硅烷交联聚乙烯技术改进及其应用

硅烷交联聚乙烯是交联聚乙烯中普遍使用的交联技术,通过优势接枝单体扩大接枝率、优选催化剂在室温下或较低温度下接枝、严格控制接枝体系中的水分以及提高硅烷在聚乙烯中的分散性等工艺控制来提高硅烷交联聚乙烯产品的接枝、交联速率及凝胶率,可大大提高交联聚乙烯产品的性能。     

硅烷接枝交联聚乙烯技术的研究

在讨论硅境接枝交联聚乙烯技术原理的基础上,探讨了影响硅烷接枝交联聚乙烯的各种主要因素及其解决办法和最佳的试验条件,如基础树脂的选择、各种助剂的选择和最佳用量、接枝工艺的选择、交联工艺的选择以及接枝设备的选择等,并对硅烷接枝交联聚乙烯技术的今后发展提出了建议。     

硅烷接枝交联LDPE、LLDPE及其共混物的结构研究

利用红外光谱、凝胶渗透色谱、热延伸试验、差示扫描量热法、扫描电子显微镜等方法研究了低密度聚乙烯（LDPE）、线型低密度聚乙烯（LLDPE）及其共混物的乙烯基硅烷接枝及交联产物的分子结构、熔融行为和形态。结果表明：硅烷接枝后，LDPE、LLDPE的重均摩尔质量小幅增加；硅烷接枝交联能力为：LLDPE〉LDPE／LLDPE共混物〉LDPE；接枝和交联使LDPE、LLDPE及其共混物的结晶度降低，晶粒变得不均匀；硅烷接枝和交联能增加LDPE／LLDPE共混物的相容性；交联结构提高了LDPE、LLDPE及其共混物的抗冲性。     

硅烷交联聚乙烯电缆绝缘料的研制

本文介绍了硅烷交联聚乙烯（ＸＬＰＥ）生产技术、材料选择及用量对电缆料性能的影响，探讨了温度等对凝胶率的影响，用两步法工艺研制了硅烷接枝温水交联聚乙烯电缆绝缘料。     

硅烷接枝交联HDPE／LLDPE共混物性能研究

采用引发剂过氧化二异丙苯（DCP）、硅烷偶联剂乙烯基三乙氧基硅烷（VTEOS）和催化剂二月桂酸二丁基锡（DBTL）,通过双螺杆挤出机对高密度聚乙烯（HDPE）和线性低密度聚乙烯（LLDPE）的共混物进行硅烷接枝交联反应。通过力学测试和DSC研究产物不同凝胶含量对其性能影响。研究表明硅烷交联聚乙烯的拉伸和冲击强度随交联度的增大而提高,但产物结晶度和熔点有所下降,同时结晶均匀性变差。     

硅烷接枝热水交联聚乙烯共混物的研究

本文介绍了采用过氧化二异丙苯（ ＤＣＰ） 为引发剂,二月桂酸二丁基锡（ ＤＢＴＬ） 为催化剂,在双螺杆挤出机中硅烷（ ＶＴＥＳ） 与聚乙烯（ＰＥ） 共混物的接枝反应,以及通过热水交联获得硅烷交联聚乙烯共混物。研究了不同牌号聚乙烯的选取,正交实验优化配方以及热水交联时间对产品性能的影响。结果表明：选取适当的高密度聚乙烯,低密度聚乙烯及线性低密度聚乙烯共混物进行硅烷接枝交联,可获得具有良好的力学性能和良好的加工性能的交联ＰＥ 共混物;正交实验获得ＤＣＰ、ＶＴＥＳ 及ＤＢＴＬ 的最佳用量分别为０ ．１０ 份、２ ．５ 份、０ ．１５ 份;热水交联的合适时间约为１２ 小时,在此之前拉伸强度、维卡软化点及凝胶率随交联时间而升高,断裂伸长率随时间而降低,此后,几者均趋于稳定。     

