Flammability Properties of Virgin and Recycled Polycarbonate (PC) and Acrylonitrile–Butadiene–Styrene (ABS) Recovered from End-of-Life Electronics

Acrylonitrile–Butadiene–Styrene (ABS), Polycarbonate (PC) and their alloys are widely used in automotive industry, computer and equipment housings. With increasing disposal of end-of-life electronic equipment, there is also an increased demand for recycling of these materials so that they do not pose environmental challenge as solid waste. One of the recycling approaches is mechanical recycling of these thermoplastics where recycled plastic is melt blended with virgin materials to obtain a high quality product. Besides obtaining desirable mechanical properties, such blends should also conform to fire safety standards. In this work, a series of blends were prepared using PC and ABS recovered from discarded computers and virgin materials using a twin-screw extruder. Their flammability properties were evaluated using burner flammability tests and Ohio State University (OSU) release rate tests. It was found that the extinguishing time, burning extent and weight loss appears to progressively decrease with the addition of both virgin or recycled PC to virgin or recycled ABS. It was also seen that the addition of the 70% of PC, virgin or recycled, to ABS virgin or recycled, appears to significantly decrease heat release and smoke evolution. The results of this study indicate that recycled polycarbonate can be used as an additive for virgin or recycled ABS, as a means of giving flame resistance to ABS in high-value applications. This result is significant when related to the result obtained by a separate study indicating that up to 25% of recycled material can be used without degradation of mechanical properties in the presence of 15% short glass fiber reinforcement.     

Chemical Recovery of Useful Chemicals from Polyester (PET) Waste for Resource Conservation: A Survey of State of the Art

In this paper we present the main technologies developed over the last decades on chemical recycle of PET from a practical and economical point of view. We show details of plants used to carry out solvolitic reactions emphasising steps of purification, which are sometimes not considered when discussing chemical, recycle but which, in fact, are the key feasibility factors. The recycling or modification of PET to obtain monomers and other useful chemicals as intermediates and additives is carefully considered.     

Evaluation of recycling policies for PET bottles based on multiattribute utility indices

This study focused on waste plastic, especially the polyethylene telephthalate (PET) bottle as representative waste, which has been assigned as goods to be recycled by the Packaging Waste Recycling Law in Japan. We developed a plastic transport model which explained the entire flow of plastic from the production stage to the disposal stage within an the evaluation model of plastic recycle policy based on multiattribute utility theory. This model is designed to be used by local municipal governments in supporting the evaluation of the PET bottle recycling policy. In evaluating the plastics recycling policy, we selected indices relating to economy, ecology, and rate of resource recycling. The results indicate that when the evaluation of the material recycling policy and thermal recycling policy in the model city were characterized in terms of their economic and environmental aspects the thermal recycling policy had the highest utility within our scenario. Received: July 31, 1998 / Accepted: January 26, 1999     

On the effect of MSW moisture content on meeting target recycling rates

A mathematical model to calculate the recycle rates for packaging materials from the municipal solid wastes (MSW) built from the dry mass values that are obtained from the corresponding wet masses and their respective moisture contents is presented in this work. A possible universal methodology is also described to be used with the previous model so that reliable comparisons between indicators for different regions are feasible. Furthermore, this mathematical model demonstrates the effect of the moisture content of packaging materials on their recycling rates and constitutes a fundamental tool for operators and persons responsible for MSW management to define new policies and technical measures viewing the improvement of recycling rates. A theoretical study and the application of the model to the MEMSW of the Lisbon region shows that the moisture content of the mixed wastes plays a dominant role in the recycling rates of packaging materials such as paper, plastics and glass. Moreover, accounting for all relevant masses in the dry basis yields higher recycling rate values: increases of 32.8% for paper, 50% for plastics and 44.6% glass are observed.     

