Dear all,
If I want to make thermoplastic polyurethanes, what are the critical parameters I have to consider? I want to know, on what this thermoset and/or thermoplastic nature of polyurethanes depends.
What is the criteria to make a PU which can be remolded(easily)?
Please help me with your suggestions.
Thanking you in advance.
A thermoplastic polyurethane "TPU" can , in principle, be obtained by reacting an aliphatic diol HO-R-OH with an aliphatic diisocyanate O=C=N-R'-N=C=O "where R&R' are linear or branched alkyls". A thermosetting PU is usually formed by the deliberate use of bifunctional monomers which give 3D network structure of the PU product or by cross-linking.
You know that polyurethanes can be tailor-made to be as soft as sponge & as tough as a pestle & mortar depending on the amount of moisture or water that is allowed/ prevented to/from enter(ing) the system during synthesis.
You need to look at laboratory manuals that describe the procedures used in PU synthesis, in general. However, a Research Gate colleague raised a question about how to prepare PTU 2 years ago. He received a good answer by my friend Professor Gyorgy Banhegyi . The link is:
https://www.researchgate.net/post/How_can_I_prepare_thermoplastic_Polyurethane_by_melt_process_in_lab
Most important is to avoid any water, i. e. the water content of the diol has to be at 0.01 % b. w. Further, calculate the error in determination of the OH number. The diisocyanate has to be free of urea and uretdion, best to use freshly distilled. Do not try first experiments with TDI as it has two groups with different reactivity and will give poor results due to stereochemistry. Easiet way to learn is to use 4,4'-dicyclohexylmethane diisocyanate. Use a tin catalyst like tin dioctoate as a catalyst with about 0.2 % b. w. After mixing and degassing you should consider annealing, use 100°C for at least three hours. a.s.o.
Thank you Gerhard Behrendt.
How to calculate the error in determination of the OH number ?
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