辐照改性制备长支链型高熔体强度聚丙烯流变性能(Ⅱ)拉伸流变

通过辐照法制备了长支链型高熔体强度聚丙烯(LCB-HMSPP)，采用Rheotens熔体拉伸流变仪研究了辐照改性PP的熔体强度和拉伸流变行为，讨论了敏化剂含量、辐照剂量、高分子量物质和温度对PP拉伸流变行为的影响。研究结果表明：PP的熔体强度、拉伸应力、拉伸黏度等拉伸流变物理量随敏化剂增加而显著增强，并随辐照剂量呈先上升后下降的趋势，辐照剂量为5kGy时，熔体强度和拉伸黏度到达最大。添加极少量高分子量物质(UHMWPE)也能有效提高PP的熔体强度。LCB-HMSPP的熔体强度活化能显著降低，熔体强度温度敏感性下降，可在较宽的温度范围内表现出较高的熔体强度。     

高熔体强度聚丙烯的研究与应用现状

普通聚丙烯(PP)由于熔体强度低和加工温度范围窄,在热成型、挤出涂布和挤出发泡等领域应用受到限制。高熔体强度聚丙烯(HMSPP)具有较高的熔体强度,使聚丙烯可以在通用设备上熔相热成型、挤出发泡、挤出涂布,从而拓宽了PP应用领域。文章综述了国内外高熔体强度聚丙烯的研究进展和应用现状。     

高熔体强度聚丙烯的研究与应用现状

普通聚丙烯（PP）由于熔体强度低和加工温度范围窄,在热成型、挤出涂布和挤出发泡等领域的应用受到限制。高熔体强度聚丙烯（HMSPP）具有较高的熔体强度,使聚丙烯可以在通用设备上熔相热成型、挤出发泡、挤出涂布,从而拓宽了PP应用领域。综述了国内外高熔体强度聚丙烯的研究进展和应用现状。     

高熔体强度聚丙烯的性能及应用

对高熔体强度PP的结构、力学性能、热力学性能、流为性能进行分析与测试，比较了高熔体强度PP与普通PP在加工应用过程的性能，例如挤出发泡、高速涂覆、吹塑薄膜和吹塑成型。     

聚丙烯/纳米TiO2复合材料的性能研究

研究了PP／纳米TiO2、PP／普通TiO2复合材料的流变行为、力学性能和抗菌性能。结果表明：在PP中加入TiO2后，熔体的表观粘度增大，PP／纳米TiO2复合材料尤其明显；熔体流变性对温度的敏感性降低，PP的加工温度范围变宽。纳米TiO2对PP的增韧作用比普通TiO2更好，在0-4％的范围内，材料的冲击强度随用量的增加而增大；而对材料拉伸性能的影响甚微。PP／纳米、普通TiO2复合材料都是有抗菌作用，PP／纳米TiO2的抗菌作用相对较强。     

高熔体强度聚丙烯的研究应用进展

通用聚丙烯（PP）由于熔体强度低和加工温度范围较窄,因而在挤出发泡、挤出涂布和热成型等条件下难以加工成型,所以限制了通用聚丙烯的应用领域。高熔体强度聚丙烯（HMSPP）具有较高的熔体强度和优异的物理机械性能,因此拓宽了聚丙烯的应用范围。文章综述了国内外高熔体强度聚丙烯的性能特点、制备方法、研究进展和应用现状。     

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。     

几种无纺布聚丙烯专用料的性能研究

选取了国内无纺布企业主要用的几种聚丙烯专用料，测定了其力学性能、流动性能，并在此基础上考察了不同热处理温度下的熔融特性以及不同降温速率下的结晶特性。结果表明：PP S2040的熔体质量流动速率较高，易于加工成型，但对温度的依赖性较大。PP1700的拉伸强度、拉伸屈服强度和缺口冲击强度比PP S2040、Exxon3155高，而断裂伸长率却最低。这是由于PP1700的熔体流动速率小，相对摩尔质量大，强度相对提高。热处理后，由于聚丙烯的结晶程度更加完善，几种专用料的熔融起始温度Tm0、熔融峰温Tmp均有所上升。随着降温速率增加，低温进入晶区的部分增多，使结晶范围变宽，结晶温度Tc和结晶峰都向低温方向移动，结晶度有所增加。在相同的降温速率下，PP S2040的结晶时间ts略小，而结晶焓较高，说明在较短的时间内达到较高的结晶度，结晶速度较快。     

