Self-reinforced polymeric composite materials are materials where both the reinforcement and matrix are in the same family of thermoplastic materials and therefore have an advantage in recycling after their end-of-life. Due to the relative homogeneity, the system allows to achieve excellent interfaces between the matrix and reinforcement, which is often not possible in conventional composites. While various studies have been conducted with different composite manufacturing methods, in situ generation of a fibrillar minor phase morphology with the fibrillation process has potential to improve the self-reinforced polymeric composite technology. The extremely large interfaces from the fine physical network structure of the minor phase in the matrix would be able to maximize the effects generated from perfect interfaces guaranteed from the homogenous self-reinforced composite system. Furthermore, a large temperature processing window of self-reinforced polymeric composites can expand the versatility of the processing route.

This thesis shows that the fibrillation process is highly beneficial to improve mechanical and rheological properties of the cyclic olefin copolymer (COC), polypropylene (PP) and polyethylene terephthalate (PET) self-reinforced polymeric system. In addition, fibrils in the matrix also enhance the foam properties of linear polymer matrix while maintaining high recyclability of the self-reinforced polymeric composite. The improvement of foam properties further leads to decrease thermal conductivity.