Designing oligomeric ethylene terephtalate building blocks by chemical recycling of polyethylene terephtalate

The intelligent recycling of plastics waste is a major concern. Because of the widespread use of polyethylene terephtalate, considerable amounts of PET waste are generated that are ideally re‐introduced into the material cycle by generating second generation products without loss of materials performance. Chemical recycling methods are often expensive and entail environmentally hazardous by‐products. Established mechanical methods generally provide materials of reduced quality, leading to products of lower quality. These drawbacks can be avoided by the development of new recycling methods that provide materials of high quality in every step of the production cycle. In the present work, oligomeric ethylene terephthalate with defined degrees of polymerization and defined molecular weight is produced by melt‐mixing PET with different quantities of adipic acid as an alternative pathway of recycling PET with respect to conventional methods, offering ecofriendly and economical aspects. Additionally, block‐copolyesters of defined block length are designed from the oligomeric products. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39786.     

废旧聚苯乙烯合成溴代聚苯乙烯研究

用废旧聚苯乙烯(PS)，以二氯甲烷为溶剂，还原铁粉为催化剂合成了阻燃剂溴代聚苯乙烯(BPS)。并用FT—IR，TG，DSC对产物的结构与性能进行了研究。实验结果表明聚苯乙烯的苯环发生了二溴代或三溴代，合成溴代聚苯乙烯的最佳条件是40～60℃，以还原铁粉为催化剂用量为5phr，聚苯乙烯的质量浓度为5％～8％，含溴可达60％以上。     

Thermal Degradation of Polystyrene

The thermal degradation of polystyrene in the absence of oxygen is examined, at temperatures above or below 300°C. The decrease in degree of polymerisation occurring either with negligible volatilisation at lower temperatures, or with evolution of low molecular weight products at higher temperatures, is simulated by Monte-Carlo procedures. The results suggest that below 300°C, scission of the polymer chains is random, and involves also a minor fraction of some abnormal, as yet unidentified, structures. Above 300°C, an extensive intermolecular transfer process seems to be the main cause of the decrease in degree of polymerisation, whereas an overall depolymerisation of 100 structural units at each chain scission is the source of volatilisation.     

天然有机溶剂回收聚苯乙烯泡沫塑料的研究

利用天然有机溶剂使废弃的聚苯乙烯泡沫塑料减容后溶解,选择液体沉淀剂使聚苯乙烯沉淀,另选择一种助剂,该助剂为一种常见液体,可与沉淀剂互溶,从而使沉淀剂与溶剂分离。溶剂、沉淀剂、助剂均无毒、无害、不会造成二次污染。三种试剂均可循环使用,其回收率都达96％以上。     

聚苯乙烯超临界催化降解

以氧化钡为催化剂分别在超临界甲苯和正己烷的介质中考察了聚苯乙烯(PS)的降解过程,结果表明甲苯的效果优于正己烷.在超临界甲苯介质中考察了反应温度和原料配比对聚苯乙烯转化率、苯乙烯收率和产物分布的影响,并确定了聚苯乙烯在超临界甲苯中催化降解的适宜工艺条件为:反应温度340℃,反应时间30 min,甲苯和PS质量比为15.0.     

The conditions of cationic exchange with the use of recycling polystyrene derivative,the product of sulfonation by silica sulfuric acid

Growing amount of waste plastics has become an environmental problem on a global scale. This study presents an investigation of the conditions of cleaning water from heavy metal ions using chemically recycled polystyrene. To get effective ion exchangers, the sulfonation of virgin polystyrene and expanded polystyrene wastes were obtained using silica sulfuric acid. As it turned out, the use of this solid sulfonating agent simplifies the separation of the polymeric product from the acid and the solvent in comparison to conventional sulfonation methods. The ion exchange behavior of copper and zinc cations in the yielded sulfonated derivatives of polystyrene was studied. Batch shaking adsorption experiments depending on contact time, pH, temperature, and dosage of adsorbate were carried out. The stability of resin to cyclical adsorption and regeneration (column experiment) was also investigated. We report that resins have a high adsorption efficiency with total ion exchange capacity (IEC) about 2.6 meq g^?1, which drops with decreasing pH owing to competition between protons H⁺ and metal cations, whereas with the increasing resin doses the removal of cations rises for a constant initial metal concentration. The speed of cation exchange for yielded adsorbents was even better than for commercial resins. After 360 cyclical adsorption and regeneration in column, resin had working IEC of about 2.3 meq g^?1. The study shows that cation exchange resin from polystyrene wastes can be used as an efficient adsorbent for the removal of heavy metal ions from water. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚苯乙烯泡沫塑料的再生与利用

