Effect of ethylene ionomers on the properties of crosslinked polyethylene

Most premature failure of underground crosslinked polyethylene (XLPE) cables in service, a matter of great concern, is due to aging induced by water treeing. To improve the water‐tree resistance, sodium‐neutralized poly (ethylene‐co‐acrylic acid) (EAA–Na) ionomers were blended with XLPE; the EAA–Na ionomers were prepared through the neutralization of sodium hydroxide and poly(ethylene‐co‐acrylic acid). A series of XLPE/EAA–Na ionomer blends were investigated through the measurement of the water absorption ratio, water treeing, and mechanical and dielectric testing; the results strongly suggested that EAA–Na ionomers could improve the water‐tree resistance of XLPE, and the XLPE/EAA–Na blends retained excellent mechanical properties and dielectric properties. Moreover, through the characterization of XLPE/EAA–Na blends with Fourier transform infrared spectrometry, dynamic mechanical analysis, and scanning electron microscopy, it was found that the neutralization reaction could be achieved completely; the XLPE and EAA–Na ionomers were partially compatible, so the EAA–Na ionomers could be dispersed well in the matrix with the process examined in this study. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3483–3490, 2007     

Influence of Ethylene Ionomers on the Electrical Properties of Crosslinked Polyethylene

Summary: Water treeing is a deterioration mechanism observed in the polymeric insulation of extruded cables, which can affect the service life of the transmission and distribution XLPE power cables. To improve the water‐tree resistance of XLPE, it was blended with sodium‐neutralized EAA‐Na ionomers which were formed by neutralization of EAA with NaOH. A series of XLPE/EAA‐Na ionomer blends were investigated for their electrical properties, such as water treeing, electrical breakdown strength, dielectric constant, and dissipation factor. The results strongly suggest that EAA‐Na ionomers can improve the water‐tree resistance of XLPE, and the XLPE/EAA‐Na blends retain excellent dielectric properties. Characterization of XLPE/EAA‐Na blends by using FTIR indicates that the neutralization reaction is effectively achieved. In addition, it can be found that XLPE/EAA‐Na blends are partially compatible from observing morphology observations made by SEM and, therefore, EAA‐Na ionomers can be well dispersed in the matrix.

Water tree length of the XLPE/EAA‐0.5Na blends.     

Effect of styrene–ethylene–butadiene–styrene and its synergetic effect with ethylene vinyl acetate on the mechanical,thermal, dielectric,and water‐treeing behaviors of crosslinked polyethylene

In this study, we investigated the effect of an aromatic polymer, styrene–ethylene–butadiene–styrene (SEBS), on the water‐tree resistance of crosslinked polyethylene (XLPE), and the synergetic effect of SEBS and ethylene vinyl acetate (EVA) was also investigated. The XLPE/SEBS and XLPE/SEBS/EVA samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, mechanical measurements, and an accelerated water‐treeing experiment, and the obtained results clearly show the relevant influence of SEBS and EVA, and as expected, the addition of SEBS and EVA was found to synergistically influence the water‐tree resistance of XLPE more positively in comparison with that without the addition of EVA. In addition, it also indicated that the blends possessed excellent dielectric behaviors, such as the dielectric constant and dissipation factor. The crystallization of the blends decreased with increasing SEBS content and addition of EVA. However, the melting temperature of the blends increased with the addition of SEBS and EVA, but the melting temperature of the blends decreased with increasing SEBS content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of Silane-Grafted and Moisture Crosslinked Low Density Polyethylene. Part II: Electrical,Thermal and Mechanical Properties

Among different polyethylene cross-linking methods, such as peroxide, irradiation, and silane cross-linking, silane-based methods are the most suitable methods for producing cable insulation and hot water pipe materials due to process simplicity and superior properties of its product. Some electrical, thermal and mechanical properties of silane-grafted water-cross-linked polyethylene were investigated. The effects of silane grafting and gel content on volume resistivity, tensile properties and melting behavior of low density polyethylene (LDPE) were studied. Results indicated that volume resistivity increased with increasing gel content. Stress at break increased with increasing grafting level and gel content. Elongation at break increased with grafting and decreased with gel content. High temperature tensile properties showed that cross-linked polyethylene (XLPE) is more stable than LDPE at high temperature. In differential scanning calorimetry (DSC) analysis a broad endothermic peak appeared for XLPE due to phase separation. Melting point and crystalline percentage decreased with increased grafting level and gel content. Incorporation of carbon black into XLPE reduced the volume resistivity and degree of crystallization.     

