Reinforcement with recycled fiber is widely investigated to improve the mechanical behavior of foam concrete. In addition, the use of recycled aggregate in concrete provides benefits in terms of ...sustainability as it reduces the use of raw materials. In this research, 6 mm-long fibers and aggregates obtained from waste polypropylene were utilized in foam concrete production. This study also presents an evaluation of the recycled polypropylene fiber (PppF) and aggregate (PppA) incorporated foam concretes using ANOVA and ANNs. The ANN model was developed to estimate the compressive and flexural strengths, dry density, and thermal conductivity. The results indicated that the use of recycled polypropylene fiber increased the compressive and flexural strengths, however, polypropene aggregates affected the strengths negatively. And mixtures with higher levels of RppA and RppF have lower thermal conductivities. The slump of fresh concrete had an apparent reduction with the increase in RppA quantity. Also, both the ANN and ANOVA approaches were appropriate for optimizing and estimating responses.
Display omitted
•This research investigates the effect of waste polypropylene fiber and aggregates on Foam Concrete.•ANN and ANOVA approaches were also appropriate for optimizing and estimating material properties.•The mutual utilization of waste polypropylene fiber and aggregates mitigates the negative impact on strengths.
The utilization of recycled waste plastics presents a promising opportunity for the development of filament for fused filament fabrication (FFF). This approach holds the potential to effectively ...conserve resources, mitigate solid waste generation, and contribute to the reduction of greenhouse gas emissions. The present study involves the processing of recycled polypropylene (rPP) into filaments with the purpose of manufacturing 3D printed components and the effects of the processing parameters on the properties of the printed parts. The selection of manufacturing parameters for 3D printing of rPP relies on the material-specific characteristic values, including glass transition temperature, melting temperature, viscosity, etc. More importantly, a novel methodology with the self-diffusion coefficient by applying the real-time cooling rate of rPP was devised to determine the total accumulated diffusion, which enables the prediction of mechanical performance by considering the local thermal conditions during material bonding between individual strands and different layers. The finding of the study indicates that the specimen fabricated by using elevated temperature and minimal time interval, which correlates with a high total accumulated diffusion, exhibited enhanced mechanical properties between the strands those are comparable to properties of the injection-molded virgin polypropylene.
Display omitted
•Effects of the processing parameters on the performance of filament fabricated rPP were studied.•Novel methodology of the self-diffusion coefficient was applied for exploring the mechanical performance of printed rPP.•The mechanical performance increased with increasing the total accumulated diffusion.•rPP performs on par with injection-molding level.
The use of recycled plastics as modifiers for asphalt binder have gained attention in recent years. Studies have confirmed the enhancement in the rutting resistance of asphalt binder with the ...addition of these types of plastics, however there are controversies with regards to their long-term cracking performance. The long-term cracking performance of asphalt binder is directly influenced by their rheological properties. This study evaluated the fatigue performance of recycled High-Density Polyethylene (rHDPE) and recycled Polypropylene (rPP) modified asphalt binders using several rheological indices including the Superpave intermediate-temperature PG (G*sin δ), fatigue life (Nf), complex modulus (G*), phase angle (δ), the Glover-Rowe (G-R) parameter, the crossover temperature (Tδ=45°), the rheological index (R-value), the peak shear stress, failure strain and the yield energy, as well as a newly developed monotonic cracking index (MCI). Additionally, the influence of the process of mixing plastic with asphalt at high temperatures and shear rate on the cracking performance was also investigated. Results indicated that long term cracking performance were not consistent across all rheological indices. While Nf indicated improved overall cracking performance with the addition of rHDPE and rPP, G*sin δ, G-R parameter, R-value, Tδ=45°, and MCI indicated susceptibility to cracking with the addition of these recycled plastics.
•Recycled HDPE and PP were assesed for their effects on asphalt binder cracking.•Long-term cracking performance varied across rheological indices.•LAS test showed improved fatigue life with rHDPE and rPP.•G*sin δ, G-R parameter, R-value, Tδ =45°, and MCI showed increased cracking susceptibility with these plastics.
