Molecular Modification and Compatibilization of Collected Polyethylene

The increasing use of plastics in packaging materials leads to growing amounts of plastic waste. Recycling material is generally regarded as advantageous. But in fact very few products are made from plastic waste, partly this can be explained by that little is known about the recycling process and the properties of collected materials. There is a need for injection moulding grades of recycled polyethylene, while large amounts of extrusion grades are available from packaging waste. A controlled way of de-branching or partly degrading PE would be desirable. Peroxides are commonly used to crosslink polyolefins, but under certain conditions a chain scission reaction occur. Another problem encountered with recycling of polyethylene are the poor miscibility of low amounts contaminations, i. e. polypropylene. A compatibilizer can improve properties of such polymer blends, in this work EPDM is used as compatibilzer. Studies of mechanical properties and viscosity measurements show that it is possible to partly degrade PE with peroxide exposing it to high temperature and oxygen. The properties of PE/PP blends were improved with EPDM as compatibilizer.     

Use of recycled fine aggregate in concretes with durable requirements

The use of construction waste materials as aggregates for concrete production is highly attractive compared to the use of non-renewable natural resources, promoting environmental protection and allowing the development of a new raw material. Several countries have recommendations for the use of recycled coarse aggregate in structural concrete, whereas the use of the fine fraction is limited because it may produce significant changes in some properties of concrete. However, during the last decade the use of recycled fine aggregates (RFA) has achieved a great international interest, mainly because of economic implications related to the shortage of natural sands suitable for the production of concrete, besides to allow an integral use of this type of waste. In this study, the durable behaviour of structural concretes made with different percentage of RFA (0%, 20%, and 30%) is evaluated. Different properties related to the durability of concretes such as absorption, sorptivity, water penetration under pressure, and carbonation are determined. In addition, the results of compressive strength, static modulus of elasticity and drying shrinkage are presented. The obtained results indicate that the recycled concretes have a suitable resistant and durable behaviour, according to the limits indicated by different international codes for structural concrete.     

Molding Method, Thermal and Mechanical Properties of Jute/PLA Injection Molding

Natural composites have been important materials system due to preservation of earth environments. Natural fibers such as jute, hemp, bagasse and so on are very good candidate of natural composites as reinforcements. On the other hand regarding matrix parts thermosetting polymer and thermoplastic polymer deriver form petrochemical products are not environmental friendly material, even if thermoplastic polymer can be recycled. In order to create fully environmental friendly material (FEFM) biodegradable polymer which can be deriver from natural resources is needed. Therefore poly(lactic acid) (PLA) polymer is very good material for the FEFM. In this paper jute fiber filled PLA resin (jute/PLA) composites was fabricated by injection moldings and mechanical properties were measured. It is believable that industries will have much attention to FEFM, so that injection molding was adopted to fabricate the composites. Long fiber pellet fabricated by pultrusion technique was adopted to prepare jute/PLA pellet. Because it is able to fabricate composite pellets with relative long length fibers for injection molding process, where, jute yarns were continuously pulled and coated with PLA resin. Here two kinds of PLA materials were used including the one with mold releasing agent and the other without it. After pass through a heated die whereby PLA resin impregnates into the jute yarns and sufficient cooling, the impregnated jute yarns were cut into pellets. Then jute/PLA pellets were fed into injection machine to make dumbbell shape specimens. In current study, the effects of temperature of PLA melting temperature i.e. impregnation temperature and the kinds of PLA were focused to get optimum molding condition. The volume fractions of jute fiber in pellet were measured by several measuring method including image analyzing, density measurement and dissolution methods. Additionally, thermal and mechanical properties were investigated. It is found that 250° is much suitable for jute/PLA long fiber pultrusion process because of its less heat degradation of jute, better impregnation, acceptable mechanical property and higher production efficiency. Additionally the jute fibers seem much effective to increase deflection temperature under load, tensile modulus and Izod strength.     