Effect of maleic anhydride/vinyltrimethoxysilane‐co‐grafting polypropylene on the properties of wood‐flour/polypropylene composites by electron‐beam preirradiation

The electron‐beam preirradiation and reactive extrusion technologies were used to prepare maleic anhydride (MAH)/vinyltrimethoxysilane (VTMS)‐co‐grafting polypropylene (PP) as a high‐performance compatibilizer for wood‐flour/PP composites. The grafting content, chemical structure, and crystallization behavior of the compatibilizers were characterized through Fourier transform infrared spectroscopy, differential scanning calorimetry, and an extraction method. The effects of the compatibilizers on the mechanical properties, water absorption, morphological structure, and torque rheological behavior of the composites were investigated comparatively. The experimental results demonstrate that MAH/VTMS‐g‐PP markedly enhanced the mechanical properties of the composites. Compared with MAH‐g‐PP and VTMS‐g‐PP, MAH/VTMS‐g‐PP clearly showed synergistic effects on the increasing mechanical properties, water absorption, and compatibility of the composites. Scanning electron microscopy further confirmed that the adhesion and dispersion of wood flours in the composites were effectively improved by MAH/VTMS‐g‐PP. These results were also proven by the best water resistance of the wood‐flour/PP composites with MAH/VTMS‐g‐PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Performance evaluation of silane crosslinking of metallocene‐based polyethylene–octene elastomer

Vinyl trimethoxysilane (VTMS) was grafted onto metallocene‐based polyethylene–octene elastomer (POE) using a free‐radical reaction of VTMS and dicumyl peroxide as an initiator, and then the grafted POE was crosslinked in the presence of water. The effects of VTMS concentration on crystallization behavior, mechanical properties, and thermal properties of POE before and after crosslinking were studied in this article. Multiple melting behaviors were found for POE after silane crosslinking by using DSC measurement. Degree of crystallization of silane‐crosslinked POE decreases from 18.0 to 14.3%, with increase of VTMS from 0 to 2.0 phr. Tensile strength of silane‐crosslinked POE reaches a maximum of 28.4 MPa when concentration of VTMS is 1.5 phr, while elongation at break is 487%. TG shows that the temperature of 10% weight loss for pure POE is 405°C, while for crosslinked POE with addition of 2.0 phr VTMS the value comes to 452°C, indicating that crosslinking significantly help improve the thermal stability of POE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5057–5061, 2006     

Enhancement of Service Life and Electrical Insulation Properties of Polymeric Cables With the Optimum Content of Aromatic Voltage Stabilizer

This article presents the possibility of extending the service life of XLPE insulation based on high voltage cables by blending the optimum concentration of the aromatic voltage stabilizer. The insulation performance of XLPE is analyzed by adding the 0.5, 1, and 3 wt% of 3-aminobenzoic acid voltage stabilizer. The investigated insulation properties include the DC step-by-step breakdown to estimate the life exponent, space charge, DC conductivity, surface potential decay, dielectric loss, and dielectric constant measurements. The results illustrate that the 1 wt% voltage stabilizer addition increases the life exponent from 10 up to 15, which is highly suitable for the high voltage cables. Moreover, it exhibits the negligible space charge accumulation and the least electrical field distortion inside the insulation bulk. It also exhibits the lower DC conductivity by one order of magnitude comparing to the pure XLPE. The highest bandgap value of 1 wt% addition further supports its better insulating properties. Furthermore, the dielectric measurements show that the XLPE with 1 wt% voltage stabilizer exhibits the least dielectric constant and dielectric loss. The differential scanning calorimetry and thermogravimetric analysis results show that the thermal properties are significantly improved after the voltage stabilizer addition. POLYM. ENG. SCI., 60:717–731, 2020. © 2020 Society of Plastics Engineers     

