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.

The Impact of the Inclusion of MgO Nano-Fillers in a Polyethylene Matrix on Dielectric Strength and Resistance to Partial Discharges

One commonly used strategy to enhance polymers specific properties such as the resistance to partial discharges erosion is the incorporation into the polymeric matrix of inorganic micro or nanoparticles. This study focused on the dielectric properties of Low-Density Polyethylene (LDPE) filled with nano-sized Magnesium Oxide (MgO) particles compounded by thermo-mechanical process and one of the purposes was to establish appropriate processing parameters in order to reach the desired dielectric properties. LDPE was used as a matrix and was reinforced by MgO particles having a nominal average size of 30 nm. The MgO nanoparticles were treated with a silane coupling agent (3-Glycidyloxypropyl Trimethoxysilane). The samples were initially prepared in a melt-mixing chamber with a MgO content of 1% wt. These pre-mixed samples were further treated by the means of thermo-mechanical mixing in a conical co-rotating twin-screw extruder in order to improve the dispersion and distribution of the MgO particles. In this report, both lifetime under a PD activity and AC dielectric strength of pure and nano-filled LDPE samples have been measured and compared. Nano-filled LDPE samples were found to exhibit an improve lifetime, without any detrimental impact on their short-term dielectric strength. This suggests that nano-filled LDPE may be for electric applications for which the dielectric materials may be exposed to partial discharge activities. This is significant result for the use of MgO-reinforced PE as an insulating material for HV cables since the resistance to PD is closely related to treeing resistance which is the main electrical degradation mechanism that leads to failure for shielded extruded power cables.

EFFECTS OF COMPATIBILIZERS ON THE MECHANICAL PROPERTIES OF LOW DENSITY POLYETHYLENE/LIGNIN BLENDS

Low density polyethylene(LDPE)/lignin blends were prepared using melt blending.Two kinds of compatibilizers, ethylene-vinylacetate(EVA) which is softer than LDPE and polyethylene grafted with maleic anhydride(PE-g-MA) which is harder than LDPE were used to improve the interfacial adhesion.Scanning electron microscope(SEM) was used to investigate the dispersion of lignin in LDPE matrix.The results showed that both of the compatibilizers could improve the interaction between the low density polyethylene and l...

Flame retardancy effect of surface-modified metal hydroxides on linear low density polyethylene

Metal hydroxides （MAH） consisting of magnesium hydroxide and aluminum hydroxide with a mass ratio of 1：2 were surface-modified by y-diethoxyphosphorous ester propyldiethoxymethylsilane, boric acid and diphenylsilanediol in xylene under dibutyl tin dilaurate catalyst at 140 ℃. Phosphorus, silicon and boron elements covalently bonded to metal hydroxide particles were detected by X-ray photoelectron spectroscopy. The degradation behavior of the surface-modified MAH was characterized by thermogravimetric analysis. The results show that linear low density polyethylene （LLDPE） composite, filled with 50% （mass fraction） of MAH modified by 5.0% （mass fraction） of modifiers, passes the V-0 rating of UL-94 test and shows the limited oxygen index of 34%, and its heat release rate and average effective heat combustion in a cone calorimeter measurement decrease obviously; The mechanical properties of MAH can be improved by surface-modification. The uniform dispersion of particles and strong interfacial bonding between particles and matrix are obtained.

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.

Development and Evaluation of the Mechanical Properties of Coconut Fibre Reinforced Low Density Polyethylene Composite

This research work developed and evaluated the mechanical properties of coconut fibre reinforced low density polyethylene (LPDE) composite material. The effect of fibre loading on the mechanical properties: tensile, flexural, and impact of the developed composite material have been investigated. Also carried out was the effect of fibre loading on the water absorptivity of the developed material. Sample categories of the developed composite were prepared by varying the fibre contents by weight at 0%, 10%, 20%, and 30%. The aim is to reduce the excessive waste disposal of LDPE materials that are largely found in the form of disposed water package materials (or pure water sachets) that usually affects the environment in the form of pollution. The water retting process was applied in extracting and cleaning fibre (or coir), while the mixed coir-LDPE (or developed composite material) was prepared by Compression Moulding Technique (CMT). The tensile and flexural properties were tested using Hounsfield Monsanto Tensometer (type w) while the impact properties were tested using the Charpy Impact testing machine. The microstructure of the composite was investigated using Scanning Electron Microscopy (SEM). The fractured surface morphology of the composite samples indicated a homogeneous mixture of the coir fibre and LDPE matrix. However, weak interfacial bonding between the coir fibre and LDPE matrix was also observed. The analysis of the water absorptivity showed that the developed composite materials have low water absorptivity at low fibre loading. However, at higher fibre loading, the water absorptivity increases significantly.

