Recycled Composites Research Articles

Characterization of the dielectric endurance of reinforced recycled PET using electro-thermal aging test

This paper presents the advantages of dielectric characterization by electro-thermal aging testing in the durability analysis of reinforced recycled polyethylene terephthalate (PET), as compared to short-term dielectric breakdown strength measurements. Dielectric breakdown strength measurements were carried out at room temperature according to ASTM D149-a, while electro-thermal aging tests were conducted in air at different constant temperatures ranging from 140 to 170 °C, using an experiment setup comprising a cell test arranged in a point-to-plane configuration, with a very small air gap of 50±1 μm. The tests were conducted at an AC voltage of amplitude 7 kV rms on eight different reinforced recycled PET samples. The degradation of recycled PET-based composites during exposure to corona discharges at elevated temperatures was characterized by optical microscopy and scanning electron microscopy (SEM). The main goal of this study is to characterize and to determine the relationship between the addition of different inorganic reinforcements, such as mica and glass fibers, to a recycled PET matrix, as well as the resistance to dielectric failure during electro-thermal aging. The effect of plasticizers on the dielectric endurance of recycled PET-based composites was also investigated. Results obtained showed that glass fibers contribute to the enhancement of the resistance to dielectric failure. Our experiments also revealed that the dielectric behaviour of these composites can be affected by the presence of plasticizers. In addition, the size of additives such as mica can greatly improve the resistance to the dielectric breakdown caused by electrothermal aging.

ЗАРУБЕЖНЫЙ ОПЫТ РАЗВИТИЯ ПРОИЗВОДСТВА ИЗДЕЛИЙ С ИСПОЛЬЗОВАНИЕМ ВТОРИЧНО ПЕРЕРАБОТАННЫХ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ (обзор)

ЗАРУБЕЖНЫЙ ОПЫТ РАЗВИТИЯ ПРОИЗВОДСТВА ИЗДЕЛИЙ С ИСПОЛЬЗОВАНИЕМ ВТОРИЧНО ПЕРЕРАБОТАННЫХ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ (обзор)

Mechanical Characterization of Low Cost Natural Fiber Particles Reinforced with Polymer Composites

In the present decade, the center of concentration is on the growth of making polymer composites using agro wastes materials as reinforcements for recyclable composites. The objective of this work is to generate and investigate the mechanical properties of an eco-friendly low cost natural fiber reinforced polymer composite. Cotton Shell (CS) particles are less expensive natural fiber material which can be used as a filler material with Epoxy resin matrices. The filler material was integrated with Epoxy matrix in 0, 5, 10 and 15 weight %. Compression molding technique was used to prepare composites of Epoxy and CS. X-ray diffraction and Fourier transform infrared (FTIR) examination of the fibers revealed the existence of cellulose and lignin. Mechanical properties like Tensile, Impact and Hardness were examined. Results showed that the Tensile strength was increased with augment in particle loading and the impact strength decreases with the adding up of particle materials. Also it was observed that the hardness values are increasing with the increase in particle content.

Effect of recycling on polypropylene composites reinforced with glass fibres

The aim of the work was to investigate the effect of recycling on the mechanical behaviour of polypropylene composites reinforced with glass fibres (GFs), starting from a material already used in automotive for vehicle components, obtained by injection moulding. Formerly specimens of pristine composites were subjected to tensile and flexural tests, then the specimens were grinded, reprocessed and recycled only once. The recycled composites showed a slight decrease in the elastic modulus and tensile and flexural strength values. Morphological investigations, carried out by scanning electron microscopy and optical microscopy, were also performed to study the microstructure and the fibre–polymer interfaces, together with the GFs’ orientation and distribution within the polymeric matrix before and after the mechanical recycling. The results revealed that the mechanical recycling had no significant effect on the final microstructure and performance of the fully recycled composites, which can be still successfully used for structural applications in the automotive field.

Statistical Distributions of the Strength and Fracture Toughness of Recycled Polyethylene-Reinforced Laterite Composites

AbstractThis paper presents the results of combined experimental and theoretical studies of the statistical distributions of the strength and fracture toughness of recycled polyethylene-reinforced laterite composites for potential applications in building materials. The composites are produced with different volume percentages (0–30% v/v) and particle sizes (∼300±0.02, ∼600 ± 0.03, ∼900 ± 0.03, ∼1,200±0.02, ∼1,500±0.04, and 1,800±0.03 μm) of powdered polyethylene (PE) in a laterite matrix. The composites with ∼900±0.03 μm and 20-volume percentage of PE are shown to have the best combination of flexural-compressive strengths and fracture toughness. The statistical variations in the flexural-compressive strengths and fracture toughness are well characterized by the Weibull distributions.

