Melt-processing, moisture-resistance and strength retention properties of supercritical CO2-processed thermoplastic starch resins

Abstract

This paper represents the first report of thermoplastic starch (scCO 2 TPS) and glutaraldehyde (GA) modified TPS resins (scCO 2 TPS 100 GA x), gelatinized and/or modified with the aid of supercritical carbon dioxide (scCO 2). The melt flow rate, initial and retention values of tensile strength (σ f) of TPS and GA-modified TPS prepared using scCO 2 fluid were considerably higher than those of TPS and TPS 100 GA x materials prepared in the conventional way. After conditioning at 20°C/50% RH for 56 days, the σ f of properly prepared scCO 2 TPS 100 GA 0.1 still remained at 17.5 MPa, which is around 3.5 times of that of the corresponding conditioned TPS 100 GA 0.1. The moisture contents of conditioned scCO 2 TPS and scCO 2 TPS 100 GA x were considerably lower than those of the corresponding TPS and TPS 100 GA x aged for the same amounts of time. Conditioned scCO 2 TPS and scCO 2 TPS 100 GA x exhibited only V h-type crystals with melting temperatures ~20°C lower than those of corresponding conditioned TPS and TPS 100 GA x. In comparison to TPS and TPS 100 GA x , more dissociated amylopectin chains with loosely hydrogen-bonded-OH groups and significantly less retrogradation was found for conditioned scCO 2 TPS and scCO 2 TPS 100 GA x .

Utilization of supercritical CO2 as a processing aid for preparation of ultrahigh molecular weight polyethylene/functionalized activated nanocarbon fibers

“…Application of scCO 2 not only can obtain products with higher purity and quality but also lead to better properties as compared with those prepared with conventional techniques and solvents. Our recent investigations demonstrated that the ease of melt‐processing and moisture‐resistance properties of thermoplastic starch (scCO 2 TPS), GA‐modified TPS (scCO 2 TPS 100 GA x ), and PVA‐modified scCO 2 TPS resins (scCO 2 TPS x PVA 05 y ) were considerably improved with the aid of scCO 2 during their gelatinization and/or modification processes. That is to say, what is particularly important is the promotion of the gelation process and the destruction of starch molecular organization with the help of scCO 2 .…”

Bio-Based Thermoplastic Starch Composites Reinforced by Dialdehyde Lignocellulose

“…The peaks around 1420 cm −1 are assigned to O–H bonding. The peaks at 1155 cm −1 and 1040 cm −1 were attributed to the C–O bond stretching of the C–O–H group in starch and the C–O bond stretching of the C–O–C group in the anhydroglucose ring, respectively [ 30 , 31 ]. In curve (c), the absorption bands at 1721 cm −1 disappeared, the –OH absorbance at 3288 cm −1 and 1420 cm −1 weakened, and the peaks at 1155 cm −1 and 1040 cm −1 also weakened, which could be due to the reaction between the –OH of the starch and the –CHO of the DLC in the DLC/TPS composites.…”

Thermoplastic starch and glutaraldehyde modified thermoplastic starch foams prepared using supercritical carbon dioxide fluid as a blowing agent

“…Disruption of hydrogen bonds, particularly disruption of those linking adjacent double helices within the original starch, become much easier with the aid of scCO 2 in gelatinization and foaming processes. These free hydroxyl groups obtained after disruption could form hydrogen bonds much easier with the plasticizers (ie, glycerol and water) during gelatinization and foaming . As a consequence, much more loosely starch hydrogen‐bonded ‐OH groups were found in FTIR spectra of the scCO 2 a TPS 100 CNF 0.02 and scCO 2 a TPS 100 CNF 0.02 GA x foam series as scCO 2 pressure increased.…”