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The current paper covers an experimental study, mathematical modelling, and design optimization of the laser treatment process of denim fabrics. Laser fading is used in the finishing phase of garment production, unfortunately, it decreases fabric durability. Denim fabric is known as a cotton fabric but nowadays it is blended with other fibres to improve fabric properties. For this reason, the main purpose of this study was to test multicomponent fabric longevity after laser treatment. The knowledge from this study is used by garment production company. The tear force, abrasion resistance, and colour difference are considered as performance characteristics of laser treated denim fabrics subjected to maximization. To achieve the goals, novel, mathematical models were developed. In the preliminary tests, the design space was determined. The full factorial design of experiments was utilized in the experimental study and the values of the performance characteristics are measured. Based on the results of the experimental study the artificial neural network and Haar wavelet based mathematical models were developed to predict the behaviour of the tear force, abrasion resistance, and colour difference. The artificial intelligence-based multicriteria design optimization procedure is developed.

The effect of nanoclay additive on polyamide film oxygen permeability is investigated from the perspective of possible use as a laminate component for low-cost food packaging material. Montmorillonite nanoclay was melt-mixed in an industrial grade polyamide by twin-screw extrusion and the mixture was hot-pressed to a ~50 µm thick film. The film with 10 wt.% of nanoclay loading showed a 17 % decrease in the oxygen transmission rate (OTR), as compared to the pristine polyamide film (72 and 87 cm3/m2∙24 h, respectively). Despite the relatively high loading of the filler the obtained OTR exceeds that of the food packaging preferred upper limit of 10 cm3/m2∙24 h. XRD measurements confirmed the near-complete exfoliation of the nanoclay platelets. The platelets were found to be at an average angle of 9.5 degrees relative to the film’s surface plane. To comply with the requirements for food packaging, this angle needs to be decreased down to 0.4 degrees. To achieve this, different film-making methods enabling better control over the filler particles’ orientation need to be explored. Nanoclay addition increased the films’ yield strength (23 % for 10 wt.% film) and stiffness, while not affecting the films’ optical appearance.

Characteristics and serviceability of denim fabrics have undergone major changes. Nowadays denim is commonly used for casual wear. Durability and comfort are important parameters for consumers when choosing a denim garment. Therefore, in this study, abrasion resistance, tear and tensile properties of core–spun yarns and air permeability of denim fabrics with different weft yarns per centimetre and fibre content were analysed. The test results showed that weft yarns per centimetre influences fabric air permeability negatively but abrasion resistance increases. Higher weft yarns per centimetre influences fabric air permeability negatively but abrasion resistance increases. Polyester, elastane, modal, viscose and Lycra T400 were used in the core of weft yarn to analyse the impact of those fibres on the durability and comfort properties. Elastane is used to add stretchability to the fabric, which provides comfort to the wearer. The higher the elastomeric fibre content in the fabric, the greater is its elasticity; however, the tensile properties of the woven fabric decrease. The tear strength of the fabric was increased by the presence of the polyester fibre in the core.

This study examines the effect of different post cure parameters to a polymer matrix particulate reinforced composite material. The goal is to evaluate the importance of different factors and to suggest a well-balanced post cure mode that supports the application of the material.Polymer matrix composites are post cured at elevated temperature to increase the amount of cross linking to achieve better chemical and heat resistance and mechanical properties. Every material has an individual post cure process that depends from the raw materials. Post curing variables include temperature, duration of cure, the time between initial curing and post curing and temperature profile gradient.There are several ways to determine the cure state of a polymer. It can be evaluated based on the mechanical and physical properties, residual styrene content, glass transition temperature, residual exotherm or solvent swelling test. For the determination of the suitable post cure parameters test slabs were casted and post cured with varying time and temperature. Glass transition temperature, residual exotherm, softening in ethanol, surface hardness, flexural strength and flexural modulus were determined. It is shown that the material should be cured at 60 °C – 80 °C. With higher temperature and extended time of cure the glass transition temperature raises but the material becomes too brittle.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2435

Blends of high-density polyethylene (HDPE), moderate and hyper-branched LLDPEs (LLDPE and HbPE, respectively) have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has been handicapped by the absence of a consensus concerning the degrees of mixing of the components. Moreover, usually the blends are obtained by melt blending, which may not ensure the initial homogeneity of the components. In our work the mixtures were prepared by dissolving the conventional LLDPE having branching content 7.2 wt% with HbPE with comonomer content 17.8 wt% in xylene at 130 °C and stirring for 2 hours. The same procedure was applied for the blending of HDPE with HbPE. After dissolving the mixtures were cooled in liquid nitrogen and after that freeze dried in vacuum line. The ratio of components in the blends was varied. Differential scanning calorimetry has been used to investigate the miscibility and thermal behavior of the blends. For this purpose isothermal and non-isothermal treatment of prepared blends were conducted. By preliminary study the double melting peaks in non-isothermal endotherms have been observed in all the studied blends. The presence of two peaks in DSC scan can be attributed to the formation of separated crystals from both the high density/linear low density and highly branched components. However, certain limited degree of co-crystallization is detected in all the LLDPE/HbPE blends and HDPE/HbPE blend rich in HbPE component.http://dx.doi.org/10.5755/j01.ms.17.3.589

A bimodal high density polyethylene (HDPE) has been successfully fractionated by analytical size exclusion chromatography into molar mass fractions with Mw's ranging from 3.6 kg/mol to 8 000 kg/mol, and subsequently deposited on germanium disks using the Lab Connections Transform method. After removal of the fractions from the disks, having masses in between 10 µg - 150 µg, differential scanning calorimetry has been successful in measuring the (re)crystallization and melting behavior of these fractions. Comparing the crystallization and melting peak temperatures of the fractions with those of narrow molar mass linear polyethylenes points to the HDPE being linear below and short chain branched above 100 kg/mol respectively. This value coincides roughly with the 'split' between the molar mass distributions resulting from the first and the second polymerization reactor - confirming the addition of 1-butene in the second reactor.http://dx.doi.org/10.5755/j01.ms.17.3.590

In our work we studied composites of poly(lactic) acid (PLA) and low density polyethylene filled with cellulose fibres. The studied composite materials were manufactured with a twin-screw extruder. The extruded compound was processed in to samples using compression moulding. The content of cellulose in polymer/cellulose composites was varied. Effect of low amounts of cellulose on the rheological and tensile properties was studied. Tensile tests showed that the incorporation of cellulose into PLA matrix lead to stiffer but slightly more brittle and weaker materials, since Young's modulus increases and tensile strength and elongation at break slightly decrease. Mechanical results are in agreement with rheological behaviour: the composites exhibit the improvement in the storage and loss moduli of composites compared with that of matrix polymers. The composite dynamic viscosity increases with cellulose content in the same manner as loss and storage moduli. The processing and material properties of PLA/cellulose composites were compared to the more commonly used low-density-polyethylene/cellulose composites.http://dx.doi.org/10.5755/j01.ms.17.1.245