Emerging low-density polyethylene/paraffin wax/aluminum composite as a form-stable phase change thermal interface material

Thermal interface materials(TIMs) play a vital role in the thermal management of electronic devices and can significantly reduce thermal contact resistance(TCR). The TCR between the solid–liquid contact surface is much smaller than that of the solid–solid contact surface, but conventional solid–liquid phase change materials are likely to cause serious leakage. Therefore, this work has prepared a new formstable phase change thermal interface material. Through the melt blending of paraffin wax(PW) and low-density polyethylene(LDPE), the stability is improved and it has an excellent coating effect on PW. The addition of aluminum(Al) powder improves the low thermal conductivity of PW/LDPE, and the addition of 15wt% Al powder improves the thermal conductivity of the internal structure of the matrix by 67%. In addition, the influence of the addition of Al powder on the internal structure, thermal properties, and phase change behavior of the PW/LDPE matrix was systematically studied. The results confirmed that the addition of Al powder improved the thermal conductivity of the material without a significant impact on other properties, and the thermal conductivity increased with the increase of Al addition. Therefore, morphologically stable PW/LDPE/Al is an important development direction for TIMs.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Synthesis and Characterization of Storage Energy Materials Prepared from Nano-crystalline Cellulose/Polyethylene Glycol

This paper gives a brief report of the synthesis of a new kind of solid-solid phase change materials （SSPCMs）, nano-crystalline cellulose/polyethylene glycol （NCC/PEG）. These PCMs have very high ability for energy storage, and their enthalpies reach 103.8 J/g. They are composed of two parts, PEG as functional branches for energy storage, and NCC as skeleton. The flexible polymer PEG was grafted onto the surface of rigid powder of NCC by covalent bonds. The results of DSC, FT-IR were briefly introduced, and some comments were also given.

Mica-stabilized polyethylene glycol composite phase change materials for thermal energy storage

Mica was used as a supporting matrix for composite phase change materials(PCMs)in this work because of its distinctive morphology and structure.Composite PCMs were prepared using the vacuum impregnation method,in which mica served as the supporting material and polyethylene glycol(PEG)served as the PCM.Fourier transform infrared and X-ray diffraction analysis confirmed that the addition of PEG had no effect on the crystal structure of mica.Moreover,no chemical reaction occurred between PEG and mica during the vacuum impregnation process,and no new substance was formed.The maximum load of mica-stabilized PEG was 46.24%,the phase change temperature of M_(400)/PEG was 46.03℃,and the latent heat values of melting and cooling were 77.75 and 77.73 J·g^(−1),respectively.The thermal conductivity of M_(400)/PEG was 2.4 times that of pure PEG.The thermal infrared images indicated that the thermal response of M_(400)/PEG improved relative to that of pure PEG.The leakage test confirmed that mica could stabilize PEG and that M_(400)/PEG had great form-stabilized property.These results demonstrate that M_(400)/PEG has potential in the field of building energy conservation.

Structure and Properties of Self-reinforced Material Made from Ultra-high Molecular Weight Polyethylene-montmorillonite Nanocomposite

High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.

Effect of Free Cells and Additional Supporting Material on Performance of Polyethylene Glycol (PEG)-Pellet Reactor to Treat NH4-N Contaminated Groundwater

To study the effect of free cells (suspended bacteria) on performance of entrapped bacteria system (i.e. polyethylene glycol (PEG)-pellet reactor) to treat NH4-N contaminated groundwater, two PEG-pellet reactors with a lot of free cells - Reactor A containing PEG-pellet and Reactor B containing PEG-pellet and supporting material - and the another control reactor without free cells (Reactor C) were set-up. Three reactors were operated under various NH4-N concentrations (40-60 mg/L) and various temperatures (5-25oC). The results show that the free cells effected on the NH4-N removal efficiency significantly. The free cells developed to be a biofilm layer on the pellet surface for Reactor A, the biofilm layer caused the decreasing NH4-N diffusion and incomplete nitrification eventually. On the other hand, most free cells attached to the supporting material for Reactor B. Although the NH4-N could diffuse properly, the free cells consuming acetate caused the added acetate was insufficient for complete denitrification. However, the results suggest that the supporting material could reduce the effect of free cells on the reactor performance at low temperature as indicated by 1) higher efficiency and 2) lower activation energy (Ea) for nitrification and denitrification in Reactor B than Reactor A.

