Key Engineering Materials Vol. 850

Abstract: Geopolymer is known as an alkaline alumino-silicate material that has many potential advantages to replace for cement-based materials. Geopolymer is a green material with low or non-CO₂ emission technology, high strength and heat resistance, high chemical resistance, and low energy production. Geopolymer has synthesized from activated alumino-silicate resources in high alkaline conditions. After formed, the geopolymer samples are cured in different conditions such as room temperature, drying oven temperature (from 40°C to 150°C), high pressure and temperature conditions of autoclave equipment. In this study, the paper would like to introduce a new technique for curing the specimens. The geopolymer samples were cured in a microwave oven set by various regimes of curing time. After cured in microwave conditions, the samples were tested for engineering properties such as compressive strength (MPa), volumetric weight (kg/m³), and water absorption (kg/m³). This technology is a useful solution because of saving time for curing the geopolymer specimens in comparison with others (normally, it takes time for curing in 28 days). Microstructural characteristics of the fly ash-based geopolymer were analyzed and evaluated using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR).

Abstract: For a simulation of pultrusion processes with polyester resin C-L ISO 112 G, the curing kinetic model for the matrix material should be developed. This resin is characterized by excellent glass fibre wet out properties and for this reason is suitable for the utilization in pultrusion processes. The first order, n-th order, Prout-Tompkins and Kamal-Sourour models were used to build the curing kinetic models for the examined resin. The models’ accuracy was determined by calculating the relative errors between theoretical and experimental results. The curing kinetic models with the best accuracy are recommended for the development of future pultrusion processes.

Abstract: One type of birch plywood production by-product: plywood sanding dust (PSD) and virgin polypropylene (PP) composites adhesive activity was investigated. To improve of the WP (PP+40 wt.% PSD) composites sheets as overlay bonding strength against birch plywood surface and water resistance of these laminated systems the industrially produced WPC material was modified with maleated polypropylene wax (MAPP) additives. These studies showed possibility of the usage of presented by-product as an excellent reinforcement for PP based wood plastic composites and addition of the coupling agent (MAPP) gives the considerable increase of adhesive activity of the used WPC. Due to the presence of MAPP (up to 4%) significantly increases not only adhesive strength of the laminates but also water resistance of the laminated sandwich specimens. As the example adhesive bonding strength could reach 2,74 N/mm2 and increases up to 4 times to compare with unmodified WPC adhesives.

Abstract: The recycling of paper and paperboard waste for obtaining powder cellulose has a positive impact on environmental and economic benefits due to its possibility to be applied in various fields of industry, including the fabrication of wood-polymer composite^1,2. The extraction of cellulose from cellulose-containing wastes can be carried out by their mechanical disintegration with acid or alkali hydrolysis. In comparison with the known method³ the proposed method can be realized under more gentle conditions. For this aim, recycled de-inked waste paper was cut into small pieces (d < 5 mm) which were soaked in 0,05% hydrochloric solution at hydromodulus 1/20 (paper/water) for 2 hours at the intensive mechanical stirring for paper pieces disintegration. After soaking, the excessive water was pressed, and the disintegrated paper mass was dried, at first, at 60 °C for 16 hours and then at 120 °C for 2 hours. After drying, the paper mass was milled in a planetary mill for 15 minutes at a moderate rotation speed. The obtained cellulose particles were characterized by physicochemical properties. It was found, that obtained recycled paper particles (RPAP) had a similar contact angles with water compared to reference cellulose powder. However, polarity of RPAP was 20,5%, but of reference cellulose – 43,5%. RPAP could be characterized as more amorphous than cellulose because its crystallinity index was 61%, but reference cellulose powder – 81%. Using laser granulometry, it was found, that 99% of particles were less than 200 μm, and 90% of particles were less than 140 μm.