From Aminolysis Product of PET Waste to Novel Biodegradable Polyurethanes

Chemical recycling of PET has been developed by various methods. Aminolysis is one of chemical recycling methods of PET has been developed recently. The obtained product using aminolysis, Bis (2-hydroxy ethylene) terephthalamide (BHETA), has the potential for further reactions to obtain useful products. There are few reports on usage of recycled BHETA from PET waste to synthesis of polyurethanes. On the other hand, various biodegradable polyurethanes have been synthesized using polycaprolactone diol. Therefore, caprolactone is a new potential in synthesis of biodegradable polyurethanes from PET waste. In this work, novel biodegradable polyurethanes have been synthesized using BHETA. In this order, at first polyols with different molecular weights have been synthesized through ring opening polymerization of caprolactone by BHETA, then urethane linkages were formed using HDI (Hexamethylene Diisocyanate) without chain extender. Chemical, thermal, mechanical and dynamic mechanical properties, biodegradability, morphology and UV resistance of synthesized polyurethanes have been investigated.     

Behaviour and opinions concerning a mandatory newspaper recycling programme: A statistical correlation analysis

Source-separation recycling of municipal waste is becoming increasing popular in the USA and Canada, but little is known concerning the behaviour and opinions of residents subject to recycling programmes. Residents of a Pennsylvania county subject to a mandatory newspaper recycling programme in 1985 were surveyed in 1986 concerning their behaviour and opinions with respect to that programme. Survey responses were analysed by Pearson correlation and other statistical methods. Among the conclusions of that analysis are the following: The use of drop-off sites did not decrease recycling rates; Newspaper publicity can increase recycling rates; Larger households required more time than smaller for recycling compliance; Willingness to recycle additional materials decreases as time spent on current recycling activities increases.     

Physical and mechanical properties of mortars containing PET and PC waste aggregates

Non-biodegradable plastic aggregates made of polycarbonate (PC) and polyethylene terephthalate (PET) waste are used as partial replacement of natural aggregates in mortar. Various volume fractions of sand 3%, 10%, 20% and 50% are replaced by the same volume of plastic. This paper investigates the physical and mechanical properties of the obtained composites. The main results of this study show the feasibility of the reuse of PC and PET waste aggregates materials as partial volume substitutes for natural aggregates in cementitious materials. Despite of some drawbacks like a decrease in compressive strength, the use of PC and PET waste aggregates presents various advantages. A reduction of the specific weight of the cementitious materials and a significant improvement of their post-peak flexural behaviour are observed. The calculated flexural toughness factors increase significantly with increasing volume fraction of PET and PC-aggregates. Thus, addition of PC and PET plastic aggregates in cementitious materials seems to give good energy absorbing materials which is very interesting for several civil engineering applications like structures subjected to dynamic or impact efforts. The present study has shown quite encouraging results and opened new way for the recycling of PC waste aggregate in cement and concrete composites.     

Injection Molded Wheat Straw and Corn Stem Filled Polypropylene Composites

Environmentally friendly composite materials can be prepared using wood fibers and/or various types of agro-derived fibers as reinforcements. In this study, agro-residues such as wheat straw and corn stem filled polypropylene were prepared and their suitability was investigated as a reinforcing filler in thermoplastics and as an alternative to the wood flour filled plastics. Effect of compounding techniques, compatibilizer and fungal treatment of agro-residues on the mechanical properties of the composites were evaluated. It was found that high shear compounding of wheat straw fibers exhibited similar properties to that produced by the milled wheat straw. This may be due to the extensive fiber breakage occurred during the high shear compounding that results in a similar aspect ratio to that of milled straw. Compatibilizer is needed for improving the strength properties of the agro-residue filled PP composites. Fungal treatment of milled wheat straw did not show much improvement in the strength properties of the composites. Comparison of mechanical properties of the agro-residue filled PP with that of the wood flour and the old newsprint filled PP showed the suitability of the agro-residues as alternative filler for thermoplastics.     