Carbon Nano Material Synthesis from Polyethylene by Chemical Vapour Deposition

Three different types of Polyethylene family, High Density Polyethylene, (HDPE), Low Density polyethylene (LDPE) and Linear Low Density polyethylene (LLDPE) polymers having different molecular weight and density;were pyrolyzed in the temperature range of 550°C - 1050°C under H2, N2 and Ar gases. Taguchi Optimization technique was applied to find out the best operating conditions to get maximum yield of carbon nano material (CNM). For Taguchi op- timization, experimental set up was done in two different temperature ranges i.e. 550°C - 750°C and 850°C - 1050°C. CNMs synthesized were characterized by SEM, TEM, Micro Raman and XRD analysis. HDPE was found to yield maximum CNM. Its pyrolysis at 750°C under hydrogen atmosphere for 2h gave carbon nano beads and some carbon nano tubes. Whereas under same conditions at 1050°C more multi wall carbon nano tubes (MWCNT) were produced, with some carbon nano beads. XRD data confirmed the graphitic nature of carbon-nanotube. The intensities of G-band and D-band of Raman spectra suggested that CNM has more defect sites and spectra were similar for CNM obtained in both the temperature ranges. The TGA analysis of CNM obtained at 550°C - 750°C, indicated that they are not amor- phous carbon and CNM obtained at 850°C - 1050°C decomposed at 624°C - 668°C;suggesting that CNT synthesized at this temperature range were more crystalline than what was obtained at the 550°C - 750°C.

Manufacturing of Ultra-high Molecular Weight Polyethylene Fiber Reinforced Tape and the Loss of Strength

Due to the low density and excellent mechanical proper-ties,high performance fiber reinforced materials have aconsiderable application in the area of high technologyand dally usage.In this paper,the Ultra-high Molecu-lar Weight Polyethylene(UHMWPE)fiber reinforcedPE tape prepared with the method of powder impregnat-ion was studied.The effect of impregnate length and thetensile force of the yarn on the fiber content as well as on the strength and modulus of the tape were discussed.Calculation shows that the strength and the modulus ofthe ULMWPE fiber can keep about 85％ after it undergothe process.

Synergistic Effect of Atmospheric Pressure Plasma Pre-Treatment on Alkaline Etching of Polyethylene Terephthalate Fabrics and Films

Dyeing of PET materials by traditional methods presents several problems.Plasma technology has received enormous attention as a solution for the environmental problems related with textile surface modifications,and there has been a rapid development and commercialization of plasma technology over the past decade.In this work,the synergistic effect of atmospheric pressure plasma on alkaline etching and deep coloring of dyeing properties on polyethylene terephthalate（PET）fabrics and films was investigated.The topographical changes of the PET surface were investigated by atomic force microscopy（AFM）images,which revealed a smooth surface morphology of the untreated sample whereas a high surface roughness for the plasma and/or alkaline treated samples.The effects of atmospheric pressure plasma on alkaline etching of the structure and properties of PET were investigated by means of differential scanning calorimetry（DSC）,the main objective of performing DSC was to investigate the effect of the plasma pre-treatment on the T_g and T_m.Using a tensile strength tester YG065 H and following a standard procedure the maximum force and elongation at maximum force of PET materials was investigated.Oxygen and argon plasma pre-treatment was found to increase the PET fabric weight loss rate.The color strength of PET fabrics was increased by various plasma pre-treatment times.The penetration of plasma and alkaline reactive species deep into the PET structure results in better dyeability and leaves a significant effect on the K/S values of the plasma pre-treated PET.It indicated that plasma pre-treatment has a great synergistic effect with the alkaline treatment of PET.

Polyethylene glycol/polylactic acid block co‐polymers as solid–solid phase change materials

Phase change materials(PCMs)are promising thermal energy storage materials due to their high specific latent heat.Conventional PCMs typically exploit the solid–liquid(s–l)transition.However,leakage and leaching are common issues for solid–liquid PCMs,which have to be addressed before usage in practical applications.In contrast,solid–solid(s–s)PCMs would naturally overcome these issues due to their inherent form stability and homogeneity.In this study,we report a new type of s–s PCM based on chemically linked polyethylene glycol(PEG,the PCM portion)with polylactic acid(PLA,the support portion)in the form of a block co‐polymer.Solid‐solid latent heat of up to 56 J/g could be achieved,with melting points of between 44°C and 55°C.For comparison,PEG was physically mixed into a PLA matrix to form a PEG:PLA composite.However,the composite material saw leakage of up to 9%upon heating,with a corresponding loss in thermal storage capacity.In contrast,the mPEG/PLA block co‐polymers were found to be completely homogeneous and thermally stable even when heated above its phase transition temperature,with no observable leakage,demonstrating the superiority of chemical linking strategies in ensuring form stability.

