH)阻燃复合材料性能的影响。通过高压毛细管流变仪、LO I、力学测试、DSC和SEM对PP/纳米MH复合体系的结构与性能进行了研究。结果表明,所选偶联剂能有效地降低复合体系的表观黏度,改善体系的流动性。未改性的纳米MH对PP基体有异相成核作用;而表面改性剂能削弱填料对基体的异相成核作用。改性后的纳米MH粒子以独立形式均匀分散在基体中,PP与纳米MH界面的粘接力得到了加强,复合材料的拉伸性能和冲击强度有较大幅度的提高,阻燃性能也得到了改善。     

汽车薄壁保险杠蒙皮材料特性分析与服役性能研究

目的 优化薄壁保险杠蒙皮材料的力学性能,评价薄壁保险杠蒙皮的服役性能。方法 以纳米碳酸钙(nano-CaCO3)、蒙脱土(MMT)和氢化苯乙烯-丁二烯嵌段共聚物(SEBS)为添加剂对PP进行协同改性。采用双螺杆挤压机制备PP/SEBS/nano-CaCO3和PP/SEBS/MMT共混材料,研究刚性粒子与SEBS对薄壁注塑用聚丙烯(PP)的强韧协同效应。研究无机填料/弹性体协同改性作用对薄壁注塑用聚丙烯结晶行为、力学性能与微观结构的影响规律。建立薄壁注塑用聚丙烯保险杠蒙皮有限元仿真模型,通过多个工况有限元仿真和实验来评价薄壁保险杠蒙皮的服役性能。结果 共混材料的结晶度相比PP/SEBS提高了1.2%~7.3%,结晶温度未产生显著变化;nano-CaCO3质量分数为4%的PP/SEBS/nano-CaCO3综合性能最好。仿真结果表明,薄壁保险杠蒙皮具有较好的服役性能,并且通过实验验证了该评价方法的有效性。结论 薄壁保险杠蒙皮材料可以通过共混改性达到理想的刚韧平衡效果,基于材料性能-成形质量-服役性能的方法为高效设计薄壁汽车保险杠蒙皮提供了新途径。     

Influence of Carbon Nanofiber Addition on Mechanical Properties and Crystallization Behavior of Polypropylene

1.IntroductionOne of the important applications for carbon nan-otubes(CNTs)is to be used as reinforcing filler,becauseCNTs have unique mechanical properties and large as-pect ratio.Various polymers have been used as the ma-trices to investigate the reinforcing effect of CNTs[1~5].Poly(propylene)(PP)as a common plastic and semicrys-talline polymer has attracted much attention in the re-search of CNT/polymer composites,including the influ-ence of GNTs on the mechanical properties[6~10],cr…     

mPP对PP/TLCP共混物结晶行为的影响

探讨了聚丙烯马来酸酐接枝共聚物对热致液晶共聚酯与聚丙烯共混物的等温和非等温结晶行为的影响,研究结果表明,该共聚物强化了热致液晶共聚酯和聚丙烯的相间联系,结晶速度提高,结晶温度提前,结晶度降低并易形成横穿晶。