Physical Characteristics of PLLA/PMMA Blends and Their CO2 Blowing Foams

Abstract

This article reports on sample preparation, characterization, CO2 sorption behavior, and foaming of blends of poly L-lactic acid (PLLA) and poly methyl methacrylate (PMMA) in compositions of 75/25, 50/50, and 25/75 wt.%. The crystallization and thermal decomposition behavior of the polymer blends were found to be dependant on concentration of PLLA in the samples. Annealing the specimens in air at 90°C for 24 h resulted in complete recrystallization in the 75/25 and 50/50 wt.% samples. Detailed studies on the sorption kinetics of CO2 in the prepared blend samples indicated gas solubilities to be comparable to those observed in neat PMMA, however, foam morphologies significantly improved in the blends when compared to neat PLLA.

Structure evolution driven by phase separation and the corresponding foaming behavior of polystyrene/poly(methyl methacrylate) blends via a batch foaming process

“…Both PS20/PMMA80 and PS80/PMMA20 showed sea‐island phase structure during the annealing, and the former one had larger phase domain. PS40/PMMA60 showed a bi‐continuous phase structure with the annealing for no more than 15 min, and with longer annealing, the bi‐continuous phase structure gradually changed into sea‐island structure . PS60/PMMA40 showed similar phase structure as PS40/PMMA60 did, while with smaller phase domains.…”

“…Whether the phase morphology evolution would impact the foaming behavior of immiscible polymer blends and thus the cell structures still remains an issue to be addressed. Based on the previous studies concerning the effect of phase morphology on foaming behavior, the mostly applied variable to tune the morphology is through varying the composition. For that approach, both the composition and the morphology are changed, and the morphology is not the only variable.…”

Poly(Lactic Acid) Blends

“…Separate T g 's were observed for the PMMA phase and the PLA phase for the films prepared by solution casting, which indicates the immiscible nature of the two phases that were produced by these techniques. Yao et al [72] investigated PLA/PMMA blend foams at 75/25, 50/50, and 25/75 wt% compositions for medical applications such as cell growth. Factors such as solubility and carbon dioxide diffusivity played an important role in these applications.…”

Highly Crystalline Poly(l-lactic acid) Porous Films Prepared with CO2-philic, Hybrid, Liquid Cell Nucleators

“…This is possibly a consequence of lower CO 2 solubility in the highly crystalline matrix and the increased chain stiffness and modulus of the matrix inhibiting the pore growth. Using a similar technique, Yao et al was able to obtain only regional foaming in P l LA with 38% crystallinity when the foaming was carried out at 343 K . In supercritical batch foaming of a highly crystalline P l LA, where the polymer is saturated at supercritical temperatures and pressures, high processing temperatures greater than 353 K are required at or above moderate pressures around 20 MPa in order to foam the polymer. − When the crystallinity was 80%, a porous structure could not even be obtained with scCO 2 batch foaming process carried out at 393 K and 12 MPa …”