硅烷交联LDPE的微观分析

用扫描电子显微镜、凝胶渗透色谱、差示扫描量热法等分析了低密度聚乙烯(LDPE)接枝及交联前后微观结构的变化。结果表明,LDPE被接枝后交联,形成了明显的网状结构;LDPE2102TN00被硅烷A15l接枝后,交联形成的网状结构比采用2种硅烷A151／A171接枝具有更好的规整性。A151／A171接枝LDPE每11个分子中有1个硅原子。     

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。     

硅烷接枝交联HDPE、LLDPE及其共混物的结构研究

利用红外光谱、差示扫描量热法等方法研究了高密度聚乙烯(HDPE)、线性低密度聚乙烯(LLDPE)及其共混物的乙烯基三乙氧基硅烷(VTEOS)接枝及交联产物的分子结构、熔融行为。结果表明,VTEOS接枝交联PE能力为:LLDPE>HDPE/LLDPE共混物>HDPE;接枝和交联使HDPE、LLDPE及其共混物的结晶度和熔点降低,晶粒变得不均匀。     

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。     

硅烷交联聚乙烯电缆料的研制

研究探讨了硅烷交联聚乙烯4种不同分子结构(LDPE、LDPE/LLDPE、LDPE/LLDPE/HDPE、LLDPE/HDPE)的树脂对产品加工性能及综合力学性能的影响;考察了3种硅烷接枝单体(A-151、A- 171、A- 172)、2种自由基捕捉剂(K1、K2)对产品凝胶率及加工性能的影响,成功地解决了在硅烷接枝反...     

硅烷接枝HDPE和LLDPE的反应动力学研究

用差示扫描量热法研究了过氧化二异丙苯引发的硅烷接枝高密度聚乙烯(HDPE)、线型低密度聚乙烯(LLDPE)反应及其动力学特性。结果表明,该反应可按假定的自由基反应机理,用简化的动力学模型描述,遵循一级反应动力学,得出HDPE、LLDPE的接枝反应活化能分别为(190±5)kJ/mol、(160±5)kJ/mol,LLDPE的接枝反应热和反应程度大于HDPE。     

交联聚乙烯绝缘料用基础树脂的性能研究

利用拉伸试验、红外光谱、凝胶渗透色谱、差示扫描量热法、流变表征等方法测试了交联聚乙烯绝缘料用基础树脂的性能,并研究了制备硅烷交联和过氧化物交联聚乙烯绝缘料的基础树脂组成。结果表明,交联聚乙烯绝缘料用LDPE树脂的基本性能:MFR为2.0g/10 min,密度为0.920g/cm3,熔点为107℃左右,拉伸强度大于12MPa,断裂伸长率大于580%,介电常数小于2.3,相对支化度2.34左右。硅烷交联聚乙烯绝缘料宜用LLDPE和LDPE的共混物做基础树脂,而过氧化物交联聚乙烯绝缘料的基础树脂用LDPE即可。     

LDPE/LLDPE共混物的研制

通过低密度聚乙烯 (LDPE)与线型低密度聚乙烯 (LLDPE)并用 ,采用双辊开炼机共混制成LDPE/LLDPE共混物 ,并对共混物的比例和稳定剂的加入量进行了探讨 ,结果表明共混物的力学性能明显提高     

硅烷交联高密度聚乙烯的正交实验研究

研究了硅烷交联聚乙烯的整个反应过程,以HDPE、过氧化物和不饱和硅烷为基本原料,首先通过挤出熔融法将不饱和硅烷接枝到聚乙烯链上,然后将接枝物进行水解交联反应制得交联产品。通过实验研究了引发剂、硅烷、催化剂对拉伸强度的影响。在工艺条件得到优化的情况下,应用三因素四变量正交设计确定了最佳配方。引发剂、硅烷、催化剂的用量分别为 1phr、1.4phr、0.6phr。讨论了交联温度、交联时间对拉伸强度以及交联时间对凝胶率和维卡软化点的影响     

悬浮法聚乙烯接枝马来酸酐反应的影响因素

用悬浮法以低密度聚乙烯(LDPE)为分散相,水作分散介质,分别以过硫酸铵(APS)和过氧化二苯甲酰(BPO)作引发剂,引发LDPE与马来酸酐(MAH)的接枝反应.在讨论引发剂用量、MAH浓度、反应时间、反应温度等单因素对接校率影响规律的基础上,考察了界面剂对交联度的作用.结果表明;APS和BPO都能引发LDPE与MAH接枝反应,但APS的接枝率低(不大于0.31%,质量分数),BP0的较高;采用BPO作引发剂时,随MAH浓度和引发剂用量的增加、反应时间的延长、反应温度的升高,产物的接枝率均有所提高,但产物的交联度也随之增加;界面剂的加入不仅大大地提高了产物的接枝率(达到3.00%),而且检测不到产物的交联度.     

