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.

Adsorption and Kinetic Study of Activated Carbon Produced from Post-Consumer Low-Density Polyethylene (LDPE) Wastes

Post-consumer polymeric wastes in form of low-density polyethylene (LDPE) can now be considered suitable as a precursor for the synthesis of low-cost activated carbon (AC). This study produced AC from LDPE using sulphuric acid (H2SO4) and potassium hydroxide (KOH) as the activating agent. The reaction conditions for pyrolysis were varied in the range of 0.50 - 2.00 M, 400°C - 500°C, and 45 - 60 minutes. Physico-chemical investigations reveal that AC yield is significantly dependent on both carbonization temperatures and time. The obtained optimum values of 446.50°C and 51.09 mins gave a yield of 24% for the base-activated carbon. The high iodine numbers obtained strongly indicate the presence of large surface area and pore volumes is further confirmed using the Scanning Electron Microscopy (SEM) analysis which reveals the presence of pores on the external surface of the carbons. Fourier Transform Infrared Technique (FTIR) analysis further shows that the synthesized compounds are purely carbon with rich oxy-gen-surface complexes on the surface which is as a result of the introduction of the chemical oxidizing agents. The produced carbons were found to have high adsorption affinity for selected inorganic ions which are: Mn7+, Co2+, and Cr6+. Adsorption isotherm results show the adsorption process to be favourable with the Langmuir isotherm parameter RL having values of <1, while the Freudlich adsorption model was found to perfectly fit the data at selected adsorbent dosages and adsorbate concentrations. The pseu-do-second-order model provides the best correlation for the kinetic analysis. The acid-activated carbon was found to have better adsorption capacities than the base-activated carbon.

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS: EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.

低密度聚乙烯内衬袋对‘富士’苹果贮藏品质及虎皮病的影响

为研究新型低密度聚乙烯(LDPE)内衬袋对‘富士’苹果贮藏品质和虎皮病发病情况的影响,以生产上常用的聚乙烯(PE)打孔内衬袋为对照,对比新型LDPE微孔内衬袋在(0±0.5)℃冷藏条件下对‘富士’苹果的影响。定期监测内衬袋微环境中的CO_(2)、O_(2)体积分数和乙烯含量,同时对果实品质指标及挥发性物质、酚类物质含量进行测定,并调查贮藏期间虎皮病发病情况。结果表明:与PE打孔内衬袋相比,LDPE内衬袋可以形成低氧高二氧化碳的微环境;苹果最早在冷藏150 d时出现虎皮病,LDPE组果实虎皮病发病指数低于PE组,货架7 d时LDPE组果实虎皮病发病率和发病指数均小于PE组;贮藏150 d时LDPE组果实失重率比PE组降低了0.48个百分点;LDPE内衬袋包装可提高果实的呼吸速率和乙烯释放速率,且对果实的质地、内在品质无不良影响;其还可促进苹果水杨酸、根皮苷等酚类物质积累;促进贮藏后期果皮挥发性物质中醇类含量的上升,延缓酯类尤其是丁酸戊酯、2-甲基丙酸丁酯和2-甲基乙酸丁酯含量的降低。综上,LDPE微孔内衬袋保鲜效果优于传统的PE打孔内衬袋,适合作为传统内衬袋的升级替换产品。研究结果可为企业规模化应用LDPE微孔内衬袋提供理论依据。

Constructing the Al deficiency in Si-O(H)-Al units based on Pt/ZSM-5 for enhanced hydrocracking of polyethylene into high-quality liquid fuel

Hydrocracking catalysis is a controllable route to plastic waste upgrading. However, the mismatched acid site-driven C-C cleavage and C=C hydrogenation process on metal restrict the efficiency and selectivity in conventional metal/acid bi-functional catalyst. Herein, we introduce Al deficiency in Si-O(H)-Al structural units of Pt/zeolite socony mobil-5 (Pt/ZSM-5) through discharge driven reduction (DR) process to precisely control the ratio of metal to acid, achieving hydrocracking of low-density polyethylene (LDPE) waste at 270 °C with 87.7% conversion and liquid fuel (C5-C21) selectivity of 77.8%. Pair distribution function (PDF) and nuclear magnetic resonance (NMR) spectroscopy demonstrate the partial absent Al sites further resulting short-range local disorder Si-O(H)-Al. Upon pyridine infrared spectroscopy (Py-IR) and CO diffuse reflectance Fourier-transform infrared (CO DRIFT) analysis, the extraction of Al modulates Brønsted acid density of Pt/ZSM-5 with DR process (Pt/Z5DR), improves the interaction between Pt and ZSM-5 support, enhances the cationic of Pt. The metal-acid balance and electron-deficient Pt favor the matching speed of light olefins hydrogenation and the cracking of macromolecule intermediates. Moreover, density functional theory (DFT) calculations identify the thermodynamic stability of Pt/Z5DR and moderate adsorption capability towards light olefins. This work confirms the great potential of precisely controlled molar of metal to acid in metal/zeolite catalysts for LDPE upcycling, providing a viable path for dealing with PE plastic wastes.