Development of composite materials by mechanochemical treatment of post-consumer plastic waste

Improvement of mechanical properties of recycled mixed plastic waste is one of the fundamental goals in any recycling process. However, polymer immiscibility makes the development of any effective reprocessing method difficult. In this work, a polymer milling process with liquid CO2 was applied to polymeric mixed waste, obtaining a powder material which was successfully utilized as a matrix for a new composite material. Developed materials have interesting mechanical properties and material performance can easily be improved. Investigations on selected mixtures of PP and PE clearly showed evidence of chemical compatibilization.     

Mineral wool waste in Europe: a review of mineral wool waste quantity,quality, and current recycling methods

The construction and demolition (C&D) industry has been identified as a major source of waste. European Union legislation states that, by 2020, 70 % of C&D waste must be prepared for reuse, recycled or recovered. European Union member states must increase their C&D waste recycling percentages in order to meet this binding target. Utilization of mineral wool waste, often considered unrecyclable, could improve the recycling percentage of C&D waste. In this article, mineral wool production and waste volumes are estimated based on information from the Eurostat database. A literature survey is conducted to collect information about mineral wool material properties, current recycling methods, and barriers to recycling of mineral wool, and suitable methods for separating mineral wool from C&D waste streams and the economic viability of mineral wool recycling are discussed. It is noted that accurate estimation of mineral wool waste volumes is problematic due to the fragmented nature of available data. Based on the literature review, current methods for recycling mineral wool waste include utilization of mineral wool waste as a raw material in various products. Barriers to recycling include economic questions and issues related to the purity and health effects of mineral wool waste. Material properties of mineral wool waste, such as fire resistance, could provide improved properties in products utilizing mineral wool waste as a raw material.     

Rheological, Mechanical and Thermal Behaviour of Wood Polymer Composites Based on Recycled Polypropylene

The aim of this paper was to investigate the effect of recycled polypropylene (PP) on the rheological, mechanical and thermal properties of wood flour polypropylene composites. Beforehand, the influence of wood flour treated with a coupling agent on the rheological behaviour had been looked at. By analysing moduli and viscosity curves and studying the thermal and mechanical properties of samples with 10% filler it was possible to see that the recycled PP that was added change in either its physical properties or its rheology. In the other wood plastic composites (WPC) studied, slight changes in the rheology behaviour were observed. However, the same processing parameters may be used with and without recycled PP. Recycled PP is appropriate for these kinds of composites to maintain the optimal rheological properties that make it easier to process the material by extrusion. Furthermore, it is also possible to maintain the thermal and mechanical properties in comparison with the behaviour of virgin PP/wood flour composites.     

Amino-Modified Halloysite Nanotubes to Reduce Polymer Degradation and Improve the Performance of Mechanically Recycled Poly(lactic acid)

From an environmental point of view, mechanical recycling is, in general, a good end-of-life option for poly(lactic acid) (PLA), one of the most important biobased polymers. However, the degradation of PLA during the service life and, especially, during the mechanical recycling process, leads to a decrease in the properties of PLA, thus reducing the applications of the recycled plastic. The main aim of this work was to study the addition of small amounts of halloysite nanotubes, during the recycling step, as the basis of a cost-effective method for improving the properties of the recycled PLA. Raw halloysite was modified with an aminosilane, and 2% by weight of both raw and modified halloysite were melt compounded with PLA previously subjected to accelerated ageing. The addition of the nanotubes led to recycled materials with improved properties because halloysite reduces the degradation of PLA by blocking the carboxyl groups, generated during the ageing and washing steps, which catalyze the degradation during the recycling process. This effect was more intense in the silanized nanotubes, because the carboxyl groups were effectively blocked by acid–base interactions with the amino groups of the chemical modification. The properties of the recycled plastic with only 2 wt% of silanized halloysite were very close to those of the virgin plastic.     