Abstract: This article is aimed at evaluating newly synthesized HPMC/BW composite films, applied for preservation of seedless lime fruit. Factors influenced to formation of the films as well as characteristics of HPMC/BW edible composite films were researched and analyzed based on experimental results and previous studies. The HPMC/BW edible composite films were created based on the components included HPMC (5% w/v), Glycerol plasticizer (Gly-2% v/v), BW (5% w/v); Oleic Acid emulsifier (OA-1% v/v). Characteristics of the composite film were evaluated via the analytical techniques known as Sensory, Tensile Strength (TS), Elongation at Break (EB), ThermoGravimetric Analyzer (TGA), Scanning Electron Microscope (SEM), Fourier Transform InfraRed (FTIR). HPMC/BW composite films applied in preserving seedless limes. Evaluations of preservation processes were based on effects of characteristics such as Sensory evaluation, Respiratory intensity, Weight loss, Vitamin C content, Total acid of before and after fruits preservation.

Abstract: In order to provide good adhesion for natural nail coatings and to avoid loss of adhesion between the substrate and the coating, the mechanical properties of the coating should be close to those of the substrate. Three different mono-functional monomers (HPMA, THFA, THFMA) and one bi-functional monomer (EGDMA) have been added to decrease the viscosity of un-polymerized composition. Optimal monomer concentration was found evaluating monomer concentration effect on viscosity. Polymerized coatings were tested with monomer concentrations of 30% and 40%. The tensile strength properties of the polymerized coatings were determined 24 hours after polymerization. Polymerization T and conversion rate of unsaturated links were also studied to find the best monomer for natural nail coatings.

Abstract: Thin film coatings on fingernails and toenails are used for aesthetic reasons or to strengthen fragile nails. Coating disintegration is one of the most important characteristics of short-term coatings. The aim of this research was to investigate adhesion test methods for UV-cured urethane acrylate coatings. Coatings was compared evaluating gel fraction and degree of conversion of C=C bonds. Adhesion was measured using pull-off adhesion test and coating removability was evaluated after coating soak-off in solvent media with cross-cut tester. Systems with four different monomers in two concentrations was evaluated. All systems show a strong correlation of adhesion with the time of disintegration.

Abstract: Functional properties of composite material based on mechanically grinded scrap tires with different particle size of fractioned crumb and polyurethane type polymer binder were investigated to estimate influence of rubber particles size and content on composite material properties (Shore C hardness, compressive stress at 10 % deformation, tensile strength, elastic modulus and elongation at break, apparent density). Optimization possibilities of composite material consisting of rubber particles with different sizes or fractions were investigated. The obtained results show that variation of composition of the composite material by changing size of rubber granulate have definite influence on selected properties of the material. Purposeful selection and mutual combination of rubber particles size included in material can ensure desirable and predictable mechanical properties of composite material.

Abstract: In this study, Fourier-transform infrared spectroscopy (FTIR) of polylactide (PLA) biocomposites reinforced with hemp fibers were analyzed. Three samples of biocomposites with different proportions of hemp fibers in the PLA matrix were compared. Hemp and PLA fibers in biocomposite were evenly blended using carding technology. Samples before and after water absorption were compared using scanning electron microscopy (SEM). Thermoset treated polylactide and hemp fiber biocomposites have high mechanical properties, that allow to reduce the number of materials in the product. The developed biocomposite can be used as a slab material and for molded parts of furniture, etc.

Abstract: Within the current report the first results of the upcoming multi-stage research cycle on the development of high-performance environmentally friendly PLA/PBAT blend based composite materials are presented. Development and basic characterization of PLA/PBAT blends at various wt.-to-wt. ratios of the base polymeric components is performed. Rheological properties of PLA and PBAT have been investigated by means of rotational viscometry to define the optimal blending parameters. PLA/PBAT blends have been obtained by using twin-screw extrusion. Structural features of the obtained polymer blend compositions have been revealed by means of Fourier transform infrared spectroscopy. Crystallization behavior of the obtained polymer blend compositions have been characterized by means of differential scanning calorimetry. Thermal stability of the obtained polymer blend compositions has been studied by using thermogravimetric analysis. Mechanical behavior of the obtained polymer blend compositions has been studied by means of both quasistatic (in respects to tensile and flexural properties) and dynamic tests (impact resistance).