硅烷交联聚乙烯电缆料抗预交联添加剂的研究

研究了抑制硅烷交联聚乙烯电缆料预交联反应的方法。测试不同储存时间下的硅烷接枝聚乙烯的熔体流动速率和硅烷交联聚乙烯电缆料在挤出机中停留不同时间后挤出物的表面状况、凝胶含量等。实验结果表明,抗预交联添加剂SRA能有效地抑制硅烷接枝聚乙烯在储存和挤出加工过程中的预交联反应,提高硅烷交联聚乙烯电缆料的挤出加工性。     

硅烷交联聚乙烯加工流变性及其预交联研究

就硅烷接枝和交联聚乙烯的加工流变性能与预交联之间紧密的关系进行探讨。结果表明：加工转矩和预交联度随聚乙烯、硅烷、引发剂品种与用量的不同而不同,提高转速和温度有利于降低预交联度。实验还表明VTEOS（乙烯基三乙基硅烷）比VTMOS（乙烯基三甲氧基硅烷）更易于接枝。     

硅烷交联聚乙烯电力电缆绝缘料的研制

采用两步法制备了硅烷交联聚乙烯（PE）电力电缆绝缘料。以双螺杆挤出机为反应器,以低密度聚乙烯（LDPE）和线型低密度聚乙烯（LLDPE）为基础树脂,考察了影响PE接枝交联的主要因素（如基础树脂的配比,交联剂的用量及种类,引发剂、抗氧剂的用量等）,得出了具有良好性能的硅烷交联PE电力电缆绝缘料的配方（质量份数）：LDPE为85．00phr,LLDPE为15．0H0phr,硅烷W为0．60phr,硅烷Q为1．40phr,引发剂为0．12phr,抗氧剂为0．20phr。     

硅烷交联聚乙烯的结构研究

将硅烷接枝交联技术应用于电线电缆用的硅烷交联聚乙烯绝缘材料,将已接枝硅烷的聚乙烯A料和含有催化剂的B料混合,通过进一步水解和缩合反应,生成硅烷交联聚乙烯,并用于工业生产.根据X射线衍射实验可知,A料、B料及交联前后的电缆料均为聚乙烯材料,结合拉曼光谱和理论计算研究,研究了聚乙烯主链上的分子基团结构,进一步证实了水解缩合...     

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。     

Optimisation of silane grafting in single screw extruder

Abstract

Reactive extrusion is an attractive means of polymer processing since the shaping and reaction takes place in a single operation. Silane grafting of low density polyethylene has been achieved in a single screw extruder. The optimum conditions for silane grafting, i.e. temperature, shear rate, and silane and dicumyl peroxide concentrations, were determined on a torque rheometer and extrusion was then performed under optimum conditions. The study shows that an optimum low level of grafting/crosslinking can be introduced into polyethylene during extrusion for better mechanical behaviour and/or thermal stability without aecting the processability.     

Kinetics of silane grafting and moisture crosslinking of polyethylene and ethylene propylene rubber

Peroxide initiated graft copolymerization of vinyl trimethoxy silane (VTMO) and vinyl triethoxy silane (VTEO) onto polyethylene (PE) and ethylene propylene copolymer (EPR) was studied. The kinetics of grafting, studied by differential scanning calorimetry, are the same for all the systems and the activation energy for VTMO is 170 ± 4 KJ/mol. Activation energy for VTEO is 185 ± 5 KJ/mol. The VTMO and VTEO graft copolymers of PE and EPR were prepared by reactive processing in a Brabender extruder in the temperature range of 150–200°C. Moisture catalyzed crosslinking of the silane grafted copolymer was also studied. The influence of the structure of the catalyst, its concentration, moisture concentration, temperature, and time on degree and rate of crosslinking has been evaluated. Crosslinking reactions follow first order kinetics with respect to both catalyst and moisture concentration. Activation energy (E_a) of the crosslinking reaction has been determined as 65 KJ mol^?1. The mechanism of grafting and crosslinking is discussed.     

