Thermo-sensitive polyurethane membrane with controllable water vapor permeation for food packaging

Abstract

The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at 53 o C (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature (T s ) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the T ·d, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

Chain folding in main-chain liquid crystalline polyesters: from π–π stacking toward shape memory

“…[1][2][3][4][5][6] In the last decade, shape memory materials have been the focus of attention due to their 30 great potential for application in smart fabrics, [7] films for food packaging, [8] deployable structures in spacecraft, [9] autochoke element for automobile engines, [10] biomedical applications for minimally invasive surgery, [11] et al [12] The relaxation to the original shape is associated with elastic deformation stored during 35 prior manipulation. Generally speaking, shape memory polymer consists of molecular switch or soft segment and netpoints or hard segment.…”

On-demand drug delivery from temperature-responsive polyurethane membrane

“…After PCL4000 segment covalently linked with MDI/BDO, the above two characteristic transitions still existed in the synthesized TRPU, despite some shifts in both transition temperatures. Additionally, another small endothermic peak located at 216.1 ± 0.3°C was also detected in the synthesized TRPU, which, according to previous literatures [16][17][18][19], should be ascribed to the crystalline melting of MDI/BDO segment. Based on these results, it was implied that the synthesized TRPU was phase-separated into a fixed phase (MDI/BDO) and a reversible phase (PCL4000) due to the thermodynamic immiscibility of the components.…”

“…In our previous studies, segmented TRPUs with glass transition or crystalline melting transition reversible phase respectively were successfully synthesized and applied as intelligent leather/textile coating [16], food packaging [17] and selective desalination material [18]. As continuous work, the present research was carried out to investigate the temperature-dependent drug release behavior of TRPU membrane containing melting transition reversible phase.…”

Vegetable oil-based polyurethane membrane for gas separation

“…Physicomechanical properties of polyurethanes are highly dependent on the type, content and functionality of the materials used for their synthesis, which can be varied from soft thermoplastic to hard and brittle thermoset elastomers [14][15][16]. Application of polyurethane membranes to separate gases, mixtures of organic liquids, as well as biological and thermosensitive membranes have been the focus of many studies [17][18][19][20]. The properties of polyurethanes may be controlled by changing their molecular weight, chemical nature, and the contents of materials used in their synthesis [21,22].…”