Low Density Linear Polyethylene Reinforced with Alkali and MAPE Treated Fibers from Coffee Pulp

In this work fibers derived from coffee, hulls have been incorporated into Linear Low Density Polyethylene (LLDPE). The influence of the filler content on the thermal and physicomechanical properties of the composites obtained was assessed. The results showed that the incorporation of fibers was able to improve the thermostability of LLDPE/Coffee hulls fibers;comparing the treated fiber composite with untreated fiber composites, the chemical treatment reduces by 58.3% the water absorption, while increasing the elongation and tensile strength by about 48% and 17% respectively. Moreover, due to better interfacial interaction induced by MAPE, the corresponding composite exhibited better properties compared to the untreated fiber composite. Results are indicative of the fact that both mercerization and MAPE (coupling agent) have significant positive effects on the fiber-matrix interaction in terms of adhesion, wetting and dispersion, this treatment produced a better fiber distribution and consequently a more uniform composite morphology without voids and gaps between the fibers and the matrix, allowing the possibility to use higher fiber contents (up to 30% wt.) with acceptable mechanical properties.

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。

LLDPE/碳纤维网复合膜的制备及性能

为了提高线型低密度聚乙烯(LLDPE)的拉伸强度和模量,将碳纤维(CF)梳理成均匀的碳纤维网,将其作为增强材料与LLDPE复合制备LLDPE/CF复合膜,综合利用热失重分析(TG)、扫描示差量热分析(DSC)、扫描电子显微镜(SEM)及拉伸测试等手段分析碳纤维网含量对复合膜结构及性能的影响。结果表明:与LLDPE膜相比,LLDPE/CF复合膜的拉伸强度和杨氏模量显著提高并随碳纤维网含量增加而增大,当碳纤维网质量分数仅为1%时,拉伸强度从10.6MPa提高到28.7MPa,提高了171%,杨氏模量由75MPa增大到1119MPa,约提高到原来的15倍;碳纤维网的引入有利于LLDPE/CF复合膜热稳定性能的提高,当碳纤维网含量仅为1%时,LLDPE/CF的初始热分解温度和最大热分解速率温度与LLDPE相比分别提高了21℃和11℃;碳纤维网的引入促进了LLDPE分子链的结晶,使LLDPE/CF复合膜的结晶度增大,有利于拉伸强度和模量提高;SEM结果显示碳纤维网与LLDPE基体间的界面结合较强,有利于力学性能的提高。研究成果可为高性能聚合物/碳纤维复合材料的制备提供实验依据和理论指导价值。

国外LLDPE价格对我国LLDPE价格的非对称传导分析

选取2010年1月至2023年12月我国、中东、东南亚及美国线性低密度聚乙烯(LLDPE)现货价格,采用非线性自回归分布滞后模型(NARDL)探讨国外地区市场价格对我国LLDPE价格传导的非对称效应。实证结果表明,相较于美国和东南亚,我国LLDPE对中东LLDPE市场的依存程度比较高;同时,东南亚、中东地区及美国对我国LLDPE价格传导存在非对称性,且在价格非对称传导程度和速度上呈现异质特点,其中,美国LLDPE价格下跌的传导程度与速度均大于价格上涨的传导程度与速度,东南亚地区在价格传导程度上也体现出负向非对称性,但传导速度的非对称性不显著,而中东地区LLDPE价格上涨的传导程度大于价格下跌的传导程度,在传导速度上差异较小。

