FORMATION OF LEATHER QUALITY INDICATORS OF DIFFERENT TYPES OF LEATHER RAW MATERIALS WITH THE USE OF MONTMORILONITE

The tanning process is important in stabilizing the collagen structure of the derma. Сhrome tanning is the traditional option. The basic chromium sulfate is used in the production of 80% of leather in use. A peculiarity of chromium tanning turns out to be an inefficient use of chromium compounds, since almost 40% of tannins remain in wastewater. Considering the disadvantages of using chromium compounds, scientific research on the replacement and use of rather eco-friendlier substances has been conducted for a long time. One of the directions of ecologization of leather manufacturing is the use of modified montmorillonite dispersions in various technological processes such as tanning, filling, dyeing, fat-liquoring, etc. Researches have been aimed at identifying the feasibility of making leather for the uppers of children’s shoes from different types of leather raw materials using modified dispersions of montmorillonite at the stage of tanning. According to the technology of making leather, cattle (medium heifer), goat and sheep skins were used for the upper of the shoes. The analysis of leather quality indicators from different types of raw materials obtained with the use of chromefree tanning. It is proved that hides from raw materials of goats and sheepskins in comparison with cattle are characterized by increased yield area by 3.5-7.2 %, thickness by 0.8-2.6 %, volume yield by 4.5-6.1 % and uniformity of quality indicators in different topographic areas. The level of indicators of physical and mechanical, hygienic properties and chemical composition of leather of different types of raw materials is almost identical within the requirements of regulatory documents. It is advisable to use for children’s shoes leather from raw goat and sheepskin given the peculiarities of the manufacture of children’s shoes, dimensional characteristics of parts, requirements for dimensional stability and shape conservation.

The acrylic/montmorillonite nanocomposites for leather finishing

Leather finishing is carried out by application of coatings that include polymer, pigment, solvents and any auxiliary products. The acrylic resins are employed in leather finishing to produce polymer film to create a uniform protective coating on the leather surface. To increase the operational properties of the polymer coating for leather finishing, it is proposed to use nanocomposites based on acrylic resin and modified dispersions of montmorillonite (AMC). The introduction of montmorillonite allows the polymer to be structured and provides improved physical and mechanical indexes of the leather coating. Acrylic polymers and colored modified dispersions of montmorillonite (CMDM) were used for the study. The colored montmorillonite was obtained by treating water dispersions of montmorillonite by sodium carbonate, basic chromium sulfate and anionic dyes. The AMC contained 1.5–2.0% montmorillonite of the dry polymer residues. The use of AMC enhances the physical and mechanical properties of the leather coating. It is shown that the use of temperature at 60°C for the formation of finishing coating enhances the structuring of the polymer matrix, which is confirmed by the 40 % increase in the tensile strength of films and the 10 % reduction in relative elongation at break.

The Effect of Fiber Surface Treatment on the Water Absorption and Morphological Properties of Linear Low Density Polyethylene/Poly(Vinyl Alcohol)/Kenaf Composites

The effect of untreated and treated (chromium sulfate and sodium bicarbonate) kenaf (KNF) on the water uptake and morphological properties of linear low density polyethylene/poly(vinyl alcohol)/kenaf (LLDPE/PVOH/KNF) composites was studied. The composites were prepared by using an internal mixer (Haake Polydrive) at 150 °C and 50 rpm for 10 min. The results showed that the untreated composites tend to absorb greater amount of water compared to the treated composites. This shows that the chromium sulfate and sodium bicarbonate treatment on KNF had improved the interfacial adhesion between KNF and LLDPE/PVOH matrices. Consequently, the capability of water absorption by the treated composites was reduced. Scanning electron microscope (SEM) result shows that lesser traces of filler pull-out and better filler-matrix interfacial adhesion were observed in the tensile fractured surfaces of treated composites.