Synthesis,Characterization of Polyethylene Ionomers and Their Antibacterial Properties

Owing to its high production volume and wide range of application s,polyethylene has gained a great deal of attention,but its low surface energy and non-polar nature have limited its application in some important fields.In this study,ethylene/11-iodo-1-undecene copolymers were prepared and used as the intermediates to afford a series of imidazolium-based ionomers bearing methanesulfonate(CH_(3)SO_(3)^(-)),trifluoromethanesulfonate(CF_(3)SO_(3)^(-)),or bis(trifluoromethane)sulfonimide(Tf_(2)N^(-))counteranions.The tensile test results showed that the stress-at-break(7.8-25.6 MPa)and the elongation-at-break(445%-847%)of the ionomers could be adjusted by changing the counterion species and the ionic group contents.Most importantly,the ionomers exhibited marvelous antibacterial activities against Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli).The ionomers bearing Tf_(2)N^(-)exhibited antibacterial activities>99%against both S.aureus and E.coli when ionic content reached 9.1%.The imidazolium-based ionomers prepared in this work demonstrated excellent comprehensive properties,especially highefficient and broad-spectrum antibacterial ability,exhibiting the potential fo r the application as the antibacterial materials in packaging,medical,and other fields.

Energy Storage Properties of Phase Change Materials Prepared from PEG/CPP

New kinds of solid-solid phase change materials have been prepared in our laboratory. In these materials, the rigid polymer chlorinated polypropylene is taken as skeletons and the flexible polymer polyethylene glycol 6000 and polyethylene glycol 10000 are taken as functional chains. Results show that chlorinated polypropylene grafted by polyethylene glycol 10000 has greater enthalpy than chlorinated polypropylene grafted by polyethylene glycol 6000.

A New Kind of Shape-stabilized Phase Change Materials

Based on the lowest melting point and Schroeder’s theoretical calculation formula,nano- modified organic composite phase change materials（PCMs）were prepared.The phase transition temperature and the latent heat of the materials were 24℃and 172 J/g,respectively.A new shape-stabilized phase change materials were prepared,using high density polyethylene as supporting material.The PCM kept the shape when temperature was higher than melting point.Thus,it can directly contact with heat transfer media.The structure,morphology and thermal behavior of PCM were analyzed by FTIR,SEM and DSC.

茂金属聚乙烯薄膜料结构与性能

对3种茂金属聚乙烯薄膜料的基础性能、分子量及分布、熔融行为、力学性能和光学性能进行了分析测试,考察了不同工艺下制得的茂金属聚乙烯薄膜料的结构与性能的关系。结果表明:三种薄膜料的分子量分布均比较窄,呈单峰分布,且密度在0.921g/cm^(3)左右,其中具有更低分子量和更高支化度的3~#茂金属聚乙烯薄膜料具有更好的加工性能,并且其断裂标称应变较高、鱼眼少、雾度低。

LDPE/MLLDPE共混改性及发泡性能

以低密度聚乙烯(LDPE)为基体树脂、4,4'-氧代双苯磺酰肼(OBSH)为发泡剂、茂金属线性低密度聚乙烯(MLLDPE)为改性剂,采用化学发泡法和辐照交联技术制备一系列LDPE/MLLDPE发泡材料。研究不同MLLDPE含量对LDPE/MLLDPE复合材料的熔体流动速率、热性能、发泡行为及力学性能的影响。结果表明,MLLDPE能提高LDPE/MLLDPE复合体系的结晶度,降低其熔体流动速率。随着MLLDPE含量的增加,LDPE/MLLDPE复合发泡材料的拉伸强度、撕裂强度和压缩永久变形呈现先上升后下降的趋势,而断裂伸长率、回弹率逐渐提高。当MLLDPE含量为15份时,LDPE/MLLDPE复合发泡材料的表观密度、拉伸强度、撕裂强度和压缩永久变形量分别提高了6.8%、24.4%、11.4%和24.2%。当辐照剂量为80 kGy、LDPE∶MLLDPE=85∶15时,LDPE/MLLDPE复合发泡材料的力学性能和泡孔结构更佳,满足胶带型片材的综合性能要求。

低密度聚乙烯在新型建材中的应用研究进展

建设能源节约型社会为新型建材的使用提供了庞大的市场机遇。综述了低密度聚乙烯(LDPE)在LDPE/木质素复合建材、透光储能混凝土、隔热保温材料中的应用,重点综述了LDPE在隔热保温材料领域的研究进展。建议加强LDPE在新型建材中的应用研究,加强材料降本研究,尽快实现大规模应用。

