A complete TSDC description of molecular mobilities in polylactide/starch blends from local to normal modes: Effect of composition, moisture, and crystallinity

Abstract

Thermally stimulated depolarization current is applied to study the dielectric relaxations coexisting from 80 to 380 K in the PLLA/starch, immiscible biodegradable blend system. The relaxation parameters are determined for chain mobilities at different ranges, whether in the amorphous or coldcrystallized state for PLLA, and totally amorphous one for starch as demonstrated by wide-angle X-ray scattering experiments. The PLLA crystallization is favored by the presence of starch, in both the crystallinity degree reached and the crystallization time. The effect of moisture is followed for both the local modes and the segmental mobilities, where a bimodal relaxation for starch sweeps the temperature range, thus evidencing the heterogeneities existing in the starch disordered phase. The moisture plasticization effect is estimated and shows differences in the water absorption in starch either neat or as a minority component. The onset of the segmental mobility in PLLA is independent of composition or crystallinity, but the large intensity decrease observed when PLLA coldcrystallizes evidences the simultaneous formation of a rigid amorphous fraction and the crystallites. The normal relaxation mode is recorded in amorphous PLLA whether neat or blended, which again demonstrates the absence of interactions among the blend components. V C 2015 Wiley Periodicals, Inc. J.

Segmental relaxation and partial crystallization of chain‐extended Poly(l‐lactic acid) reinforced with carboxylated carbon nanotube

“…Both primary and secondary relaxations of PLLA were observed in previous BDS studies . Instead, we did not find any clear spectroscopic evidence for the presence of a normal mode shifting to higher frequency with increasing, contrary to previous reports on pristine PLLA (without chain extension) …”

Direct and indirect effects on molecular mobility in renewable polylactide–poly(propylene adipate) block copolymers as studied via dielectric spectroscopy and calorimetry

“…b PLA relaxation originates from fluctuations or local twisting motions of the -CQO group at the backbone of PLA. [68][69][70] Schematically, this can be seen in the inset of Fig. 6a.…”

Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

“…In Figure 12 , we present the overall maps for the initial PPAd and neat amorphous PLA. Therein, for PLA, β PLA is shown, a local process originating from fluctuations or twisting motions of the –C=O group at the backbone of PLA (inset to Figure 12 ) [ 57 , 58 , 59 ]. β PLA exhibits linear behavior (obeying the Arrhenius law) and an activation energy of ~50 kJ/mol.…”