Effects of Gas Adsorption on the Mechanical Properties of Amorphous Polymer

• Published in: Polymers Vol. 11; no. 5; p. 817
• Main Authors: Kim, Shin Won, Sohn, Joo Seong, Kim, Hyun Keun, Ryu, Youngjae, Cha, Sung Woon
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 07.05.2019; MDPI
• Subjects: Adsorption; Amorphous materials; amorphous region; Carbon dioxide; Cushions; Density; Dissolution; Dissolved gases; Experiments; gas adsorption; Gas mixtures; Gases; Impact strength; Impact tests; Mechanical properties; network density; Partial pressure; Polyethylene terephthalate; polymer; polymer-gas mixture; Polymers; Pressure vessels; Sorption; Stress-strain curves; Tensile strength; Van der Waals forces; Viscosity; gas adsorption; impact strength; polymer; carbon dioxide; tensile strength; network density; amorphous region; polymer-gas mixture
• DOI: 10.3390/polym11050817
• ISSN: 2073-4360

This study investigates the properties of a polymer-gas mixture formed through diffusion, based on the changes in the partial pressure and observed changes in the impact and tensile strengths owing to the gas dissolution. The high-pressure gas dissolves into a solid-state polymer through diffusion based on the difference in the partial pressure. This dissolved gas is present in the amorphous region within the polymeric material temporarily, which results in the polymer exhibiting different mechanical properties, while the gas remains dissolved in the polymer. In this study, the mechanical properties of amorphous polyethylene terephthalate (APET) specimens prepared by dissolving CO using a high-pressure vessel were investigated, and the resulting impact and tensile strengths were measured. These experiments showed that the increase in sorption rate of CO caused an increase in the impact strength. At 2.9% CO absorption, the impact strength of APET increased 956% compared to that of the reference specimen. Furthermore, the tensile strength decreased by up to 71.7% at 5.48% CO sorption; the stress-strain curves varied with the gas sorption rate. This phenomenon can be associated with the change in the volume caused by CO dissolution. When the APET absorbed more than 2.0% CO gas, sample volume increased. A decrease in the network density can occur when the volume is increased while maintaining constant mass. The CO gas in the polymer acted as a cushion in impact tests which have sorption rates above 2%. In addition to the reduction in the network density in the polymer chain, Van Der Waals forces are decreased causing a decrease in tensile strength only while CO is present in the APET. These observations only occur prior to CO desorption from the polymer.