Selective separation of virgin and post-consumer polymers (PET and PVC) by flotation method

More and more polymer wastes are generated by industry and householders today. Recycling is an important process to reduce the amount of waste resulting from human activities. Currently, recycling technologies use relatively homogeneous polymers because hand-sorting waste is costly. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. At present, most waste polymers cause serious environmental problems. Burning polymers for recycling is not practiced since poisonous gases are released during the burning process. Particularly, polyvinyl chloride (PVC) materials among waste polymers generate hazardous HCl gas, dioxins containing Cl, etc., which lead to air pollution and shorten the life of the incinerator. In addition, they make other polymers difficult to recycle.Both polyethylene terephthalate (PET) and PVC have densities of 1.30–1.35 g/cm³ and cannot be separated using conventional gravity separation techniques. For this reason, polymer recycling needs new techniques. Among these techniques, froth flotation, which is also used in mineral processing, can be useful because of its low cost and simplicity.The main objective of this research is to recycle PET and PVC selectively from post-consumer polymer wastes and virgin polymers by using froth flotation. According to the results, all PVC particles were floated with 98.8% efficiency in virgin polymer separation while PET particles were obtained with 99.7% purity and 57.0% efficiency in post-consumer polymer separation.     

Valorization of post-consumer waste plastic in cementitious concrete composites

The sheer amount of disposable bottles being produced nowadays makes it imperative to identify alternative procedures for recycling them since they are non-biodegradable. This paper describes an innovative use of consumed plastic bottle waste as sand-substitution aggregate within composite materials for building application. Particularly, bottles made of polyethylene terephthalate (PET) have been used as partial and complete substitutes for sand in concrete composites. Various volume fractions of sand varying from 2% to 100% were substituted by the same volume of granulated plastic, and various sizes of PET aggregates were used. The bulk density and mechanical characteristics of the composites produced were evaluated. To study the relationship between mechanical properties and composite microstructure, scanning electron microscopy technique was employed. The results presented show that substituting sand at a level below 50% by volume with granulated PET, whose upper granular limit equals 5mm, affects neither the compressive strength nor the flexural strength of composites. This study demonstrates that plastic bottles shredded into small PET particles may be used successfully as sand-substitution aggregates in cementitious concrete composites. These new composites would appear to offer an attractive low-cost material with consistent properties; moreover, they would help in resolving some of the solid waste problems created by plastics production and in saving energy.     

Improvement of Waste Recycling in PET Fiber Production

Production of polyethylene teraphtalate (PET) fiber in the world is increasing every year and reached to an amount of about 20 million tons a year in 2001. The wastes occur in the production of PET fiber in the amount of about 3–5% of total production. The PET does not degrade for a long time in nature. Since PET is a derivative of petroleum, the wastes of PET are valuable and must be recycled. One of the recycling method of PET wastes is re-melting. Thus, various properties of the PET wastes were improved using the re-melting method by employing an extruder manufactured for the work. Degradation during re-melting decreases the properties of the final product. The results indicate that the properties of recycled PET wastes can be monitored by designing the parameters of the extruder. Also, the further degradation of the material can be prevented and the recycling costs are minimized.     

Effect of Nanoscale SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> as the Fillers on the Mechanical Properties and Aging Behavior of Linear Low-Density Polyethylene/Low-Density Polyethylene Blends

Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO₂ and TiO₂ at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO₂ contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO₂ and TiO₂, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area.     

The consumption and recycling collection system of PET bottles: A case study of Beijing,China