Technology readiness level assessment of composites recycling technologies

Composite materials made of glass and carbon fibres have revolutionised many industries. Demand for composites is experiencing rapid growth and global demand is expected to double. As demand for composites grows it is clear that waste management will become an important issue for businesses. Technically composite materials evoke difficult recycling challenges due to the heterogeneity of their composition. As current waste management practices in composites are dominated by landfilling, governments and businesses themselves foresee that this will need to change in the future. The recycling of composites will play a vital role in the future especially for the aerospace, automotive, construction and marine sectors. These industries will require different recycling options for their products based on compliance with current legislation, the business model as well as cost effectiveness. In order to be able to evaluate waste management strategies for composites, a review of recycling technologies has been conducted based on technology readiness levels and waste management hierarchy. This paper analyses 56 research projects to identify growing trends in composite recycling technologies with pyrolysis, solvolysis and mechanical grinding as the most prominent technologies. These recycling technologies attained high scores on the waste management hierarchy (either recycling or reuse applications) suggesting potential development as future viable alternatives to composite landfilling. The research concluded that recycling as a waste management strategy is most popular exploration area. It was found mechanical grinding to be most mature for glass fibre applications while pyrolysis has been most mature in the context of carbon fibre. The paper also highlights the need to understand the use of reclaimed material as important assessment element of recycling efforts. This paper contributes to the widening and systematising knowledge on maturity and understanding composites recycling technologies.

The Recycling of Sugarcane Fiber/Polypropylene Composites

Mechanical recycling is utilized to reuse waste and obtain other plastic products via the reprocessing of a material in industrial equipment. Natural fiber composites have become more popular in recent years; however, these composites' mechanical behavior remains less well-understood than single polymers’ behavior after recycling. Therefore, the objective of this work was to study the degradation of different sugarcane fibers/polypropylene composites using new grinding and injection processes and to evaluate the mechanical properties of these materials using analysis of variance (ANOVA). This work reveals the mechanical behaviors of recycled natural fiber composites that contain thermal stabilizer additives. Polypropylene composites reinforced with differently treated bagasse and straw fibers (10 and 20 wt%/PP) were obtained through melt mixing using a high-intensity thermokinetic mixer and were subsequently injected. The recycled composites exhibited decreased tensile strength relative to the original composites. However, when thermal stabilizers were added, the mechanical properties were maintained or increased, depending on the fiber and additive types.

Determining the mechanism controlling glass fibre strength loss during thermal recycling of waste composites

This paper presents an experimental investigation into the large reductions to the tensile fracture stress and the associated strength loss mechanism of E-glass fibres during thermal recycling. Fractographic analysis reveals the fracture process is controlled by surface flaws, irrespective of heat treatment temperature and duration. The fracture toughness is an important material property in order to understand possible changes in the strength–flaw relationship during heat treatment. Focussed ion beam (FIB) milling is used to artificially create a single nano-sized deep notch (between 30 and 1000nm) in glass fibres. The strength loss, fracture toughness, fracture mirror constant and fracture mechanism observed for nano-notched and thermally recycled fibres are identical, indicating bulk property changes do not occur during thermal recycling. The study proves conclusively that surface flaw growth is the controlling mechanism reducing fibreglass strength during thermal recycling of waste polymer composites.

Characterization of composite materials made from discontinuous carbon fibres within the framework of composite recycling

Recycling carbon fibres from waste composite materials would only be efficient if it were possible to separate the fibres and the matrix and to re-use the recycled fibres as new reinforcements. The challenge is to use non-continuous fibres to produce high-strength materials. The formation of defects in “semi-long” fibre composites has not yet been taken into account. In this paper the influence of fibre length and fibre alignment on the strength and the modulus of composite materials is illustrated. It is shown that the presence of defects may be modelled in order to understand what the quality of a second generation composite material would be.