几种无卤膨胀型阻燃剂对聚丙烯性能的影响

聚丙烯(PP)为基体树脂,分别加入无卤膨胀型阻燃剂FR-1420、FP2200和HS20制备了阻燃PP复合材料,考察了三种阻燃剂及其含量对材料的阻燃性能、力学性能、熔体质量流动速率及加工性的影响,通过热重分析(TG)研究了材料的热分解行为。结果表明,三种阻燃剂均能提高PP的阻燃性能,当阻燃剂质量分数达到20%时,阻燃PP复合材料垂直燃烧等级均可达到V-0级;随阻燃剂含量的增加,阻燃PP复合材料的阻燃性不断提高,拉伸强度、冲击强度、熔体质量流动速率下降;阻燃剂对阻燃PP复合材料的力学性能、熔体流动速率及加工性有较大影响,阻燃剂FR-1420和FP2200效果较好,且其加工温度可达250℃,阻燃剂HS20效果较差,其加工温度仅为200℃;TG分析表明,加入阻燃剂使阻燃PP复合材料初始分解温度提前,残炭率增加,有利于提高PP材料的阻燃性能。     

聚丙烯片材挤出发泡工艺及发泡体系研究

采用自行研制的高熔体强度聚丙烯(PP),通过挤出片材发泡实验,研究了口模温度、挤出温度、螺杆转速等工艺条件以及PP熔体强度和发泡成核剂对片材发泡效果的影响。PP发泡片材最佳挤出工艺条件为:挤出温度210℃,口模温度160℃,螺杆转速40 r/min。PP熔体强度为13 cN,发泡成核剂用量为6 phr时,发泡片材密度最低(0.450g/cm~3),片材表面光滑平整,挤出发泡效果最好。     

Melt strength of polypropylene: Its relevance to thermoforming

The melt strength of homopolymer, copolymer and high melt strength (HMS) grades of polypropylene (PP) was measured to assess the sagging resistance of PP for thermoforming applications. Acrylonitrile-butadiene-styrene (ABS), which can be easily processed during thermoforming, was also studied in this work. A polymer with high melt strength is considered to have a better sagging resistance. The melt strength measurements were carried out using a Gottfert “Rheotens” melt strength tester. The melt strength of the polymers increased with decreasing temperature and increasing extrusion rate. ABS generally had the highest melt strength in the low extrusion temperature region approaching the thermoforming region, indicating that it has a good sagging resistance during thermoforming. The HMS PP had significantly higher melt strength than conventional PP grades; therefore HMS PP is expected to have an improved sagging resistance. For conventional PP, melt strength was higher for the lower melt flow index (MFI) grades. A sharp increase in the melt strength was observed for conventional PP at low extrusion temperature, probably due to flow-induced crystallization of the PP. These results indicate that to minimise the sagging problem with conventional PP, low MFI grades should be used and thermoforming should be performed at temperatures close to the melting point of PP.     

Microcellular foaming of PE/PP blends

Three different polyethylene/polypropylene (PE/PP) blends were microcellular foamed and their crystallinities and melt strengths were investigated. The relationship between crystallinity, melt strength, and cellular structure was studied. Experimental results showed that the three blends had similar variation patterns in respect of crystallinity, melt strength, and cellular structure, and these variation patterns were correlative for each blend. For all blends, the melt strength and PP melting point initially heightened and then lowered, the PP crystallinity first decreased, and then increased as the PE content increased. At PE content of 30%, the melt strength and PP melting point were highest and the PP crystallinity was least. The blend with lower PP crystallinity and higher melt strength had better cellular structure and broader microcellular foaming temperature range. So, three blends had best cellular structure at PE content of 30%. Furthermore, when compared with PE/homopolymer (hPP) blend, the PE/copolymer PP (cPP) blend had higher melt strength, better cellular structure, and wider microcellular foaming temperature range, so it was more suited to be microcellular foamed. Whereas LDPE/cPP blend had the broadest microcellular foaming temperature range because of its highest melt strength within three blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4149–4159, 2007     

动态硫化聚丙烯的研究

研究了聚丙烯动态硫化体系及工艺对聚丙烯复合材料力学性能熔体强度的影响，结果表明，交联剂，闻并助剂、改性剂，加料程度及加工温度是影响Ｉｚｏｄ冲击强度和熔体强度的主要因素。     

动态硫化聚丙烯复合材料的制备

研究了聚丙烯动态硫化体系及工艺对聚丙烯复合材料力学性能及熔体强度的影响,结果表明交联剂、交联助剂、改性剂、填充剂、喂料速度、加工温度是影响力学性能和熔体强度的主要因素。用双螺杆挤出机和动态硫化技术制备出了综合力学性能好、熔体强度高的聚丙烯复合材料。     

