Recycling Of Polymer Waste Research Articles

Estudo cinético da reação heterogênea de despolimerização do PET pós-consumo em meio alcalino: influência da velocidade de agitação

Existe grande preocupação ambiental e econômica quanto à reutilização dos materiais poliméricos pós-consumo, devido ao grande volume de descarte destes nos lixos urbanos e ao valor agregado que esses materiais apresentam. Por isso existem vários estudos relacionados à pesquisa para o desenvolvimento de métodos de reciclagem mecânica e química dessa categoria de materiais, principalmente o PET. Neste trabalho o PET pós-consumo, obtido a partir de garrafas, foi submetido à reciclagem química usando solução de hidróxido de sódio em etilenoglicol. Foi verificado que o rendimento da reação e a cinética de despolimerização foram influenciadas pela velocidade de agitação do meio reacional. A 1360 rpm a resistência ao processo de transferência de massa do produto sólido a partir da superfície das amostras de PET não reagidas para a solução foi eliminada e a reação passou a ser controlada pela etapa química. A equação cinética deduzida a partir do modelo considerando o meio heterogêneo apresentou boa concordância com os resultados experimentais e os valores das constantes de velocidade aparentes foram altos, comparados com valores de outros trabalhos da literatura. Estes resultados sugerem que o meio alcalino usado é bastante eficiente, pois a 1360 rpm e a 170 °C apenas 6 min foram suficientes para obter 100% de tereftalato de dissódio.

Waste catalysts for waste polymer

Catalytic cracking of high-density polyethylene (HDPE) over fluid catalytic cracking (FCC) catalysts (1:6 ratio) was carried out using a laboratory fluidized bed reactor operating at 450 °C. Two fresh and two steam deactivated commercial FCC catalysts with different levels of rare earth oxide (REO) were compared as well as two used FCC catalysts (E-Cats) with different levels of metal poisoning. Also, inert microspheres (MS3) were used as a fluidizing agent to compare with thermal cracking process at BP pilot plant at Grangemouth, Scotland, which used sand as its fluidizing agent. The results of HDPE degradation in terms of yield of volatile hydrocarbon product are fresh FCC catalysts ≫ steamed FCC catalysts ≈ used FCC catalysts. The thermal cracking process using MS3 showed that at 450 °C, the product distribution gave 46 wt% wax, 14% hydrocarbon gases, 8% gasoline, 0.1% coke and 32% nonvolatile product. In general, the product yields from HDPE cracking showed that the level of metal contamination (nickel and vanadium) did not affect the product stream generated from polymer cracking. This study gives promising results as an alternative technique for the cracking and recycling of polymer waste.

Recycling of Polymer Waste with Fluid Catalytic Cracking Catalysts

Feedstock recycling of high-density polyethylene (HDPE) over fluid catalytic cracking (FCC) catalysts (1:6 ratio) was carried out using a laboratory fluidized bed reactor operating at 450°C. Fresh and steam deactivated commercial FCC catalysts with different levels of rare earth oxide (REO) were compared as well as used FCC catalysts (E-Cats) with different levels of metal poisoning. Fresh FCC catalysts gave the highest results of HDPE degradation in terms of yield of volatile hydrocarbon product. Meanwhile, steamed FCC catalysts and used FCC catalysts showed similar but lower yields. Overall, the product yields from HDPE cracking showed that the level of metal contamination (nickel and vanadium) did not affect the product stream generated from polymer cracking. This study gives promising results as an alternative technique for the cracking and recycling of polymer waste.

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

AbstractSummary: 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.magnified imageRecycling of PET polymer by different chemical routes.

Feedstock recycling of polymer wastes

Current common polymer waste recycling methods, mechanical recycling and energy recovery, have drawbacks such as labour intensive sorting and atmospheric pollution. Feedstock recycling has emerged as an environmentally successful alternative for polymer waste management.

99/00234 Transfer system in thermal decomposition device for recycling polymer waste to fuel oil

99/00234 Transfer system in thermal decomposition device for recycling polymer waste to fuel oil

Food pollution by bilayer package with a recycled polymer: Effect of some parameters

AbstractA way of recycling waste polymers consists in reusing them as new food packages. Because of potential contamination, bilayer packages are made with a virgin polymer located between the recycled polymer layer and the food. The virgin polymer layer plays the role of a functional barrier to contamination. Some emphasis is placed on the thickness of each polymer layer by keeping the thickness of the package constant as well as on the volume of food. The process of contaminant transfer is controlled by transient diffusion through the bilayer package and convection into the liquid food. A numerical model, predicting the kinetics of contaminant transfer in the food and the profiles of concentration of contaminant developed through the package, was elaborated. The thickness of the package is 0.03 cm and the volume of food around 730 cm3. The characteristics are those of polypropylene for packaging and olive oil for food. The effect of the volume of the food in liquid state on the kinetics of transfer is also considered.