Synthesis of silane‐grafted ethylene vinyl acetate copolymer and its application to compatibilize the blend of ethylene‐propylene‐diene copolymer and silicone rubber

Vinyltrimethoxysilane‐grafted ethylene vinyl acetate copolymer (EVA‐g‐VTMS) was synthesized and applied to compatibilize ethylene‐propylene‐diene copolymer (EPDM)/methyl vinyl silicone rubber (MVQ) blends. The silane‐grafting was successfully proved by differential scanning calorimetry, FTIR spectroscopy and XPS spectroscopy. The additive amount of the compatibilizer (EVA‐g‐VTMS) was optimized to be 10 phr (parts per hundred of rubber in weight) based on analysis of scanning electron microscopy, mechanical properties, aging properties, dynamic mechanical properties, rheological properties and thermal properties. Compared with the blend without EVA‐g‐VTMS, results show that the blend with 10 phr of EVA‐g‐VTMS exhibits the finest morphology. Tensile strength, elongation at break, modulus at 100% elongation, tear strength and TE index increase by 82.5%, 16.9%, 60.0%, 40.9%, and 41.9%, respectively. Dynamic mechanical analysis reveals storage modulus increase and glass transition temperatures of EPDM and MVQ move closer to each other. Rheological analysis shows a decrease in complex modulus and complex viscosity, and the processibility of the blend was improved. Furthermore, thermogravimetric analysis shows enhancement of thermal stability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

An investigation of the effect of silane water‐crosslinking on the properties of poly(L‐lactide)

A silane‐grafting water‐crosslinking approach was developed to crosslink poly(L ‐lactide) (PLLA) by grafting vinylalkoxysilane onto PLLA using dicumyl peroxide, followed by silane hydrolysis to form siloxane linkages between PLLA chains. The degree of silane grafting onto PLLA was qualitatively characterized using Fourier transform infrared spectroscopy and quantitatively determined using inductively coupled plasma mass spectrometry. Crosslinked PLLA films were obtained by curing of silane‐grafted PLLA in hot water. Gel fractions were evaluated in order to calculate the crosslinking reaction kinetics and crosslinking density. Various techniques were used to investigate the effect of silane water‐crosslinking on the thermomechanical properties, hydrolysis resistance and biodegradation of PLLA. In addition to an improvement in thermal stability and mechanical properties, hydrolysis resistance was significantly enhanced as a result of silane water‐crosslinking of PLLA. Moreover, the biodegradation of silane water‐crosslinked PLLA was retarded compared with neat PLLA. Copyright © 2010 Society of Chemical Industry     

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     

Analysis of failure of crosslinked polyethylene cables because of electrical treeing: A physicochemical approach

The present work investigated the breakdown characteristics of high‐voltage crosslinked polyethylene (XLPE) cable by electrical trees under ac and composite voltages. The electrical trees resemble either a tree or a bushy structure. The importance of the Weibull parameters for the present study was emphasized. The failure zone of the XLPE cables was characterized by experimental techniques such as wide‐angle X‐ray diffraction, differential scanning calorimetry, and thermogravimetric–differential thermal analysis, to understand the phase constituents affected by electrical trees. The impact test and flexural test results indicate that material with high stiffness/toughness allows tree formation and causes early failure of the material. The characteristic variation of the aged XLPE cables was investigated by a dynamic mechanical analyzer (DMA). The activation energy values were calculated from the DMA data. The rate of tree propagation was found to be less for materials (XLPE) with high activation energy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2169–2178, 2004     

Synthesis and evaluation of fluorosilicone‐modified starch for protection of historic stone

