Thermoplastic Starch with Poly(butylene adipate-co-terephthalate) Blends Foamed by Supercritical Carbon Dioxide

Abstract

Starch-based biodegradable foams with a high starch content are developed using industrial starch as the base material and supercritical CO2 as blowing or foaming agents. The superior cushioning properties of these foams can lead to competitiveness in the market. Despite this, a weak melting strength property of starch is not sufficient to hold the foaming agents within it. Due to the rapid diffusion of foaming gas into the environment, it is difficult for starch to maintain pore structure in starch foams. Therefore, producing starch foam by using supercritical CO2 foaming gas faces severe challenges. To overcome this, we have synthesized thermoplastic starch (TPS) by dispersing starch into water or glycerin. Consecutively, the TPS surface was modified by compatibilizer silane A (SA) to improve the dispersion with poly(butylene adipate-co-terephthalate) (PBAT) to become (TPS with SA)/PBAT composite foam. Furthermore, the foam-forming process was optimized by varying the ratios of TPS and PBAT under different forming temperatures of 85 °C to 105 °C, and two different pressures, 17 Mpa and 23 Mpa were studied in detail. The obtained results indicate that the SA surface modification on TPS can influence the great compatibility with PBAT blended foams (foam density: 0.16 g/cm3); whereas unmodified TPS and PBAT (foam density: 0.349 g/cm3) exhibit high foam density, rigid foam structure, and poor tensile properties. In addition, we have found that the 80% TPS/20% PBAT foam can be achieved with good flexible properties. Because of this flexibility, lightweight and environment-friendly nature, we have the opportunity to resolve the strong demands from the packing market.

Supercritical CO2 Impregnation of Thymol in Thermoplastic Starch-Based Blends: Chemico-Physical Properties and Release Kinetics

“…All TPS samples displayed a wide band in the range of 3600–3000 cm −1 , which corresponds to the stretching vibration of the O–H groups of starch [ 31 , 32 ] (groups of amylose, amylopectin, and adsorbed water), glycerol, and thymol ( Figure 3 a). Additionally, a slight shift of O-H absorptions to 3200 cm −1 is observed in the samples containing thymol impregnated at longer times, independent of the temperature of the scCO 2 process (6 h), and a higher percentage of impregnated thymol with a less intense band compared to neat TPS.…”

“…Additionally, intermolecular hydrogen bonding occurs between thymol and starch, while thymol and glycerol (plasticizer) interact through –OH groups [ 33 ]. In the high-frequency region of spectra of neat and impregnated TPS, the bands originating from the asymmetric ν as (CH 3 ) and asymmetric ν as (CH 2 ) valence vibrations of C − H bonds appear around 2965 cm −1 and 2926 cm −1 , respectively [ 31 , 34 ]. An additional band appears at 2866 cm −1 in the spectra of thymol-impregnated TPS samples, which is attributed to symmetric valence vibrations ( ν s ) of the C−H bonds in the −CH 3 and −CH 2 fragments.…”

Special Issue: Synthesis, Processing, Structure and Properties of Polymer Materials

“…In this Special Issue, 33 original articles have been published on various topics, including the preparation, characterization, and some examples of application of polymeric materials. This issue includes review articles [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] and research articles [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

“…The scope of research articles of papers included a Special Issue is very wide. It includes papers on the synthesis and study of the properties of new thermoplastic polymers [ 9 , 10 , 11 , 12 , 13 ], obtaining of composites [ 14 , 15 , 16 ], nanocomposites [ 17 , 18 , 19 ], microspheres [ 20 , 21 ], polymeric blends [ 22 , 23 , 24 ], hydrophobic nanostructures [ 25 ], polymeric membranes [ 26 , 27 ], hydrogels [ 28 ] and others [ 29 , 30 , 31 , 32 , 33 ].…”

“…The aim of the work by Chang et al [ 24 ] was to obtain fully biodegradable polymer blends derived from thermoplastic starch and poly (butylene adipate- co -terephthalate). These blends were further foamed with carbon dioxide to improve the flexibility and reduce the brittleness of the finished materials.…”