Structure and properties of polylactide toughened by polyurethane pre-polymer

In this study, polyurethane prepolymer (PUP) was prepared by the reaction of Poly-1,4-butylene glycol adipate diol (PBA) and 4,4′-Methylenedi-p-phenyl diisocyanate (MDI). The as-prepared PUP was then blended with Polylactide (PLA), and the impact of the PUP on the blends regarding their structure and properties were thoroughly analyzed. Also, PLA was blended with PU powder without isocyanate groups (NCO) as an important control sample (PLAPW) to study the interface interaction of the blends. Obvious yield and neck stretch were obtained after the addition of PUP, and the elongation ratio at break increased from 2.9% to 231.5%. In contrast, the mechanical properties of PLAPW decreased significantly mainly due to the simple physical blending of the polymers without the formation of covalent bonds. Also, the results of the FTIR, SEM, DSC, and DMA analysis showed that the reactions of NCO groups in PUP with the terminal hydroxyl or carboxyl groups in PLA significantly improved the compatibility of the PUP and PLA blend. Compared to pristine PLA, the highest decomposition temperature of the PLA and PUP blend (PLAPU) increased from 359.3°C to 362.6°C. Additionally the thermal stability and mechanical properties of the blended materials were exceedingly improved even with only 5% of PUP in the blended materials.