Dan Åkesson

Microwave pyrolysis as a method of recycling glass fibre from used blades of wind turbines

The possibility of recycling glass fibre-reinforced composites by using microwave pyrolysis was examined. A scrap blade from a wind turbine was fragmented and microwave-pyrolysed. The glass fibre recovered after pyrolysis represented 70% of the initial mass of glass fibre-reinforced composites. The tensile strength of the glass fibre recovered was measured after pyrolysis and compared to the tensile strength of untreated glass fibre. The test showed that the fibres lost about 25% of their tenacity. Non-woven fibre mats were prepared from the recovered fibres. Laminates were then prepared from the non-woven mats obtained, together with virgin glass fibre mats. Mechanical testing of the laminates showed that it is possible to prepare composites using 25 wt% of recycled fibres, with relatively good mechanical properties.

Novel lightweight and highly thermally insulative silica aerogel-doped poly(vinyl chloride)-coated fabric composite

Novel lightweight and highly thermal insulative aerogel-doped poly(vinyl chloride)-coated fabric composites were prepared on woven fabrics made of polyester fibres using knife coating method, and their performances were compared with neat composite. The composites were prepared by incorporating a commercial aerogel to a ‘green’ poly(vinyl chloride) (PVC) plastisol. The effect of aerogel-content, thermal insulating property, thermal degradation, surface characteristics, tensile and physical properties of the composites were investigated. Results revealed that aerogel could reduce thermal conductivity, density and hydrophilicity of the composites dramatically without significant decrease in other properties. Experimental results showed that thermal insulation properties were enhanced by ∼26% (from 205 to 152 mW/m-K), density decreased by ∼17% (from 1.132 to 0.941 g/cm3) and hydrophobicity increased by 16.4% (from 76.02 to 88.67 ± 1.48°) with respect to the unmodified coated fabric. Analyses proved that composite with 3% aerogel is the lightest by weight, while 4% showed the highest thermal insulation. The results showed that 4% is the critical percentage, and preparation of composites with aerogel content higher than 4% has limitations with the given formulation due to high viscosity of plastisol. The prepared composite has potential applications in many fields such as development of textile bioreactors for ethanol/biogas production from waste materials, temporary houses and tents, facade coverings, container linings and tarpaulins. The prepared composite can be considered ‘green’ due to usage of a non-phthalate environment-friendly plasticiser.

Glass Fibres Recovered by Microwave Pyrolysis as a Reinforcement for Polypropylene

Glass fibre composites were recycled by microwave pyrolysis. The glass fibres recovered were evaluated as a reinforcement agent for polypropylene (PP). Samples were prepared with a micro-compounder and the resulting compounds were evaluated with tensile testing, flexural testing, Charpy impact testing and scanning electron microscopy (SEM). The adhesion between fibre and glass was relatively poor, and an attempt was made to improve it. Various coupling agents were evaluated, in addition to the use of maleic anhydride-grafted PP (MA-PP). Tests showed that MA-PP had a relatively strong effect on the mechanical properties.

Production of Pectin-Cellulose Biofilms: A New Approach for Citrus Waste Recycling

While citrus waste is abundantly generated, the disposal methods used today remain unsatisfactory: they can be deleterious for ruminants, can cause soil salinity, or are not economically feasible; yet citrus waste consists of various valuable polymers. This paper introduces a novel environmentally safe approach that utilizes citrus waste polymers as a biobased and biodegradable film, for example, for food packaging. Orange waste has been investigated for biofilm production, using the gelling ability of pectin and the strength of cellulosic fibres. A casting method was used to form a film from the previously washed, dried, and milled orange waste. Two film-drying methods, a laboratory oven and an incubator shaker, were compared. FE-SEM images confirmed a smoother film morphology when the incubator shaker was used for drying. The tensile strength of the films was 31.67 ± 4.21 and 34.76 ± 2.64 MPa, respectively, for the oven-dried and incubator-dried films, which is within the range of different commodity plastics. Additionally, biodegradability of the films was confirmed under anaerobic conditions. Films showed an opaque appearance with yellowish colour.

Mechanical recycling of polylactic acid composites reinforced with wood fibres by multiple extrusion and hydrothermal ageing

The mechanical recycling of polylactic acid composites reinforced with wood fibres was studied by multiple extrusions. The composite material was extruded seven times, and the mechanical and thermal properties were monitored by tensile tests, flexural tests, differential scanning calorimetry, Fourier-transform infrared and scanning electron microscopy. The results showed that the material retained its mechanical properties relatively well, for up to five cycles after which the tensile strength decreased by 23%. Thermal characterisation further showed that the glass transition temperature (Tg) shifted several degrees centigrade towards lower temperatures, further indicating degradation of the polylactic acid polymer. Characterisation was also done on composite material, which was aged hydrothermally between each extrusion cycle in order to simulate post-consumer recycling of composite products, which had been exposed to water. Samples were aged at 50℃ in distilled water for 5 days. The thermal and mechanical testing showed that the material survived the ageing test fairly well.

Anaerobic degradation of bioplastics: A review

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW), leading to renewable energy production in the form of methane, is a preferable method for dealing with the increasing amount of waste. Food waste is separated at the source in many countries for anaerobic digestion. However, the presence of plastic bags is a major challenge for such processes. This study investigated the anaerobic degradability of different bioplastics, aiming at potential use as collecting bags for the OFMSW. The chemical composition of the bioplastics and the microbial community structure in the AD process affected the biodegradation of the bioplastics. Some biopolymers can be degraded at hydraulic retention times usually applied at the biogas plants, such as poly(hydroxyalkanoate)s, starch, cellulose and pectin, so no possible contamination would occur. In the future, updated standardization of collecting bags for the OFMSW will be required to meet the requirements of effective operation of a biogas plant.

New Solvent for Polyamide 66 and Its Use for Preparing a Single-Polymer Composite-Coated Fabric

Polyamides (PAs) are one of the most important engineering polymers; however, the difficulty in dissolving them hinders their applications. Formic acid (FA) is the most common solvent for PAs, but ...

Repeated mechanical recycling of polylactic acid filled with chalk

Polylactic acid (PLA) was compounded with 30 wt% chalk and 5 wt% of a bio-based plasticiser on a twin screw extruder. Mechanical recycling of the obtained compound was studied by multiple extrusions up to six cycles. The degradation was monitored by mechanical and thermal tests. Tensile and flexural tests did not reveal any major degradation after six cycles of processing. Characterising the material with differential scanning calorimetry (DSC) did not detect any significant change of the thermal properties. The material was also characterised by FTIR and, again, no significant change was detected. The material was finally characterised by melt flow index and by proton nuclear magnetic resonance (1H-NMR). Both tests revealed that some degradation had occurred. The 1H-NMR clearly showed that the chain length had been reduced. Also, the MFI test showed that degradation had occurred. However, the study reveals that PLA filled with chalk can be recycled by repeated extrusion for up to 6 cycles, without severe degradation. This should be of relevance when considering the end-of-life treatment of polymer products made from PLA.