Multilayer polyethylene separator with enhanced thermal properties for safe lithium-ion batteries Author links open overlay panel

The separator plays an important part in battery safety and performance.Polyolefin separators are widely used in commercial Lithium-ion batteries(LIBs),owing to their excellent properties,but they suffer from serious thermal shrinkage and poor electrolyte wettability.Thus,a multilayer separator(ASPESA)is developed by coating two thin layers of low-density polyethylene(LDPE)and Al_(2)O_(3)on both sides of a polyethylene membrane using a facile and environmentally friendly casting technique.The ASPESA separator demonstrates a shutdown function at 120℃and shows enhanced thermal stability under 185℃,with a small thermal shrinkage of 1%.Meanwhile,the LDPE and Al_(2)O_(3)layers can improve the electrolyte wettability and electrolyte uptake(407.23%).The multilayer ASPESA separator delivers an excellent cycle performance in LiFePO_(4)||Li cells with a discharge capacity of 144.5 mAh g^(-1)after 900 cycles,with a high-capacity retention of 98.9%(compared to the 5th cycle).Therefore,the multilayer ASPESA separator has great utilization potential as a high-safety separator in LIBs.

Supercritical CO2 Assisted Preparation of Open-cell Foams of Linear Low-density Polyethylene and Linear Low-density Polyethylene/Carbon Nanotube Composites

The open-cell structure foams of linear low-density polyethylene（LLDPE） and linear low-density polyethylene（LLDPE）/multi-wall carbon nanotubes（MWCNTs） composites are prepared by using supercritical carbon dioxide（sc-CO2）as a foaming agent. The effects of processing parameters（foaming temperature, saturation pressure, and depressurization rate） and the addition of MWCNTs on the evolution of cell opening are studied systematically. For LLDPE foaming, the foaming temperature and saturation pressure are two key factors for preparing open-cell foams. An increase in temperature and pressure promotes both the cell wall thinning and cell rupture, because a high temperature results in a decrease in the viscosity of the polymer, and a high pressure leads to a larger amount of cell nucleation. Moreover, for the given temperature and pressure, the high pressurization rate results in a high pressure gradient, favoring cell rupture. For LLDPE/MWCNTs foaming, the addition of MWCNTs not only promotes the cell heterogeneous nucleation, but also prevents the cell collapse during cell opening, which is critical to achieve the open-cell structures with small cell size and high cell density.

Determination of VOCs in groundwater at an industrial contamination site using a homemade low-density polyethylene passive difusion sampler

A home-made inexpensive passive diffusion bag （PDB） sampler, prepared by filling deionized water in low-density polyethylene （LDPE） tubes, was evaluated for volatile organic compounds （VOC） sampling in groundwater at industrial contamination sites. Impacts of environmentally relevant conditions on the sampling equilibration time and partitioning of VOCs between the sampler and the water sample were investigated. Sample salinity, agitation and temperature can influence the equilibration time, but generally sampling equilibration was obtained in 14 days under real field sampling of VOCs in groundwater. Both laboratory study and field testing in a contaminated site showed that the VOC concentrations in the developed sampler were equal to those in the water samples at equitibrium. Coupled with a purge and trap concentrator-gas chromatograph-mass spectrometer （P＆T-GC-MS）, the developed PDB sampler provided a low-cost sampling device for routine monitoring of VOCs in groundwater in wells, with LODs in the range of 2.9-10 μg/L. The proposed PDB was applied to determine VOCs in groundwater at an industrial contamination site, and the present results agreed well with those determined using conventional pump-and-sample monitoring. All the studied 13 VOCs were tested in the four wells in the industrial contamination sites, with their concentrations in the range of 12-73660 μg/L. In addition, while benzene and toluene were heavily contaminated up to a maximum concentration of 74000 μg/L and 6000 μg/L, respectively, 1,2,3-trichlorobenzene and bromobenzene had relatively low contamination levels （below 25 μg/L）.

