The main accomplishments of this project can be summarized below as follows:
(i) An experimental "toolbox" has been developed for the systematic characterization of the phase behavior of polymer blends and consists of the following "milestones":
- Determination of the complete phase diagram of a binary blend using shear rheology
- Composition dependence of the viscosities of homogeneous behavior of binary polymer blends (regime of enhanced concentration fluctuations near the critical point)
- Relation of segmental dynamics in polymer blends to their phase state - The effects of glass transition in arresting the phase separation of binary blends
- Determination of the gelation temperature and times of epoxy/rubber industrial blends
- Interfacial profiles of blends including copolymeric compatabilizing additives
(ii) Flow-light experiments showed the occurrence of shear-induced demixing and mixing, depending on shear rates, temperature and dynamic asymmetry between constituents.
(iii) Using the concept of a generalized Gibbs energy of mixing, a multitude of phenomena (shear-induced homogenization, shear-induced demixing, inversion of the effects plus the occurrence of islands of immiscibility) have been predicted for flowing binary or ternary polymer blends.
(iv) The synthetic efforts yielded a graft copolymer compatibilizer for the industrial SMA/PMMA blends. This important development opens the route for the industrial-scale synthesis of additives of controlled microstructure for various applications.
The proposed research is directed at optimizing the mechanical properties and processing of polymer blends. In particular, the flow-induced changes of phase behavior, that affect the morphology of the final product, will be evaluated and controlled. High resolution non-invasive experimental techniques will be applied in order to quantify the microstructural changes during processing. The effects of high shear rates and extensional flow fields will be investigated in detail. The influence of compatibilizing additives on the products' properties will be also examined under these flow conditions. Thermodynamic modelling, based on energy-of-mixing considerations, will be applied in order to develop a software predicting the above effects, with applications to a wide range of industrial processes (e.g. injection moulding, film blowing). The technical tasks are:
-Determine the quiescent phase behavior of polymer blends, with and without compatibilizing addditives.
-Monitor the effects of shear and extensional flows on blends with and without additives.
-Develop software, based on the thermodynamic modelling of the influence of flow and additives on phase structure of polymer blends.
-Characterize the microstructural and mechanical properties of the final products.
Application of the project's results will lead to a reduction in operating costs during processing, optimized mechanical properties of products, and development of low-cost high quality materials via effective recycling of plastic waste; it will also contribute to the automatic control and engineering design of polymer processes.
Funding SchemeCSC - Cost-sharing contracts
SW7 2AZ London