Starch is sensitive to moisture and is weak to durability in the protection application to ancient relics. Therefore, two fluorosilicone‐modified starches are firstly prepared and evaluated for the protection of historic stones. The fluoro‐silicone copolymer grafted starch of P(VTMS/12FMA)‐g‐starch is synthesized by grafting copolymer of vinyltrimethoxysilane (VTMS) and dodecafluoroheptyl methacrylate (12FMA) onto starch. While the fluoro‐silicone starch latex of VTMS‐starch@P(MMA/BA/3FMA) is obtained by emulsion polymerization of VTMS primarily grafted‐starch (VTMS‐starch) with methyl methacrylate (MMA), butyl acrylate (BA) and 2,2,2‐trifluoroethyl methacrylate (3FMA). The grafting fluorosilicone copolymer onto starch improves obviously their hydrophobic and thermal properties. Comparatively, VTMS‐starch@P(MMA/BA/3FMA) film performs higher water contact angle (107°) and thermal stability (350–430°C) than p(VTMS/12FMA)‐g‐starch film (72°, 250–420°C) due to the migration of fluorine‐containing group onto the surface of film during the film formation. Therefore, VTMS‐starch@P(MMA/BA/3FMA) shows much better protective performance in water‐resistance, and salt/freeze‐thaw resistance for stone samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41650.     

交联聚乙烯绝缘料在电线电缆中的地位

论述了交联聚乙烯是以电缆专用的低密度聚乙烯为基础树脂,加入过氧化物体系,抗氧化物体系等,经特殊的工艺制成的电缆绝缘料。通过它与聚乙烯、聚氯乙烯物理性能比较,可以看出交联聚乙烯的电性能、机械性能优良。它的生产工艺分五种：过氧化物交联法、辐照交联法、硅烷交联法、紫外光交联法、盐交联法。目前,我国大多数电线电缆绝缘料的生产企业采用辐照交联法和硅烷交联法。在环保方面,随着人们对环保电线电缆的要求越来越迫切,交联聚乙烯绝缘料在电线电缆行业中更是具有不可取代的地位。     

A reactive extrusion process for the free radical grafting of silanes onto polypropylene: Effects of processing conditions and properties of water cross‐linked silane‐grafted polypropylene

Silane grafting and water cross‐linking of polypropylene (PP) are a recent method to modify its properties, such as melt strength, heat, and chemical resistance. This work aims at grafting silanes onto PP by reactive extrusion. The occurrence of the grafting of silane onto PP was confirmed by Fourier transform infrared (FTIR) and a method based on FTIR was developed to quantify the amount of polymerized silane and that of silane grafted onto PP. The molar mass of the silane‐grafted PP and its melt viscosity were also measured. A multiobjective optimization strategy was used to study the effects of processing conditions on the quality of the silane‐modified PP. It was concluded that to maximize the amount of silane grafted on PP and minimize the amount of polymerized silane and the decrease in PP chain scission, screw speed and barrel temperature should be low and feed rate high. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

乙烯-醋酸乙烯共聚物的硅烷交联及无卤阻燃研究

采用过氧化物为引发剂,用熔融法制备了硅烷交联EVA和无卤阻燃硅烷交联EVA.用红外方法(IR)和差示扫描量热法(DSC)对EVA的硅烷接枝反应进行了表征.研究了过氧化物含量对体系凝胶含量,相对接枝率和力学性能的影响,同时还研究了交联对体系阻燃性能的影响.DSC实验表明,硅烷A171比硅烷A151更容易接枝到EVA上.随DCP含量增加,体系的凝胶含量,相对接枝率,拉伸强度增加,而断裂仲长率降低.氧指数结果表明,交联以后可以适当提高氧指数值,改善阻燃性能.     

Interfacial adhesion and water resistance of stainless steel–polyolefin improved by functionalized silane

