Cs. Varga

Mechanical Properties of Polypropylene/Multi Walled Carbon Nanotube Composites

Carbon nanotubes (CNTs) are promising additives for polymer composites due to their excellent special mechanical, electrical, and thermal properties. Polypropylene/multi walled carbon nanotube (PP/MWCNT) composites were produced in single and double screw extruders. The composites contained 0.5, 2, 3 and 5 wt% multi walled carbon nanotubes (MWCTN). For comparison, composites with carbon black as an additive instead of MWCNT have been made. The melt flow rate (MFR), flexural modulus, yield strength, tensile strength and heat deflection temperature (HDT) of the composites have been examined.

Improving Mechanical Properties of Glass Fibre Reinforced PBT Waste for its Recycling as a Product of Pipe System Elements

PBT [poly(butylene terephthalate)] is an important engineering thermoplastic having several advantageous properties; however, its brittle behaviour is a disadvantage. Blending with a polymer or applying various types of commercial additives are the two methods widely used for taking advantage of PBT while improving its poor impact properties. In our experimental work, different types of commercially available additives have been applied for improving the mechanical properties of glass fibre-reinforced PBT. Blending a cyclic oligomer with GF/PBT samples made them much more elastic, which was shown by better resistance against tensile, flexure, dynamic and cyclic tensile stresses.

Improving the compatibility of man-made fibre reinforced composites

Composites are made of two or more different materials which constitute the modernest family of construction materials for technical applications. Fibre reinforced composites are unique materials and are heterogeneous in composition. High strength/weight ratio is characteristic for them which is advantageous in many points of view. E.g. cost for moving them is much more lower than for conventional materials, they are advantageous environmentally either, do not need high maintenance costs and allow high creativity in shapes and functions. For properties of fibre reinforced composites interaction between the fibres and the matrix is especially important beside the mechanical properties of the building parts. As their chemical compositions significantly differ from each other the proper adhesion could be achieved by application of compatibility improving so called compatibilizing additive which is able to connect either to the fibres or the matrix due to its chemical composition. Such compatibilizing additives were produced, which are able to solve or at least reduce the incompatibility problem in carbon fibre reinforced thermoplastic and glass fibre reinforced thermoset composite systems.

A novel route for injection moulding of long carbon fibre-reinforced LLDPE:

The scope of our work has been the development of a new type of coupling agent by which processing of long carbon fibre-reinforced thermoplastic composites by conventional injection moulding can be possible. The experimental additive was expected to hinder fibre breakage and to simultaneously improve the mechanical properties of the composites. Resistance of LLDPE reinforced with 1–10 wt% long carbon fibres against tensile, flexure and impact stresses has been investigated. Tensile strength of carbon fibre/LLDPE composites has increased by 10–30%; flexure strength has gained 15–90% related to the neat polymer depending on the fibre concentration. The effect of a blowing agent on the mechanical properties has also been investigated. At least 20% higher yield strength has been measured for the foamed sample with 5% carbon fibre related to the nonfoamed one with the same fibre content. The higher the fibre content was, the higher the improvements in the mechanical properties became. Fibre–matrix interaction has been studied on scanning electron microscopy graphs where a well-connected polymer layer has been observed to the fibre surface.

Effect of a New Type of Coupling Agent on The Mechanical Properties of Various Multi-Walled Carbon Nanotube/Rubber Composites

In our experimental work application of carbon nanotubes in rubbers have been investigated. The effects of the type of the rubber matrix, the concentration of the carbon nanotubes and the effects of a coupling agent on the mechanical properties of the composites have been studied. The strength of the rubber matrix had great influence on the strengthening behaviour of the carbon nanotubes. By application of surface treated carbon nanotubes the strength of the composites made from a rubber matrix having the tensile strength under 10 MPa could be improved by 35%. However, the composites from the rubber with higher tensile strength contained treated carbon nanotubes afforded balanced performance against fatigue stresses probably due to the effect of the coupling agent and the homogenous distribution of the carbon nanotubes.

Effect of Multi-Walled Carbon Nanotube Content on Dynamic Mechanical Properties and Crystallinity of polypropilene composites

This study investigates the effect of multi-walled carbon nanotube (MWCNT) content on the dynamic mechanical properties and crystallinity of polypropylene (PP). Carbon nanotubes are promising additives for polymer composites due to their excellent mechanical, electrical, and thermal properties. Polypropylene/multi-walled carbon nanotube (PP/MWCNT) composites were produced in single and double screw extruders. The composites contained 0.5, 2, 3 and 5 wt% multi walled carbon nanotubes. The effect of MWCNT addition on the thermal transitions of the PP was investigated by differential scanning calorimetry (DSC) measurements. Dynamic mechanical analysis (DMA) studies revealed an enhancement of the storage modulus.