Synergistic Effects of Nucleating Agents and Plasticizers on the Crystallization Behavior of Poly(lactic acid)

Abstract

Abstract:The synergistic effect of nucleating agents and plasticizers on the thermal and mechanical performance of PLA nanocomposites was investigated with the objective of increasing the crystallinity and balancing the stiffness and toughness of PLA mechanical properties. Calcium carbonate, halloysite nanotubes, talc and LAK (sulfates) were compared with each other as heterogeneous nucleating agents. Both the DSC isothermal and non-isothermal studies indicated that talc and LAK were the more effective nucleating agents among the selected fillers. Poly(D-lactic acid) (PDLA) acted also as a nucleating agent due to the formation of the PLA stereocomplex. The half crystallization time was reduced by the addition of talc to about 2 min from 37.5 min of pure PLA by the isothermal crystallization study. The dynamic mechanical thermal study (DMTA) indicated that nanofillers acted as both reinforcement fillers and nucleating agents in relation to the higher storage modulus. The plasticized PLA studied by DMTA indicated a decreasing glass transition temperature with the increasing of the PEG content. The addition of nanofiller increased the Young's modulus. PEG had the plasticization effect of increasing the break deformation, while sharply decreasing the stiffness and strength of PLA. The synergistic effect of nanofillers and plasticizer achieved the balance between stiffness and toughness with well-controlled crystallization.

Composition dependence of the synergistic effect of nucleating agent and plasticizer in poly(lactic acid): A Mixture Design study

“…The response contour plot shows graphically the obtained results also in terms of interactions and quadratic effects and it is also helpful for choosing the best point at which the desired final properties can be satisfied (optimization perspective). In the contour plot the amount of each factor changes in the opposite way with respect to the usual one in simplex lattice design [38].…”

“…In this plot, the effect (y-axis) produced by the factor variation (x-axis) should be interpreted considering that each component is at the lower real value in the right side of the x-axis, and it is at the higher real value in the left side of the same axis. Generally, the graph lines explain the effect of each component on the analysed response; a horizontal line (the slope is zero) implicates that the response value does not change varying the amount of a component while linear or parabolic trend indicates a strong variation of the response value (keeping the ratio on the proportions of the remaining components constant at the reference mixture) depending by the composition [38]. The response contour plot shows graphically the obtained results also in terms of interactions and quadratic effects and it is also helpful for choosing the best point at which the desired final properties can be satisfied (optimization perspective).…”

“…PDLA was also found to behave as a nucleating agent for decreasing the half-time of crystallization [35] of PLA, with the advantage of the excellent compatibility because of the much similar structure and also thanks to the formation of stereocomplexes [36,37]. More recently Shi et al [38] evidenced again the synergistic effect of nucleating agents and plasticizer by plasticizing PLA with PEG and adding also different nucleating agents such as PDLA, LAK and talc. LAK and PDLA effects were reported to be different and both promising because LAK showed an effective promotion of PLA crystallization behavior due to heterogeneous nucleation, while the addition of PDLA to PLA resulted in the formation of PLA stereocomplexes, acting as another type of nucleation process.…”

“…LAK and PDLA effects were reported to be different and both promising because LAK showed an effective promotion of PLA crystallization behavior due to heterogeneous nucleation, while the addition of PDLA to PLA resulted in the formation of PLA stereocomplexes, acting as another type of nucleation process. In the paper of Shi et al [38] a combination of LAK as nucleation agent and talc, used also as reinforcing filler, was reported to allow a good combination of properties, as the crystallization half-time was reduced and, regarding the mechanical properties, an improved ductility of the material was attained. However, any evidence about what can be the trend of thermal and mechanical behaviour as a function of composition was not reported.…”

Effect of Chemical Treatments on the Physical Properties of Non-woven Jute/PLA Biocomposites

“…PLA is the most promising bio-based thermoplastic and offers a potential alternative to petro-based plastics because of its relatively high strength and stiffness (Rasal et al 2010;Shi et al 2015). Currently, PLA composites with natural fibers have been extensively studied (Qu et al 2010;Tawakkal et al 2012;Rasidi et al 2014;Boubekeur et al 2015).…”