Auto-Catalyzed Hydrolytic Depolymerization of Poly(Butylene Terephthalate) Waste at High Temperature

Auto-catalyzed hydrolytic depolymerization of poly(butylene terephthalate) (PBT) waste in neutral water was carried out in an autoclave at 200°, 215°, 230°, and 245°C under autogenously pressure. The effects of particle size, agitator speed, charge ratio, and reaction time on PBT hydrolyses were studied. Reaction products were terephthalic acid (TPA) and 1,4-butanediol (BD) that were recovered, analyzed, and confirmed. Yields of TPA and BD were almost equal to PBT conversion. Analyses of PBT waste samples were also undertaken. A kinetic model for PBT hydrolysis was fitted with the experimental data. Moreover, a noncatalytic PBT hydrolysis was studied to understand the effect of auto-catalyzed action during reaction. Various kinetic parameters (i.e., hydrolysis rate constant, equilibrium constant, backward rate constant, Gibbs free energy, enthalpy, and entropy) of reaction were calculated. The transfer of laboratory data is required during process commercialization through pilot plant. The dependence of the rate constant on the reaction temperature was correlated by the Arrhenius plot giving activation energy of 87 kJ/mol and the corresponding Arrhenius constant of 5.56 × 10⁹[(g ET/mol)^1.5 min^?1] for PBT hydrolysis.     

Heat Transfer Studies in an Agitated Vessel During Aqueous Alkaline Depolymerization of Poly(Ethylene Terephthalate) (PET) Waste

Depolymerization reactions of poly(ethylene terephthalate) (PET) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 150°C at atmospheric pressure. Disodium terephthalate (terephthalic acid salt) and ethylene glycol (EG) remain in the liquid phase. Terephthalic acid (TPA) salt was converted into TPA. The produced monomeric products (TPA and EG) were recovered. Various design parameters were estimated. Design of a batch reactor was undertaken for depolymerization of PET waste in aqueous sodium hydroxide solution. As expected, the Reynolds numbers, Prandtl numbers, Nusselt numbers, coil-side heat transfer coefficients, and overall heat transfer coefficients were consistent with the fluid velocities. It shows excellent potential for commercialization of the depolymerization of PET waste.     

PET聚酯化学解聚进展

废ＰＥＴ聚酯化学解聚是实现其循环利用的重要途径,本文介绍了目前国内外主要的解聚方法及研究进展状况,指出我国应大力加强该领域的研究。     

Fracture Toughness of Injection-Molded Poly(Butylene Terephthalate) Composites

Abstract:

The influences of various fiber amounts and injection molding process conditions on the fracture toughness of injection-molded short fiber-reinforced poly(butylene terephthalate) (PBT) composites were investigated. Three materials of various fiber amounts, neat PBT, 15 wt.%, and 30 wt.% short fiber-reinforced PBT composites, were used in this study. The compact tension (CT) specimens were prepared by various injection molding process conditions, wherein filling time, melt temperature, mold temperature, and packing pressure were design parameters used to measure fracture toughness. The morphology of the specimens, which consisted of frozen, intermediate, and core layers, was evaluated by scanning electron microscopy (SEM) and related to the fracture toughness. The fracture surfaces were also observed by SEM to understand the difference between the fracture mechanisms of neat PBT and fiber-reinforced PBT. It was found that the fracture toughness of neat PBT was significantly increased by the addition of short glass fibers. However, the variation of the injection molding design parameter had little effect on the fracture toughness. The fracture toughness depended on the thickness of the layers where fibers oriented perpendicular to the crack direction. The layer thickness was strongly affected by the fiber amounts.     

Recycling of Waste Poly(Ethylene Terephthalate) with Naphthalene and Neutral Water

The waste poly(ethylene terephthalate) (PET) powder dissolution/reprecipitation was carried out in a batch operation at atmospheric pressure at various temperatures ranging from 180–220°C at temperature intervals of 10°C. Particle sizes of the waste PET ranged from 50–512.5 µm and operation time, which ranged from 30–90 min, were optimized. Dissolution/reprecipitation of the waste PET was carried out in naphthalene (solvent) and neutral water (nonsolvent), respectively. Dissolution/reprecipitation of the waste PET was increased with operation time and temperature. Dissolution/reprecipitation of PET was decreased with increase in the particle size of the waste PET. The waste PET particle size and agitator speed required for complete recycling of the waste PET were also optimized. Analyses of the waste PET and the recycled PET collected after the reprecipitation process was undertaken by determination of various physical properties. The operation applied at lesser time and with cheaper solvent/nonsolvent, resulted in excellent quality of the recycled PET collected after the reprecipitation process. This process of recycling of the waste PET has an industrial significance due to most economical operation for commercialization.     