抗静电LLDPE/CNT复合材料的制备及其性能研究

目的制备特种产品用抗静电包装材料。方法采用碳纳米管(CNT)对线性低密度聚乙烯(LLDPE)进行熔融复合改性,研究CNT含量对LLDPE电学性能、力学性能、结晶行为及热稳定性的影响,并对确定的最优体系进行应用性能考核。结果CNT具有较大的长径比,直径为10~20 nm,纯度较高。LLDPE/CNT复合材料表面电阻率变化呈现明显的“渝渗”现象,当CNT质量分数从3%增加至5%时,其表面电阻率由1013Ω骤降至105Ω。随着CNT含量增加,LLDPE/CNT复合材料的拉伸强度增加,断裂伸长率和冲击强度有所降低。CNT没有改变LLDPE的熔融行为,但其结晶度和熔点随着CNT含量增加而略有降低。LLDPE/CNT复合材料起始降解温度和最大降解速率处温度随着CNT含量增加而增加。CNT质量分数为4%的LLDPE/CNT复合材料综合性能最优,热氧老化后其表面电阻率几乎无变化,相比纯LLDPE,其熔融指数有所下降,氧化诱导时间大幅提升。结论通过CNT对LLDPE树脂进行改性,制备了综合性能优良的抗静电LLDPE/CNT复合材料,在特种产品包装领域具有良好的应用前景。

LDPE/m-nZVI复合膜的制备及性能

为克服脱氧剂小袋包装与食品混装带来的安全问题,采用硼氢化钾(KBH4)液相还原法制备了油酸钠(NaOl)改性纳米零价铁(m-nZVI),将其与低密度聚乙烯(LDPE)熔融共混后热压成膜,制备了包装用LDPE/m-nZVI阻氧复合膜。利用傅里叶变换红外光谱仪、热重分析仪、差示扫描量热仪、万能拉伸试验机和气体渗透仪对复合膜的结构与性能进行表征和测定。结果表明:m-nZVI和LDPE的复合是物理共混;加入m-nZVI后,LDPE的热稳定性基本不变;随着m-nZVI含量的增加,复合膜的抗拉强度和断后伸长率先增大后减小,m-nZVI质量分数为2%时,抗拉强度和断后伸长率达到最大,较LDPE膜分别提高了41.4%和23.4%;复合膜的氧气透过系数也呈现出先减小后增大,当m-nZVI质量分数为3%时,复合膜的氧气透过系数最小,较LDPE膜降低了40.9%。复合膜结晶过程中,m-nZVI起异相成核的作用,改善了复合膜的结晶行为,使复合膜的结构和性能得到改善,力学性能和阻隔性能都得到提高。

茂金属线性低密度聚乙烯(mLLDPE)的市场及应用进展

文章综述了茂金属线性低密度聚乙烯(mLLDPE)的生产工艺、供需情况、应用领域和市售主流牌号,分析了产品性能优势,阐述了市场供应情况,介绍了下游应用特点,对比了主流产品性能差异,提出了生产和开发建议。未来,催化剂成本将成为竞争焦点,各石化企业应加快茂金属催化剂的自主开发与工业化生产,发挥产、销、研、用一体化优势,降低茂金属聚乙烯生产成本并保证稳定供应。

Ti_(3)C_(2)T_(x)和TiO_(2)(R)对LDPE复合材料阻燃性的影响及机理

本文探讨了采用刻蚀法制备的碳化钛(Ti_(3)C_(2)T_(x))和商用锐钛矿型二氧化钛[TiO_(2)(R)]作为阻燃添加剂对线型低密度聚乙烯(LDPE)阻燃性的影响及机理。结果表明,Ti_(3)C_(2)T_(x)的添加使LDPE的热释放速率峰值(PHRR)降低了29.8%,烟释放速率(SPR)降低了34.2%,而TiO_(2)(R)虽然也提高了热稳定性,但其降低效果不如Ti_(3)C_(2)T_(x)显著。极限氧指数(LOI)测试结果表明,Ti_(3)C_(2)T_(x)添加的LDPE的LOI提高了5%,达到18.7%,而添加质量分数8%TiO_(2)(R)的LDPE的LOI最高达到了19.7%。锥形量热测试进一步证实了Ti_(3)C_(2)T_(x)在阻燃方面的优越性,其添加使得LDPE的热释放总量(THR)降低了7.5%。相比之下,TiO_(2)(R)虽然提高了LDPE的热稳定性,但其对降低热释放速率和烟释放速率的效果不如Ti_(3)C_(2)T_(x)显著。热重-傅里叶红外光谱联用仪(TG-FTIR)的结果表明,Ti_(3)C_(2)T_(x)和TiO_(2)(R)均未改变LDPE的热分解路径,但在凝聚相中,Ti_(3)C_(2)T_(x)通过形成残炭层更有效地阻碍了燃烧过程。扫描电子显微镜(SEM)和元素分析(EDS)显示Ti_(3)C_(2)T_(x)在燃烧后部分维持了其片层结构,表明其在催化成炭和物理屏障方面的双重作用。本研究突出了Ti_(3)C_(2)T_(x)作为新型阻燃剂在提高LDPE阻燃性方面的潜力,并为开发新型高效阻燃聚合物材料提供了科学依据。

