反应挤出共混法制备发泡用聚丙烯的研究

采用反应型双螺杆挤出机,以过氧化苯甲酰(BPO)做引发剂,不饱和烯烃为交联助剂,一步实现聚丙烯(PP)与少量低密度聚乙烯(LDPE)的共混、接枝与交联,制备出了具有高熔体黏度的发泡用聚丙烯.研究结果表明,改性后PP的熔体流动速率(MFR)可降至0.1 g/10min以下,体系中有质量含量高达48%以上的凝胶产生,当交联助剂含量与引发剂含量的质量比例约为1.31时,可以获得最佳的改性效果.体系中的引发剂和交联助剂均显著影响改性材料的熔体流动性和凝胶含量,在引发剂质量含量达到0.8%以上时,MFR和凝胶含量变化趋势减缓;差示扫描量热分析(DSC)研究表明,交联使体系中PP相和PE相的结晶速率都下降.对改性后的样品进行发泡实验,结果表明采用反应共混改性PP可获得泡孔细密均匀、穿孔很少的高质量泡沫塑料.     

原材料对硅烷接枝交联高熔体强度聚丙烯流动性能影响的研究

采用不饱和硅烷为接枝单体,不饱和烯烃为共单体,在双螺杆挤出机上实现均聚型聚丙烯的接枝交联,制得了高熔体强度聚丙烯。实验通过熔体指数(MFR)和凝胶含量的变化研究原材料对改性PP的影响。结果显示,体系中的试剂均严重影响材料的熔体流动性能。在硅烷和共单体共存的条件下,材料的熔体流动性能随引发剂A含量的增加而下降。共单体起到稳定大分子自由基的作用,增加了硅烷的接枝效率和接枝速率,共单体与硅烷最佳摩尔比为1∶1。改性后材料的耐热性、力学性能等均有较大提高。     

一步法硅烷接枝交联改性均聚型聚丙烯的研究

通过反应挤出法一步实现均聚型聚丙烯的硅烷接枝和交联,制备出具有部分交联结构的高熔体强度聚丙烯。通过熔体强度、熔体黏度测试和熔体流动速率(MFR)、凝胶含量的变化研究了试剂体系对接枝交联改性的作用。结果显示,改性PP的MFR可降低至0.5g/10m in以下,熔体强度提高4.1倍,熔体剪切黏度提高1.707倍;加入的助剂体系中的各个组分都是有效和必要的,而且体系各个组分之间有相互协同作用;改性配方中各个组分的用量比显著影响改性PP的熔体流动速率和凝胶含量,当引发剂、接枝单体、接枝助剂的用量比为(0.36~0.54)∶1∶0.38时,可以获得最佳的改性效果。     

反应挤出法制备高熔体强度聚丙烯的研究

采用不饱和硅烷为接枝单体,不饱和烯烃为交联助剂,在双螺杆挤出机上一步法实现了均聚型聚丙烯(PP)的接枝交联,制得了高熔体强度PP。结果表明,接枝单体、交联助剂、引发剂均显著地影响PP的熔体流动性能。在硅烷和交联助剂共存的条件下,PP的熔体流动性能随引发剂过氧化苯甲酰(BPO)用量的增加而下降。交联助剂起到稳定大分子自由基的作用,增加了硅烷的接枝效率和接枝速率;并指出硅烷接枝交联法是目前制备高熔体强度PP方法中最有希望实现工业化生产的技术。     

硅烷固相接枝熔融法制备交联聚丙烯

以硅烷为接枝单体，采用固相接枝法得到硅烷接枝聚丙烯，将接枝产物水解熔融得到交联聚丙烯（MPP），研究了接枝单体和引发剂种类对聚丙烯（PP）固相接枝率的影响，选择相同条件下接枝率最大时所用单体3-（甲基丙烯酰氧）丙基三甲氧基硅烷（MAPTMS）和引发剂过氧化苯甲酸叔丁酯（TBPB）考察后续交联产物性能，进一步研究了MAPTMS和TBPB加入量对MPP熔体流动速率（MFR）、凝胶含量、结晶温度、熔融温度、弹性模量和复数黏度的影响。结果表明：与纯PP相比，MPP的MFR降低，凝胶含量、弹性模量、复数黏度均升高，当MAPTMS与TBPB加入量分别为0.06,4.00 mL时，MPP的MFR降至2.4 g/10 min，凝胶含量高达54%，弹性模量和复数黏度均达到最大；与纯PP相比，MPP显示出更高的结晶温度，更低的结晶温度，产物不发生相分离。     

