Miscible crystalline/crystalline polymer blends of polyoxymethylene copolymer/poly(ethylene oxide) with interpenetrated spherulites and enhanced properties

Miscibility and crystallization behavior of a polymer blend consisting of two crystalline components, polyoxymethylene copolymer (Co-POM) and poly(ethylene oxide) (PEO), have been investigated. Experimental results indicate that Co-POM is thermodynamically miscible with PEO, as shown by the existence of single-composition dependent glass transition temperature over the entire composition range. The crystal structures and spherulitic morphologies of (Co-POM)/PEO blends were studied by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and polarizing light microscopy. It was found that the PEO spherulites crystallized within the matrix of the crystals of the pre-existing Co-POM phase and resulted in a high extent of interfibrillar segregation. The unique interpenetrated crystalline structure was beneficial for the sufficient contact between the two components and significantly improved both the toughing and the lubricating effect of PEO on the POM matrix. On incorporation of 30 wt% PEO, the notched impact strength of POM was enhanced from 6.7 to 10.3 MPa, by about 53.7%, while the elongation at break increased from 28.5% to 121.0%, by about 3.2 times. Furthermore, the friction coefficient drastically decreased from 0.35 to 0.17, demonstrating the enhanced tribological performance of the miscible blends. J. VINYL ADDIT. TECHNOL., 22:479-486, 2016. (c) 2015 Society of Plastics Engineers