聚苯乙烯泡沫塑料因其良好的特性被广泛使用,但用后即扔对环境造成极大的污染,因此合理回收聚苯乙烯泡沫塑料,使其再生利用非常重要。主要从直接再生法,裂解法,改性利用等几方面阐述近几年来聚苯乙烯泡沫塑料再生利用的技术,并对几种方法进行了比较。     

Ultrasonic Degradation of Polystyrene for Tailoring Molecular Weight and Polydispersity of Polystyrene Fragments

Ultrasonic degradation of polymers attracts more and more attention in the field of chemical recycling of polymers due to the promising opportunity to tailor molecular weight and polydispersity of the gained polymer fragments. In this work, the influence of solvent, gas atmosphere, and ultrasound amplitude on the ultrasonic degradation process of polystyrene is investigated. Therefore, an experimental procedure to perform ultrasonic degradation of polystyrene under homogeneous temperature conditions in the solvents cyclohexane and toluene under the gas atmospheres CO₂ and N₂ for different ultrasonic amplitudes was designed. It could be shown that a significant effect on the molecular weight and polydispersity of the polymer could only be revealed for N₂ and not for CO₂ atmosphere.     

聚苯乙烯在空气中热降解的化学动力学研究

研究了聚苯乙烯在空气中的热降解化学动力学机理。实验结果显示,聚苯乙烯在空气中热降解存在两个失重阶段:第一阶段,温度范围从250.59℃开始至397.41℃,在此范围内,大约有85%的聚苯乙烯发生了分解;第二阶段为397.41～515.29℃,大约有15%的聚苯乙烯发生分解。动力学计算拟合结果表明,聚苯乙烯的主要失重阶段(第一阶段)的热解符合二级化学反应方程,其平均表观活化能Ea值为166.19kJ/mol,lnA值为32.15。     

Thermal decomposition of polystyrene in supercritical methanol

The degradation of polystyrene (PS) in supercritical methanol was carried out under reaction temperatures ranging from 340 to 420°C and pressures of 10–30 MPa. The selectivity of liquid products was investigated at various reaction conditions. As the reaction proceeded, the selectivity of styrene monomer, dimer, 1,3-diphenyl propane, and 1,3-diphenyl butane had a declining tendency, whereas that of the rest (i.e., toluene, ethyl benzene, isopropyl benzene, and 3-phenyl propanol, etc.) had an inclining tendency. The sequences of decomposition reaction could be reasoned by analyzing the variation of selectivity of liquid products. The kinetic behavior of PS in supercritical methanol had been investigated. The degradation processes of PS in such supercritical fluids could be formulated by the first-order kinetic law at the initial stage of reaction. The activation energy for the degradation in supercritical methanol was evaluated to be 117.2 kJ/mol and it was also compared with the activation energies for depolymerization in other supercritical fluids and that for thermal pyrolysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

废旧聚苯乙烯的回收利用

介绍了几种处理和利用废旧塑料的方法：再生法、化学回收法等。指出了废旧塑料回收利用的重要性。     

Environment‐friendly chemical recycling of aliphatic polyurethanes by hydrolysis in a CO2‐water system