After studying the recycling collection system of polyethylene terephthalate (PET) bottles worldwide, the authors conducted an intercept survey in Beijing. Two separate questionnaires were issued, one questionnaire to PET bottle consumers and one to PET bottle recyclers. In this study, consumers are defined as people that consume PET-bottled beverages in their daily life. Recyclers were defined as those involved in the collection and recycling of PET bottles. These include scavengers, itinerant waste buyers, small community waste-buying depots, medium/large redemption depots, and recycling companies. In total, 580 surveys were completed, including 461 by consumers and 119 by recyclers. The authors found that consumption of PET bottles in Beijing was nearly 100,000 tonnes in 2012. Age, occupation, gender, and education were identified as significant factors linked to PET-bottled beverage consumption, while income was not a significant factor. 90% Of post-consumed PET bottles were collected by informal collectors (i.e., scavengers and itinerant waste buyers). The survey also found that nearly all PET bottles were reprocessed by small factories that were not designed with pollution control equipment, which allows them to offer higher prices for waste recyclable bottles. As Beijing is trying to build a formal recycling collection system for recyclables, subsidies should be given to the formal recycling sector rather than being charged land use fees, and attention should also be given to informal recyclers that make their living from the collection of recyclables. Informal and formal sectors may work together by employing the scavengers and itinerant waste buyers for the formal sectors. In addition to the recycling of PET bottles, concern should also be allocated to reduce consumption, especially among young people, as they, compared to other groups, have a stronger demand for PET-bottled beverages and will be the main body of society.     

Crystallization and Mechanical Properties of Recycled Poly(ethylene terephthalate) Toughened by Styrene–Ethylene/Butylenes–Styrene Elastomer

Recycled poly(ethylene terephthalate) (R-PET) was blended with 15–30 wt% of styrene–ethylene/butylenes–styrene (SEBS) block copolymer and maleic anhydride grafted SEBS (SEBS-g-MA). Effects of nucleation and toughening of the elastomers were evaluated systematically by study of morphology, crystallization, thermal and mechanical properties of the blend. The addition of 30 wt% SEBS promoted the formation of co-continuous structure of the blend and caused the fracture mechanism to change from strain softening to strain hardening. Addition of SEBS-g-MA resulted in significant modification of phase morphology and obviously improved the impact strength. The compatibilization reaction of PET with SEBS-g-MA accelerated the crystallization of PET and increased the crystallinity. The shifts in glass transition temperature of PET towards that of SEBS-g-MA and the higher modulus for R-PET/SEBS-g-MA (70/30) blend found by DMA are also indications of better interactions under the conditions of compatibilization and interpenetrating structure.     

Developments in an industry-led R&D program for recycling PVC products in Japan

To facilitate recycling, not only R&D but also the creation of efficient recycling systems—collection and processing of recyclates as well as finding appropriate end-uses—is essentially important. PVC has a particular advantage in regards to mechanical recycling when compared to other major plastics. However, there is no one-size-fits-all approach to a solution. Specific situations of used or off-cut products and their applications need to be well studied. Vinyl industry in Japan has devoted itself for many years to the promotion of recycling of vinyl products. It started an R&D support program in 2007 and seven projects have been completed since then. Some of the new developments include mechanical recycling for products like wall covering and tarpaulin which were considered difficult to recycle in the past. Progress in chemical recycling has been made with a technology for the removal of chlorine from shredder dusts. Recovery of chlorine is a challenge for the future. Collaboration among the various players involved in the recycling of a specific product is essential for obtaining a successful result.     

Synthesis and Characterization of Polyols and Polyurethane Foams from PET Waste and Crude Glycerol

In this study, polyethylene terephthalate (PET) waste from post-consumer soft-drink bottles and crude glycerol from the biodiesel industry were used for the preparation of polyols and polyurethane foams. PET waste was firstly depolymerized by the glycolysis of diethylene glycol. The glycolyzed PET oligomers were then reacted with crude glycerol at different weight ratios to produce polyols via a series of reactions, such as esterification, transesterification, condensation, and polycondensation. The polyols were characterized by titration, viscometry, gel permeation chromatography (GPC), and differential scanning calorimetry. Subsequently, polyurethane (PU) foams were made via the reaction between the produced polyols and polymeric methylene-4,4′-diphenyl diisocyanate and were characterized by mechanical testing, scanning electron microscopy, and thermogravimetric analysis. Polyols from crude glycerol and their PU foams were also prepared to compare properties with those of polyols and PU foams from PET and crude glycerol. The influence of aromatic segments existing in glycolyzed PET and glycerol content on the properties of the polyols and PU foams was investigated. It was found that aromatic segments of polyols from glycolyzed PET helped increase their molecular weights and improve thermal stability of PU foams, while high glycerol content in polyols increased the hydroxyl number of polyols and the density and compressive strength of PU foams.     

