Interphases in Polymer Blends
The blending of polymers is a useful means of combining and improving the properties of already existing polymers in the development of new materials at reasonable cost. As most polymers are immiscible with each other, heterogeneous blends are often formed. The properties of such blends are strongly determined by the properties of the interphase.
The aim of the present work was to study the characteristics of interphases and their impact on the properties of heterogeneous polymer blends. Different experimental techniques were applied together with theoretical models to gain information on e.g. blend morphology, interactions, molecular mobility and interphase properties. Interphases were studied both in the bulk of compatibilized model blends and in thin interdiffusion layers. From these studies, the correlation between interfacial phenomena and the properties of polymer blends was investigated.
It was shown that the morphology of heterogeneous binary (PS/PEO and PS/PMMA) and compatibilized (PPO/PMMA/P(S-g-EO)) blends can be revealed by comparing dynamic mechanical properties with model calculations, but also that great care must be taken in the data interpretation. The compatibilization of heterogeneous PPO/PMMA blends by P(S-g-EO) copolymers resulted in the formation of a copolymer-rich interphase with specific characteristics. The correlation between the morphology, dynamic mechanical and dielectric behaviour of these blends, as well as the molecular mobility and chemical interactions in their interphases, was studied. Furthermore, an FTIR-RAS technique was developed to study interdiffusion between films (of EAA and PVEE) with a thickness of a few nanometres, which is in the range of the interphase thickness of many heterogeneous blends. Finally, simultaneous FTIR spectroscopic and mechanical (rheo-optical) measurements were used to study the molecular orientation in the dispersed LDPE phase in compatibilized PS/LDPE/SEBS blends during uniaxial elongation. The technique was found to be useful in studying interfacial interactions in compatibilized blends.
In conclusion, the present work has clearly shown that a careful combination of results from different experimental methods and theoretical calculations can help to explain interfacial phenomena and to give valuable information concerning the interphase properties of polymer blends.
dynamic mechanical properties