Functionalized siloxane-silsesquioxane resins and polypropylene-based composites: Morphological, structural, thermal, and mechanical properties

Non-functionalized and n-alkyl-functionalized siloxane-silsesquioxane resins (S4SQ) were synthesized and characterized to confirm their structure and properties. Polypropylene (PP) composites with S4SQ resins as fillers were prepared by the melt blending. The influence of the kinds and amounts of fillers on the structural, morphological and thermal properties as well as mechanical characteristics and processability was determined. High compatibility of composites with functionalized resins resulted in more homogenous dispersion of filler particles in comparison with the composites which contained a non-functionalized resin. Moreover, the introduction of S4SQ resins into PP strongly affected the crystalline structure of the polymer matrix and the free-volume properties of composites. Siloxane-silsesquioxane resins changed the contributions of the alpha- and beta-crystalline phases and they increased the crystal sizes of PP. The PP/S4SQ composites were also characterized by the improved crystallization temperature and crystallinity degree while the melting temperature and processability were changed only slightly. The mechanical properties of the PP/S4SQ materials were found to be dependent mostly on the degree of filler dispersion and crystalline structure of the composite materials. POLYM. COMPOS., 40:3101-3114, 2019. (c) 2018 Society of Plastics Engineers