The effect of metals on thermal degradation of polyethylenes
TL;DR: In this paper, a chemiluminescence study on thermal degradation of some polyethylenes (LDPE, LLDPE and HDPE) on seven metal trays in the presence of triazines as stabilisers was carried out.
About: This article is published in Polymer Degradation and Stability.The article was published on 2004-04-01. It has received 60 citations till now. The article focuses on the topics: Linear low-density polyethylene & Low-density polyethylene.
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TL;DR: A review of the state-of-the-art on biodegradable polymers can be found in this paper, where the salient features of the design and properties of these polymers are discussed.
Abstract: Recent trends in biodegradable polymers indicate significant developments in terms of novel design strategies and engineering to provide advanced polymers with comparably good performance. However, there are several inadequacies in terms of either technology or cost of production especially in the case of applications in environmental pollution. So, there is a need to have a fresh perspective on the design, properties and functions of these polymers with a view to developing strategies for future developments. The paper reviews the present state-of-art on biodegradable polymers and discusses the salient features of the design and properties of biodegradable polymers. Special emphasis is given to the problems and prospects of (1) approaches adopted to make non-biodegradable synthetic polymers such as polyethylene biodegradable and (2) biodegradable polymers and copolymers made from renewable resources especially poly(lactic acid) based polymers and copolymers which are emerging as the candidate biodegradable materials for the future.
559 citations
TL;DR: In this paper, the current scenario of the plastic recycling technology is reviewed in order to provide the reader with an in-depth analysis with respect to the pyrolysis of plastic waste as obtained in the current recycling technology.
Abstract: Due to the depleting fossil fuel sources such as crude oil, natural gas, and coal, the present rate of economic growth is unsustainable. Therefore, many sources of renewable energy have been exploited, but the potentials of some other sources such as plastics waste are yet to be fully developed as full scale economic activity. Development and modernization have brought about a huge increase in the production of all kinds of plastic commodities, which directly or indirectly generate waste due to their wide range of applications coupled with their versatility of types and relatively low cost. The current scenario of the plastic recycling technology is reviewed in this paper. The aim is to provide the reader with an in-depth analysis with respect to the pyrolysis of plastic waste as obtained in the current recycling technology. As the calorific value of the plastics is comparable to that of hydrocarbon fuel, production of fuel from plastic waste would provide a good opportunity to utilize the waste as a better alternative to dumpsites. Different techniques of converting plastics waste into fuel including thermal and catalytic pyrolysis, microwave-assisted pyrolysis and fluid catalytic cracking are discussed in detail. The co-pyrolysis of plastics waste with biomass is also highlighted. Thus, an attempt was made to address the problem of plastic waste disposal as a partial replacement of the depleting fossil fuel with the hope of promoting a sustainable environment.
439 citations
TL;DR: In this paper, the authors delineate the definition of degradability of polymers used in agriculture and place emphasis on the controversial issues regarding biodegradability issues of some of these polymers.
Abstract: The growing use of plastics in agriculture has enabled farmers to increase their crop production. One major drawback of most polymers used in agriculture is the problem with their disposal, following their useful life-time. Non-degradable polymers, being resistive to degradation (depending on the polymer, additives, conditions etc) tend to accumulate as plastic waste, creating a serious problem of plastic waste management. In cases such plastic waste ends-up in landfills or it is buried in soil, questions are raised about their possible effects on the environment, whether they biodegrade at all, and if they do, what is the rate of (bio?)degradation and what effect the products of (bio?)degradation have on the environment, including the effects of the additives used. Possible degradation of agricultural plastic waste should not result in contamination of the soil and pollution of the environment (including aesthetic pollution or problems with the agricultural products safety). Ideally, a degradable polymer should be fully biodegradable leaving no harmful substances in the environment. Most experts and acceptable standards define a fully biodegradable polymer as a polymer that is completely converted by microorganisms to carbon dioxide, water, mineral and biomass, with no negative environmental impact or ecotoxicity. However, part of the ongoing debate concerns the question of what is an acceptable period of time for the biodegradation to occur and how this is measured. Many polymers that are claimed to be ‘biodegradable’ are in fact ‘bioerodable’, ‘hydrobiodegradable’, ‘photodegradable’, controlled degradable or just partially biodegradable. This review paper attempts to delineate the definition of degradability of polymers used in agriculture. Emphasis is placed on the controversial issues regarding biodegradability of some of these polymers.
356 citations
TL;DR: The objective of this review is to outline the advances made in the microbial degradation of synthetic plastics and, overview the enzymes involved in biodegradation.