聚丙烯高发泡材料

为提高聚丙烯(PP)的熔体强度,改善PP的发泡性能,用双螺杆挤出机对PP进行硅烷交联改性,制备出了高熔体强度聚丙烯(HMSPP)后,进行了模压法发泡的研究.结果表明:HMSPP随着引发剂含量的增加,改性PP的熔体强度提高;PP发泡材料的密度降低至0.118 g/cm3.发泡剂AC的用量及成核剂的含量对发泡材料的表观密度有很大影响,当发泡剂含量为2.5份、成核剂含量为1份时,得到的PP发泡板材密度降低,发泡倍率增大,泡孔均匀致密,力学性能较好.     

一步法硅烷接枝交联改性聚丙烯的研究

采用反应挤出法一步实现聚丙烯（PP）的硅烷接枝和交联改性，制备出了具有部分交联结构的高熔体强度PP。通过改性前后红外光谱、熔体流动性能、凝胶含量、结晶行为、力学性能和发泡性能的变化考察了改性对材料性能的影响。结果表明，一步法改性后PP大分子中引入了硅烷接枝交联结构，使熔体强度、熔体黏度提高，熔体流动速率显著降低，并且体系中出现了高达48％的凝胶；交联结构的引入使PP的结晶速率减缓；改性后材料的力学性能有所提高，而发泡性能大大改善，可以获得高质量的泡沫塑料。     

发泡用高熔体强度聚丙烯的研究

以过氧化苯甲酰(BPO)为引发剂,在同向双螺杆挤出机上对聚丙烯(PP)进行硅烷交联,制备了高熔体强度聚丙烯(HMSPP),然后制得高发泡倍率的PP制品.实验对改性PP的熔体强度、力学性能、热性能和发泡性能进行了表征.结果表明:自制HMSPP的熔体强度是纯PP的5.01倍,力学性能和耐热性与纯PP相比均有较大提高,可用于成型高发泡倍率制品.     

聚丙烯的流变性能及发泡性能研究

采用凝胶渗透色谱仪(GPC),差示扫描量热仪(DSC)、高级流变扩展系统(ARES),熔体拉伸流变仪对等规聚丙烯(PP1)、接枝改性聚丙烯(PP2)及Borealis的高熔体强度聚丙烯(PP3)进行了测试和表征,并利用自行研制的超临界流体挤出发泡实验装置,对上述3种PP进行了超临界二氧化碳挤出发泡研究,初步探讨了聚丙烯的流变性能对聚丙烯发泡性能的影响。结果表明,带有支化结构的PP2和PP3具有较高的熔体强度和熔体弹性,能够得到泡孔均匀的挤出发泡样品,具有较好的可发泡性。     

接枝聚丙烯的制备及发泡研究

以过氧化二异丙苯（DCP）为引发剂、三羟甲基丙烷三丙烯酸酯（TMPTA）为接枝单体,通过转矩流变仪对聚丙烯（PP）进行了接枝改性,并探究了不同温度和单体用量对接枝聚丙烯的扭矩、熔体流动速率（MFR）以及力学性能的影响。通过热重分析仪（TG）和差示扫描量热仪（DSC）测试,分析接枝聚丙烯的热稳定性和结晶行为,对改性聚丙烯进行发泡研究。结果表明：通过红外验证聚丙烯接枝成功。综合考虑扭矩、MFR和力学性能等条件,在170℃下,m(PP)∶m(TMPTA)∶m(DCP)为100∶1.2∶0.05时,制备的接枝聚丙烯的综合性能最优。与纯PP相比,PP/TMPTA/DCP(100/1.2/0.05)的力学性能、热稳定性和发泡性能均更优异,其扭矩提高了15%,MFR减小了14.4%,拉伸强度提高了15%,断裂伸长率增加了120%。     

Mechanism of a one-step method for preparing silane grafting and cross-linking polypropylene