高流动高模量高抗冲聚丙烯复合材料的制备及性能研究

研究了弹性体（POE）、滑石粉(talc)、乙撑双硬脂酰胺（EBS）的含量对高流动、高模量、高抗冲聚丙烯（PP）复合材料的力学性能、熔体流动速率、结晶温度、热稳定性以及微观断面结构的影响。结果表明,需要25份POE才能使高流动性共聚PP发生完全脆韧转变;通过熔融共混制备PP、POE、talc复合材料（PP/POE/talc）,当复合材料的质量份数比为80∶20∶40时,制得的PP/POE/talc复合材料的熔体流动速率为22.9 g/10 min、弯曲模量为1 887.7 MPa、缺口冲击强度为31.2 kJ/m2;对比纯PP,其弯曲模量提高了102.2 %,缺口冲击强度提高了217.8 %,弯曲强度提高了2.6 %,拉伸强度降低了15.1 %;添加1份EBS能够同时提高PP/POE/talc复合材料的熔体流动速率与缺口冲击强度。     

Structure and melt rheology of long‐chain branching polypropylene/clay nanocomposites

Long‐chain branching polypropylene (LCB‐PP)/clay nanocomposites were prepared by melt blending in a twin‐screw extruder. The microstructure and melt rheology of these nanocomposites were investigated using x‐ray diffraction, transmission electron microscopy, oscillatory shear rheology, and melt elongation testing. The results show that, the clay layers are intercalated by polymer molecular chains and exfoliate well in LCB‐PP matrix in the presence of maleic anhydride grafted PP. Rheological characteristics, such as higher storage modulus at low‐frequency and solid‐like plateau in tan‐ω curve, indicate that a compact and stable filler network structure is formed when clay is loaded at 4 phr (parts per hundred parts of) or higher. The response of the nanocomposite under melt extension reveals an initial decrease in the melt strength and elongational viscosity with increasing clay concentration up to 6 phr. Later, the melt strength and elongational viscosity show slight increases with further increasing clay concentration. These results might be caused by a reduction in the molecular weight of the LCB‐PP matrix and by the intercalation of LCB‐PP molecular chains into the clay layers. Increases in the melt strength and elongational viscosity for the nanocomposites with decreasing extrusion temperature are also observed, which is due to flow‐induced crystallization under lower extrusion temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheology and melt strength of long chain branching polypropylene prepared by reactive extrusion with various peroxides

Long Chain Branching Polypropylenes were prepared in an extruder by a melt grafting reaction in the presence of various peroxides and a polyfunctional monomer of 1,6‐hexanediol diarylate. Fourier Transformed Infrared spectra and the rheological characteristics indicated that the grafting reaction added long branched chains to linear polypropylene (PP). In comparison to the initial PP, the branched samples exhibited higher melt strength, lower melt flow index, and enhancement of crystallization temperature. The branching number of the modified samples agreed well with their melt viscoelasticity and the improved degree of their melt strength. The branching level in modified PPs could be controlled by the property and structure of the peroxide used. Peroxides with lower decomposition temperature and more stable radicals after decomposition promoted the branching reaction, leading to the modified PPs with higher branching level and melt strength. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

聚丙烯熔体拉伸流变行为的研究

采用双料筒毛细管流变仪，对两种不同摩尔质量的等规聚丙烯的剪切及拉伸流变行为进行了研究，并采用Cogswell方法计算了熔体的拉伸强度。结果表明：聚丙烯为假塑性流体，随着剪切速率的增加，熔体的表观剪切黏度下降，呈现出假塑性流体典型的“剪切变稀”行为。在相同的温度和剪切速率下，平均摩尔质量较小、分布较宽的聚丙烯的表观剪切黏度及拉伸黏度均较小，但熔体的拉伸强度较大，意味着其具有较好的流动性能，并具有较高的可拉伸性，可以达到较大的拉伸比。     

PP/PA6/POE-g-MAH三元共混对聚丙烯熔体强度的影响

将尼龙6(PA6)、普通聚丙烯(PP)以及POE-g-MAH三元共混,改善聚丙烯的熔体强度。应用熔体强度测试仪直接测量了改性PP的熔体强度值,并对改性PP的动态流变特性、红外光谱以及微观形貌特点进行了研究。研究结果表明,该方法可以提高聚丙烯熔体强度。