辐照交联LDPE/HDPE发泡材料的制备与性能

采用熔融共混法和辐照交联技术制备了低密度聚乙烯(LDPE)/高密度聚乙烯(HDPE)发泡材料,研究了HDPE用量对LDPE/HDPE发泡材料加工流动性、热性能、流变性能、发泡行为、力学性能和导热性能的影响。结果表明:HDPE的加入显著提高了LDPE/HDPE发泡材料的熔体流动速率和结晶度。与纯LDPE发泡材料相比,当HDPE的质量分数为30%时,LDPE/HDPE发泡材料的拉伸强度提高了32.3%,压缩强度提高了67.5%,邵氏硬度提高了14.3%,回弹性下降了16.0%,综合性能最佳。

LDPE装置一次压缩机换热器中聚合物产生原因及解决措施

低密度聚乙烯装置一次压缩机出口换热器中会产生聚合物而出现堵塞现象。通过热重分析仪、差示扫描量热仪、凝胶渗透色谱仪表征了聚合物的分解温度、结晶性能和相对分子质量分布,并讨论了换热器堵塞的原因,提出了更换一次压缩机一段出口故障疏油器、清理一次压缩机泄漏气管线、加大一次压缩机内部油注入量、保持换热器光洁等措施,保证了装置的平稳运行。

LDPE稀相输送系统中弯头的磨损与选型对产品质量的影响

低密度聚乙烯(LDPE)装置气力输送系统常采用稀相输送,物料在输送管路中以“悬浮式”前进,该输送方法具有易于维护、适用范围广、经济性高、流速快等特点。但正是因为输送速度快,物料在较长的输送管路上摩擦,容易导致物料损失和输送设备的磨损。一方面,输送时高速流动的粒子与管壁、弯头相互摩擦、碰撞,产生细粉和丝团料。另一方面高速运动的粒子持续撞击和摩擦输送管道,导致输送管道磨损和寿命变短。因此,本文通过工程实践采用对比分析的方法从聚乙烯颗粒稀相输送的磨损机理和输送弯头的选型两个方面展开探讨,总结和分析了输送弯头选型对LDPE颗粒产品质量的影响,为同类装置稀相输送系统弯头选型提供一定的理论支持。

己烯共聚LLDPE抗老化性研究

对国内外己烯共聚的线型低密度聚乙烯(LLDPE)老化前后的力学性能、端基分布、羰基指数、聚集态结构、分子链支化及分布进行了表征分析与对比评价。结果表明:在老化过程中LLDPE容易发生交联和降解反应;与LLDPE相比,茂金属线型低密度聚乙烯(mLLDPE)的末端含有较多双键,晶片厚度较小,共聚单体更均匀,抗老化能力较差。

LLDPE-g-MAH接枝率的测定方法的建立与分析

本文通过酸碱滴定法和红外分析法建立了一种快速检测线型低密度聚乙烯接枝马来酸酐(LLDPE-g-MAH)接枝率的方法。首先,通过酸碱滴定法得到不同接枝率LLDPE-g-MAH样品的接枝率,然后通过红外分析法得到该样品的马来酸酐特征峰与LLDPE内标峰的峰高比值,通过滴定法得到的接枝率与红外特征峰峰高比值的拟合出标准曲线。该标准曲线可以用于快速测定未知LLDPE-g-MAH的接枝率。此方法操作快速便捷,对工业投产具有指导意义。