## 3 Results and Discussion  
### Cone Penetration  
Determining the tackiness of adhesive sealant samples is more challenging than testing the tackiness of pressure-sensitive adhesives. Typical methods for testing the tackiness of pressure-sensitive adhesives, such as loop tack, quick stick, rolling ball tack, or probe tack [24,25], are not suitable for adhesive sealants. In the case of sealants, due to their relatively low cohesion compared to pressure-sensitive adhesives, testing tackiness often leads to cohesive failure, which prevents reliable results from being obtained. One of the simple, indirect methods for assessing the tackiness of a material is the hardness measurement using a cone penetration method. It is assumed that butyl sealants with a penetration below 40 [1/10 mm] lose tack, while a penetration above 80 [1/10 mm] indicates high tack and a tendency toward cohesive failure during delamination. The temperature of testing and application significantly influences the results due to the viscoelastic nature of pressure-sensitive sealants. For most construction applications, the useful penetration range for general-purpose butyl sealants is between 50 and 80 [1/10 mm]. Figure 1 presents penetration changes depending on modifier content. Based on the conducted studies, it can be stated that the introduction of BIPB into the VTMOS-10B had a significant impact on increasing the penetration value. In the case of the MPTES-10B system, a decrease in this parameter was observed, reaching a value of 75 [1/10 mm], which may suggest structural changes in the material. Both IIR and PIB tended to degrade in the presence of radicals by \(\beta\)-scission (Figure 2), which was associated with the presence of a tertiary carbon atom in their chains [26,27]. Figure 1: Penetration changes depending on modifier content. Sample compositions in Table 1.  
The introduction of MPTES at concentrations of 1, 2.5, and 5 PHR into the systems had a minimal effect on the change in penetration values. For the system containing the highest silane content with thiol groups (MPTES-10), an increase in penetration to 79 [1/10 mm] was observed. In the case of the MPTES-10B blend, with the inclusion of a radical source, penetration decreased (75 [1/10 mm]) compared to MPTES-10 (79 [1/10 mm]). In the presence of radicals, the IIR chain may have been grafted with MPTES, forming a network under high-humidity conditions [28]. In this scenario, competing grafting and degradation processes may have occurred. The addition of VTMOS did not have a significant impact on the properties of the blends. Apart from the sample VTMOS-10B containing BIPB peroxide, the penetration values remained in the range of 75-78 [1/10 mm] in the series. VTMOS carries a vinyl group that is capable of radical or addition reactions under the right conditions. However, the butyl rubber matrix is predominantly composed of saturated hydrocarbon chains derived from isobutylene. The low level of unsaturation and the lack of readily available radical initiators or other reactive sites at standard processing conditions limit the possibility of grafting or crosslinking. The vinyl group on VTMOS often requires either strong radical initiation (e.g., peroxides under carefully controlled conditions) or specific coagents that facilitate bond formation [29]. Without these conditions, VTMOS may remain largely unreacted and simply act as a low-viscosity additive, slightly altering rheology but not significantly enhancing mechanical properties. The inclusion of BIPB peroxide in VTMOS-10B as a radical source led to blend degradation, softening the blend and increasing its penetration value compared to VTMOS-10. The introduction of APTES and GLYEOS silanes into the systems resulted in a significant increase in penetration. This effect was attributed to the unreacted silanes, which acted as plasticizers in the systems, leading to their softening [30; 31; 32; 33].