Mathematical modeling of the graft reaction between polystyrene and polyethylene

Polystyrene (PS) and polyethylene (PE) are two major components of household plastic waste whose blends are immiscible. Recycling them together is an attractive option that requires a compatibilization process to improve the blend mechanical properties. If a PE/PS copolymer is added or formed in situ, it may act as compatibilizer. The structure and molecular properties of this copolymer are key factors to assure its effectivity as a compatibilizer. In this work, we study the graft copolymerization reaction between polystyrene and polyethylene using the catalytic system composed of AlCl₃ and styrene. We develop a model of this process which considers that PE/PS grafting and PS degradation occur simultaneously. We propose a kinetic mechanism for the whole process and apply the method of moments to solve the mass balance equations. The model is able to calculate average molecular weights as well as the amount of grafted PS. It accurately describes the available experimental data, constituting a valuable tool for simulation and optimization purposes.     

The removal characteristics of natural organic matter in the recycling of drinking water treatment sludge: Role of solubilized organics

To clarify the role of solubilized organics derived from drinking water treatment sludge (DWTS) in the elimination of natural organic matter (NOM) in the DWTS recycling process, a probe sonoreactor at a frequency of 25 kHz was used to solubilize the organics at varied specific energies. The coagulation behavior related to NOM removal in recycling the sonicated DWTS with and without solubilized organics was evaluated, and the effect on organic fractionations in coagulated water was determined. The study results could provide useful implications in designing DWTS recycling processes that avoid the enrichment of organic matter. Our results indicate that DWTS was disrupted through a low release of soluble chemical oxygen demand (SCOD) and proteins, which could deteriorate the coagulated water quality under the specific energy of 37.87–1212.1 kW h/kg TS. The optimal coagulation behavior for NOM removal was achieved by recycling the sonicated DWTS without solubilized organics at 151.5 kW h/kg TS specific energy. Recycling the sonicated DWTS could increase the enrichment potential of weakly hydrophobic acid, hydrophilic matter, and <3 kDa fractions; the enrichment risks could be reduced by discharging the solubilized organics. Fluorescent characteristic analysis indicated that when recycling the sonicated DWTS without solubilized organics, the removal of humic-like substances was limited, whereas removal of protein-like substances was enhanced, lowering the enrichment potential of protein-like substances.     

Nano indium oxide catalyzed efficient synthesis of propargylamines via C-H and C-Cl bond activations

A simple, and efficient nano In₂O₃ catalyzed one-pot three-component coupling of terminal alkyne, dichloromethane, and secondary amine has been developed for the synthesis of propargylamines under mild reaction conditions. The catalyst was recovered and reused for three times without significant loss of catalytic activity.     

Recycling of PVC wastes

PVC is a universal polymer which can be processed into a wide variety of short-life or long-life products. As a result of increasing consumption of PVC-made products in recent years, the quantity of used PVC items entering the waste stream is gradually increased. Currently, there is a considerable public concern about the problem of plastic wastes, from which PVC has not escaped and the material or energy recycling may be a suitable way to overcome this problem. This review considers the various aspects of the PVC recycling such as recycling methods of PVC, special problems about some proposed processes, separation techniques, and recycling of mixed PVC wastes. In addition, an attempt is made to portray the current status of PVC recycling, the most recent technologies of recycling, and some recent scientific research in the field.     

The selective recycling of mixed plastic waste of polylactic acid and polyethylene terephthalate by control of process conditions

The glycolysis of postconsumer polyethylene terephthalate (PET) waste was evaluated with catalysts of zinc acetate, zinc stearate and zinc sulfate, showing that zinc acetate was the most soluble and effective. The chemical recycling by solvolysis of polylactic acid (PLA) and PET waste in either methanol or ethanol was investigated. Zinc acetate as a catalyst was found to be necessary to yield an effective depolymerization of waste PLA giving lactate esters, while with the same reaction conditions PET remains as an unconverted solid. This provides a strategy to selectively recycle mixed plastic waste by converting one plastic to a liquid and recovering the unreacted solid plastic by filtration.     

再循环对密度极限破裂的影响

用简化的再循环模型和破裂模型,研究了边缘发生的电离与电荷交换的能量损失与密度极限破裂的关系,得到HL 1M装置的临界破裂密度nc≤1.6×1020m-3。     

Pd/CaCO3 in liquid poly(ethylene glycol) (PEG): an easy and efficient recycle system for partial reduction of alkynes to cis-olefins under a hydrogen atmosphere

Lindlar’s catalyst (Pd/CaCO₃) in PEG (400) has been found to be the most reusable reaction medium for selective reduction of alkynes to cis-olefins. The catalyst and PEG were recycled five times without loss of activity.     

Mechanical,thermal, and morphological properties of powder coating waste reinforced acetal copolymer

The present study investigates the individual effects of three different thermosetting waste materials, used as fillers, on the mechanical, thermal and flow properties of acetal copolymers (POM). Different amounts ranging from 5% to 30% by weight of hydrolyzed powder coating recyclates were mixed as filler material in POM. The matrix and the fillers were first dry-mixed and then compounds were prepared through melt extrusion. The resulting compounds were cooled, granulated, and then standard tensile test bars were produced through use of an injection-molding machine. We investigated the mechanical and thermal properties of test specimens, and tensile strength, bending strength and impact strength were evaluated as a function of type and amount of filler material in the POM matrix. In addition, the change in melt flow index of POM/filler mixtures was determined, before and after extrusion. Furthermore, the morphology of the specimens was examined via electron microscopy. The results of this investigation are encouraging and present an innovative approach to reutilize hydrolyzed electrostatic powder coating wastes with thermoset structures as fillers in acetal copolymers.     

Recycling of bioplastics,their blends and biocomposites: A review

This review presents scientific findings concerning the recycling of bioplastics, their blends and thermoplastic biocomposites, with special focus on mechanical recycling of bio-based materials. The paper does not include bio-based commodity plastics such as bio-derived polyolefins that are identical to their petroleum-based counterparts and that can be recycled in the same way. During the past few years, recycling of biopolymers and their blends has been studied using both mechanical and chemical methods, whereas in biocomposites, the focus has been on mechanical recycling. This review goes through the findings on the recyclability of various materials, the strengths and weaknesses of applied methods, as well as the potential strategies and opportunities for future improvements. There are still many blends that have not been investigated for their recyclability. Information about commercially available blends containing bioplastics is summarised in the Appendix because of the importance of their possible effects on the conventional plastic recycling streams.     

Studies on the recycling of glycolyzed nylon 66 using novel chain extenders

Nylon 66 (NY66) polymer based products widely used in automotive applications undergo deterioration in their mechanical properties when repeatedly exposed to ethylene glycol (EG) solution. In this study, recycling of glycolyzed NY66 (g-NY66) samples was carried out through melt-compounding with novel isocyanate based chain extenders namely hexamethylene 1,6-dicarbamoyl dicaprolactam (HDC) and tolylene 2,4-dicarbamoyl dicaprolactam (TDC). The recycling efficiency of HDC and TDC on g-NY66 was compared with two commercially available chain extenders 1,1-carbonyl biscaprolactam (CBC) and 1,3-phenylene bis(2-oxazoline) (PBO), and the resultant changes in molecular weight, melt flow, and crystallization behavior in the modified NY66 samples were confirmed from intrinsic viscosity, rheology, and differential scanning calorimetry measurements, respectively. The active ingredients (isocyanate and ?-caprolactam) liberated from HDC and TDC during the melt-compounding process reacted efficiently with the end groups of g-NY66 (-OH and -NH₂) resulting in improved molecular weight compared to g-NY66 and the results are reported in detail.