Low‐cost mineral fillers, including mica, calcium carbonate (CaCO3), and alumina oxide (Al2O3) were used to modify poly(vinyl chloride) (PVC)/α‐methylstyrene–acrylonitrile copolymer (α‐MSAN)/chlorinated polyethylene (CPE) blend. With the addition of mineral fillers, the thermal conductivity, flexural modulus and overall thermal stability were improved; however, loss in tensile properties, impact and flexural strength, and initial thermal stability accompanied the other improved properties. The theoretical modeling results indicate that mica has a more effective potential to increase the thermal conductivity and better interfacial interaction with the polymeric matrix. Therefore, mica is the best candidate for enhancing the properties of the composites. POLYM. COMPOS., 39:553–559, 2018. © 2016 Society of Plastics Engineers