Properties of Block Copolymers of Poly(Butylene Terephthalate) and Polyoxytetramethylene Glycol

Synthesis of polyester thermoelastoplasts, block copolymers of polyoxytetramethylene glycol and poly(butylene terephthalate) of the polyblock type, was developed and implemented in pilot industrial conditions. POTM blocks act as flexible molecular decouplings that give the copolymer elasticity, while PBT blocks form physical linkages and are responsible for the mechanical strength and hardness of the material. The composition of the reaction systems, process stage sequence, and synthesis parameters are optimized for block copolymers with a concentration of the flexible POTM block of 65-10 wt. % and a molecular weight of 1000. The structure is investigated, and the physicochemical and mechanical properties of the material obtained are determined. It was found that the concentration of flexible blocks has a determining effect on the physicochemical structure and properties of the block copolymers. For a 40% concentration of the flexible block, the character of the concentration curves of the physicomechanical indexes changes significantly due to phase-structural transformations in the block copolymers.     

Chemical Kinetics,Simulation, and Thermodynamics of Glycolytic Depolymerization of Poly(ethylene terephthalate) Waste with Catalyst Optimization for Recycling of Value Added Monomeric Products

Reaction of poly(ethylene terephthalate) (PET) waste powder with ethylene glycol (EG) was carried out in a batch reactor at 1 atm pressure and at various temperatures ranging from 100–220 °C at the intervals of 10 °C. Particle size from 50–512.5 μm, reaction time from 30–150 min, amount of catalyst from 0.001–0.009 mol, and type of catalysts required for glycolysis of PET were optimized. To increase the PET weight (%) loss, various external catalysts were introduced during the reaction at different reaction parameters. Depolymerization of PET was increased with reaction time and temperature. Depolymerization of PET was decreased with increase in the particle size of PET. Reaction rate was found to depend on concentrations of liquid ethylene glycol and ethylene diester groups in the polyester. Analyses of value added monomeric products (DMT and EG) as well as PET were undertaken. Yields of monomers were agreed with PET conversion. A kinetic model was proposed and simulated, and observed consistent with experimental data. Comparisons of effect of various amounts of catalysts and type of catalysts on glycolysis rate were undertaken. Dependence of the rate constant on reaction temperature was correlated by Arrhenius plot, which shows activation energy of 46.2 kJ/mol and Arrhenius constant of 99 783 min^?1.

Arrhenius plot of the rate constant of glycolysis at 1 atm pressure for 127.5 μm PET particle size (KZA = rate constant using zinc acetate as a catalyst, KMA = rate constant using manganese acetate as a catalyst).     

New Motivation for the Depolymerization Products Derived from Poly(Ethylene Terephthalate) (PET) Waste: a Review

Summary: Over the last several decades, the process of recycling polymer waste has been attracting the attention of many scientists working on this issue. Polymer recycling is very important for at least two main reasons: firstly, to reduce the ever increasing volumes of polymer waste coming from many sources: from daily life packaging materials and disposables and secondly, to generate value‐added materials from low cost sources by converting them into valuable materials similar, to some extent, to virgin materials. Poly(ethylene terephthalate) (PET) occupies the top of the list of polymers to be recycled due to its easy recycling by different ways, which, in accordance, give variable products that can be introduced as starting ingredients for the synthesis of many other polymers. PET can by recycled by hydrolysis, acidolysis, alkalolysis, aminolysis, alcoholysis and glycolysis. Glycolysis is the breakdown of the ester linkages by a glycol, resulting in oligomers or oligoester diols/polyols with hydroxyl terminal groups. Oligoesters coming from the glycolysis of PET waste have been well known for a number of decades to be utilized as a starting material in the manufacture of polyurethanes, unsaturated polyesters and saturated polyester plasticizers. But, as a current motivation, we are reporting on a new application for these oligoester diols/polyols by converting the hydroxyl terminals into acrylate/methacrylate groups. These new acrylated/methacrylated oligoesters have been tested as UV curable monomers and gave promising results from the point of view of their curability by UV and their mechanical properties. The new motivations open the potential for the market to apply the depolymerization products of PET waste for UV curable coatings, useful for wood surfaces, paints and other applications.

Recycling of PET polymer by different chemical routes.     

Preparation of HALS-Functional Core-Shell Nanoparticles and their Application in Poly(Butylene Terephthalate)

HALS-functional core-shell nanoparticles, poly(BA-MMA-PMPA), were prepared by emulsion polymerization. The chemical structure and the microstructure of the particles was confirmed by Fourier transformed infrared (FTIR) and transmission electron microscopy (TEM), respectively. The nanoparticles were used to modify PBT and had good compatibility with PBT. The mechanical properties before and after UV-irradiation analysis demonstrated that the UV-resistance and impact resistance of PBT were obviously improved by poly(BA-MMA-PMPA). The degradation degree of PBT was retarded by poly(BA-MMA-PMPA) as studied by thermogravimetry analysis (TGA). The surface chemical functional groups changes revealed that the surface of PBT was greatly protected by poly(BA-MMA-PMPA).     

