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Combinatorial chemistry as a tool for the development of sustainable polyurethane materials

Final Activity Report Summary - COMBIPUR (Combinatorial chemistry as a tool for the development of sustainable polyurethane materials)

The main purpose of the COMBIPUR project was to examine the potential of combinatorial and high throughput techniques in the area of polyurethane research. The project is a feasibility study on the use of combinatorial techniques as a tool for polyurethane research and development. By means of automation and downscaling / miniaturising lab experiments, it is aimed to speed-up the PU R&D process (10 times faster) and to do experiments in a more reproducible way.

During the first period of the project, main activities have been focused on training of the basics of the polyurethane chemistry and technology in one way, and the principles and techniques of parallel synthesis in polymer research, in the other way.

The objective for 2007 was the development of high throughput experimentation of PU prepolymers in solution using combinatorial equipment of TU/e. High-throughput experimentation (HTE) represents a promising and versatile approach for polyurethane (PU) prepolymer research as a tool to screen and characterise a large number of samples in an automated way. For the realisation of a HTE workflow for PU prepolymers, the use of a Chemspeed Accelerator(TM) SLT106 automated parallel synthesiser was explored. To evaluate the possibility of these techniques, we studied the synthesis of prepolymers from isophorone diisocyanate and polypropylene gelycol in mass and solution. Several optimisation steps, transfer to solution polymerisation, and downscaling prepolymerisation have been carried out in a manual way before implementation into the Chemspeed Accelerator(TM). As a next step, reproducibility investigations and kinetic studies were performed in an automated manner. All experiments were evaluated by characterisation with gel permeation chromatography, MALDI-TOF mass spectrometry and H-NMR spectroscopy. These results provide a basis to use the HTE technique for screening different PU prepolymers in the future.

The main objective for 2008 was the development of a tool for the high throughput experimentation of PU elastomers. In 2008 activities have been focused on:
1) a (theoretical) design of a workflow platform for the fast sequential synthesis of elastomer samples; and
2) a (practical) feasibility study for the synthesis of these samples.

Through numerous discussions and brainstorms internally as well as with potential suppliers of high throughput systems, a proposal for the design of a workflow has been set. For reasons of robustness, flexibility and maximum usability a modular workstation has been worked out, including three independent modules:
1) a compounding module for the preparation of isocyanate and polyol formulations;
2) a mixing and dispensing module for the preparation and pouring of the reactive PU mix, incl. doctor blading draw-down process; and
3) a characterisation module, for the determination of macroscopic properties of final PU samples.

For each module a list of specifications has been set-up, taking already into account specific requirements for foam synthesis because the modules will need to be able to easily switch from elastomer to foam sample synthesis.

A feasibility study for the synthesis of PU elastomers has been set-up in a 'semi-automated' way using the existing workflow platforms at Flamac (Flanders Material Centre, a competence centre in high throughput methodologies to support research for the materials industry). Main objective of this study was an extensive evaluation of the correlation of properties between the small elastomer samples and the corresponding conventional handmix elastomer samples. More than 40 experiments revealed that similar properties (e-modulus, tensile strength, IRHD hardness) were obtained for small samples (10 * 6.5 cm) versus the conventional samples (40 * 13 cm). It is concluded that combinatorial methods for the synthesis of elastomer samples not only lead to faster, but also seems to have the potential to lead to more accurate and reproducible results compared to the current handmix process.

The positive outcome of the above study has strengthened the objective to continue the project in 2009 with focus on the synthesis of small foam samples.