Methodological aspects of strength testing of building products based on thermoplastic waste

The urgency of the problem of recycling polymer waste is increasing every year. It is promising to use thermoplastic waste as binders in polymer-mineral compositions for the production of small-piece construction products such as paving slabs, curbs, parking limiters, elements of landscape design, etc. Technical requirements for the compositions of polymer-mineral compositions, the properties of their products, test methods are not regulated. One of the most informative characteristics is static uniaxial compression tests. It is necessary to accumulate statistics on strength tests of composites based on secondary thermoplastics and develop mathematical patterns of the influence of sample size, primarily their thickness, on strength properties. Therefore, the work is aimed at improving the methodological aspects of assessing the compressive strength of polymer-mineral samples based on thermoplastic matrices. Crushed polymer waste of polyethylene terephthalate and polypropylene, a combination additive ethylene vinyl acetate, and limestone flour were used to make the samples. Samples of various thicknesses were made by pressing from hot mixtures, then their compressive strength was determined. As a result, a differentiated approach to the geometry of the samples is proposed, taking into account the peculiarities of their manufacture and the complexity of obtaining samples of exactly the same thickness. A linear basic dependence of strength on the thickness of the sample is obtained, and a method for calculating compressive strength from the experimental thickness of the sample to the control one is proposed. It is proposed to take the sample thickness of 4 cm as a control, by analogy with the current standards for cement composites. Using the basic dependence and the proposed conversion method, it is possible to design formulations of compositions using various powdered mineral fillers (filling degree of more than 50% by weight) and various thermoplastic wastes, combining rigid thermoplastic polyethylene terephthalate and polyolefins in compositions.