相变路面抑制降温效果研究

本文以混凝土路面为研究对象,向路面主体材料中添加PEG300和PEG400作为相变材料,膨胀石墨为封装材料制备相变储能路面,利用COMSOL Multiphysics多物理仿真软件对路面模型进行模拟研究,探究复合相变材料(PCMs)不同掺量下的路面抑制降温能力的变化规律。结果表明:对4种不同PCMs掺量的相变储能路面传热3 h后6.76 cm深度的温度进行对比分析,发现掺量为4%,8%,12%的相变路面温度分别比水泥路面温度高1℃,1.4℃,1.6℃,掺量为4%时温度增加量最大。相变储能路面在深度为4 cm时降为0℃需要的时间均大于水泥混凝土路面需要的时间,水泥混凝土路面在4 cm时达到0℃需要的时间为3 h,PCMs掺量为4%的相变储能路面需要4.4 h,延缓了1.4 h;掺量为8%的相变储能路面需要5.6 h,延缓了1.2 h;掺量为12%的相变储能路面需要6.6 h,延缓了1 h。PCMs掺量每增加4%,其增加的延缓时间在降低,从0%掺量增加到4%时,增加的延缓时间最长。综上两种分析,最优的PCMs掺量为4%。相变储能路面抑制降温的能力可延缓路面温度降为0℃的时间,从而抑制结冰,减少路面损伤。

新型XPE健美操地垫特性分析及制备工艺影响研究

健美操在居家运动甚至高校课程中都被广泛关注,各项性能均衡的健美操地垫也随之被关注,人们生活工作中应用材料的环保性越来越得到重视,新型环保材料XPE在绿色领域具有很大的发展前景,因其特殊的泡孔结构和优异的吸音性、隔热性、缓冲性及耐化学腐蚀性等,被广泛应用于各个设施行业等领域,同时PE也是最早实现工业化批量生产和应用的发泡材料之一。XPE材料是用聚乙烯树脂加交联剂和发泡剂经过高温连续发泡而成,材料的化学性相对稳定,不容易发生分解,本文就健美操地垫的高强度XPE材料的性能优势及影响因素展开分析。

热黏合聚乙烯/聚丙烯双组分纺黏非织造材料性能及其过滤机制

为研究热黏合加固技术对双组分纺黏非织造材料结构和性能的影响,以聚乙烯(PE)为皮层组分、聚丙烯(PP)为芯层组分,采取热轧和热风2种热黏合方式制备了PE/PP皮芯型双组分纺黏非织造材料,借助扫描电子显微镜、自动滤料测试仪、孔径测试仪、渗水性测定仪等对2种方法制备的纺黏非织造材料的结构和性能进行测试与表征,并对造成过滤性能不同的原因进行理论分析,阐释纤维滤材的过滤机制。结果表明:随着面密度的增加,热轧黏合纺黏非织造材料的平均孔径逐渐减小,耐静水压逐渐增加,其中面密度为80 g/m^(2)时,平均孔径为25.74μm,耐静水压为3.14 kPa;热风黏合纺黏非织造材料在低阻力、高容尘、品质因数方面的表现均优于热轧黏合纺黏非织造材料,其中面密度为80 g/m^(2)时,以质量中值直径为0.26μm的NaCl气溶胶为过滤媒介,在32 L/min的测试流量下,电晕驻极后热风黏合纺黏非织造材料的过滤效率为76.62%,过滤阻力仅为15.85 Pa;纤维过滤材料的孔隙率越大其过滤阻力越小,容尘量越高。

乙烯基非交联电缆屏蔽料性能与分散剂含量关系研究

非交联绝缘材料具有优异的电气机械性能,同时生产能耗少、可回收利用,成为目前电缆绝缘料的研究热点,但与之匹配的非交联半导电屏蔽料的研究还鲜有报道。导电炭黑的分散性对屏蔽料的性能影响重大。文中选用线性低密度聚乙烯(LLDPE)为基体树脂,白油为分散剂,采用熔融共混法制备了非交联电缆屏蔽料。研究了白油含量对屏蔽料中炭黑分散、结晶性能、体积电阻率和机械性能的影响。结果表明添加白油会促进炭黑的分散,但白油含量过大会降低屏蔽料的结晶度,增加其体积电阻率并降低拉伸强度和断裂伸长率。当白油含量为2 wt%时,屏蔽料体积电阻率最小,力学性能最佳。该研究为非交联半导电屏蔽料在乙烯基非交联电缆的应用研究提供了参考。