Abstract
The thermal, morphological and mechanical properties of polypropylene blends as influenced by the molecular weight and tacticity were investigated. Polypropylene sample blends (50/50 wt.%) were injection moulded into standard disks for morphological and mechanical tests. The thermal properties of the polypropylene blends were measured by differential scanning calorimetry (DSC), while the morphological and mechanical properties of specimens were investigated by means of optical microscope (OM), scanning electron microscopy (SEM), microhardness (MH) and dynamic mechanical analysis (DMA). DSC results of the bulk crystallization of the various isotactic polypropylene blends showed one melting peak, which indicates that cocrystallization of the blends occurred. However, the crystallization behavior of the polymer blends was strongly affected by the configuration (tacticity) and molecular weight of the polypropylene polymers. In addition, the MH and DMA measurements showed that blends of two different isotactic polypropylenes presented MH and storage modulus values between the values of the respective two MH and storage modulus values of the homopolymer samples, which in turn, depended on the type and degree of the crystallinity of the blends. However, the presence of syndiotactic polypropylene in a blend with isotactic polypropylene leads to a decrease in the MH value of the isotactic polypropylene samples. Normal 0 19 false false false LT X-NONE X-NONE DOI: http://dx.doi.org/10.5755/j01.ms.22.3.9056
Highlights
Polypropylene is one of the most widely used commercial polymers today
This morphology and the associated phase behaviour strongly depend on the cocrystallization between the components of the blend
Blending allows us to determine the effect of the molecular weight and tacticity on the crystallinity of the new materials
Summary
Polypropylene is one of the most widely used commercial polymers today. Its continuously increasing application accelerates research in all correlated areas, including the preparation of isotactic polypropylene based composites and blends [1]. The mechanical and physical properties of polypropylene are affected by a number of factors. The mechanical properties of the majority of polypropylene polymers are, apart from the processing conditions, influenced by their rheological and crystallization behavior. The degree of crystallinity is considered to be the most significant property influencing the physical and mechanical properties of a polypropylene sample [2 − 4]. An increase in crystallinity is often associated with an increase in properties such as the stiffness or modulus of a sample, while other factors, such as the impact strength, generally decrease with increasing crystallinity. The effects of molecular weight [5, 6], molecular weight distribution [7] and tacticity [8, 9] on the crystallization have been investigated by several authors
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