Poly(Butylene Terephthalate)/Polyacrylic Blends with Enhanced Toughness

An improved toughness-stiffness balance was achieved in PBT matrix by adding poly(n-butyl acrylate)/poly(methyl methacrylate-co-glycidyl methacrylate) (PBMG) core-shell structured copolymer.

A series of poly(n-butyl acrylate)/poly(methyl methacrylate-co-glycidyl methacrylate) (PBMG), core-shell structured modifiers with different contents of functional monomer (glycidyl methacrylate) were prepared, and the effects on mechanical properties of poly(butylene terephthalate) (PBT) blends were investigated. The morphology of the core-shell structure was confirmed by means of transmission electron microscopy. Scanning electron microscopy was used to observe the morphology of the fractured surfaces. The dynamic mechanical analyses of PBT/PBMG blends showed two merged transition peaks of the PBT matrix, with the presence of PBMG core-shell structured modifier, which were responsible for the improvement of PBT toughness.      

Chemical Degradation of Poly(Ethylene Terephthalate)

The possibility of converting polyethylene terephthalate (PET) waste into terephthalic acid as a primary material by using different techniques through trans-esterification, with an alcohol and through hydrolysis in basic medium, has been investigated. In addition, utilization of activating agents such as inorganic salts and phase transfer catalysts has been investigated.Mineral water and beverage bottles were collected, cleaned and crushed into flakes suitable for the intended experiments. Also, the main products of chemical conversion of such wastes were isolated and confirmed by authentication with standard terephthalic acid through Thin Layer Chromatography (TLC) technique. The reaction yield % was determined to optimize the corresponding experimental conditions and the obtained results have been presented and discussed.     

On the Degradation and Stabilization of Poly(Methyl Methacrylate) in a Continuous Process

Thermally unstable polymers such as poly(methyl methacrylate) are degraded considerably during industrial processing. This degradation and its reduction to a minimum have been investigated in both lab and continuous pilot‐scale experiments. A three‐step degradation mechanism, starting at 180 °C, was proved by Thermogravimetrical Analysis (TGA) and a kinetic approach to describe it was derived. The knowledge of this degradation behavior was then applied to a pilot‐scale process with a production rate of 10 kg/h and the process yield loss during the devolatilization step was investigated. Using heat stabilizers, the overall process yield could be improved by 10 %, whereas the residual organic volatiles concentration (VOC) was drastically reduced to values below 1000 ppm. In order to preserve the molecular weight of the final product these stabilizers were added into the process, separately, at the end of the polymerization reaction but before the devolatilization step.     

M－POE－g－MAH增韧PBT的力学性能和形貌

研究了一种新型增韧剂(M—POE-g-MAH)对PBT树脂的增韧效果。与传统的纯POE-g-MAH增韧剂(POE-g-MAH)进行对比，考察了增韧剂的组成、用量对共混物力学性能的不同影响，并结合共混物的室温缺口冲击断面SEM照片，分析了共混物发生脆韧转变所对应的微观形貌特征。实验结果表明，在M-POE-g-MAH／PBT共混体系中，POE-g-MAH用量占体系10％左右时共混物发生明显的脆韧转变，而在传统的纯POE-g-MAH／PBT共混体系中，POE-g-MAH用量为15％左右才使共混物发生脆韧转变。M-POE-g-MAH增韧PBT在性能和成本上具有较大的优势，所得共混物产品的性价比较高。     

聚对苯二甲酸丁二醇酯/多壁碳纳米管复合材料的流变及结晶行为

采用熔融共混的方法制备了对聚对苯二甲酸丁二醇酯(PBT)/多壁碳纳米管(MWNT)复合材料,研究了复合体系的流变及结晶行为.结果表明MWNT具有显著的增强作用,使得复合体系低频区的模量出现类固态黏弹响应,这源于MWNT逾渗网络结构的形成.MWNT的加入并未改变PBT的α晶型结构,但其异相成核作用却能有效地促进复合体系PBT基体的结晶.     

Conversion of Poly(Ethylene Terephthalate) Waste into Activated Carbon: Chemical Activation and Characterization

Due to its high carbon content, low impurities, low cost and easy availability, poly(ethylene terephthalate) (PET) waste is considered as a suitable precursor for the production of activated carbon. The chemical activation of PET wastes using different chemical agents such as H₃PO₄, H₂SO₄, ZnCl₂, and KOH was investigated. KOH‐ and ZnCl₂‐activated PET were found to be the best choices for the adsorption of small and large molecules. The capacities of the adsorbents towards I₂, methylene blue, N₂, CH₄, and CO₂ followed the order KOH‐PET >H₃PO₄‐PET > ZnCl₂‐PET > H₂SO₄‐PET; however, in the molasses uptake and selective adsorption of CO₂ compared to CH₄, ZnCl₂‐PET performed better than the other adsorbents.     

