Modified design and use of a high-pressure environmental stage for laboratory X-ray powder diffractometers

The popularity of supercritical CO2 for materials processing makes the in situ study of pressures up to 10 MPa in the laboratory particularly interesting. This paper describes a modified design for a 12.4 MPa (1800 psi) variable-temperature pressure vessel based on an existing cell reported by Koster van Groos, Guggenheim & Cornell [Rev. Sci. Instrum. (2003), 74, 273-275]. The modifications satisfied the demands of the American Society of Mechanical Engineers design code 31.3, leading to legal design registration, construction and subsequent hydrostatic test. The thinner windows that the finite element analysis indicated as sufficient allow for rapid data collection, even using a laboratory-based Mo source. This type of application is demonstrated with a time-resolved data set showing the crystallization of a polylactic acid-clay nanocomposite under 6.8 MPa CO2.Peer reviewed: YesNRC publication: Ye

Layered open pore poly(l-lactic acid) nanomorphology

This paper reports on specific open and interconnected CO\u2082 foams of poly(L-lactic acid). The effect of varying gas concentration and hence physical changes induced by CO\u2082 has been investigated and thus used to generate specific structures. The developed morphologies have a skin core structure with larger pores in the core and open and interconnected smaller pores in the skin.Peer reviewed: YesNRC publication: Ye

Physical characteristics of PLLA/PMMA blends and their CO2 blowing foams

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

Physical characteristics of PLLA/PMMA blends and their CO2 blown foams

This paper reports on sample preparation, characterization, CO2 sorption behaviour, 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 behaviours 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 hours resulted in complete recrystallization in the 75/25 and 50/50 wt% samples. The interaction of CO2 with PLLA/PMMA blends was investigated and the resultant equilibrium solubility, diffusion coefficient and foam morphologies were compared to those previously reported for neat PLLA and PMMA-CO2 systems