Mechanically recycled plastics used in food packaging are consistent with the current circular economy concept. In this study, the effects of recycled polypropylene (rPP) content on film properties ...and the migration of processing aids in the film to food simulant and milk were studied by self-made rPP films. The results showed that the rPP and processing aids increased the transparency of the films. However, the presence of tiny particles in the rPP film reduced its elongation at break. Furthermore, rPP and processing aids decreased the thermal stability of the film. At 70 °C for 2 h, the total migration order of the processing aids to food simulant and milk was 50 % ethanol (55.78–64.17 mg/kg) > whole milk (10.32–10.66 mg/kg) > low-fat milk (6.39–7.04 mg/kg) > skim milk (4.88–5.47 mg/kg). The migration of processing aids into milk in films containing 50 % and 100 % rPP was similar to that of virgin polypropylene (vPP) films, which indicates that rPP does not promote processing aid migration. Moreover the overall migration order of processing aids to 2 % (w/v) food ingredient aqueous solution was lecithin (3.05 mg/kg) > glyceryl trilaurate (2.68 mg/kg) > cholesterol (1.33 mg/kg) > NaCl (0.33 mg/kg) > casein (0.32 mg/kg) > lactose (0.29 mg/kg) > water (0.16 mg/kg). This confirmed that milk fat was the primary cause of processing aids migration from the film, and the kind of milk fat also had an effect on processing aids migration. Therefore, as long as the basic performance and food safety of packaging are met, a certain proportion of rPP can be added to vPP to achieve sustainable development of packaging.
Display omitted
•rPP and processing aids increased transparency but decreased thermal stability and elongation at break.•Milk fat (especially glyceryl trilaurate) promotesd the migration of processing aids in the film into milk.•For food packaging materials, rPP and vPP faced the same risk of migration of processing aids.
•Photooxidation affected the physico-chemical properties of UD composites with flax fibers.•Photooxidation caused surface degradation, leaving the bulk of the composite unaffected.•Recycled ...polypropylene composites showed good mechanical resistance to UV exposure.
Previous studies on the photooxidation of natural fiber composites have focused on using short fibers and virgin matrices. In this work, unidirectional flax fiber composites with virgin and recycled polypropylene matrix were prepared by thermocompression to compare their accelerated aging. These composites were exposed to two accelerated xenon arc UV exposures where only the irradiance was modified. A multi-scale characterization was carried out to evaluate the consequences of the photooxidation on their mechanical and physicochemical properties with time. Results show that the photooxidation was limited to the surface. In addition, the photo-degradation of the surfaces of both composites was identified by the appearance of cracks, the variation of crystallinity, the decrease in weight average molar mass, and the appearance of new chemical products. These physicochemical variations are more evident with increasing irradiance. Despite these variations, the mechanical tensile properties of recycled matrix composites remain relatively indifferent to the two UV exposures compared to those with virgin polypropylene. It can be concluded that recycled polypropylene, if well selected, can replace virgin polypropylene in natural fiber composites for better mechanical resistance to photooxidation.
Display omitted
•Valorization of waste printed circuit boards and polypropylene.•Increased impact strength compared to the recycled polypropylene without additives.•Improved fire performance of the ...recycled polypropylene elastomeric composites.
In the last several years, the electronic waste, especially printed circuit boards have significantly increased over the world, generating one of the highest rates of solid waste. The recycling process of the printed circuit boards implies mainly the recovery of metals and glass fibers, while the reuse of the polymeric support has remained largely in the phase of research. In this paper, the non-metallic part of printed circuit boards was used as filler (up to 30%), but also to improve the fire resistance of thermoplastic composites based on recycled polypropylene and diene block-copolymers. The synergy between the elastic effect of elastomers and the reinforcing effect of the waste powder into the thermoplastic matrix was studied by mechanical and dynamo-mechanical analysis, X-ray diffraction, optical microscopy, micro-calorimetry and thermo-gravimetrical analysis. Improved mechanical properties, especially impact strength was observed. The compatibization of components considering the interactions between the ethylene-butylene blocks from the hydrogenated and maleinized styrene-butadiene block-copolymer and recycled polypropylene, respectively between the MA groups and the functionalities of the waste powder, evidenced by FTIR, was highlighted by changes in the X-ray pattern and an increased fire resistance and thermal stability.
In this study, the effect of different polypropylene (PP) matrices (homopolymer (HPP), impact copolymer (ICP), and recycled polypropylene (rPP)) on the mechanical, morphological, and thermal ...properties of date palm fiber (DPF)-reinforced PP composites was investigated. The DPFs were treated with an alkali solution, and composites were fabricated with different DPF loadings (5, 10, and 15 wt %) and lengths (less than 2 mm and 8-12 mm). It was found that the tensile properties of the DPF/ICP and DPF/rPP composites were similar to those of the DPF/HPP composites. The addition of fiber to the matrix reduced its tensile strength but increased the modulus. The alkali treatment improved the compatibility between the fibers and the matrix by removing hemicellulose and other impurities. Fourier transform infrared spectroscopy confirmed hemicellulose removal. The morphology of the alkali-treated fractured tensile specimen revealed improved adhesion and less fiber pull out. Differential scanning calorimetry revealed that the alkali treatment enhanced the crystallinity index. Thermogravimetric analysis showed that the addition of DPFs into the PP matrix reduced the thermal stability of the composite. However, the thermal stability of the treated fiber-reinforced rPP and ICP composites was similar to that of the DPF/HPP composite. Hence, rPP can be used as an alternative to HPP with DPFs.
PDF