Thermal and mechanical properties of silane‐grafted water crosslinked polyethylene

The effects of linear low density polyethylene (LLDPE) grafting with vinyltrimethoxysilane by different types and contents of peroxide were studied. When grafting silane onto LLDPE, with 0.10 phr of Dicumyl peroxide (DCP) or 0.05 phr content of 2,5‐Dimethyl‐2,5‐di (tert‐butyl‐peroxy)‐hexane (DHBP), it was found that the grafting effect was improved; however, as Di(2‐tert‐butylperoxypropyl ‐(2))‐benzene (DIPP) or excess DHBP was used, LLDPE was supposed to cause self‐crosslinking, which reduced the grafting effect of silane and was invalid in the processing of extrusion. In this study, vinyl trimethoxysilane (VTMS) was grafted onto various polyethylenes (HDPE, LLDPE, and LDPE) using DCP as an initiator in a twin screw extruder. The grafted polyethylenes were able to crosslink utilizing water as the crosslinking agent. The effects of varied crosslinking time on the mechanical properties of the crosslinked polyethylenes were studied. It was found that the HDPE and LLDPE were apt to crosslink during the grafting process and thus decreased the grafting ratio. Multiple melting behavior was observed for crosslinked LDPE and LLDPE. Mechanical and thermal properties of the crosslinked PE are much better than that of uncrosslinked PE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2383–2391, 2005     

乙烯-辛烯共聚物(POE)界面粘接性改进

聚烯烃是一种新型的太阳能组件封装材料,文中对其核心技术进行了描述。使用双螺杆挤出机,以过氧化物TBEC为交联剂,成功将乙烯基三甲氧基硅氧烷VTMS接枝到POE分子链段上。用傅里叶红外光谱法研究了TBEC、VTMS浓度以及加工温度对接枝率的影响,进而评价了对剥离力的影响。最后考察了硅烷接枝POE材料在湿热老化后剥离力保持的情况。     

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.     

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     

Thermal properties of silane-grafted water-crosslinked polyethylene

Vinyl trimethoxysilane grafting reactions of low-density polyethylene (LDPE) were performed in an extruder, followed by crosslinking with boiled water. The thermal properties of both silane-grafted and silane-grafted water-crosslinked LDPE were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data showed that the silane grafts on the LDPE molecules were thermal stable in the absence of moisture under 130°C under which the silane-grafted LDPE could be processed or recycled. The silane grafts on the LDPE molecules reduced the melting point of LDPE and gave rise to an endotherm shoulder at about 85°C. TGA data showed that the decomposition temperature of the silane-grafted LDPE was much higher than that of LDPE. It was demonstrated that the cause of the increase in the decomposition temperature was not due to the silane grafts but due to the peroxide-induced crosslinking reactions during the silane grafting reactions performed in an extruder. Silane-grafted water-crosslinked LDPE displayed multiple melting behavior resulting from phase separation during crosslinking of LDPE with water. The phase separation gave rise to two melting points, including one at about 94°C, and the other at about 107°C. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1075–1082, 1998     

Experimental study of maleation of polypropylene in various twin‐screw extruder systems

A range of continuous mixing machines were used as continuous reactors for grafting maleic anhydride onto polypropylene. The machines used were (1) a nonintermeshing modular counterrotating twin‐screw extruder, (2) an intermeshing modular corotating twin‐screw extruder, (3) intermeshing modular counterrotating twin‐screw extruder, and (4) a Kobelco Nex‐T continuous mixer. The grafting reaction of maleic anhydride onto polypropylene and degradation of polypropylene during the grafting reaction were investigated as means for comparing these different machines for reactive extrusion. The influence of processing variables such as screw speed and processing temperature on polymer characteristics also was investigated. Generally, in a comparison of the different machines, the intermeshing counterrotating twin‐screw extruder had the lowest levels of grafted maleic anhydride, whereas the Kobelco Nex‐T continuous mixer under the conditions used had the highest levels of grafted maleic anhydride. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1755–1764, 2003