J. Cañavate

Changes in Crystallinity of the HDPE Matrix in Composites with Cellulosic Fiber Using DSC and FTIR

The ageing of HDPE/cellulosic fiber composite exposed to drastic weather and the percentages of cellulosic fibers are responsible for some changes in the crystallinity of component matrix (HDPE). Two types of samples have been evaluated during different periods of time (up to 90 days). One in which cellulosic fibers have not been treated and another in which fibers have been given a treatment with a coupling agent, silane type, which favours the fiber adhesion to the matrix. Two instrumental analysis techniques have been used to determine the crystallinity changes of HDPE: Fourier Transform Infrared spectrophotometry (FTIR) and Differential Scanning Calorimetry (DSC).

Formulations for thermoplastic vulcanizates based on high density polyethylene, ethylene-propylene-diene monomer, and ground tyre rubber

Thermoplastic vulcanizates (TPVs) are a specific group of the so called thermoplastic elastomers. The main characteristic is the existence of a crosslinked rubber phase obtained by dynamic vulcanization in the presence of the thermoplastic matrix. This article studies TPVs based on ground tyre rubber (GTR), high-density polyethylene, and ethylene propylene diene monomer rubber. Vulcanization is performed by a new peroxide developed to resist high temperatures and an standard one. The aim of this study is optimize the formulation in order to include GTR, while maintaining a good balance of properties in the final TPV material. The use of GTR would improve the possibilities of recovering tyre waste. A detailed study regarding the influence of each component in the final mechanical properties has been carried out. The swelling properties, ATR infrared spectroscopy, TGA, and DSC analysis indicated a high degree of crosslink and good adhesion between the matrix and the rubber phase. Morphology of the composites was assessed by scanning electron microscopy. A composite containing a combination of peroxides and 40/30/30 of HDPE, EPDM, and GTR was found to show a good balance of characteristics regarding mechanical properties, crosslinking, and adhesion between phases.

The Use of Waxes and Wetting Additives to Improve Compatibility Between HDPE and Ground Tyre Rubber

The concern about the amounts of used tyres that end in landfills and the environmental problems that they produce have led to research on ways to use these residues in common applications. A general starting point in the recovering procedures is the grinding of the tyres in order to obtain a powder known as ground tyre rubber (GTR). This paper proposes an alternative way of recycling the used tyres by means of a new material composed by a polyolefin matrix, high-density polyethylene (HDPE) reinforced with GTR. The crosslinked structure and surface characteristics of the GTR hampers good interaction with the polymeric matrix, leading to weak adhesion between the two phases and consequently a decrease of the mechanical properties. The aim of this work is to improve adhesion, achieving better wetting of GTR particles by HDPE. For this purpose, waxes and wetting additives were added to the mixture. The influence of these additives was determined by mechanical properties, attenuated total reflection infrared spectroscopy, differential scanning calorimetry analysis, scanning electron microscopy, and optical microscopy. An acidic wetting additive and a polyethylene wax showed good results regarding mechanical properties, dispersion of the GTR particles and adhesion.

Acoustic and mechanical properties of recycled polyvinyl chloride/ground tyre rubber composites

In order to provide another way of reducing the stock of used tyres and polyvinyl chloride waste, a new material is developed and studied. Formulation includes a matrix constituted by a compound of recycled polyvinyl chloride with plasticized polyvinyl chloride and a reinforcement of ground tyre rubber. Acoustic and mechanical properties of different compositions of polyvinyl chloride/ground tyre rubber were tested in order to determine their suitability for applications fulfilling industry requirements. Sound absorption has been analyzed, showing interesting results at frequencies higher than 2500 Hz. The obtained values are found to be depending on the thickness of the sample, the content of the ground tyre rubber and the existence of gaps, pores and voids either between layers or in the interphase between the matrix and reinforcement. From the study of the mechanical properties, we may observe that the ground tyre rubber act as filler, improving stiffness of polyvinyl chloride/ground tyre rubber composites with an increase of Young Modulus. The tensile strength, elongation at break and toughness decrease slowly. The decrease of these mechanical properties is observed to be lower than in the case of composites made by using high-density polyethylene as a matrix.

Biocomposites using waste whole chicken feathers and thermoplastic matrices

This study deals with the preparation and characterization of thermoplastic composites using polypropylene, high-density polyethylene and polylactic acid matrices and including whole chicken feathers as reinforcement. The behaviour of the composites was determined in terms of physical and mechanical properties, which were related to the fibre–matrix compatibility analysed by Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that the addition of chicken feathers into the thermoplastic matrices results in a slight increase in the stiffness when small amounts of chicken feathers (5–10% vol/vol) were incorporated into the composites. Tensile strength at maximum load, elongation at break and toughness properties decreased when the chicken feather concentration was increased. Results for chicken feather–polypropylene composites were analogous to chicken feather–high-density polyethylene and chicken feather–polylactic acid composites. The Fourier transform infrared spectroscopic study and the scanning electron micrographs suggest that the insufficient compatibility of chicken feather and polymer matrices is the main reason for the decrease in tensile properties.