A high-melt-strength polypropylene (HMSPP) with partially cross-linking, modified from a normal isotactic polypropylene (IPP), is prepared by a one-step silane grafting and cross-linking method in a twin-screw reactive extruder. The melt grafting and cross-linking of IPP is achieved by using vinyl unsaturated silane with long chain as a grafting monomer, benzoyl peroxide (BPO) as an initiator, styrene as a coagent, and a little water as a catalyst for cross-linking. By analyzing the difference of the Fourier transformed infrared spectra between raw and modified PP, comparing the variety of the melt flow rate (MFR) and gel percentage between cured and uncured PP samples, and investigating the effect of catalyst on the MFR and gel percentage of modified PP, the partially cross-linked polypropylene in the way of one-step reactive extrusion has been verified. We put forward the reactive mechanism of one-step method based on our experimental results. In this mechanism, the hydrolysis and condensation of silane occur first through the catalysis of water and a compound with two or more double-bond is formed, which then the compound reacts with PP macroradicals to form the partially cross-linked PP. POLYM. ENG. SCI., 47:1004–1008, 2007. © 2007 Society of Plastics Engineers     

Foaming polypropylene prepared by a novel one-step silane-grafting and crosslinking method

High-melt-strength polypropylene (HMSPP) used for foaming was prepared by a novel one-step of silane grafting and crosslinking of a normal isotactic polypropylene (IPP) in a twin-screw extruder. The HMSPP has been achieved using vinyl unsaturated silane with long chain as a grafting monomer, benzoyl peroxide (BPO) as an initiator, styrene as a coagent, trace amounts of water as a catalyst for crosslinking. The function of each agent in the formulation for the IPP modification was investigated. The results indicate that all of the agents are effective and necessary, and the proportions of the components, especially BPO, highly influenced the melt flow rate (MFR) of the HMSPP. Due to the presence of traced water in the system, the crosslinking of IPP is accompanied by the grafting of silane, which leads to a one-step production of crosslinked IPP. A high-qualified foam with uniform, closed and independent cells were fabricated from the HMSPP with appropriate MFR. With the decrement of the MFR of the HMSPP, the average size of the cells and the number of the unclosed cells decrease while the density of the cells increases.     

Foaming polypropylene prepared by a novel one-step silane-grafting and crosslinking method

High-melt-strength polypropylene (HMSPP) used for foaming was prepared by a novel one-step of silane grafting and crosslinking of a normal isotactic polypropylene (IPP) in a twin-screw extruder. The HMSPP has been achieved using vinyl unsaturated silane with long chain as a grafting monomer, benzoyl peroxide (BPO) as an initiator, styrene as a coagent, trace amounts of water as a catalyst for crosslinking. The function of each agent in the formulation for the IPP modification was investigated. The results indicate that all of the agents are effective and necessary, and the proportions of the components, especially BPO, highly influenced the melt flow rate (MFR) of the HMSPP. Due to the presence of traced water in the system, the crosslinking of IPP is accompanied by the grafting of silane, which leads to a one-step production of crosslinked IPP. A high-qualified foam with uniform, closed and independent cells were fabricated from the HMSPP with appropriate MFR. With the decrement of the MFR of the HMSPP, the average size of the cells and the number of the unclosed cells decrease while the density of the cells increases.     

GMA/St双组分单体熔融接枝聚丙烯的研究

分别以甲基丙烯酸缩水甘油酯（GMA）和马来酸酐（MAH）为接枝单体，苯乙烯（St）为接枝共单体，过氧化二异丙苯（DCP）为引发剂对聚丙烯（PP）进行熔融接枝，研究了接枝单体的种类、组分配比等因素对PP的接枝率和熔体流动速率等的影响，并研究了接枝PP的力学性能和耐热变形性能。实验结果表明：作为接枝单体，GMA比MAH更具有优越性；双组分单体熔融接枝PP的接枝率和性能优于单组分单体熔融接枝；接枝PP的结晶参数受其接枝率的影响；当PP／GMA／St／DCP=100／6／3／0、3时，PP—g^-（GMA—CO—St）的接枝率最高，力学性能和耐热变形性能最好。     

Gel formed during the solid‐state graft copolymerization of styrene and spherical polypropylene granules. I. Influence of reaction conditions on the gelation and its mechanism