Abstract: Synthetic plastics are pivotal in our current lifestyle and therefore, its accumulation is a major concern for environment and human health. Petroleum-derived (petro-)polymers such as polyethylene (PE), polyethylene terephthalate (PET), polyurethane (PU), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) are extremely recalcitrant to natural biodegradation pathways. Some microorganisms with the ability to degrade petro-polymers under in vitro conditions have been isolated and characterized. In some cases, the enzymes expressed by these microbes have been cloned and sequenced. The rate of polymer biodegradation depends on several factors including chemical structures, molecular weights, and degrees of crystallinity. Polymers are large molecules having both regular crystals (crystalline region) and irregular groups (amorphous region), where the latter provides polymers with flexibility. Highly crystalline polymers like polyethylene (95%), are rigid with a low capacity to resist impacts. PET-based plastics possess a high degree of crystallinity (30-50%), which is one of the principal reasons for their low rate of microbial degradation, which is projected to take more than 50 years for complete degraded in the natural environment, and hundreds of years if discarded into the oceans, due to their lower temperature and oxygen availability. The enzymatic degradation occurs in two stages: adsorption of enzymes on the polymer surface, followed by hydro-peroxidation/hydrolysis of the bonds. The sources of plastic-degrading enzymes can be found in microorganisms from various environments as well as digestive intestine of some invertebrates. Microbial and enzymatic degradation of waste petro-plastics is a promising strategy for depolymerization of waste petro-plastics into polymer monomers for recycling, or to covert waste plastics into higher value bioproducts, such as biodegradable polymers via mineralization. The objective of this review is to outline the advances made in the microbial degradation of synthetic plastics and, overview the enzymes involved in biodegradation.
301 citations
TL;DR: The different stages of biodegradation are described and several techniques used by some authors working in this domain are state, including use of various techniques for the analysis of degradation in vitro.
Abstract: Biodegradation is considered to take place throughout three stages: biodeterioration, biofragmentation and assimilation, without neglect the participation of abiotic factors. However, most of the techniques used by researchers in this area are inadequate to provide evidence of the final stage: assimilation. In this review, we describe the different stages of biodegradation and we state several techniques used by some authors working in this domain. Validate assimilation (including mineralization) is an important aspect to guarantee the real biodegradability of items of consumption (in particular friendly environmental new materials). Since LDPE is considered to be practically inert, efforts were made to isolate unique microorganisms capable of utilizing LDPEs. Recent data showed that biodegradation of LDPE waste with selected microbial strains became a viable solution. Among biological agents, microbial enzymes are one of the most powerful tools for the biodegradation of LDPEs. Activity of biodegradation of most enzymes is higher in fungi than in bacteria. It is important to consider fungal degradation of LDPE in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of LDPEs have been carried out in order to overcome the environmental problems associated with LDPE waste. This paper reviews the current research on the biodegradation of LDPEs and also use of various techniques for the analysis of degradation in vitro.
253 citations
References
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Book•
01 Jan 1990
TL;DR: In this paper, a two volume publication provides an overview of processes developed to inhibit oxidative deterioration of organic materials, including the major mechanisms involved, oxidation inhibitors classes, and practices in oxidation inhibition.
Abstract: This two volume publication provides an overview of processes developed to inhibit oxidative deterioration of organic materials. It discusses aspects of auto-oxidation, photo-oxidation and combustion, the major mechanisms involved, oxidation inhibitors classes, and practices in oxidation inhibition. The books include physical phenomena in polymer oxidation, and thermoanalytical methods for studying oxidation inhibition. Covered are analytical methods for inhibitors in organic materials, and scientific and technical prospects in the stabilization of organic materials. This comprehensive title is useful for investigators and students at all levels who have interest in polymer sciences.
284 citations
TL;DR: In this article, the role of metal compounds in the degradation of polyolefins has been investigated and some typical examples of degradation by metallic compounds, mostly commercial pigments and transition metal compounds of stearic acid and acetylacetone, in typical commercial polymers are discussed.
141 citations
TL;DR: The weak chemiluminescence observed when partially oxidised samples of polypropylene are heated in an inert atmosphere has been studied as a function of oxidation as discussed by the authors, and the integrated luminescence is shown to be proportional to titratable peroxides in the early stages of oxidation but the relation is curved at higher oxidation levels.
103 citations
TL;DR: Differential thermal analysis offers a convenient and rapid way of determining stabilization levels in polyolefin compositions as discussed by the authors, however, because the chemistry of the polymer system at these temperatures may be quite different from that at normal use temperatures, judgment must be exercised in attempting to extrapolate high temperature data.
Abstract: Differential thermal analysis offers a convenient and rapid way of determining stabilization levels in polyolefin compositions. Since it is normally used at temperatures in the fabrication range, it provides a direct readout of processing stability. At the same time, because the chemistry of the polymer system at these temperatures may be quite different from that at normal use temperatures, judgment must be exercised in attempting to extrapolate high temperature data. New factors can come in at either end of the temperature range which are inoperative at the other extreme.
The experimental procedures used are described, and the special precautions necessary for operation down to the 140–150°C range indicated. Problems arising from sample inhomogeneities are discussed, and the critical importance of stabilizer migration in the solid state pointed out, including invalidation of extrapolation down to normal temperatures of data taken above the melting range.
69 citations