The adhesion strength and water resistance of stainless steel and adhesive resin composites determine the long‐term performance of wires and cables; however, adhesion at stainless steel interfaces is difficult. Herein, we prepared ethylene acrylic acid/linear low‐density polyethylene (EAA/LLDPE) blends with good mechanical and adhesive properties. Silane was anchored to the surface of stainless steel. The effects of silane functionalization on the adhesion surface were investigated by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The reaction mechanism between the stainless steel, silane, and EAA/LLDPE revealed adhesion was optimized when a 3:7 volume ratio of 3‐methacryloxypropyltrimethoxysilane (MEMO): 3‐aminopropyltrimethoxysilane (A‐1110) was used to modify the stainless steel substrate. SEM images of EAA/LLDPE film peel surfaces found the silane‐treated stainless steel substrates produced rough surfaces with a uniform void indicating the silane treatment enhanced the stainless steel and EAA/LLDPE film interaction. The stainless steel and EAA/LLDPE film adhesion and water resistance improved and the peel strength after water resistance testing at 68°C for 168 h increased from 3.18 N/cm to 9.37 N/cm compared to untreated stainless steel. Silane‐modified stainless steel and EAA/LLDPE blend film composite materials demonstrate potential for application in wires and cables used in environmental corrosion‐resistant applications. POLYM. ENG. SCI., 59:1866–1873, 2019. © 2019 Society of Plastics Engineers     

Quantification of silane grafting efficacy,weak IR vibration bands and percentage crystallinity in post e-beam irradiated UHMWPE

Vinyl-tri-methoxy silane (VTMS) and vinyl-tri-ethoxy silane (VTES) were grafted onto ultra-high molecular weight polyethylene (UHMWPE) by irradiating the UHMWPE/silane hybrids with e-beam. The samples were irradiated under high moisture contents for total dose values of 30, 65 and 100 kGy, respectively. The synergistic effect of silane and irradiation on the grafting efficacy, concentration of weak bonds like trans-vinylene (–CH=CH–) and vinyl (–CH=CH₂) and percentage values of crystallinity were studied using FTIR spectroscopy. For the estimation of grafting reactions efficiency, absorption due to characteristic infrared absorption bands of –Si–CH– in the region ~800 cm^?1 was monitored and found that grafting efficacy of VTMS on UHMWPE was higher as compared to VTES and increased with irradiation. The relative amounts of grafting extension (R) for 100 kGy irradiated UHMWPE/VTMS and UHMWPE/VTES hybrids were found to increase 20 and 15 %, respectively. The concentration of trans-vinylene in UHMWPE was found to increase from 0.015 to 0.035 mmol/l due to synergistic effects of silane and irradiation. Moreover, crystallinity of UHWMPE was found to decrease from 65 to 55 % due to the abovementioned synergistic effects which was also confirmed with DSC tests. Furthermore, oxidation index values were measured to confirm the efficacy of silane as free radical quencher via silane grafting extension reactions.     

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。     

硅烷/马来酸酐混合接枝高密度聚乙烯的制备与应用

以硅烷(VTMS)、马来酸酐(MAH)为单体,过氧化二异丙苯(DCP)为引发剂,制备硅烷/马来酸酐接枝高密度聚乙烯(PE-HD),研究引发剂DCP、单体VTMS和MAH含量对接枝产物性能的影响,用红外光谱(FTIR)对接枝产物进行分析,并将接枝产物作为相容剂添加到复合材料中。结果显示：VTMS和MAH能够在PE-HD上进行接枝,随着DCP、VTMS和MAH含量的增加,接枝产物的接枝性能先增加后减小;和VTMS和MAH单种单体接枝PE-HD比较,硅烷/马来酸酐接枝高密度聚乙烯(MAH/VTMS -g-PE-HD)能够显著提高复合材料的力学性能。     

Properties and Characterization of Filled Poly(Propylene) Composites Crosslinked Through Siloxane Linkage

Summary: The silane‐grafting and water‐crosslinking of poly(propylene) (PP) and its composites with calcium carbonate are described. Particular consideration is made on the properties and characterization of the grafted‐ and crosslinked‐products. Silane‐grafting of the polymers was performed in the melt by the use of vinyltrimethoxysilane and dicumyl peroxide. The results show that during the grafting process, PP chain‐scission was accompanied as a side reaction. Peroxide concentration was found to be a major factor in determining the extents of grafting and PP degradation. After conducting a crosslinking reaction, the degree of crosslink determined from the direct measurement of gel content and indirect method by evaluating FTIR data was compared. The effects of silane crosslink on the thermal and mechanical properties of the PP composites were discussed. A combined effect of filler and silane crosslink network in enhancing composite modulus, tensile stress, heat distortion, and decomposition temperatures is evident.

Formation of stable siloxane linkages.