Sorption kinetics of parent and substituted PAHs for low-density polyethylene（LDPE）:Determining their partition coefficients between LDPE and water(KLDPE) for passive sampling

Low-density polyethylene(LDPE)has been widely used as a sorbent for passive sampling of hydrophobic organic contaminants(HOCs)in aquatic environments.However,it has seen only limited application in passive sampling for measurement of freely dissolved concentrations of parent and substituted PAHs(SPAHs),which are known to be toxic,mutagenic and carcinogenic.Here,the 16 priority PAHs and some typical PAHs were selected as target compounds and were simultaneously determined by gas chromatography–mass spectrometer(GC–MS).Some batch experiments were conducted in the laboratory to explore the adsorption kinetics of the target compounds in LDPE membranes.The results showed that both PAHs and SPAHs could reach equilibrium status within19–38 days in sorption kinetic experiments.The coefficients of partitioning between LDPE film(50μm thickness)and water(KLDPE)for the 16 priority PAHs were in good agreement with previously reported values,and the values of KLDPEfor the 9 SPAHs are reported in this study for the first time.Significant linear relationships were observed,i.e.,log KLDPE=0.705×log KOW+1.534 for PAHs(R^2=0.8361,p<0.001)and log KLDPE=0.458×log KOW+3.092 for SPAHs(R^2=0.5609,p=0.0077).The selected LDPE film was also proven to meet the condition of"zero sink"for the selected target compounds.These results could provide basic support for the configuration and in situ application of passive samplers.

套袋对鸭梨果实蜡质组分及贮藏品质的影响

为了探究套袋对鸭梨果实蜡质和贮藏品质的影响,本研究设定两组处理:聚乙烯(Polyethylene,PE)塑膜袋、三层纸袋,均在盛花后60 d完成套袋,采后摘袋,以未套袋为对照,于25℃±1℃贮藏14 d并分析不同处理果实蜡质组分含量和分布规律、营养和品质指标、抗氧化性的差异及相关性。结果表明:贮藏14 d内,PE塑膜袋处理的果实失重率最高,且对照和处理三者之间果实硬度、脆度和紧实度均无差异。两组处理均明显延缓蜡质组分烯烃、脂肪醛、脂肪醇、酯质、和总蜡质含量的增加。两组处理中烷烃C_(27)和C_(29)、烯烃C_(24)-C_(26)、脂肪酸C_(18:1)、脂肪醛C_(26)和C_(34)、偶数脂肪醇C_(22)-C_(28)、七种酯质、及三萜类α-法尼烯、β-香树酯醇、羽扇豆醇和β-香树酯酮等主要组分的含量均低于对照组。另外相比PE塑膜袋,三层纸袋处理延缓烯烃C_(26)、脂肪酸C_(16)和C_(18:1)、偶数脂肪醛C_(28)-C_(32)、两种酯质C_(22):1醇-C_(18):1酸和C_(24:1)醇-C_(18:1)酸、三萜类Urs-12-en-28-al,3-(acetyloxy)-,(3á)-和Urs-12-en-28-al等蜡质组分含量的下降,且三层纸袋处理后果皮黄酮、果皮总酚(14 d时)、果实可滴定酸和果实V_(C)(14 d时)的含量以及果皮DPPH清除率均高于PE塑膜袋处理。蜡质组分PCA分析将对照组和三层纸袋处理归为一类,而PE塑膜袋处理为另一类。相关分析发现不同处理中烷烃、脂肪醛、三萜类等组分和总蜡质含量与果皮黄酮含量正相关(P<0.05),而脂肪醇、酯质组分和总蜡质含量与果实V_(C)含量正相关(P<0.05或P<0.01)。综上说明三层纸袋通过延缓果实蜡质一些组分含量的下降,使果皮保持较高抗氧化能力,进而提高鸭梨果实的品质。

Comparative study of two modeling approaches for predicting heavy metals contaminant migration from polyethylene bags

