Papers by Author: Tibor Czigány

Abstract: Nowadays, we can choose a carrier bag made of traditional LDPE or a biodegradable polymer to pack vegetables, bakery products, and other products in more and more shops. However, the customers and the selective waste collection system are not yet prepared for the separate collection of compostable biopolymers. Therefore, they are mixed in the plastic waste stream. Therefore, the aim of the study was to analyze the mechanical and optical properties, and the compostability of different low-density polyethylene (LDPE) and poly (butylene adipate-co-terephthalate) (PBAT) compounds. We made different compounds from LDPE and PBAT by twin-screw extrusion and blown films from the regranulates. We investigated the tensile and optical properties and the biodegradability of the blown films. The tensile test showed that the "contaminants" had a more significant effect on elongation at break than tensile strength. We observed that the haze of the LDPE-based blends increased with an increasing weight fraction of PBAT. We found that PBAT-based samples were completely disintegrated in 42 days, regardless of the weight fraction of LDPE.

Abstract: Melamine-formaldehyde (PMF) coated microcapsules were produced with liquid pentaerythritol-tetrakis (3-merkaptopropionate) (PETMP) and UV-sensitive indicator colored PETMP cores. Capsules with an average diameter of 43 μm formed due to the adjustments on magnetic stirring, compound ratios, acidity and reaction time. Reproducible recipe was found to produce colored PETMP filled capsules with yields of 1-10%. Optical microscopic investigations were conducted to follow the formation of the particles, and scanning electron-microscope (SEM) was used to verify that the capsules did not break up as an effect of the brittle failure of the epoxy matrix specimens. Improvement of the shell-matrix adhesion was attempted with silane compounds and investigated with X-ray photoelectron spectroscopy (XPS) and SEM.

Abstract: The possibilities of the application of microbond test and cylinder tests for determining the interfacial shear strength at the fiber-matrix interface in thermoplastic matrix polymer composites were investigated. Possibilities of test specimen preparation were also investigated. Finally the applicability of the method to make high precision measurement of interfacial shear strength was evaluated.

Abstract: The geometry and mechanical properties of solid and hollow carbon fibres were investigated by light-and scanning electron microscopy, and by single fibre tensile tests. The hollowness factor of fibres was determined by their external and internal diameter. The tensile strength was determined by single fibre tensile break tests. It was shown that the bigger the diameter of the fibres the lower the mechanical properties is. It was found that the hollow carbon fibres are suitable for preparation of a self-repairing composite with the advantage over other solutions because of their geometrical and mechanical properties.

Abstract: In this paper, melamin-formaldehyde microcapsules filled with pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) or epoxy were prepared via oil-in-water emulsion polymerization method. Two different routes were chosen from literature, and applied with some changes. The effects of modification of reaction conditions on the resulting capsules were studied. It was found that too low pH value in the emulsion causes burst polymerization of the wall material, without microcapsule formation. When pH was set to 4.5 spherical microcapsules were formed. Optical microscopy was used to evaluate the microcapsules.

Abstract: Due to the effect of graphite and montmorrilonit additives, the impact strenght slightly decreases, but by the influence of softening material, the value of impact strength can be three times more than the pure PA6. It is determined that graphite can be added until 3%, montmorrilonit can be added until 6% and softening material can be added until 15% to the base matrix. These samples give basis for special characteristics examinations.

Abstract: Composite sheets were made of cyclic butylene terephthalate as matrix and carbon fibers as reinforcing material.Hot press method was used at different temperatures for composite processing. The mechanical properties of these materials and the effect of processing temperature were tested. The samples were kept in a climate chamber, and the effect of air humidity was examined through the change of the mechanical properties. Pictures were taken by a scanning electron microscope of the broken surfaces of the specimens. The results give conclusions about the outdoor application of these composites.

Abstract: Basalt fiber reinforced polyamide composites were investigated to determine their static and dynamic mechanical properties. The composites were compounded in an extruder and were injection molded. A glass fiber reinforced composite also was investigated. Two different basalt fibers were used with silane sizing and one of them was used also without sizing. The results show that composites with silane sized basalt fibers have properties similar to glass fiber reinforced composites, while unsized basalt fibers eventuate smaller strength and higher brittleness.

Abstract: To improve the properties of polypropylene (PP), a new route that combines nanoparticles filling with self-reinforced technique was applied in this work. That is, nano-silica particles were firstly modified by graft polymerization to increase interfacial interaction between nanoparticles and matrix. Then the grafted nanoparticles were melt-compounded with PP producing composites sheets, and the sheets were stretched under a temperature slight lower than the melt point of PP at a constant velocity. Finally, the stretched sheets were film-stacked with random PP copolymer by a special designed mold and were hot pressd at different processing temperature (T=150-175°C) and holding pressure (2.0-5.0MPa) under constant holding time of 5min. The resultant self-reinforced nanocomposite are much stronger and stiffer than the unfilled polymer as characterized by mechanical test. The results show that the optimum processing conditions for hot consolidation are 160°C and 2.5MPa. Addition of nanoparticles increases crystallinity of PP, and induces the formation of craze and cause much more surrounding matrix polymer to involve in large-scale plastic deformation, which might ensure an overall improvement of mechanical properties.

Abstract: In this work, plastic foams were prepared from plant oil resins based on soybean oil and castor oil. Firstly, epoxidized soybean oil (ESO) reacted with acrylic acid using N, N-dimethyl benzyl amine as the catalyst, and castor oil was modified with maleic anhydride, respectively. Acid number was used to monitor the reaction process, and structures of the resultant acrylated epoxidized soybean oil (AESO) and maleate castor oil (MACO) were proved by Fourier Transform Infrared (FTIR) measurements. It was found that the catalyst is quite effective in synthesizing AESO. Then, plastic foams based on AESO and MACO were synthesized through free radical initiated copolymerization with diluent monomers including styrene and methyl methacrylate. Mechanical properties, reinforcing effect of sisal fiber and biodegradable feature of the foams were characterized, showing the suitability of the bio-foams for acting as packaging materials.