In order to develop a chemical recycling system of polyurethanes (PUs), environment‐friendly hydrolysis of two types of aliphatic PUs was studied under pressured CO₂ in water, in which the carbonic acid generated from CO₂ acted as an acid catalyst. Two PUs, namely H‐PU or I‐PU, were synthesized starting from 1,4‐butanediol and 1,6‐hexamethylene diisocyanate or isophorone diisocyanate, respectively. The hydrolysis of PUs depended on the experimental conditions, such as the temperature and CO₂ pressure. As a result, 98% of H‐PU and 91% of I‐PU were successfully hydrolyzed under the typical conditions of 190 °C for 24 h at 8.0 MPa CO₂. The reaction mixtures afforded 1,4‐butanediol and diamines without the formation of any byproducts. Both of these raw materials generated from the originated PUs by selective hydrolytic cleavage of the urethane linkages, and they were easily isolated in high yields simply by evaporation of the water‐soluble components within the reaction mixture. By comparing the results of the two aliphatic PUs with those of an aromatic PU (M‐PU), the hydrolyzability was found to decrease in the order H‐PU, I‐PU, and M‐PU. The difference can be ascribed to the hydrophilicity of the aliphatic or aromatic groups connected to the urethane moieties at the terminals of PUs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45897.     

The effect of mechanical recycling on the microstructure and properties of PA66 composites reinforced with carbon fibers

This article aims to prepare by injection molding recycled polymeric composites based on PA66 reinforced with short carbon fibers after artificial aging for applications in the automotive field. The aging cycles involves the combined action of UV radiation, moisture, and temperature in order to simulate the common outdoor conditions. The 100% recycled composites are obtained by the regranulation of the aged specimens followed by the remelting and re‐injection molding. The study is focused on the comparison between the mechanical behavior and the microstructure of the composites before and after mechanical recycling. The results of mechanical, thermal, and morphological investigations reveal that the recycling process had no significant effect on the final properties and microstructure of the recycled composites. Therefore the recycled PA66CF30 composites could be successfully used for structural or semi‐structural automotive applications guaranteeing good final performances and advantages from the environmental point of view. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42275.     

Chemical Recycling of Polystyrene by Pyrolysis: Potential Use of the Liquid Product for the Reproduction of Polymer

The potential use of the liquid product obtained from the pyrolysis of polystyrene as a raw material for the reproduction of the polymer was investigated in this study. Catalytic and non‐catalytic pyrolysis experiments were carried out in a fixed bed reactor using either model polymer or commercial waste products as the feedstock. The liquid fraction produced from all the pyrolysis experiments consisted mainly of the styrene monomer and this was subjected to re‐polymerization without any further purification, in a DSC with AIBN initiator. It was found that the pyrolysis oil fraction could be re‐polymerized to again produce polymer. However, aromatic compounds included in this fraction may act as chain transfer agents, resulting in alterations in the shape of the reaction rate curve and lowering significantly the average molecular weight and the T_g of the polymer produced.

     

Windshield recycling focused on effective separation of PVB sheet

The study is focused on windshield recycling process resulting in poly(vinyl butyral) (PVB) sheets with very low amout of remain glass particles. PVB sheets were obtained from worldwide manufacturer DuPont and then they were laminated by standard autoclaving process. One sample of PVB sheet was modified by multi‐functional organic acid in order to compare various levels of adhesion. Three‐stage technology was proposed for recycling PVB sheets. In the first‐stage laminated safety glass was mechanically cracked. In the second‐stage the adhesion reduction to minimal degree was followed by chemical‐physical assisted separation. It causes self‐release of the glass out of the PVB sheet. The third‐stage was mechanical peeling of the remaining glass from the PVB sheet which completed the recycling process. The optimal process conditions for the most effective delamination process were found. Delamination technology produces PVB sheet with minimal residual glass content (up to 300 ppm) and minimal change in PVB sheet properties. Described recycling technology is ecologically friendly (the effluent is fully recyclable as well) and could reduce the worldwide problem with windshield waste disposal. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39879.     

Fabrication of microfluidic chips using controlled dissolution of 3D printed scaffolds

Microfluidic chips are commonly fabricated using soft lithography, which often requires a clean room and micropatterning equipment. Recently, microfluidic chips are increasingly fabricated using 3D printing, but this technology is still limited in smallest channel printability, transparency, supports residue, and biocompatibility. In this work, a simple, fast, and inexpensive step is introduced to fabricate polydimethylsiloxane (PDMS) microfluidic chips using enhanced internal scaffold removal (eISR). It is found that final channel dimension decreases by 0.22 ± 0.02 μm/revolution with a 7% error using eISR. Surface topology is inspected after dissolution using scanning electron microscopy. A T-junction device, bifurcation channels, and curved channels are fabricated to demonstrate the usability of eISR in multiple applications. Compared to previous methods, eISR provides acrylonitrile–butadiene–styrene dissolution before PDMS casting to achieve thinner and smoother channels produced using a commercial 3D printer.     

