Structure and properties of polylactide toughened by polyurethane prepolymer

Abstract

In this study, polyurethane prepolymer (PUP) was prepared by the reaction of Poly-1,4-butylene glycol adipate diol (PBA) and 4,4 0 -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 359.38C to 362.68C. Additionally the thermal stability and mechanical properties of the blended materials were exceedingly improved even with only 5% of PUP in the blended materials.

Improved thermal and mechanical performance of ramie fibers reinforced poly(lactic acid) biocomposites via fiber surface modifications and composites thermal annealing

“…After blending PLA with 5 wt% of ramie fibers, the crystallinity increased to 27.6 6 0.6%. This can be ascribed to the presence of ramie fibers capable of reducing the mobility of molten PLA, and thus the PLA molecules adopted sufficient nucleating sites to crystallize [24,32]. Moreover, at the same time, the reactive molecular segments of PLA polymer with a carboxylic acid group (COOH) established interaction bond with the ramie fiber OH, as schematically illustrated in Scheme 1.…”

Simultaneously enhanced fracture toughness and flame‐retardant property of poly(l‐lactic acid) via reactive blending with ammonium polyphosphate andin situformed polyurethane

“…As shown in Fig. 2(c), compared with the pristine PLLA, the characteristic absorption peaks of the urethane bond and the conjugated double bonds of benzene were observed at 1533 and 1597 cm −1 respectively in the FTIR spectrum of the L8U2 sample 24,25 . This indicated that the –NCO groups reacted successfully in the blending process.…”

“…2(c), compared with the pristine PLLA, the characteristic absorption peaks of the urethane bond and the conjugated double bonds of benzene were observed at 1533 and 1597 cm −1 respectively in the FTIR spectrum of the L8U2 sample. 24,25 This indicated that the -NCO groups reacted successfully in the blending process. In the case of APP*, the stretching vibrations of P=O (υ P=O ) and P-O-P (υ P-O-P ) were found at 1242 and 1058 cm −1 compared with the IR spectrum of pristine APP.…”

Polyurethane Prepolymer Modified Cassava Starch Based Poly(butylene adipate‐co‐terephthalate) Composites with Excellent Compatibility and High Toughness

“…In addition, two new peaks at 1538 and 1600 cm −1 occurred in MS spectra. The former peak originated from the urethane bonds and the latter peak was ascribed to the conjugated double bonds of benzene . Besides, peaks at 1646 and 1738 cm −1 could be assigned to the stretching vibration of the CO bonds and the CO bonds, respectively .…”