The effect of mechanical recycling on the microstructure and properties of PA66 composites reinforced with carbon fibers

ABSTRACTThis article aims to prepare by injection molding recycled polymeric composites based on PA66 reinforced with short carbon fibers after artificial aging for applications in the automotive field. The aging cycles involves the combined action of UV radiation, moisture, and temperature in order to simulate the common outdoor conditions. The 100% recycled composites are obtained by the regranulation of the aged specimens followed by the remelting and re‐injection molding. The study is focused on the comparison between the mechanical behavior and the microstructure of the composites before and after mechanical recycling. The results of mechanical, thermal, and morphological investigations reveal that the recycling process had no significant effect on the final properties and microstructure of the recycled composites. Therefore the recycled PA66CF30 composites could be successfully used for structural or semi‐structural automotive applications guaranteeing good final performances and advantages from the environmental point of view. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42275.

The Study of Health and Insulation Composite Recycling Far Infrared Fiber Laminated Non-Woven

In this study the experiment used the two kinds of fibers, respectively are the recycled far-infrared polyethylene terephthalate (RFPET) fibers and the low melting temperature polyethylene terephthalate (LPET) fibers. Needle punching and compare with laminated in different layers, through hot pressing to make the fabric thin, observation and testing , surface observation, air permeability test, stiffness test, and far infrared emissivity test. The study shows the far-infrared radiation rate and will not increase because of the laminate, but is a relationship with a thickness comparison.

The Effect of Coarse Particle Size on the Properties of Recycled Copper-Filled Epoxy Composites

The effect of coarse particle size of recycled copper filled epoxy composites on mechanical, electrical, thermal and physical properties was investigated. The recycled copper was collected as a waste from the milling machine and ground into a coarse (300-400 µm) particle size. The recycled copper filled epoxy composite was fabricated using a mechanical stirrer. The effect of volume fraction of recycled copper of the epoxy composites was also studied based on the flexural properties, coefficient of thermal analysis (CTE), electrical conductivity, hardness and density. Incorporation of recycled copper decreased the CTE of the composites. The flexural properties, electrical conductivity, hardness and density of the composites increased with increasing volume fraction and filler loading.

Mechanical recycling and composition effects on the properties and structure of hardwood cellulose-reinforced high density polyethylene eco-composites

Knowledge of recycling capability of cellulose-reinforced eco-composites is of great interest due to sustainability and market reasons. Reprocessing by injection molding of hardwood cellulose-reinforced HDPE composites with a wide fiber content range (10–48wt%) and two coupling agents with different molecular weights and maleic anhydride (MA) contents was studied. Recycling and composition effects on composite structure and properties were analyzed by ATR–FTIR, SEM, AFM, flow and tensile testing. Increases in fiber content resulted in lower tensile strength (σt) increases for reprocessed composites. σt was revealed as the property with the highest sensitivity to the fiber breakage found upon recycling. The greater M‾w and MA content coupling agent was revealed as the less sensitive to reprocessing and experienced a lower degradation upon recycling, still benefiting the recycled composites σt. Statistically-contrasted models for quantitative prediction of composite flow and tensile properties upon recycling were developed. Composites withstood five severe reprocessing cycles without unacceptable property detriments.

Fabrication of mesoporous Fe3O4@SiO2@CTAB–SiO2 magnetic microspheres with a core/shell structure and their efficient adsorption performance for the removal of trace PFOS from water

• A novel adsorbent for trace PFOS removal from water was prepared by a simple method. • Morphology, porosity, composition, and structure of adsorbent were well characterized. • The adsorbent was successfully applied to remove trace PFOS from water at pH = 3. • The impact factors on the trace PFOS removal from water were systematically studied. • Stable adsorption ability is attributed to strong interaction between CTAB and SiO 2 . Novel mesoporous CTAB-functionalized magnetic microspheres with a core/shell structure (mesoporous Fe 3 O 4 @SiO 2 @CTAB–SiO 2 ) was fabricated via a simple sol–gel method combined with selective etching strategy. The morphology, porosity, magnetic property, composition, and structure of mesoporous Fe 3 O 4 @SiO 2 @CTAB–SiO 2 were characterized. Subsequently, the as-prepared composites were successfully applied to remove trace PFOS (500 ng L −1 ) from water at acidic conditions (pH = 3). The fabrication mechanism of mesoporous Fe 3 O 4 @SiO 2 @CTAB–SiO 2 and the impact of various factors on the removal of trace PFOS from water were systematically studied. The recyclability of the as-prepared composites was tested for, five times, at the same conditions.

