The effects of orientation and crystallinity on the solvent‐induced crystallization of poly(ethylene terephthalate). I. Sorption‐ and diffusion‐related phenomena

“…Polymer chains will rearrange themselves into a lower free‐energy state. As a consequence of this there is a small increase in the amorphous region of the treated materials 11, 12…”

Section: Resultsmentioning

confidence: 98%

Effect of acetonitrile pretreatment on the physicochemical behavior of 100% polyester fabric

Muralidharan

Mathanmohan

Ethiraj

2004

“…At higher pressure under isothermal condition, the absorption of more CO 2 results in substantial swelling of polymer and profound plasticization effect to polymer which favors polymer chains rearrange themselves into a lower free energy. [27][28][29] Similarly, the higher temperature under isobaric conditions contributes to increasing mobility of polymer chain segments and a longer period for crystalline growth, so the crystallinity of polymer ascends markedly too. [27][28][29][30][31] In this study for the PLA/starch composites, from Figure 4, the areas of the fusion peak of virgin and foamed composite are 22.81 and 30.98 J/g, respectively.…”

Section: Crystallinity Of the Foaming Materialsmentioning

confidence: 98%

Study of different effects on foaming process of biodegradable PLA/starch composites in supercritical/compressed carbon dioxide

Hao

Geng

et al. 2008

Microcellular foaming of biodegradable and biocompatible PLA/starch composites in supercritical/compressed CO 2 has been studied. The purpose of this study is to explore the potential application of this kind of materials in medical materials or drug containers. The rate of CO 2 uptake and CO 2 equilibrium concentration in PLA/starch composites were studied by performing sorption and desorption experiments. The effects of a series of variable factors, such as saturation time and saturation temperature on the foaming morphology were studied through SEM observation and density measurement. The experimental results show that, while keeping other variables unchanged, longer saturation time leads to reduced bulk foam densities and different saturation pressures result in different bulk foam densities. The crystallinity of PLA-starch sample was characterized by differential scanning calorimetry. It indicates that the foaming treatment with supercritical CO 2 increased the crystallinity of PLA/starch composites.

“…This might be explained in terms of solvent‐induced crystallization (SINC) that may have occurred when the polymer was swollen in THF. SINC is a well‐documented phenomenon in which interactive penetrants produce physical modifications in PET 34–37. Moreover, SINC has been found in sulfonated PET 38.…”

Section: Resultsmentioning

confidence: 99%

[Poly(ethylene terephthalate) ionomer]/silicate hybrid materials via polymer–in situ sol‐gel reactions

Lambert

Mauritz

Schiraldi³

2002

A scheme was developed for producing poly(ethylene terephthalate (PET) ionomer)/silicate hybrid materials via polymer-in situ sol-gel reactions for tetraethylorthosilicate (TEOS) using different solvents. Scanning electron microscopy/EDAX studies revealed that silicate structures existed deep within PET ionomer films that were melt pressed from silicate-incorporated resin pellets.29 Si solid-state NMR spectroscopy revealed considerable Si-O-Si bond formation, but also a significant fraction of SiOH groups.23 Na solid-state NMR spectra suggested the presence of ionic aggregates within the unfilled PET ionomer, and that these aggregates do not suffer major structural rearrangements by silicate incorporation. For an ionomer treated with TEOS using MeCl 2 , Na ϩ ions are less associated with each other than in the unfilled control, suggesting silicate intrusion between PET-SO 3 Ϫ Na ϩ ion pair associations. The ionomer treated with TEOS ϩ tetrachloroethane had more poorly formed ionic aggregates, which illustrates the influence of solvent type on ionic aggregation. First-scan DSC thermograms for the ionomers demonstrate an increase in crystallinity after the incorporation of silicates, but solvent-induced crystallization also appears to be operative. Second-scan DSC thermograms also suggest that the addition of silicate particles is not the only factor implicated in recrystallization, and that solvent type is important even in second-scan behavior. Silicate incorporation does not profoundly affect the second scan T g vs. solvent type, i.e., chain mobility in the amorphous regions is not severely restricted by silicate incorporation. Recrystallization and melting in these hybrids appears to be due to an interplay between a solvent-induced crystallization that strongly depends on solvent type and interactions between PET chains and in situgrown, sol-gel-derived silicate particles.