Blends of HDPE wastes: study of the properties

In this work we have analysed the properties of blends of recycled high-density polyethylene (HDPE) filled with talc. We have used two kinds of polymer matrices. The first one came entirely from ground injection moulded parts whereas the second was bimodal, incorporating 80% of the previous HDPE and 20% of recycled HDPE coming from bottles. We have also used two kinds of commercial talc characterized by a medium particle size of 2 microm and 10 microm, respectively. The amount of talc added to both matrices weighed of 10% and 20%. With regards to the mechanical properties of the analysed composites, greater values of Young's modulus and break stresses were found using a smaller particle size and higher talc content. On the other hand, the combination of the two HDPEs with very different viscosities produced a notable increase in the strain at break and in the absorbed energy; both measured at high and low strain rates. Despite the differences in viscosities between the two HDPEs, we did not observe separation of phases during either the processing or testing. Under impact loading, the higher energy absorption in the composites was observed when the finest talc grade with a 10% content weight was added to the bimodal matrix.     

Leaching assessment of concrete made of recycled coarse aggregate: Physical and environmental characterisation of aggregates and hardened concrete

Each year, millions of tonnes of waste are generated worldwide, partially through the construction and demolition of buildings. Recycling the resulting waste could reduce the amount of materials that need to be manufactured. Accordingly, the present work has analysed the potential reuse of construction waste in concrete manufacturing by replacing the natural aggregate with recycled concrete coarse aggregate.However, incorporating alternative materials in concrete manufacturing may increase the pollutant potential of the product, presenting an environmental risk via ground water contamination.The present work has tested two types of concrete batches that were manufactured with different replacement percentages. The experimental procedure analyses not only the effect of the portion of recycled aggregate on the physical properties of concrete but also on the leaching behaviour as indicative of the contamination degree. Thus, parameters such as slump, density, porosity and absorption of hardened concrete, were studied. Leaching behaviour was evaluated based on the availability test performed to three aggregates (raw materials of the concrete batches) and on the diffusion test performed to all concrete.From an environmental point of view, the question of whether the cumulative amount of heavy metals that are released by diffusion reaches the availability threshold was answered. The analysis of concentration levels allowed the establishment of different groups of metals according to the observed behaviour, the analysis of the role of pH and the identification of the main release mechanisms. Finally, through a statistical analysis, physical parameters and diffusion data were interrelated. It allowed estimating the relevance of porosity, density and absorption of hardened concrete on diffusion release of the metals in study.     

Wood Polypropylene (PP) Composites Manufactured by Mango Wood Waste with Virgin or Recycled PP: Mechanical,Morphology, Melt Flow Index and Crystalline Behaviour

Compositions of wood-polypropylene composites (WPCs) are prepared through melt compounding followed by injection moulding. WPCs are formulated for eight compositions with a different weight ratio of wood, virgin or recycled polypropylene and coupling agent. WPCs compositions are compared in terms of Melt Flow Index, Tensile, FESEM images, Flexural and crystallinity index for same operating variable conditions. From the results, recycled polypropylene based WPCs are superior in comparison to virgin polypropylene based WPCs. With the addition of 5 % coupling agent in recycled polypropylene-based composites for 45:50 composition, tensile and flexural values of WPCs are higher in comparison to all composition and neat virgin or recycled polypropylene. This work stands for the utilization of waste wood with recycled plastic for replacement of wood and virgin plastic.     

Effect of carbon dioxide injection on production of wood cement composites from waste medium density fiberboard (MDF)

The possibility of recycling waste medium density fiberboard (MDF) into wood-cement composites was evaluated. Both new fibers and recycled steam exploded MDF fibers had poor compatibility with cement if no treatment was applied, due to interference of the hydration process by the water soluble components of the fiber. However, this issue was resolved when a rapid hardening process with carbon dioxide injection was adopted. It appears that the rapid carbonation allowed the board to develop considerable strength before the adverse effects of the wood extractives could take effect. After 3-5 min of carbon dioxide injection, the composites reached 22-27% of total carbonation and developed 50-70% of their final (28-day) strength. Composites containing recycled MDF fibers had slightly lower splitting tensile strength and lower tensile toughness properties than those containing new fibers especially at a high fiber/cement ratio. Composites containing recycled MDF fibers also showed lower values of water absorption. Unlike composites cured conventionally, composites cured under CO(2) injection developed higher strength and toughness with increased fiber content. Incorporation of recycled MDF fibers into wood cement composites with CO(2) injection during the production stage presents a viable option for recycling of this difficult to manage waste material.     

