Tailoring Oligomeric Plasticizers for Polylactide through Structural Control

Abstract

Structural variations (oligolactide segments, functionalized end groups, and different plasticizer cores) were utilized to tailor the performances of biobased plasticizers for polylactide (PLA). Six plasticizers were developed starting from 1,4-butanediol and isosorbide as cores: two monomeric (1,4-butanediol levulinate and isosorbide levulinate) and four oligomeric plasticizers with hydroxyl or levulinate ester end groups (1,4-butanediol-based oligolactide, isosorbide-based oligolactide, 1,4-butanediol-based oligomeric levulinate, and isosorbide-based oligomeric levulinate). Structural variations in plasticizer design were reflected in the thermal stability, plasticizing efficiency, and migration resistance. The monomeric plasticizer 1,4-butanediol levulinate decreased the glass-transition temperature of PLA from 59 to 16 °C and increased the strain at break substantially from 6 to 227% with 20 wt % addition. 1,4-Butanediol-based oligomeric levulinate exhibited better thermal stability and migration resistance, though the plasticizing efficiency was slightly lower (glass-transition temperature = 28 °C; strain at break = 202%). Compared to PLA films plasticized by plasticizers with flexible butanediol cores, those plasticized by plasticizers with rigid isosorbide cores exhibited higher Young’s modulus and thermal stability and lower plasticizing efficiency. Furthermore, plasticizers with levulinate ester end groups had improved thermal stability, plasticizing efficiency, and migration resistance compared to the corresponding plasticizers with hydroxyl end groups. Hence, a set of controlled structural variations in plasticizer design were successfully demonstrated as a potent route to tailor the plasticizer performances.

Tri(3‐alkoxyl‐3‐oxopropyl) phosphine oxides derived from PH3 tail gas as a novel phosphorus‐containing plasticizer for polylactide

“…As shown in Figure 7A, the fracture surface of the PLA/PC4 system was almost identical and did not show visible phase separation structure. These results indicated that the plasticizer PC4 was completely miscible with the PLA matrix and formed a homogenous system after melting systeming, 8,9,18 this observation was consistent with the preceding DSC results (Figure 3). However, the surface morphologies of the PLA/PC6 and PLA/PC8 samples were different compare to that of the PLA/PC4 system.…”

“…Therefore, to improve its processing performance, a plasticizer is added to the PLA matrix to enhance the ductility and film-forming ability of PLA. [8][9][10][11][12][13][14] Although many kinds of plasticizers 15 are available in the plastic industry, the plasticizer of PLA should be carefully selected to preserve its virtue of environmental friendliness. Hence, most PLA plasticizers belonged to aliphatic esters or low-molecular-weight aliphatic polyester without any aromatic structure.…”

“…Citrate ester and its derivatives are common PLA plasticizers that exhibit high plasticization efficiency to PLA 16 ; the glass transition temperature of PLA with 20% BTC decreased from 53.1 C of neat PLA to 5.4 C. 17 Although the lactides are efficient plasticizers of PLA, the molecular weight of monomeric lactides is very low and migrates easily from the PLA matrix. Hence, to avoid this shortage, end-capped oligomeric PLA with different core units 9,18 was recommended to replace monomeric lactide in plasticized PLA. These lactide-based plasticizers possess chemical structure similar to that of PLA.…”

“…21 Other ester-like PLA plasticizers reported in previous studies included bis (2-ethylhexyl) adipate and di-2-ethylhexyl sebacate, 22 hexadecyl lactate, 6 diethylene glycol monobutyl ether adipate, 23 and 1,4-butanediol levulinate. 9 In addition to the ester-like plasticizers, poly(ethylene glycol) 12,24 and its copolymer are effective plasticizers for PLA, and these moderate-molecularweight plasticizers show relatively low migration rate than low-molecular-weight low molecular weight plasticizers.…”

“…However, the broad application potential of PLA is restricted by its intrinsic brittleness, which renders PLA processing difficult due to a lack of plastic deformation ability. Therefore, to improve its processing performance, a plasticizer is added to the PLA matrix to enhance the ductility and film‐forming ability of PLA 8–14 …”