PP and Nanofibrillated-PET Composites from Melt Blowing: Fundamentals to Scale-Up
Recent research has extensively focused on the production of micro- or nano-fibrillated composite (M/NFC) materials. In these composites, a polymer-reinforced polymer is created by extensionally drawing blends with a sea-island morphology. Initially, the reinforcement domains are dispersed within the matrix, and then a large extensional deformation is applied, causing the domains to in-situ fibrillate into long-aspect ratio fibrils. These micro-/nano-scale diameter fibrils, with their high interfacial surface area, significantly enhance mechanical properties such as strength and toughness, and can provide functional properties. The use of inexpensive commodity polymers makes this a cost-effective method for nanocomposite creation, with polyethylene terephthalate (PET) reinforced for polypropylene (PP) explored in this thesis.Melt blowing is a widely utilized technique for creating polymeric non-woven materials by drawing polymer above its melting temperature using high-speed, high-temperature air. This results in higher extensibility during drawing, thereby producing super-fine diameter fibers with tighter pore morphologies. Despite the significant capabilities of melt blowing machines, their full potential remains underexplored for M/NFC creation. To better understand the key factors influencing melt blown nanofibrillation, the formation of non-woven PP fabrics was systematically analyzed. While optimizing these parameters to produce finer fibers and pores, high quality fabrics were created, which could be suitable for applications such as N95 masks and HEPA filters. Therefore, the filtration and permeability properties of the fabrics were analyzed and related to the structural changes. Additional UV photocatalytic capabilities were provided by incorporating TiO2 nanoparticles, which enabled wastewater cleansing and E. coli bacteria removal. Both melt blown and spunbonded nanofibrils were compared in terms of their morphology and final reinforcement performance after creating solid and foam injection-molded samples. Melt blown nanofibrils, partly due to their smaller diameter, provided superior mechanical reinforcement at equal loadings. Furthermore, the addition of a coupling agent further decreased the nanofibril diameter and increased mechanical properties. The nanofibrils were also effective in increasing the cell density of the foamed parts. This thesis explores the formation of melt blown M/NFCs, their application in injection molding, and their differences from other M/NFC processes.
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