Optimizing a recycling process of SMC composite waste

Investigations about the recycling of sheet moulding compounds (SMC) waste as incorporation material for thermoplastic polymer matrix are reported in this paper. A new efficient process is developed in order to strongly increase the reinforcement glass fraction of SMC leading to good mechanical performance of the new thermoplastic compounds. The overall process is composed of two main steps: mechanical and chemical. The second stage is characterised in terms of optimization and capability by means of experimental design and statistical process control techniques for finding the optimal chemical conditions and validating the process.     

Modification of mechanical properties of recycled polypropylene from post-consumer containers

This study is conducted to look at the modification of mechanical properties of recycled polypropylene (PP) from post-consumer containers with the addition of stabilizers, elastomer (ethylene-octene rubber, EOR) and calcium carbonate (CaCO(3)). The mechanical and thermal properties of the blends were evaluated. The results showed limited changes with the addition of elastomer and calcium carbonate on the mechanical properties of the recycled polypropylene. Some differences were observed, but the trends were not reproducible over the different compositions. DSC analysis confirmed the presence of polyethylene (PE) in the recycled polypropylene. The polyethylene impurity and the presence of many different qualities of polypropylene in the recycled material may have prevented any possible improvement in the mechanical properties by the addition of EOR and CaCO(3), improvements seen in previous studies on virgin polypropylene. The compatibility of the different homopolymers and copolymers of PP used in consumer packaging is not known, while polyethylene and polypropylene are known not to be miscible with each other. The mixture of qualities and materials may explain such a poor blending. Reusing and upgrading of recycled PP from post-consumer containers would therefore first require a better sorting of the post-consumer waste. The use of an adequate compatibilizer that would allow a uniform and homogeneous blending of the raw material mixture might enhance the mechanical properties.     

A new approach to metal- and polymer-recovery from metallized plastic waste using mechanical treatment and subcritical solvents

Galvanized or “chromium-plated” plastics are well known to the consumer from the automotive sector and sanitary area. Polymers such as acrylonitrile butadiene styrene (ABS) are typically coated with a layer system of chromium, nickel and copper to obtain the characteristic optical surface and resistance properties. Due to the complex manufacturing process and high quality requirements, the production of these plastic metal composites generates 10–30% of rejects. We, therefore, developed an innovative process cascade for the recovery of both components (metal and polymer) applying established technologies (mechanical pre-treatment, classification, melt filtration, CreaSolv^® Process) and were able to obtain ABS regranulate having excellent properties regarding the characteristic values for strength but slight compromises in impact characteristics. Blends with different amounts of virgin ABS, virgin PC and recycled ABS material as well as the pure cases were successfully re-metallized, all of them passing adhesion test, thermal shock resistance and CASS test. The high purity of the recovered materials led to increased redemption prices for metal and polymer by a factor of 6 and 2.5, respectively. Thus, the value added of metallized plastic waste is maximized, revealing a highly positive economic prognosis of a commercial implementation of the developed process—even at moderate scale.     

