## 3 Results and Discussion
### Melt Volume Rate and Density  
The Melt Volume Rate (MVR) is a simple measure used to assess the processing properties of butyl sealants. Due to the sealant's inherent tackiness, determining the mass flow rate can be challenging. The MVR measurement helps determine whether a sealant has the appropriate viscosity for processing by a given method. Butyl sealants intended for processing using screw extruders typically have an MVR in the range of 40-150 mL/10 min (5 kg/140 \({}^{\circ}\)C), whereas processing with barrel extruders is feasible when the MVR is greater than 50 mL/10 min (2.16 kg/140 \({}^{\circ}\)C). The typical viscosity of sealants extruded from barrels is in the range of 50,000-150,000 mPas. The MVR can be converted to viscosity [36; 37].  
Butyl-based pressure-sensitive sealants typically contain fillers in the range of 30-70% by weight. Fillers generally serve as thickeners or reinforce the blends [15]. Density testing is a simple and quick method that allows for estimating the degree of filler content in a blend. Due to the high tackiness, an easy method is the displacement density measure  
Figure 4: (**A**) Cohesion changes depending on modifier content. (**B**) Cohesion changes after water immersion, depending on modifier content. Sample compositions in Table 1.  
ment. By knowing the density of the individual components of the blend, the theoretical density of the blend can be estimated [38]. Figure 5 illustrates MVR changes depending on modifier content.  
The addition of MPTES up to 2.5 PHR to the investigated systems did not significantly affect their processing properties, as evidenced by the stability of the MVR, which ranged from 76 to 78 cm\({}^{3}\)/10 min for samples MPTES-0 to MPTES-2.5. Only when the MPTES content was increased to 5 and 10 PHR was a noticeable rise in MVR observed, which indicated the plasticizing effect of silane. A similar trend was observed for the GLYEOS and APTES silanes: up to a concentration of 2.5 PHR, changes in MVR were negligible, but, at higher contents of functional silanes, this parameter increased. In particular, for APTES-10, a significant jump in the melt flow rate was recorded, reaching 109 cm\({}^{3}\)/10 min, which represented a 56% increase compared to APTES-0. In contrast, the addition of VTMOS did not cause significant changes in the MVR, which remained constant across all samples in this series. However, the introduction of BIPB peroxide as a radical source led to polymer blend degradation, as evidenced by an increase in the melt flow rate. This effect was observed in every tested system: for MPTES-10B, the MVR increased by 23% compared to MPTES-0; for GLYEOS-10B, the MVR rose by 69% compared to GLYEOS-0; and for VTMOS-10B, the increase was as high as 80% relative to VTMOS-0.  
Table 3 summarizes the density changes depending on the modifier content. Density measurements were performed using Archimedes' method, which offers remarkable accuracy despite its simplicity. The sample's weight was first measured using an analytical balance, followed by measuring the weight of the displaced liquid while the sample was fully submerged. This allowed for the precise calculation of the sample's volume. The density was determined with an accuracy of 0.01 g/cm\({}^{3}\). Based on the obtained results, it can be concluded that the density values for the mixtures fell within the range of 1.43-1.44 g/cm\({}^{3}\)  
Figure 5: MVR changes depending on modifier content. Sample compositions in Table 1.