Energy intensity and environmental analysis of mechanical recycling of carbon fibre composite

Abstract The increased usage of composites in industry coupled with European Union restrictions on landfill disposal has resulted in an urgent need to develop resource efficient recycling technologies. The purpose of this work was to model the electrical energy requirements of milling as a recycling option for carbon fibre composite. By separating the contributions to the total energy required of the machine tool, material cutting energy and material removal rate, the energy demand of carbon fibre composite recycling can be theoretically calculated for any milling process. The model was validated experimentally by comparing the theoretical energy demand to the measured energy demand of an industrial scale milling machine. It was found that at a processing (recycling) rate of 10 kg/hr, the specific energy was significantly less than the embodied energy of virgin carbon fibre (2.03 MJ/kg compared to approximately 200 MJ/kg). Although the form of the recyclate fibres (short, single filaments and bundles) was vastly different to their virgin equivalents (continuous tows), the energy difference highlights the potential environmental benefit of utilising recyclate fibres in place of virgin ones in short fibre composites where mechanical performance is less critical. The relationship between specific energy of recycling and processing rate was also calculated, which highlighted that further energy savings can be achieved at higher processing rates. This work is fundamentally important to provide new data sets for Life Cycle Assessment in order to assess the potential environmental benefits of utilising recyclate fibres.

Microstructure and properties of AA7075/Al–SiC composites fabricated using powder metallurgy and hot pressing

Solid state recycling of AA7075 chips by hot pressing is a novel processing technique that uses remarkably lower energies compared to conventional recycling by casting. In this study, AA7075 chips were recycled to fabricate SiC particle (2.5, 5 and 10wt.%) and Al powder (10, 20, 30 and 50wt.%) reinforced AA7075 alloy matrix composites by the combination of powder metallurgy and hot pressing techniques. The effects of the amounts of SiC particles and Al powder on the microstructure of the recycling AA7075/Al–SiC composites were investigated. The density, porosity and hardness of the composites were also examined. It was observed that the Al powders in the AA7075/Al–SiC composites were distributed non-homogeneously and randomly between the AA7075 chip regions. The results showed that the green density of the AA7075/Al–SiC composites increased with increasing amounts of Al powder, while SiC showed the opposite effect. The hot pressed density (final density) of the composites decreased with increasing amounts of Al powders and SiC content. An increase in the weight percentage of the SiC particles (from 0 to 10wt.%) in the AA7075/Al–SiC composites improved the hardness of the recycled composites due to the high hardness of the SiC particles.

Modification of bitumen-based roof covering material by glass reinforced polyester recyclate

In boat building industry, environmental legislations promoting recycling of thermoset composites have been the main driver globally. Recycling of glass-reinforced plastics (GRP), which is widely used in the industry, has been very problematic due to its inherent heterogeneous structure. Considering the urgent need of the industry, several investigations have been carried out to find the beneficial uses of GRP recyclate after mechanical recycling which is the most cost-effective technique. In this study that can be considered an effort to find proper way to recycle GRP containing polyester as the matrix, the recyclate of waste GRP boat material was adopted as modifier for bitumen-based roof covering materials. Fine grounded GRP recyclates were added to the hot bitumen mix with the dosages of 1, 3, 5, 10, 20 and 30 % as a part of roof covering material production process. Performances of the modified end product have been tested conventionally. The tests were also repeated for environmentally aged blends that contain 30 % of GRP recyclate. Results indicate that use of GRP recyclate in the modification of bitumen-based materials is an effective way to improve roof covering materials’ performance in terms of temperature susceptibility in particular and has the potential to solve the recycling problems of the industry.

Properties of recycled poly (ethylene terephthalate) (PET)/hyperbranched polyester (HBPET) composite fibers

Hyperbranched polyester (HBPET) with aliphatic–aromatic structure was synthesized and extruded with recycled poly (ethylene terephthalate) (RPET) chips obtained from used water bottles, with ratio of 0.5% and 1 wt% of HBPET. Filament fibers from pure recycled PET (RPET-0) and (RPET-0.5 and RPET-1) composite were spun using a melt spinning process and drawn by a thermal drawing process to improve their mechanical properties. The effects of addition of HBPET on the properties of produced fibers as well as draw ratio are investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), universal tensile analysis, and sonic velocity. It was found that mechanical properties of the (RPET-0.5 and RPET-1) fibers were improved with respect to pure recycled PET (PET-0) fibers. Moreover, the crystallinity of composites fibers was also increased with an increasing of HBPET content. The improvement in mechanical properties may be due to the increase of orientation of fiber molecules along the fiber axis. Moreover, addition of HBPET serves as lubricant within recycled PET matrix which increased its mechanical properties.

