Experimental characterization of liquid film behavior during droplets–polyethylene particle collision

Nowadays, the droplet–particle collision characteristics in the gas-phase ethylene polymerization process are still unclear. The high-speed photography and a quasi-circle imaging approach are employed to study the collision interaction characteristics between liquid droplets and polyethylene particles. The liquid film evolution is studied through variations of the film thickness on the particle north pole, the dynamic contact angle, center angle and film thickness at the maximum extension. Results have found that for n-hexane the threshold temperature of the recoil happening increases with increasing initial Weber number, but for 1-hexene it is stable. Over 70°C evaporation and splash occurs immediately. Under low Weber numbers, the water droplet stays for damping oscillations, the reference stable height of which is linearly related to temperatures. Moreover, three regimes of film thickness variation with time are identified and mathematically described, while Regime 3 characteristics are found strongly dependent on the liquid species, Weber number, and particle temperature.     

Improved compatibility of PET/HDPE blend by using GMA grafted thermoplastic elastomer

ABSTRACT

Herein, graft-modified ethylene-1-octene copolymer (POE-g-GMA) and styrene-butadiene-styrene triblock copolymer (SBS-g-GMA) were found to be excellent reactive compatibilizers for immiscible poly(ethylene terephthalate) (PET)/high-density polyethylene (HDPE) blends via in-situ reaction compatibilization. With increase in compatibilizer amount, uniform phase morphology was observed in all the blends. Thus, exhibiting enhanced mechanical properties, especially, the notched Izod impact strength. In comparison with SBS-g-GMA, compatibilizer POE-g-GMA demonstrated greater impact on the compatibility. The addition of 15% POE-g-GMA produced blends with best mechanical properties. Besides, both POE-g-GMA and SBS-g-GMA enhanced the melt viscosity of PET/HDPE blends.     

Mechanical and thermal characterization of as-received recycled polyethylene filled with rice husk and their relationship to the end use of these composites

ABSTRACT

Waste can be considered a crisis across the world, especially in the Global South where landfills are collapsing and vector-borne illnesses are increasing. Due to the increase in the amount of waste plastic in the environment, different uses of recycled plastics are being investigated. One such use is roofing tiles. This has been put in place in Sri Lanka through the Waste for Life organization. Here, recycled polyethylene is filled with rice husk particles. Due to the hydrophilic nature of the rice husk, the strength of the polyethylene composites decreased with increasing rice husk filler. Since the roofing tiles do not need to support a large load, the loss in strength should not be too detrimental. However, the creep behavior was improved with 10% and 20% filler. This is important in that the temperature on the roof can reach high temperatures.     

Comprehensive branching analysis of polyethylene by combined fractionation and thermal analysis

Linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) differ significantly in their branching types and branching distributions. For a comprehensive analysis, preparative temperature rising elution fractionation and/or preparative molar mass fractionation are used to fractionate typical LLDPE and LDPE bulk resins into narrowly distributed fractions. The chain structures of the bulk resins and their fractions are further analysed using SEC, crystallization analysis fractionation, DSC and high‐temperature HPLC to provide detailed information on short chain branching in LLDPE and long chain branching in LDPE. For LDPE it is shown that the multiple fractionation approach is a powerful source of sample libraries that may have similar molar masses and different branching structures or alternatively similar branching but different molar masses. The analysis of these library samples by thermal analysis provides a much deeper insight into the molecular heterogeneity of the samples compared to bulk sample analysis. © 2018 Society of Chemical Industry     

Synthesis and two-step sintering behavior of solution derived corundum abrasives with plate-like grains

Corundum abrasives with plate-like grains were fabricated by a two-step sintering technique using the solution-based process with the addition of the ternary compound additive Na₃AlF₆-CaO-SiO₂. The two-step sintering method showed obvious advantages over conventional sintering methods in promoting sample densification, suppressing grain growth, and homogenizing the microstructure of the corundum abrasives. The sample doped with 2.5?wt% Na₃AlF₆ and 4?wt% CaO + SiO₂ in the molar ratio of 1:1 possessed a relative density of 99.3%, average grain size of 0.54?µm, and single-particle compressive strength of 49?N. The introduction of seeds reduced the temperature of θ- to α-Al₂O₃ phase transformation. The relationship between the microstructure and the mechanical properties of the abrasives was also discussed.     

木质素与高密度聚乙烯共热解特性研究

生物质与塑料共热解是一种非常有效的生物质利用方法之一,但由于生物质结构的复杂性,共热解过程的机理尚不明晰。木质素是生物质的主要组分之一,本文通过热重-质谱联用仪和裂解器-气相色谱质谱仪研究其与高密度聚乙烯共热解过程,获取共热解特性及热解产物分布特性,以揭示共热解过程机制。结果显示,木质素与高密度聚乙烯共热解过程存在协同效应,使得热解失重速率加快,热解固体残渣含量减少。共热解过程有利于CH₄、H₂O、CO和C₂H₄的生成,抑制CO₂的生成。同时,酚类、醇类和糖类等含氧化合物产量减少,烷烃和烯烃类化合物产量增加。结果表明,共热解过程会发生氢转移现象,氢与木质素衍生热解产物结合发生反应,从而抑制含氧化合物的生成,促进烷烃类和烯烃类化合物生成。     

Effect of hyperbranched poly(citric polyethylene glycol) with various polyethylene glycol chain lengths on starch plasticization and retrogradation

A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry     

聚乙烯催化剂用烷氧基镁载体的研究进展

基于烷氧基镁载体的Ziegler-Natta聚乙烯催化剂具有活性高、氢调性能好等优点,是目前聚烯烃工业中的研究热点。介绍了烷氧基镁载体的发展进程,综述了烷氧基镁载体的制备及改进方法,分析了烷氧基镁载体在催化剂制备过程中的作用,并对开发适用于乙烯聚合的烷氧基镁载体提出了展望。