Reaction of Model Compounds of Phenol Resin and Molding Materials of Phenol Resin in Supercritical Water for Chemical Recycling of Polymer Waste

Abstract Oxygen supply reaction by supercritical water (SCW) to diphenylmethane was confirmed by the production of benzophenone. Molding materials of phenol resin were decomposed into their monomers by the reaction in SCW and addition of polycarbonate accelerated the decomposition reaction of molding material.

Yield strength of low-density polyethylene-polypropylene blends

Polymer waste recycling is becoming a major problem, because huge amounts of synthetic polymers are manufactured every year for many different purposes. Polymer scraps are gathered from the Municipal Solid Waste (MSW). Within those wastes there are several different polyolefins—such as polyethylene, polypropylene, and polystyrene—all incompatible with each other. In order to recycle these polymers, compatibilization of these polyolefins is needed to avoid high sorting costs and unacceptably low market-value products. In this work, the compatibilization of low-density polyethylene with polypropylene is accomplished through the addition of maleated polyethylene and maleated polypropylene. Prediction of the tensile properties of these blends is attempted, using a model based on continuity of phases in a two-components mixture of thermoplastics. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 275–281, 1997

A Review of Commercial Polyblends Based on PVC, ABS, and PC

Abstract Information available from recent literature (1—6) is presented in this report on PVC-based, ABS-based, and PC-based polyblends. Property profiles of polyblends are superior to those of component homopolymers. Enhanced properties, combined with the low cost of polyblends, make them economically attractive for special markets (e.g., automotive engineering plastics) and result in better resin utilization. Blend resin attributes which result in a myriad of property improvements in different polyblends are highlighted. A survey of commercially available polyblends has been presented and their commercial utility is indicated. Much polymer science has gone into making polyblends a commercial success. Polyblend technology is a frontier area not only for current research; it will also continue to figure prominently in future developments. Polyblend technology provides attractive opportunities for reuse and recycling of polymer wastes. The discussion covers various compatibility criteria and the use of co...

Prerequisites for successful recycling of polymer waste

An increasing awareness of ecological problems will enhance all activities towards recycling of polymers. In other words, we have to expect a fast increasing amount of recycled polymers. Today, most activities concentrate on the economical feasible part of recycling - waste of higher prized plastics, only slightly contaminated plastic waste. Public pressure and legislation request solutions for heavily contaminated commodity plastics from household waste as well. The strategy to produce thick walled, profiles out of comingled plastics will be a contribution towards, but not the solution of the problem. We have to make the serious attempt to separate specific polymers like PE, PS, PET from the waste and to introduce these recyclates into the plastic market. In other words, we have to establish closed loops for all our products. Tremendous problems lay ahead of us in order to accomplish it. We need markets for recyclate, we have to change specifications accordingly, we have to improve existing technologies for work up, we have to develop “raw material” specifications when we turn waste in an economic good, we have to develop scenarios for unsufficient economics. The paper will deal with all these aspects in detail and will discuss the present situation in Germany.

Recycling of polymer waste: Part II—Stress degraded polypropylene

Rheological and mechanical properties of blends of polypropylene and degraded polypropylene have been studied. Both properties, and particularly the elongation at break, depend on the composition and on the extent of degradation. The unusual behaviour of the elongation at break is correlated with crystalline phase segregation which appears with decreasing molecular weight of the degraded component.

Recycling of polymer waste: Part 1—Photo-oxidized polypropylene

In order to recycle photo-oxidized polypropylene, blends of this polymer waste with virgin polypropylene have been prepared with different compositions. Both rheological and mechanical properties depend on composition. Rheological properties indicate some interactions between the two polymers at low shear rates. On the other hand, at high shear rates there is evidence of incompatibility. The nominal tensile strength is almost independent of the composition, while the other mechanical properties are similar to those of the degraded material up to a virgin PP content of about 75%, after which they quickly reach the values for the virgin polypropylene. These features are correlated with the large spherulite size of these blends.