The Use of Straw, Coal and Foam to Improve Thermal and Mechanical Properties of Polyurethane
Authors: Antibas I. R. 
Published: February 2025

Introduction. Polyurethane, a material composed of polyol and isocyanate, has been recognized as one of the most efficient thermal insulation materials. However, its insulating properties can be further enhanced by incorporating additives such as straw, coal, or foam. Nevertheless, there is a concern regarding the potential for reduced adhesion. The literature describes the introduction of additives into polyurethane as strengthening components. The limited volumes of fillers are justified by the need to maintain the uniformity of the samples. It should be noted that most additives did not significantly impact the thermal properties of the material. The aim of this research is to investigate the possibility of improving thermal and mechanical characteristics of polyurethane by adding fillers.

Materials and Methods. Samples of polyurethane from the company "Daumerk" (Turkey), with various additives, were experimentally studied. In the first stage, four samples were prepared without fillers, and in the second stage, six more samples were created with 5% and 10% additions of coal, straw, and foam. Thermal conductivity was assessed using a hot plate method, while compression testing was conducted using a device that could apply loads up to 5,000 N. Acoustic properties were measured with an instrument that evaluated the sound absorption coefficient.

Results. The sample containing 63% isocyanate and 37% polyol had the lowest density of 33 kg/m³. This was due to the absence of fillers and the homogeneous structure of the material. Adding 5% fillers did not significantly affect the density of the sample because the densities of straw and foam were close to the density of polyurethane without additives. Low water absorption was found in samples without additives (50% isocyanate and 50% polyol) and with 5% addition of foam (62% isocyanate and 33% polyol). As the proportion of isocyanate increased, water absorption increased. Samples with higher density and no fillers had better sound absorption. With a low additive content (5%), sound absorption increased due to the homogeneity of the structure. However, with a higher additive volume (10%), sound absorption decreased due to weaker bonds in the material. Adding 10% foam provided maximum resistance to water.

Discussion and Conclusion. The optimal filler content improves thermal, mechanical, and acoustic properties of polyurethane, opening up new possibilities for its application. However, a large volume of fillers can have a negative effect on the material's properties. For example, a high straw content can significantly increase water absorption. Therefore, it is recommended to use 5% straw content in combination with 62% isocyanate and 33% polyol, resulting in a thermal conductivity of 0.023 W/m·K, a density of 37 kg/m³, and a compressive strength of 358 kN/m². These results confirm the feasibility and possibility of using fillers, such as coal and straw, in the production of polyurethane materials. A modified composition with these fillers would be cheaper and possess better physical properties than the original material. Further research could focus on studying other types of fillers for polyurethane.