Plasto-Foam brand,medium size of 30 mm thickness(black and green)commonly used polyethylene bags for preparing foods were selected from those available in local markets.The polyethylene bag samples were crushed into pieces,ashed and then acid digested to determine the concentrations of heavy metals selected(Pb,Cr,Co and Cd)using Atomic Absorption spectrophotometer.All the polyethylene samples were tested positive for heavy metals.Concentrations of heavy metals in polyethylene bags ranged from 1080 ppm to 1725 ppm,76 ppm to 112 ppm,35 ppm to 52 ppm,18 ppm to 31 ppm for Pb,Cd,Cr and Co,respectively.Forty-eight posho(Ugali)samples were prepared and wrapped in these polyethylene bags and migration studies were carried out at 65°C and 80°C.The experimental data obtained were then compared to the modeled data using the models developed by Baner et al.,and Limm and Hollifield to determine which model was a better estimator.Model fitting was done based on Non-linear least square analysis using Microsoft EXCEL 2003.Diffusion and partition coefficients both between food and the contact material were also obtained by fitting experimental data to the model equation.The modeling approaching could best describe the experimental data of the measured contaminants.The study revealed that all polyethylene bags showed highest contaminant concentration(above USFDA limit)of Pb,Cd,Cr and Co,respectively confirming the potential health risk to individuals if continuously eat food thermally prepared in polyethylene bags.

不同保鲜袋包装对菠菜采后保鲜效果的影响

以菠菜为试材,通过对其贮藏期间感官品质及各项生理指标的测定,探究不同保鲜袋对采后菠菜的保鲜效果。结果表明:在(20±1)℃下,与保鲜袋1包装组相比,保鲜袋2包装组的菠菜在贮藏期内可以较好的维持感官品质;减缓水分散失;控制丙二醛(malondialdehyde,MDA)含量的上升速度,减少细胞膜的受损程度;同时,还可抑制叶绿素的分解及维生素C含量的下降,使过氧化物酶(peroxidase,POD)、过氧化氢酶(catalase,CAT)及抗坏血酸过氧化物酶(ascorbate peroxidase,APX)的活性维持在较高水平,对菠菜起到较好的贮藏保鲜效果。

浮式塑料薄膜袋培养海洋微藻的研究

将塑料薄膜袋悬浮于水泥池中进行海洋微藻的三级培养。结果表明,此方法既保证了藻种培养过程中的良好条件,又能够有效地避免薄膜袋的破损漏水,操作简单,运用灵活,生产效率大大提高。

气调包装对果蔬保鲜效果的影响

气调包装主要是使用低密度聚乙烯薄膜袋进行果蔬包装,通过薄膜袋的自发气调作用来延长果蔬的贮运寿命。研究表明,当使用低密度聚乙烯薄膜气调包装果蔬时,O_2,CO_2体积分数和贮藏时间3个因素对果蔬品质的影响如下:贮藏时间为果蔬采后含糖量的主要影响因素,O_2体积分数为次要影响因素,CO_2体积分数为最小影响因素。随着果蔬采后贮藏时间的增加,果蔬的外观品质越来越差,失质量率越来越小。

高性能三元聚乙烯专用料在重包装膜袋(FFS袋)减薄降塑应用及循环回收利用的研究

本文主要分析了重包装膜袋(FFS袋)产业的发展现状与趋势。深入探讨和研究了高性能三元聚乙烯专用料在重包装膜袋(FFS袋)减薄降塑应用,提出了推进产业转型升级的可借鉴经济性方案和回收利用的措施和建议,以促进产业高质量健康发展。

Formation and migration of space charge packet in low density polyethylene

Pressure wave propagation (PWP) method was utilized to observe the space charges packet-like behavior in sheet samples of low-density polyethylene (LDPE) under the relative low electric field. The experimental results show that space charge packets are always generated at the anode and move across the sample to the cathode regardless of the polarity of DC voltage. This paper discusses the migration of space charge packets at 30–40°C, the possible charge resource of space charge packets carriers and trap level of the space charge.

