László Mészáros

Ground tyre rubber (GTR) in thermoplastics, thermosets, and rubbers

The disposal of worn tyres and their economic recycling mean a great challenge nowadays. Material recycling is the preferred way supported by legislative actions and economical/ecological arguments. This paper surveys the recent developments devoted to the reclamation, surface treatments, and to the use of ground tyre rubber (GTR) in thermoplastics, thermosetting resins, and rubber formulations. This review discloses also the principle underlying compatibilization to improve the adhesion of GTR to the corresponding matrix. It was concluded that value-added application of GTR can especially be expected in thermoplastic elastomers, and rubber combinations.

Effect of nanotube content on mechanical properties of basalt fibre reinforced polyamide 6

Abstract In this study, 30 mass-% basalt fibre and 0·5–2 mass-% multiwall carbon nanotube (MWCNT) reinforced polyamide 6 hybrid systems were prepared by extrusion and injection moulding. The effect of nanotube content on the mechanical properties was investigated by tensile and flexural tests. The results showed that the combination of macroscopic and nanosized reinforcements improved the mechanical properties significantly, and synergetic effects can also be observed. Good dispersion of the MWCNT was proven by transmission and scanning electron microscopy.

Crystallinity of Electrospun and Centrifugal Spun Polycaprolactone Fibers: A Comparative Study

Crystalline properties of semicrystalline polymers are very important parameters that can influence the application area. The internal structure, like the mentioned crystalline properties, of polymers can be influenced by the production technology itself and by changing technology parameters. The present work is devoted to testing of electrospun and centrifugal spun fibrous and nanofibrous materials and compare them to foils and granules made from the same raw polymer. The test setup reveals the structural differences caused by the production technology. Effects of average molecular weight are also exhibited. The applied biodegradable and biocompatible polymer is polycaprolactone (PCL) as it is a widespread material for medical purposes. The crystallinity of PCL has significant effect on rate of degradation that is an important parameter for a biodegradable material and determines the applicability. The results of differential scanning calorimetry (DSC) showed that, at the degree of crystallinity, there is a minor difference between the electrospun and centrifugal spun fibrous materials. However, the significant influence of polymer molecular weight was exhibited. The morphology of the fibrous materials, represented by fiber diameter, also did not demonstrate any connection to final measured crystallinity degree of the tested materials.

Influence of extrusion temperature on thermal properties of polyamide 6/MMT nanocomposites

Abstract The effect of processing temperature on the melt flow and thermal behaviour of polyamide 6 (PA6)/organophillic montmorillonite (MMT) nanocomposite was investigated. PA6/MMT nanocomposites were prepared by melt extrusion at five different processing temperatures. Neat PA6 was also extruded as a reference. The composites were characterised by melt flow measurement, differential scanning calorimetry, dynamic mechanical analysis and X-ray diffraction.

The Effect of Pre-Electron Beam Irradiation of HDPE on the Thermal and Mechanical Properties of HDPE/PET Blends

The effect of electron beam (EB) irradiation of high density polyethylene (HDPE) on polyethylene-terephthalate (PET)/HDPE blends has been investigated. The HDPE component was radiation treated before the blend was melt mixed. Although the radiation treatment of HDPE component with 50-200 kGy caused some decrease in the tensile strength and elasticity modulus, the maximum tensile elongation of the blend showed a significant increase (+40%) at optimum dose (100 kGy). The DSC results and the scanning electron microscope images of the fracture surfaces also showed the benefit of a 100 kGy EB-dose in the connection the otherwise thermodynamically incompatible part of the blend.

Low-cycle fatigue properties of basalt fiber and graphene reinforced polyamide 6 hybrid composites

In this study, the effect of graphene content on quasi-static and fatigue mechanical properties of basalt fiber reinforced polyamide 6 is investigated. Hybrid composites and reference monocomposites were melt compounded, and then specimens were injection molded. Although the presence of graphene caused moderate change in quasi-static tensile properties, remarkable increment in the fatigue properties of hybrid composites was experienced. Hybrid composites with low graphene content withstood higher number of cycles in fatigue tests at the same loading compared to basalt fiber reinforced monocomposites. Scanning electron microscopy of the fracture surfaces revealed proper dispersion of reinforcement in the hybrid materials, an explanation to the better fatigue performance at lower graphene contents.

Synergistic effects of carbon nanotubes on the mechanical properties of basalt and carbon fiber-reinforced polyamide 6 hybrid composites

In this study, a new type of carbon nanotube (CNT) and micro fiber (carbon or basalt)-reinforced polyamide 6 hybrid composites were prepared and investigated. Hybrid composites were produced by melt compounding, and specimens were injection molded. Thanks to the proper dispersion of CNT, a remarkable increment in tensile properties was exhibited. The scanning electron microscopy of the fracture surfaces of the tensile-tested materials revealed that during composite preparation the presence of the fibers in the melt facilitated a better dispersion of the CNT, which explains the enhancement in the tensile properties. The deformation components of the materials were also examined at different load levels. The presence of carbon nanotubes decreased residual deformation at every applied load level. Protruding fiber length investigation revealed that improved mechanical properties are not related to fiber-matrix adhesion but to the reinforcing and stress homogenization effect of nanotubes in the matrix.

Influence of Cryogenic Attrition Ball Milling on the Particle Size of Microcrystalline Cellulose at Different Moisture Contents

In this study the effect of attrition ball milling on cellulose particle size distribution was studied. The effect of moisture content of cellulose and grinding time were examined and grinding was carried out at room temperature and under cryogenic conditions, as well. The grinds obtained were studied with electron microscope, and the characteristic dimensions of ground particles were determined using image processing software. Results revealed that effective size decrease of cellulose particles was achieved at low moisture content at room temperature, while under cryogenic conditions high moisture content was necessary, i.e. frozen moisture enhances grinding efficiency in the latter case.

Hybrid Thermoset Matrix Carbon Fibre Reinforced Composites, a Study of Interlaminar Properties

In this study carbon fibre reinforced epoxy, unsaturated polyester, and vinyl ester based, binary (two-component) hybrid matrix polymer composites were produced and mechanically characterized by interlaminar shear tests. Fracture surface of tested composites were investigated by scanning electron microscopy. Toughness of hybrid matrix composites were identified and compared to that of the reference, non-hybrid matrix ones.

The Influence of the Extrusion Temperature on the Mechanical Properties of MMT Filled PA 6 Composite

Effects of varying extrusion temperatures on the mechanical properties of polyamide 6 (PA 6) matrix montmorillonite (MMT) filled composites were investigated in this paper. Five different temperature programs were used for producing composites with 1 wt.% nanoparticles content. The mechanical properties were evaluated by tensile and flexural tests and SEM pictures were taken from the fracture surfaces. X-ray diffraction patterns were also measured to obtain some information about the structures of the materials. The results showed that the lower extrusion temperatures resulted in better mechanical properties of the composite.