POLİ (EPİKLOROHİDRİN-KO-(ETİLEN OKSİT)-KO-(ALLİL GLİSİDİL ETER)) ESASLI VE SİLİKA DOLGULU KOMPOZİT ELASTOMERLERİN HAZIRLANMASI VE KARAKTERİZASYONU
Özet
The aim of this thesis is to investigate the impact of modified and unmodified silicas on the properties of elastomers based on Poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) or P(ECH-co-EO-co-AGE), commonly known name in the industry as GECO. The P(ECH-co-EO-co-AGE) polymer is a random terpolymer derived from the monomers epichlorohydrin, ethylene oxide, and allyl glycidyl. GECO-based elastomers exhibit unique characteristics due to the diverse properties of each monomer comprising the polymer. It is recognized that, in addition to various functional groups present in the main chain structure of the elastomer, the type and quantity of filler material used in compounds contribute to different properties.
Within the scope of this thesis, compounds of poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) terpolymer were prepared using different types of silica. Silanized and non-silanized silica types were used at ratios of 20 phr and 40 phr to examine the effect of filler content on the properties of the elastomer. The prepared compounds were evaluated for curing and rheological properties, mechanical characteristics, compression tests, temperature-dependent stress relaxation behaviors, and dynamic mechanical properties.
The composite elastomers were prepared and characterized using silica types modified with silane groups, including Coupsil 6109, Coupsil 8113, and Coupsil VP6411, as well as unmodified Ultrasil VN2 and Ultrasil VN3 silicas, serving as filler materials. The key distinction between Ultrasil VN2 and Ultrasil VN3 lies in the surface area, where Ultrasil VN3 possesses a higher surface area than Ultrasil VN2. Coupsil 6109 is a product obtained by modifying Ultrasil VN2 with Si-69 organosilane, while Coupsil VP6411 is the result of modifying Ultrasil VN2 with Si-264 organosilane. On the other hand, Coupsil 8113 is a product derived from modifying Ultrasil VN3 with Si-69 organosilane.
In this thesis, the silica ratio and type were systematically altered in the formulations while maintaining a constant proportion of other auxiliary chemicals. The investigation of curing and rheological properties revealed notable changes in the characteristics of elastomers when modified silica types were employed in preparing GECO elastomers. The influence of silica particle size on the modification of rheological properties and network structure has been intricately analyzed in the context of this thesis. This exploration sheds light on the intricate relationship between silica characteristics and the fundamental properties of elastomeric compounds.
Mechanical testing studies on elastomers have revealed the impact of silica fillers on reinforcing the rubber matrix. The addition of silica has increased tensile strength, elongation at break, and elastic modulus values. Cyclic compression behaviors of elastomers were investigated using a universal testing machine. The results indicate that modified silicas exhibit a lower level of relative hysteresis loss compared to unmodified silicas. This highlights the potential to reduce energy loss and enhance mechanical efficiency. In other words, the findings suggest that modified silicas possess superior elastic properties compared to their unmodified counterparts. During the relaxation process, it was observed that unmodified silicas experienced a greater stress reduction compared to modified silicas. This result indicates that specific modifications applied to silicas enhance their resistance to relaxation, contributing to preserving mechanical properties over time.
In the investigation of tan delta values for compounds containing 20 phr of different silica types, it was determined that elastomers containing silicas modified with Si-69 silane exhibit lower tan delta values than other elastomers. This is attributed to Si-69 contributing more sulfur to the system, leading to a higher cross-link density and, consequently, lower tan delta values in elastomers with silicas modified by Si-69 than in other elastomers. Additionally, in Payne effect analyses, the storage modulus (G') values of unmodified silicas (VN2 and VN3) were higher than modified silicas. However, in compounds containing 20 phr of silica, the change in storage modulus (G') between modified and unmodified silicas is not very pronounced. In general, the findings indicate that both modified and unmodified silicas significantly affect the mechanical and performance properties of GECO elastomer, providing crucial insights for optimizing silica content to achieve desired material characteristics.
Keywords: Poly(epichlorohydrin), GECO, Elastomer, Silica, Silane, Modified silica, Si-69, Si-264, Damping
