Effects of star-shaped PCL having different numbers of arms on the mechanical, morphological, and thermal properties of PLA/PCL blends

In this work, a series of linear and star-shaped poly(epsilon -caprolactone)s (SPCL) with various arm numbers were successfully synthesized with ring-opening polymerization (ROP) with the initiators having different number of hydroxyl functional groups. The molecular characteristics of synthesized PCLs were analyzed via Fourier Transform Infrared Spectroscopy (FTIR), proton nuclear magnetic resonance spectra (H-1 NMR), thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) measurements. Then PCLs were melted with poly(lactic acid) (PLA) by utilizing a micro-compounder at a constant blending ratio (90/10% weight) and constant 1,4-phenylene diisocyanate (PDI) (1% weight) as a commercial compatibilizer. It was reported that adding SPCL improved mechanical properties of PLA. The three-armed star shaped PCL (3SPCL) caused significant decrease in modulus due to its high molecular chain mobility when compared linear, four- and six-armed PCLs. An increment was observed in the elongation at break values with incorporation of star polymers and it increased from 4 to 9%. Scanning electron microscopy (SEM) photos indicated that immiscibility of the two biodegradable polymers were enhanced and thus mechanical improvement were achieved.