塑料薄膜包裹转运法对早产儿体温影响的研究

目的比较塑料薄膜包裹转运早产儿与传统转运对体温的影响。方法将极低出生体质量儿与超低出生体质量儿各140例,分别分为观察组与对照组各70例。对照组采用常规方法包裹转运,观察组采用塑料薄膜包裹,转运到新生儿病房后记录转运时间、体温与14 d内并发症情况。结果两组包裹时间差异无统计学意义(P>0.05);进入NICU时与进入NICU后1 h,观察组早产儿体温均高于对照组(P<0.01或P<0.05);进入NICU后2 h,超低出生体质量早产儿观察组体温高于对照组(P<0.01);观察组新生儿脑室内出血与脑室周围白质软化的发生率低于对照组(P<0.05)。结论应用塑料薄膜包裹法可防止早产儿低体温,利于早产儿的生长发育。

低密度聚乙烯袋厚度对杏鲍菇减压贮藏品质的影响

为了探寻杏鲍菇减压贮藏适宜的包装材料厚度,以杏鲍菇为试材,分别采用0.03、0.05、0.07 mm低密度聚乙烯袋(low density polyethylene,LDPE)抽真空减压至0.06 MPa包装后,置于4℃冷藏30 d,探究不同厚度包装材料对减压贮藏条件下杏鲍菇的生理生化指标及品质的变化规律。结果表明:到贮藏结束时,与0.03、0.05 mm处理组相比,0.07 mm低密度聚乙烯袋组的杏鲍菇水分含量最高,为80.42%,其能有效减少杏鲍菇失水,抑制呼吸速率,缓减过氧化氢酶(catalase,CAT)和超氧化物歧化酶(superoxide dismutase,SOD)活性下降,抑制丙二醛(malondialdehyde,MDA)含量及多酚氧化酶(polyphenol oxidase,PPO)活性的上升,对杏鲍菇的硬度、内聚性、弹性、咀嚼性等质构特性及色泽品质影响越小。因此,0.07 mm厚的低密度聚乙烯袋为杏鲍菇减压贮藏的适宜包装材料厚度,其能有效延缓杏鲍菇的后熟衰老,延长杏鲍菇的保鲜期。

Decision Making in Sustainable Development: Some Methods to Evaluate Energy and Nonrenewable Resources Waste When Using Some Plastics

This paper explores a decision making model for a multidisciplinary problem in nature. This problem considers the role of energy use in sustainable development and the potential sources to increase energy efficiency during its whole life cycle;it also deals with multicriteria decision making of plastic materials used in a day to day basis. Exergy analysis of plastic materials used to the manufacture of disposable polyethylene bags comparing them with other materials that can be used for substitution will be important to take decisions. We are also interested in plastic poly (ethylene Terephthalate or PET) bottles. The calculation of the incoming and outgoing Exergy flows during the production processes are carried out. The Exergy loss considering the sustainability concept, Green House Gases emissions, real energy flows needed to the chain of processes, material balances in the productions chains and value added, are presented as a set of criteria to make decisions of alternative materials including the actual ones. A case study for Mexico’s market will be developed in order to prove the methodology. It offers some interesting data about consumption and production of bags and bottles.

室内袋式和管道式光生物反应器对湛江等鞭金藻生长及生化组分的比较分析

为探索湛江等鞭金藻室内大规模培养的可行性,分析比较了在管道式光生物反应器和聚乙烯袋培养模式下,湛江等鞭金藻生长密度、比生长速率、叶绿素含量及有机物含量的变化情况。试验将接种藻密度控制在10.0×10^(4) cells/mL,培养周期为16 d。结果显示,在管道式光生物反应器培养模式下,藻密度可达1.97×10^(6) cells/mL,显著高于聚乙烯袋培养模式下的藻密度(0.99×10^(6) cells/mL)(P<0.05);两种模式下,湛江等鞭金藻的比生长速率分别达到0.3967、0.3275/d;管道式光生物反应器模式下,叶绿素a、叶绿素b、总叶绿素、最高总蛋白、最大可溶性糖的质量浓度分别为0.46、0.44、0.92、107.2677、9.5878 mg/L,最大生物量(干质量)为0.1601 g/L,聚乙烯袋培养模式下,叶绿素a、叶绿素b、总叶绿素、最高总蛋白、最大可溶性糖的质量浓度分别为0.26、0.26、0.52、62.5645、5.5591 mg/L,最大生物量(干质量)为0.0986 g/L,管道式光生物反应器模式显著高于聚乙烯袋培养模式(P<0.05)。结果表明,对于湛江等鞭金藻的培养,管道式光生物反应器是一种较优的培养模式,具有潜在的开发和利用价值。