国内外复合材料回收再利用现状

介绍目前国内外复合材料废弃物循环再利用技术的主要方法和研究现状。指出在国家宏观政策指引下,应大力研究和发展复合材料废弃物的综合利用技术,实现废弃物的资源化循环再利用。火车枕木、耐火砖、水泥和石膏是复合材料废弃物回收利用的研究方向。     

Synthesize and Crystallization Kinetics of Biodegradable Aliphatic Poly(Butylene Succinate-Co-Diethylene Glycol)

Biodegradable aliphatic poly(butylene succinate-co-diethylene succinate) (PBDEGS) were synthesized from succinic acid and diethylene glycol through a two step polycondensation with titanium tetraisoproxide (TTP) as catalyzer and polyphosphate (PPA) as the stablilizer at high temperature. The differential scanning calorimeter (DSC) was used to investigate the melting behavior, crystallization behavior and non-isothermal crystallization kinetics of this copolyester. The melting behavior showed that the melting temperature of the copolyester decreased gradually with increaseing of diethylene glycol in the copolyester. The crystallization mechanism of PBDEGSs were analyzed with the Avrami equation. The result showed that the DEG chains affected the crystallization mechanism of PBS and decreased overall crystallization rate in some extent. The contrastive method of Mo analysis showed similar rasult. At the same time, because of the flexible ether bond existed in the DEG molecules, the crystallization activation energy of PBDEGSs is obviously lower than that of PBS.     

废旧PVC塑料的回收利用

本文综述了废旧聚氯乙烯（PVC）的资源化利用和存在的问题;介绍了几种回收废IEIPVC（聚氯乙烯）的工艺,包括溶剂法、机械法、化学法及焚烧法,介绍了当前PVC的回收利用及其对环境影响的研究进展,并对PVC未来的应用及其回收利用进行了一些思考。     

PBS不同化学结构共聚物的性能

采用改变原料的组分合成不同化学结构的聚丁二酸丁二醇酯(PBS)改性共聚物:聚丁二酸丁二醇/己二酸丁二醇酯(PBS-co-BA)、聚丁二酸丁二醇酯/聚丁二酸乙二醇酯(PBS-co-ES)、聚丁二酸丁二醇酯/聚丁二酸己二醇酯(PBS-co-HS),利用FT-IR和1H-NMR表征共聚物的化学结构,并对共聚物的结构与物理性能、降解性能的关系进行对比.研究结果表明:所有共聚物的结晶度、熔点较其均聚物有所降低;但所有共聚物的断裂伸长率都有所提高.热分析结果表明:PBS-co-HS热性能有所提高,PBS-co-BA和PBS-co-ES有所下降.堆肥降解实验表明:所有共聚物的降解性都比均聚物有显著提高,其降解速度大小顺序为:PBS-co-BA>PBS-co-HS>PBS-co-ES>PBS,PBS-co-HS是综合性能最优良的材料.     

Chemical Recycling of Poly(ethylene terephthalate)

This paper covers the recent research carried out by the authors on the chemical recycling of poly(ethylene terephthalate) (PET) taken from post‐consumer soft‐drink bottles. The chemical recycling techniques used are critically reviewed and the authors' contribution is highlighted. Hydrolysis in either an alkaline or acid environment was employed in order to recover pure terephthalic acid monomer that could be repolymerized to form the polymer again. Alkaline hydrolysis was carried out in either an aqueous NaOH solution or in a non‐aqueous solution of KOH in methyl cellosolve. A phase‐transfer catalyst was introduced in alkaline hydrolysis, in order that the reaction takes place at atmospheric pressure and in mild experimental conditions. The reaction kinetics were thoroughly investigated, both experimentally and theoretically, using a simple, yet precise, kinetic model. Moreover, glycolysis was examined as an effective way for the production of secondary value‐added materials. The glycolysated PET products (oligomers) can be used as raw materials for the production of either unsaturated polyester resins (UPR) or methacrylated oligoesters (MO). UPR can subsequently be cured with styrene in ambient temperature to produce alkyd resins used as enamel paints or coatings. MO are potential monomers that can be cured either by UV irradiation or temperature to produce formulations used as coatings for wood surfaces, paints, or other applications. Thus, recycling of PET does not only serve as a partial solution to the solid‐waste problem, but also contributes to the conservation of raw petrochemical products and energy.