Graft copolymers of polystyrene (PSt) with spherical polypropylene (PP) granules were synthesized by solid‐state reaction. In the copolymerization as a by‐product some gel was formed. The effects of the amount of free radical initiator, feed ratio of St monomer, species of free radical initiator, and composition of the spherical polyolefin granules on the grafting degree of PSt and the gelation were studied. It is found that larger amount of initiator used, and higher feed ratio of St monomer lead to a higher grafting degree and higher content of gel. During the cross‐link reaction process, both styrene and free‐radical participate in the reaction that discloses the reason of the increment of gel with the increment of styrene consumption or initiator consumption. Using PPR, which is a random copolymer of 95.1 mol % propylene units and 4.9 mol % ethylene units, as grafting matrix, higher grafting degree and higher content of gel can be reached than that using isotactic PP as grafting matrix. Using tert‐butyl peroxy benzoate (TBPB) as initiator, under the same conditions there were more PSt grafted to the spherical PP granules and more gel formed than that using benzoyl peroxide (BPO) as initiator. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3682–3687, 2007     

LDPE-g-GMA的接枝率和流动性研究

利用熔融接枝法制备了聚甲基丙烯酸缩水甘油酯接枝低密度聚乙烯(LDPE-g-GMA),用红外光谱对接枝产物进行了表征,研究了接枝单体、接枝共单体和引发剂对LDPE-g-GMA接枝率和熔体流动速率(MFR)的影响。结果表明:随着接枝单体用量的增加,LDPE-g-GMA的接枝率提高,MFR下降;随着接枝共单体用量的增加,LDPE-g-GMA的接枝率提高,MFR在小范围内波动,变化不大;随着引发剂用量的增加,LDPE-g-GMA的接枝率先升后降,MFR大幅下降。     

固相接枝物PE—g—DEM的制备,分析及应用

采用固相接枝技术,以马来酸二乙酯为单体对ＰＥ进行功能化改性,研究了单体用量,引发剂用量,反应温度,反应时间对接枝率及反应体系熔体流动速率的影响,用红光谱对接枝进行了表征。将接枝物用于ＰＶＣ合金的制备,结果表明,在ＰＶＣ／ＰＥ－Ｃ合金中接枝物引起了增韧,增强的双重作用。     

硅烷接枝ABS树脂及其水解交联的研究

在Haake密炼机中进行硅烷和ABS树脂的接枝反应,接枝产物在沸水中进行水解交联。研究了硅烷种类和用量、引发剂种类和用量对接枝率和凝胶率的影响,同时考察了反应条件对凝胶率的影响。结果表明,在本研究范围内,对于ABS树脂,只有使用3－甲基丙烯酰氧基三甲氧基硅烷（VMMS）作为接枝单体和丙烯酰胺作为引发剂才能得到一定的凝胶率。接枝率随单体用量增加而增加,凝胶率则先升高后趋于一定值。接枝率和疑胶率还随引发剂用量的增加先迅速增加后趋于一定值。温度和转速较低时,对凝胶率没有明显影响,但温度和转速很高时,凝胶率有所下降。     

Influence of grafting formulations and extrusion conditions on properties of silane‐grafted polypropylenes

The melt grafting of unsaturated silanes onto powdered polypropylene (PP) in a Haake TW100 twin‐screw extruder and curing in hot water were studied. The influence of grafting formulations and extrusion conditions on the melt flow rates of grafted PP and the gel percentages of crosslinked PP was investigated. The gel percentages of methacryloylpropyltrimethoxysilane (VMMS)‐grafted PP were markedly higher than those of vinyltriethoxysilane (VTES)‐ and vinyltrimethoxysilane (VTMS)‐grafted PP, while significantly less degradation of PP during grafting was observed for VMMS‐grafted PP. When benzoyl peroxide (BPO) was used as an initiator, no degradation of PP during grafting was observed, and the melt flow rates of grafted PP decreased with increasing BPO concentration. In contrast, use of dicumyl peroxide (DCP) as an initiator resulted in severe degradation of PP, and the melt flow rates of grafted PP increased gradually with increasing DCP concentration. BPO resulted in higher gel percentages than those of DCP at a fixed initiator concentration. Introduction of styrene into the grafting system greatly improved the gel percentage of crosslinked PP and reduced the degradation of PP during grafting. The optimum molar ratio of styrene to monomer is at about 1.5:1. Relatively low processing temperatures and high screw speeds are favorable. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1233–1238, 2000