Silicone pressure-sensitive adhesives (Si-PSA) are relatively new to the adhesive industry. The first Si-PSA adhesives used in industry were presented in the 1960s, but only in the last two decades has the interest in this type of adhesives increased due to new possible applications, such as medical plasters and assembly tapes. Products based on Si-PSA materials are used especially in systems exposed to very high and low temperatures due to their effective range of use, even in the range of –70–300 °C. Silicone tapes can also be used on high surface energy substrates such as metals and low surface energy substrates such as PTFE, polyolefins, and silicones. The self-adhesive and mechanical properties of silicone pressure-sensitive adhesives depend largely on the type and concentration of the crosslinking agent. Most often, organic peroxides are mainly used, such as benzoyl peroxide (BPO) or dichlorobenzoyl peroxide (DClBPO) at temperatures from 120 to 150 °C. Small amounts of silicon fillers are added to commercial peroxide-crosslinked silicone resins, to increase their resistance and thermal stability. In the present work, commercially available silicone prepolymers were modified to increase the thermal stability of silicone pressure-sensitive adhesives. An example of such a physical modification was the introduction of powdered kaolin to polydimethylsiloxane resins from Dow (USA), with different concentrations. No significant impact on important functional properties such as adhesion, tack, cohesion, and shrinkage was found during the tests. The thermal resistance of prepared Si-PSA tapes has been improved.