Syntheses and properties of pentaerythritol-containing urethane prepolymers and crosslinked films

Two series of polyhydroxyl urethane-prepolymers (Pre-PU) were synthesized from pentaery-thritol (PETH), toluene diisocyanate (TDI), and polyglycols (PG). One is a single molecular type of PETH-(TDI-PG)_n-TDI-PETH Pre-PU (S-Pre-PU). The other is a mixture of (PETH-TDI)_n-PETH and S-Pre-PU. The Pre-PU mixed with an equivalent triisocyanate regenerator (Desmodur AP-Stable, a crosslinking agent) were baked to form the crosslinked PU films. The mechanical properties such as tensile strengths, elongation at break, and viscoelasticities of PG-modified crosslinked films were studied.