In many polyolefin applications, such as electrical cables or automotive applications, the fire protection is a very important task. Unfortunately flame-retardant polymeric materials are often halogenated and form toxic substances in case of fire, which explains the general requirement to reduce the halogen content to zero. Non-halogenated, state-of-the-art flame retardants must be incorporated into the polymer in very high grades (> 40 wt%) leading to massive decrease in mechanical properties and/or processability. In this research work halogen-free flame-retardant polypropylene/expandable graphite were filled with minerals fillers such as layered silicates, magnesium hydroxide, zeolite and expanded perlite in order to enhance the flame-retardant effect. The rheological, mechanical and thermal properties of these materials were investigated to gain more fundamental knowledge about synergistic combinations of flame retardants and other additives. The rheological properties were characterized with a rotational rheometer with cone-plate setup. As representative value for the mechanical properties the Young’s modulus was chosen. Thermo gravimetric analysis (TGA) was utilized to investigate the material with respect to volatile substances and combustion behaviour. The combustion behavior of these materials was characterized by cone calorimeter tests. Combined compounds obtain good results for protection of the material against combustion.