Microwave heating has a number of advantages in comparison to the conventional method due to the ability to heat a part of composite material directly through specific interaction of electromagnetic radiation with selected types of materials. Most thermoplastics are relatively transparent for microwave irradiation and they do not absorb microwaves to a sufficient extent to be heated. Enhanced microwave heating can result from the use of fillers such as carbon black. Different types of carbon black were used to increase the susceptibility of polypropylene (PP) for microwave processing. Measurements were carried out on PP filled with carbon black of different grades. Relative temperature rises and heat efficiency versus the content of carbon black in PP were analyzed. The temperature changes of different mass samples of these materials under microwave irradiation with various power were also investigated. Moreover, polypropylene composites with additive of chemical blowing agents were blown under microwave irradiation and the influence of foaming conditions on cell structure and selected properties of porous products were estimated.