Hydrothermal recycling of waste and performance of the recycled wooden particleboards

Recycling today constitutes the most environmentally friendly method of managing wood waste. A large proportion of the wood waste generated consists of used furniture and other constructed wooden items, which are composed mainly of particleboard, a material which can potentially be reused. In the current research, four different hydrothermal treatments were applied in order to recover wood particles from laboratory particleboards and use them in the production of new (recycled) ones. Quality was evaluated by determining the main properties of the original (control) and the recycled boards. Furthermore, the impact of a second recycling process on the properties of recycled particleboards was studied. With the exception of the modulus of elasticity in static bending, all of the mechanical properties of the recycled boards tested decreased in comparison with the control boards. Furthermore, the recycling process had an adverse effect on their hygroscopic properties and a beneficial effect on the formaldehyde content of the recycled boards. The results indicated that when the 1st and 2nd particleboard recycling processes were compared, it was the 2nd recycling process that caused the strongest deterioration in the quality of the recycled boards. Further research is needed in order to explain the causes of the recycled board quality falloff and also to determine the factors in the recycling process that influence the quality degradation of the recycled boards.     

Monotonic aspects of the mechanical behaviour of bottom ash from municipal solid waste incineration and its potential use for road construction

Municipal solid waste incineration (MSWI) bottom ash is an atypical granular material because it may include industrial by-products that result from the incineration of domestic waste. The prospects for the beneficial use of this particular material mainly lie in the field of road construction, as a substitute for the traditional natural aggregates. However, its mechanical properties are still little known, particularly in term of stiffness and deformability, characteristics that are essential to the construction of a durable roadway. The purpose of this paper is to describe better the mechanical behaviour of this recycled material. In order to reach this objective, a large experimental campaign is presented. The first part of this paper presents and comments in detail on the results obtained from static monotonic tests. Oedometric and triaxial shear tests were performed on MSWI bottom ash both before and after treatment with a specific hydraulic binder. These tests allow specification of the mechanical characteristics of the MSWI bottom ash, such as the initial Young's modulus, Poisson's ratio, the compressibility index, the friction angle, and the contracting or dilating behaviour of the material. The results reveal a mechanical behaviour similar to that of initially dense standard materials (sands, unbound granular materials) and a dependence on the applied average pressure, characteristic of the mechanical behaviour of granular media. More laboratory data on other samples of MSWI bottom ash are required to ensure that this comparison is statistically valid.     

Processing and Properties of Biopolymer/Polyhydroxyalkanoates Blends

In this paper, the processability and the performance of a biodegradable polymer, Mater-Bi, and of its blends with either a sample of poly (hydroxy alkanoates) (PHA) or with bacterial biomass containing PHAs were compared. Adding PHA or directly the biomass containing it allows improving the processability of the matrix. Moreover, the mechanical behaviour of the systems was compared considering two different preparation methods, namely compression and injection moulding. The injection moulded samples show poorer mechanical performances than those of the compression moulded systems. The impact strength significantly improves when PHA is added while it reduces when bacterial biomass is used instead. In this latter case this was likely due to the easier propagation of micro-cracks during the impact tests.     

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.     

LDPE/EPDM Multilayer Films Containing Recycled LDPE for Greenhouse Applications

In this paper the reuse of recycled LDPE in combination with the incorporation of EPDM modifier in the production of greenhouse films has been investigated. A three-layer film (60-100-40 micron thickness) containing recycled LDPE in the middle layer and a high UV-stabilized 40-micron outer layer was developed and proven to be commercially successful. Films with 25% and 50% recycled material content were produced. The effect of natural weathering on the film properties over a period of 15 months has been observed. Changes in physical and mechanical property were determined. The addition of EPDM to the raw resin was found to improve the extrudability of the compound and improve the weather resistivity of the film. The EPDM-modified films containing 25% to 50% recycled material retained approximately 95% and 75%, respectively, of their original extensibility after 9 months' exposure to natural weathering. Optimization of EPDM and UV stabilizer concentration was carried out to develop a balanced film with excellent mechanical and physical properties and resistance to weathering conditions. The use of UV stabilizer concentrations slightly higher than commercial practice in the outer layer of the multilayer film can be justified by the cost reduction by the incorporation of recycled LDPE materials.