Molecular mobility and physical ageing of plasticized poly(lactide)

Abstract

Molecular mobility and physical ageing of amorphous plasticized polylactide (PLA) with two different contents of mesolactide are studied with the help of thermal analysis. Used plasticizers are acetyl tributyl citrate (ATBC) and triacetin (TA), two molecules with established miscibility and plasticizing efficiency. Lower plasticizer permanence of TA compared with ATBC is found. The plasticizer molecules decreased the size of the cooperativity domains at the glass transition temperature Tg and likely in the glassy state by decreasing intermacromolecular interactions and notwithstanding the mesolactide content of PLA and the chemical identity of the plasticizer. The recovery function is given and shows a significant effect of the plasticizer on the physical ageing. The supplementary free volume brought by the plasticizer enhances molecular mobility in the glassy state and increases structural relaxation at one order of magnitude. The comparison between different plasticizers reveals that the structural relaxation is however independent from the type of plasticizer and the percentage of mesolactide in PLA. POLYM. ENG. SCI., 55:858–865, 2015. © 2014 Society of Plastics Engineers

Molecular dynamics in electrospun amorphous plasticized polylactide fibers

“…7B is similar but the glass transition as well as the peak in the non-reversing heat flow signal are significantly broadened. This observation is consistent with previous observations on plasticized polylactide [11,33] and is related to an increase of the relaxation temperature distribution induced by the plasticizer addition. We cannot be definitive concerning the nature of this peak.…”

“…We cannot be definitive concerning the nature of this peak. Nevertheless, its enlargement with plasticization coincides with the increase of the dynamic heterogeneity in the amorphous phase [11]. Typically this heterogeneity reflects in the structural relaxation [11,47] so the initial hypothesis of physical aging is reinforced.…”

“…In the second case, the approach of Donth has widely been used to investigate the decrease of cooperativity for two kinds of structural hindrances namely external and internal hindrances. External hindrances are related to geometrical restrictions like the confinement between nanolayers [7,8] or the addition of additives such as fillers [9,10] or plasticizer [11]. On the other hand, internal hindrances are related to the materials itself, in other words its microstructural modifications such as spherulitic crystallization [12,13] or orientation/crystallization of the amorphous phase induced by drawing [5,14].…”

“…Because of the strong dependence of PLA macroscopic properties on its microstructure [15] and molecular dynamics [16], the cooperativity of the alpha relaxation process has been particularly investigated when the relaxation dynamics of the amorphous phase are modified by orientation [17], crystallization [13], or even plasticization [11]. However, the impact of several microstructural modifications on the amorphous phase dynamics remains unknown.…”

Plasticizing effect of biobased epoxidized fatty acid esters on mechanical and thermal properties of poly(lactic acid)

“…which can lead to tailored properties in terms of mechanical response, biodegradation rate, etc. Another interesting approach is the use of environmentally friendly and non-toxic plasticizers such as poly(ethylene glycol), PEG [16][17][18], poly(propylene glycol), PPG [19], oligomeric lactic acid, OLA [20], citrates such as acetyl tributyl citrate (ATBC) [21][22][23] or tributyl citrate (TBC) [22,[24][25][26].…”