The effects of dioctyl phthalate plasticization on the morphology and thermal, mechanical, and rheological properties of chemical crosslinked polylactide

Abstract

The tensile strength and thermal stability of polylactide (PLA) were significantly improved through chemical crosslinking. However, it became much more rigid and brittle. To obtain a material with good thermal stability and enhanced ability to plastic deformation, chemical crosslinked PLA with 0.5 wt % triallyl isocyanurate and 0.5 wt % dicumyl peroxide was blended with different contents of dioctyl phthalate (DOP). The advantage of using DOP is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. The morphology and the thermal and mechanical properties of the crosslinked PLA and the blends of crosslinked PLA with various contents of DOP were investigated by means of scanning electron microscope, differential scanning calorimetry, tensile test, and dynamic mechanical analysis. The rheological properties of samples were also explored by using a capillary rheometer. The results showed that the DOP was an effective plasticizer for the chemical crosslinked PLA, resulting in a significantly decreased Tg, lower yield stress, and improved elongation at break. The plasticization effect was enhanced by adding higher DOP content. In addition, the DOP enhanced the crystallinity of crosslinked PLA, and all the crosslinked samples showed better heat stability than neat PLA. The apparent viscosity of the blends decreased with the increase of DOP content and a phase separation occurred when the content of DOP exceeded 12.5 wt %. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1136–1145, 2009

Comparative Study of Chemical, Mechanical, Thermal, and Barrier Properties of Poly(Lactic Acid) Plasticized with Epoxidized Soybean Oil and Epoxidized Palm Oil

“…The present morphology trend of PLA/ESO blends could be similar to the trend reported by Yang et al (2009), where microvoids occurred when excess plasticizer was added. Yang and co-workers (2009) added dioctyl phthalate (DOP) plasticizer into crosslinked PLA.…”

“…It is the phase separation that caused the insignificant reduction in Tg in the present work. Similarly, Yang et al (2009) and Kulinski et al (2006) reported minor decrease of Tg when the plasticizers DOP and poly (propylene glycol) (PPG) loading reached a certain amount where phase separation within PLA matrix occurred.…”

Extrusion Foaming of Poly (lactic acid)/Soy Protein Concentrate Blends

“…However, PEOX did not provide strong interfacial adhesion between two phases 16, 20. pMDI, as a strong interfacial modifier, reacted with the hydroxyl groups of PLA and SPC and the amine groups of SPC,20 establishing cross‐links between PLA and SPC which led to higher viscosity of the PLA/SPC blends 20, 24, 25. Therefore, the pressure drop was increased as addition of pMDI.…”

Poly(Lactic Acid) Blends

“…Yang et al [277] produced PLA cross-linked with 0.5 wt% triallyl isocyanurate (TAIC) and 0.5 wt% DCP, plasticized with dioctyl phthalate (DOP) plasticizer. Cross-linking helped in improving the thermal stability of PLA, and plasticization helped in dispersing the cross-linking agents.…”

“…The T m of PLA also dropped from 179 to 161 C. Nonhomogeneous blends and phase separation were observed for 12.5% and 15% DOP in PLA. SEM micrographs obtained from fractured surfaces revealed DOP droplets in the PLA matrix at 15% DOP concentration (Figure 16.19) [277].…”