STUDY OF THE PROPERTIES OF POLYSTYRENE CONTAINING SECONDARY GRANULES OF EXPANDED POLYSTYRENE
Lost-foam casting is one of the high-precision casting techniques. This technique usually relies on the use of foundry polystyrene. The use of secondary grаnules of expanded polystyrene in evaporative patterns can eventually result in the lower cost of castings. The purpose of this research was to determine the optimum concentration of expanded polystyrene granules in the pattern. For this purpose, patterns of various compositions were manufactured using mathematical planning methods and in the production environment of Karaganda Machine Building Plant named after Parkhomenko. Such patterns were then used for casting. The patterns were tested for porosity, roughness, penetration and vaporization degree. The experiments conducted relied on both the national standards and the common practice, as well as on advanced instruments and equipment. Originality: This research marks the first time when a precision lost-foam casting technique is being developed that relies on the use of polystyrene with secondary granules of expanded polystyrene. The range of 10 to 50% has been identified as the optimum concentration of secondary polystyrene for lost-foam casting. Based on the results of experimental studies, the use of 35-40% of secondary granules from waste construction polystyrene was found as optimum. Due to this, one can obtain high-quality polystyrene patterns with low roughness, high dimensional accuracy and uniform bulk density across the entire pattern section. This is due to low foamability of the secondary polystyrene granules which can be found on the surface of the pattern. Besides, the cost of such polystyrene is much lower than the cost of the conventional foundry polystyrene which is currently used in most casting applications. The article also describes the results of studies in which the proposed polystyrene composition was tested for porosity, roughness, penetration and vaporization degree.