Diesel auto-thermal reforming for solid oxide fuel cell systems: Anode off-gas recycle simulation

Diesel auto-thermal reformation (ATR) with solid oxide fuel cell (SOFC) stack anode off-gas recycle (AOGR) has a reliable steam recycling supply to the reformer and improves overall system efficiency. For the lab-scale experiments, it is crucial to develop a cost-effective technique to simulate the AOGR effects on hydrocarbon catalytic reformation due to safety and cost considerations of providing the full recycle composition in the absence of fuel cell stack hardware. The present work combined thermodynamic modeling and experiments to compare diesel ATR performance with AOGR and with direct water/air inputs as recycle simulation (RS). Variations of input water and air flow were employed to simulate the effects of recycle gas on syngas production and to analyze the contribution of recycled CO2 dry reforming. A single-tube reformer with Rh/CeO2–ZrO2 catalyst was used for diesel ATR experiments with a photo-acoustic micro-soot meter to monitor carbon formation in the reformate effluent. Experimental results suggest water and air input flows are two key variables to simulate performance of diesel ATR with AOGR, whereas gas hourly space velocity and reforming temperature do not significantly affect the recycle simulation process in syngas production. The optimum AOGR ratio for an SOFC stack with 65% fuel utilization was identified as 45% for diesel ATR to achieve maximum syngas production and reforming efficiency with a given input air flow.

GEOCHEMISTRY AND HEAVY MINERALS ANALYSES ON "BLACK SANDS" OF THE LOWER CAMBRIAN FISH RIVER SUBGROUP (NAMA GROUP, NAMIBIA)

Heavy mineral rich-sandstones (“black sands”) of the Lower Cambrian upper Fish River Subgroup in Namibia were used to reveal the provenance of the detrital material. The host rocks of the black sands from the Haribes and Rosenhof Members are mainly composed of partially rounded quartz, feldspar (K-feldspar > plagioclase), polycrystalline quartz, few siltstone fragments and labile altered or metamorphosed volcanic lithoclasts. Geochemical proxies are similar to those from typical foreland deposits and point to slightly recycled upper continental crustal composition, e.g.: Th/Sc ratios between 1.23 and 1.95, Zr/Sc ranging from 24 to 38 and La/Sc from 4.8 to 10.8. Heavy mineral addition of up to 30% does not significantly change Th/Sc, La/Sc and La/Th values, but slightly changed the Zr/Sc ratios, which range from 38 to 53. The heavy mineral-enriched beds (50 to 75% of the whole rock), display nearly similar La/Sc ratios compared with other lithotypes. They are 9x enriched in rare earth elements and show a significantly stronger negative Eu-anomaly, and an enrichment of heavy over light rare earth elements, as well as higher Zr/Sc ratios (82 to 299), typical for reworked passive margin or foreland deposits. The chemical composition of separated heavy minerals point to a relatively strong influence of metapelitic and metamorphosed mafic sources, which were not identified using geochemical data. Mineral chemical analyses of chromian spinels point to island arc and mid-ocean ridge basalts as protoliths, whereas rutiles were derived from metamorphosed mafic and pelitic rocks, and abundant garnet (mainly almandine) derived from high-grade and low-grade metapelitic sources. Titanite shows dominance of felsic and mafic plutonic rocks as sources, while epidote point to low-grade metamorphic protoliths. Magnetite was eroded from felsic plutonic and/or mafic metamorphosed rocks. Previous works using U-Pb detrital zircon dating show typical Namaquan and Pan-African age populations as expected for a collisional tectonic setting. Palaeocurrents indicate that the main source region of the heavy and the host rock minerals is within the Damara Belt which resulted from the convergence of Congo and Kalahari Cratons. Although the exact age of thrusting is debated, the data presented suggest the exhumation of metamorphosed crustal fragments and plutonism related to the Damara orogeny during the deposition of the upper Nama Group (ca. 520 Ma).