Silane grafting reactions of LDPE,HDPE, and LLDPE

Vinyl trimethoxysilane and vinyl triethoxysilane grafting reactions, induced by dicumyl peroxide, of LDPE, HDPE, and LLDPE were investigated. The apparent activation energy of vinyl trimethoxysilane grafting reactions was positive when the reactions were induced by 0.2 phr of the peroxide. The apparent activation energies were negative when 0.05, 0.1, 0.15, and 0.25 phr of peroxide were used. The extents of vinyl trimethoxysilane grafting reactions of polyethylenes were in the order of LLDPE > LDPE > HDPE, although the extents of peroxide cross‐linking were in the order of LDPE > LLDPE > HDPE. As compared with vinyl trimethoxysilane, vinyl triethoxysilane produced a relatively high extent of grafting reactions of LDPE but showed a relatively low rate of water cross‐linking reactions of the silane‐grafted LDPE. The investigation of effects of the amount of peroxide on the vinyl trimethoxysilane grafting reaction heats demonstrated that the extent of silane grafting reactions increased proportionally as peroxide was increased until a certain amount (the value was dependent on the amount of silane used). Beyond this amount of peroxide, the silane grafting did not increase, whereas the peroxide cross‐linking appeared to increase significantly with increasing amounts of peroxide. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3404–3411, 1999     

Silane grafting reactions of low-density polyethylene

Reactions of vinyl trimethoxysilane grafting onto low-density polyethylene (LDPE) were investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis. The silane grafting reactions were induced by a fixed amount of dicumyl peroxide at 0.2 part of reagent per hundred parts with respect to LDPE. Fourier transform infrared data demonstrated that the extent of the silane grafting reaction was increased as the amount of silane used, the reaction time, or the reaction temperature was increased. The apparent activation energy of the silane grafting reaction was 9.7 kJ mol⁻¹. Differential scanning calorimetry was used to follow the silane grafting reactions in situ at a heating rate of 20°C per minute. The silane grafting reaction was exothermic starting at about 150°C and ending at about 230°C, indicating a completion of the reaction in 4 min. The grafting reaction heat has linear relations to the amount of silane used. The grafting reaction heat of about 1 J/g of sample was generated during reaction per part of reagent per hundred parts of silane used. The reaction heat of silane grafting onto LDPE per mol of silane used was 14.5 kJ mol⁻¹ silane, and the reaction heat of peroxide that reacted with LDPE was −12 kJ mol⁻¹ peroxide. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 255–261, 1998     

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     

Preparation of Silane-Grafted and Moisture Cross-Linked Low Density Polyethylene: Part I: Factors Affecting Performance of Grafting and Cross-Linking

In the present work, the silane grafting and water cross-linking of low density polyethylene (LDPE) were investigated. The grafting reaction was carried out in an internal mixer and polyethylene cross-linking was done in hot water. The effect of silane, peroxide, catalyst, carbon black, cross-linking time, and cross-linking temperature on the grafting and cross-linking processes are reported. Vinyl trimethoxy silane (VTMO) and di-cumyl peroxide (DCP) were selected as grafting agent and initiator respectively. Silane grafting on polyethylene was determined using Fourier transform infrared (FTIR) spectroscopy and torque monitoring of the mixer. Absorption peak due to –Si–OCH₃ groups in FTIR and torque increasing due to silane grafting in the mixer illustrated that silane-grafting reactions occurred. The FTIR data demonstrated that the extent of silane grafting was increased as the concentration of silane and peroxide was increased. Thermogravimetry analysis (TGA) determined that the thermal stability of LDPE increased by increasing the amount of silane grafting. Gel fraction increased with silane and peroxide concentration. As the percent of of catalyst increase the time scale for specified gel content shifted to shorter times. Incorporation of carbon black into LDPE decreased the extent of silane grafting and gel fraction. Water temperature increasing in cross-linking stage reduced the time to maximum degree of cross-linking.     

An investigation of water crosslinking reactions of silane‐grafted LDPE

Factors—including time, temperature, morphology, and thickness of sample, the extent of silane grafting, and water concentration—that affect the rate and degree of water crosslinking reactions of the silane‐grafted LDPE are investigated. The gel content of the water‐crosslinked sample increases with increasing time, temperature, and water concentration, but with decreasing content of the crystalline component in the sample and thickness of the sample. The relationship between the gel content and the crosslinking time is dependent on thickness and morphology of the sample, and the extent of silane grafting in the sample. The crosslinking rates and the resultant gel content are inversely proportional to the content of crystalline component of the sample, suggesting that the crosslinking reactions occur mainly in the amorphous domain of the sample. For those samples with high resultant gel contents, the crystallizations of the samples are significantly enhanced by crosslinking when the gel contents are higher than about 40%, leading to a dual relationship between the gel contents of the samples and the crosslinking times. For low temperatures, the rate‐determining step of the crosslinking reactions is the diffusion of water, rather than the hydrolysis and the subsequent condensation reactions of the silyl trimethoxy groups. For high temperatures and high extents of silane grafting in the samples, however, the chemical reactions dominate the crosslinking process. The overall activation energy of the crosslinking reactions is dependent on thickness of the sample. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 186–196, 2001     

Silane grafting and moisture crosslinking of polypropylene

Peroxide initiated vinylsilane grafting of polypropylene in an intensive mixer, and the subsequent water crosslinking process were studied. Different concentrations of vinyl trimethoxysilane and dicumyl peroxide were used. The materials obtained after mixing in the rheocord were hot pressed at 190°C. The melt viscosity of the obtained sheets, the melting enthalpy and melting temperature (DSC, differential scanning calorimetry), the mechanical properties and the thermal decomposition behavior (TG, thermogravimetric analysis) were studied. No evidence of grafting during the rheocord processing was observed. Nevertheless, for the hot pressed sheets with concentrations higher than 4 phr of vinyl silane an important increase in the melt viscosity was observed. This increase agrees with the change observed in the mechanical properties, which show a maximum for the water crosslinked samples containing 4 phr of vinyl silane. The modulus increases by 39% at 90°C and 33% at 130°C, while the tensile strength rises by ～22% at both temperatures. The silane grafted water crosslinked samples show a more stable thermal behavior than both the silane grafted samples and the unmodified polypropylene.