Reutilization of thermostable polyester wastes by means of agglomeration with phenolic resins

We report on the possibility of obtaining organic polymeric matrixes allowing the development of new high performance fire-resistant products by recycling downsized thermostable waste materials. Phenolic resins have been used as binders for recycled waste. Furthermore, considering that reinforced plastic triturations have superior properties (chemical, mechanical, water resistance, etc.) to wood agglomerates, significant advantages over conventional materials are anticipated. In summary, we propose a viable solution to some of the known problems caused by the consumption of wood and to the needs of strengthened plastic processing engineering. Using resins as a binder, several fire-resistant prototypes were prepared from polyester waste, and their mechanical properties, thermal stability, and fire-resistant properties were analyzed.     

Modification of Thermo-Mechanical Properties of Recycled PET by Vinyl Acetate (VAc) Monomer Grafting Using Gamma Irradiation

Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25?% to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83?%. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95?°C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.     

Waste collection systems for recyclables: An environmental and economic assessment for the municipality of Aarhus (Denmark)

Recycling of paper and glass from household waste is an integrated part of waste management in Denmark, however, increased recycling is a legislative target. The questions are: how much more can the recycling rate be increased through improvements of collection schemes when organisational and technical limitations are respected, and what will the environmental and economic consequences be? This was investigated in a case study of a municipal waste management system. Five scenarios with alternative collection systems for recyclables (paper, glass, metal and plastic packaging) were assessed by means of a life cycle assessment and an assessment of the municipality’s costs. Kerbside collection would provide the highest recycling rate, 31% compared to 25% in the baseline scenario, but bring schemes with drop-off containers would also be a reasonable solution. Collection of recyclables at recycling centres was not recommendable because the recycling rate would decrease to 20%. In general, the results showed that enhancing recycling and avoiding incineration was recommendable because the environmental performance was improved in several impact categories. The municipal costs for collection and treatment of waste were reduced with increasing recycling, mainly because the high cost for incineration was avoided. However, solutions for mitigation of air pollution caused by increased collection and transport should be sought.     

Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review

The world’s waste electrical and electronic equipment (WEEE) consumption has increased incredibly in recent decades, which have drawn much attention from the public. However, the major economic driving force for recycling of WEEE is the value of the metallic fractions (MFs). The non-metallic fractions (NMFs), which take up a large proportion of E-wastes, were treated by incineration or landfill in the past. NMFs from WEEE contain heavy metals, brominated flame retardant (BFRs) and other toxic and hazardous substances. Combustion as well as landfill may cause serious environmental problems. Therefore, research on resource reutilization and safe disposal of the NMFs from WEEE has a great significance from the viewpoint of environmental protection. Among the enormous variety of NMFs from WEEE, some of them are quite easy to recycle while others are difficult, such as plastics, glass and NMFs from waste printed circuit boards (WPCBs). In this paper, we mainly focus on the intractable NMFs from WEEE. Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glass are reviewed in this paper. For WEEE plastics, the pyrolysis technology has the lowest energy consumption and the pyrolysis oil could be obtained, but the containing of BFRs makes the pyrolysis recycling process problematic. Supercritical fluids (SCF) and gasification technology have a potentially smaller environmental impact than pyrolysis process, but the energy consumption is higher. With regard to WEEE glass, lead removing is requisite before the reutilization of the cathode ray tube (CRT) funnel glass, and the recycling of liquid crystal display (LCD) glass is economically viable for the containing of precious metals (indium and tin). However, the environmental assessment of the recycling process is essential and important before the industrialized production stage. For example, noise and dust should be evaluated during the glass cutting process. This study could contribute significantly to understanding the recycling methods of NMFs from WEEE and serve as guidance for the future technology research and development.