Properties and optimal manufacturing conditions of chicken feathers/poly(lactic acid) biocomposites

Chicken feathers waste from poultry industry was incorporated in poly(lactic acid) matrix to obtain an environmental friendly biocomposite taking advantage of the unique properties of chicken feathers, such as low density, biodegradability and good thermal and acoustic properties, and of the biodegradability of the poly(lactic acid). The effect of manufacturing conditions on the final properties of the composite and on the matrix–fiber compatibility was studied. Optimal manufacturing conditions, in order to obtain the best mechanical results, were found at a temperature of 170–180℃ for a processing time of 5 min and a speed of mixing of 50 r/min. Young’s modulus was not very affected by the chicken feather’s content showing a maximal variation of less than 8%, indicating that is possible to include chicken feathers in a composite maintaining its stiffness. However, tensile strength and elongation decreased up to 58 and 12%, respectively, when chicken feather content was 25% because of the restraining effect of the fibers. Moreover, dimensional stability was negatively affected with the inclusion of chicken feathers. Infrared spectroscopy and scanning electron microscopy studies show that fiber–matrix interaction exists but it is weak.

High modulus regenerated cellulose fiber-reinforced cellulose acetate butyrate biocomposites

The properties of composites prepared with a matrix of biodegradable cellulose ester (cellulose acetate butyrate, CAB) and reinforced with regenerated cellulose lyocell fibers (lyocell/CAB) were studied and compared with short flax fiber-reinforced composites (flax/CAB), used as reference. The effect of the lyocell fiber content on the composite properties was also investigated. Tensile properties, dimensional stability, fiber—matrix compatibility, and biodegradability were investigated by tensile testing, water absorption test, scanning electron microscopic analysis, and soil burial test, respectively. From the results, it was shown how the Young’s modulus of lyocell/CAB composites increased from 2 GPa for neat CAB to 4 GPa for a composite with a lyocell fiber content of 34.8% (v/v). Similar trend was obtained for flax/CAB biocomposites which showed higher modulus than lyocell/CAB composites, with values of 5 GPa for a flax/CAB composite with the same composition. Moreover, tensile strength of lyocell/CAB composites with fiber content higher than 16.7% (v/v) resulted in lower values than neat CAB, indicating a high probability of failure cracks on lyocell/CAB composite samples when increasing fiber composition. In addition, compared to neat CAB, elongation at break decreased for all the composites studied. It was also observed that increasing the fiber content, the water absorption of the composites increased compared to neat CAB matrix due to the hydrophilic nature of the lyocell and flax fibers. The biodegradation test showed, after 60 days of soil burial, about 10% and 25% of mass lost for 34.8% (v/v) of lyocell/ CAB and flax/CAB composites, respectively.

Properties and optimal manufacturing conditions of chicken feathers thermoplastic biocomposites

The aim of this study was the analysis and characterization of composites based on thermoplastics (ethylene vinyl acetate, polypropilene and high-density polyethylene) and chicken feathers. Several composite samples with a content of 20% v/v of chicken feathers have been studied to determine the optimal manufacturing conditions of temperature, mixing time, and mixing speed to achieve the best tensile properties. The results have shown that the addition of micronized chicken feather (20% v/v) to thermoplastic matrices increases stiffness and provides a more brittle behavior. Ethylene vinyl acetate matrix also shows an ability to participate in second-order intermolecular interactions with chicken feathers, providing better tensile properties (tensile strength and toughness) than polypropilene and high-density polyethylene. Optimal manufacturing conditions were found for a mixing time of around 5 min; a mixing speed of 50 r min−1; and temperature values of 160℃ in case of high-density polyethylene, 120℃ for ethylene vinyl acetate, and 170℃ for polypropilene. Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy analysis have been performed in order to provide further understanding of the compatibility and microstructural features that support the tensile properties of the materials.

Effect of chemical treatments and additives on properties of chicken feathers thermoplastic biocomposites

The valorisation of chicken feathers waste was researched in this work through the preparation of composites using ground chicken feathers as a filler (20% vol/vol) and polypropylene or low-density polyethylene matrices. In order to improve the compatibility between chicken feathers and the matrices, two different strategies were followed: first, by the chemical modification of the chicken feathers by either acetylation or silanization and second, by the addition of adhesion promoters like maleated polypropylene and maleated polyethylene. The effect of those treatments on the physical, mechanical and structural properties of the thermoplastic-chicken feathers biocomposites, which are mainly related to the fibre–matrix compatibility, was analysed. Results show that the addition of 20% (vol/vol) of unmodified chicken feathers to the thermoplastic matrices results in a significant decrease of the tensile strength associated to a weak interfacial adhesion as it was demonstrated by scanning electron microscopy. However, when the adhesion promoters were added to the mixture, a significant increase in the tensile strength was noticed, particularly when the composites were obtained by a process at 180℃. On the contrary, acetylation and silane treatments of the chicken feathers did not result in any practical improvement of the macroscopic properties of the biocomposites.

Structural and physico-mechanical properties of natural rubber/GTR composites devulcanized by microwaves: Influence of GTR source and irradiation time:

Ground tire rubber from car and truck was modified using microwave irradiation at variable time. The irradiated ground tire rubber was used as filler in composites based on natural rubber. The composites, with high content of ground tire rubber, were prepared using an internal batch mixer and subsequently cross-linked at 160℃. The influence of the ground tire rubber source (car/truck) and irradiation time on structure, physico-mechanical behaviour, thermal properties and morphology of natural rubber/ground tire rubber composites was studied. The interfacial interactions between ground tire rubber and natural rubber as function of ground tire rubber source and irradiation time were evaluated by Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile tests, swelling measurements and scanning electron microscopy. The results showed that irradiation of ground tire rubber slightly enhanced tensile properties and cross-link density of natural rubber/ground tire rubber composites. This effect was more evident in the case of ground tire rubbertruck because of its higher content of natural rubber and was reflected in changes in the interfacial adhesion, which were confirmed by the results of Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy analysis.