Midhat Nabil Ahmad Salimi
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Midhat Nabil Ahmad Salimi
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Midhat Nabil, Ahmad Salimi
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Ahmad Salimi, Midhat Nabil
Salimi, Midhat Nabil
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54788410200

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Toughening mechanism of thermoplastic starch nano-biocomposite with the hybrid of nanocellulose/nanobentonite

2023 , Lai Di Sheng , Azlin Fazlina Osman , Sinar Arzuria Adnan , Mariatti Jaafar@Mustapha , Ismail Ibrahim , Midhat Nabil Ahmad Salimi

High flexibility and toughness are key criteria for an effective bioplastic packaging film. However, in most studies, the flexibility of thermoplastic starch (TPS) films is always neglected when targeting their tensile strength improvement. Low film flexibility has limited the development of TPS films in replacing the petrochemical-based plastic packaging films. In this communication, we report a method to produce thermoplastic corn starch (TPCS) films with excellent mechanical strength, high flexibility and high toughness through the hybridization of two natural nanofillers: nanobentonite and nanocellulose. The synergistic effect of the hybrid nanofillers can be observed through the arrangement of alternating nacre structures where the nanobentonite silicate layers are responsible for mechanical strength, while the nanocellulose promotes free volume in the TPCS matrix and triggers high film elongation at break. Structural, morphological, and thermomechanical analysis were conducted, and the detailed strengthening mechanism of the TPCS hybrid nano-biocomposite films was revealed.

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Thermoplastic starch hybrid biocomposite films with improved strength and flexibility produced through crosslinking via carboxylic acid

2023 , Di Sheng Lai , Azlin Fazlina Osman , Sinar Arzuria Adnan , Ismail Ibrahim , Mariatti Jaafar @ Mustapha , Midhat Nabil Ahmad Salimi

Thermoplastic starch (TPS) suffers from its intrinsic low mechanical strength and high brittleness due to its strong hydrogen bonding and low chain mobility. The conventional way to crosslink the TPS film can improve the strength and stiffness of the films, but usually reduces the flexibility of the film, and increases its brittleness. In this study, the incorporation of the hybrid nanofiller [1 wt% nanocellulose (C) and 4 wt% nano bentonite (B)] into the TPS proved to improve greatly the films’ strength and flexibility. The hybrid nanofillers with ratio 4B:1C was incorporated into the crosslinked thermoplastic corn starch (CR-TPCS) film to increase the its flexibility and toughness and produced a high mechanical strength fully biodegradable film. Two different aqueous carboxylic acids: citric acid (CA) and tartaric acid (TA) with different pH values (2,4,6) as the green crosslinker were employed. Substantial increase of tensile strength (3.98 to 9.17 MPa), Young’s modulus (9.10 to 46.30 MPa) and elongation at break (55.2 to 135.7%) was observed for the CA- 4B1C/pH2 films compared to the CR-TPCS films. The melting temperature (Tm) of the CA-4B1C/pH2 improved compared to the TPCS/4B1C (un-crosslinked) film due to its crosslinking effect. Meanwhile, the CA-4B1C films exhibited the highest degree of substitution and di-esterification with the lowest swelling and water solubility properties due to the formation of a special “bridge” structure between the CA, nanocellulose and plasticizer. The “bridge” structure developed between the TPCS chains serves as the toughener to motivate higher chain stress relaxation and load endurance. The crosslinked “bridge structure” also proved to effectively reduce the retrogradation phenomenal in the TPCS films. This combination method of hybridization and crosslinking is an efficient, low cost, and environmentally friendly technique to overcome the low flexibility and brittleness problem of the TPS based packaging film.

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