交联聚苯乙烯的热分解与燃烧性能研究

采用二乙烯基苯(DVB)为交联剂,与苯乙烯(St)单体进行共聚合成了一系列交联聚苯乙烯(PS)。采用热重分析、高温热分解、水平燃烧、氧指数、锥形量热分析等方法研究了交联PS的热分解行为和燃烧性能。结果表明:与线型PS相比,交联PS的热分解温度提高,成炭量增加,热稳定性显著增强;交联PS在燃烧时熔融滴落和发烟量显著减少,热释放速率、质量损失速率和燃烧速率降低,氧指数增加,阻燃性能增强;当St/DVB的质量比为100/3时得到的交联PS的阻燃性能最佳;交联PS在燃烧时生成的大量炭残余物覆盖在聚合物表面形成保护层,对热量传递、氧气和燃料分子的迁移产生屏蔽和阻隔作用,降低了聚合物的热分解速率,提高了其阻燃性能。     

聚苯乙烯在超临界甲苯中的可视降解及动力学

采用微型可视反应器考察了在超临界甲苯中聚苯乙烯降解的相变过程. 随温度升高聚苯乙烯在甲苯中迅速溶解,体系在略高于甲苯临界点处气液两相界面消失,且伴随着临界乳光现象,随后反应体系呈均相. 考察了聚苯乙烯超临界降解和热降解的反应特性,结果表明,聚苯乙烯超临界降解转化率明显高于热降解转化率;聚苯乙烯超临界降解初期分子量迅速降低的同时转化率也快速上升,而聚苯乙烯热降解初期分子量迅速降低过程中转化率很低. 由于聚苯乙烯在超临界甲苯中降解是均相反应,显著降低了反应体系的密度和粘度,改善了传递效果,因此超临界降解速率明显提高. 聚苯乙烯降解反应为一级反应,在温度为330~370℃时热降解活化能为186.1 kJ/mol,超临界体系改善了降解环境,活化能明显降低,为143.5 kJ/mol.     

废硬质聚氨酯泡沫塑料的回收利用技术研究

采用物理化学回收方法回收废硬质聚氯酯泡沫塑料,探讨了再生硬质聚氯酯泡沫塑料(RRPUF)、马来酸酐(MAH)接枝聚丙烯(PP)(PP-g-MAH)的用量及不同类型降解剂对PP/RRPUF/PP-g-MAH共混材料性能的影响,用傅里叶变换红外光谱和偏光显微镜表征了RRPUF和PP/RRPUF/PP-g-MAH.在适当温度...     

Polystyrene photodegradation with a novel titanium dioxide/poly(ethylene oxide)/methyl linoleate paint photocatalyst system

The photodegradation of a polystyrene (PS) film was performed by a titanium dioxide (TiO₂)/poly(ethylene oxide) (PEO)/methyl linoleate (ML) paint photocatalyst system. The PS surface was catalytically photodegraded by the TiO₂/PEO component, and a conjugated carbon–carbon double bond was partially produced. A crosslinking reaction occurred between the PS carbon–carbon double bond and radical spices; as a result, the photodegradation diffusion into the inner region was blocked. The additional ML component certainly blocked the crosslinking reaction and accelerated the photodegradation rate. The fraction of less than 10,000 molecular weight of the 4‐h‐photodegaraded film with the TiO₂/PEO/ML paint was 15.1%, and its photodegradation yield increased four times compared with that with the TiO₂/PEO one. The weight loss values of the photodegraded PS part were 9.9, 10.7, and 11.7% at 4, 8, and 12 h, respectively, and gradually increased with increasing irradiation time. Some part of the film was violently photodegraded by the paint, and its photocatalytic effect lasted. The ML was graft‐polymerized into the film, and a phase separation was caused. The photodegradation behavior between the 0.05‐ and 0.1‐mm films was remarkably different; this showed that the diffusion of the ML radical was affected by the film thickness. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013