Mechanical properties and water resistance improvement of thermoplastic modified starch, carboxymethyl cellulose, and zinc oxide nanometal particles by reactive blending.

Novel biodegradable thermoplastic starch (TPS) with high mechanical properties and water resistance was developed using reactive blending technique. Effect of zinc oxide (ZnO) addition to TPS properties and reaction was investigated. Thermoplastic modified starch (TPMS) was prepared by melt-mixing modified starch with glycerol 70/30%wt/wt. Carboxy methyl cellulose (CMC) 5%wt was incorporated with modified starch, glycerol, and zinc oxide (ZnO) 0-5 %wt. Fourier-transform infrared (FTIR) spectroscopy analysis confirmed the formation of the carboxyl anion (OZn) between the -COO- of CMC and the free Zn+ ion of ZnO. The tensile strength of the TPMS/CMC/ZnO blend increased 7 time with ZnO 5 % (14 MPa) addition compared to TPMS (2 MPa). The color (∆E) of TPMS/CMC/ZnO differed notably at high ZnO concentrations (1-5 %wt). The TPMS/CMC blend displayed a smooth fracture surface due to the miscibility of the materials. Small particles of ZnO dispersed finely in the TPMS matrix and increased the interfacial tension and water contact angle of the blends. The miscibility of TPS with CMC and the occurrence of ionic interactions of -COO- of CMC and -OH of starch with the Zn+ ion as physical crosslinking were indicated to improve the mechanical properties and water resistance of the blends.

Antimicrobial thermoplastic starch reactive blend with chlorhexidine gluconate and epoxy resin.

An antimicrobial thermoplastic starch (TPS) was developed by melt-mixing TPS with chlorhexidine gluconate (CHG) and epoxy resin (Er). The tensile strength and hardness of the TPSCh blend increased with the addition of Er (TPSCh/Er), especially at 5 wt% Er (TPSCh/Er5) (19.5 MPa and 95 %, respectively). The water contact angle of TPSCh/Er was higher than those of TPS and TPSCh because of the improved interfacial tension. Fourier transform infrared and nuclear magnetic resonance analyses confirmed the reaction between the epoxy groups of Er, hydroxyl groups of starch, and amino groups of CHG. TPSCh/Er5 exhibited a significantly lower CHG release than TPSCh owing to the rearrangement of TPSCh chains via Er crosslinking. TPSCh/Er0.5 and TPSCh/Er1 showed inhibition zones against both tested bacteria (Staphylococcus aureus and Bacillus cereus), whereas TPSCh/Er2.5, TPSCh/Er5, and TPSCh/Er10 showed inhibition zones only against S. aureus. Moreover, TPSCh and TPSCh/Er0.5-2.5 exhibited inhibition zones with Saccharomyces cerevisiae.

Effects of storage temperature on the quality of eggs coated by cassava starch blended with carboxymethyl cellulose and paraffin wax.

A blend of cassava starch (CS), carboxymethyl cellulose (CMC), and paraffin was prepared as a coating material to maintain the quality of eggs during 4 wk of storage at different temperatures. The efficacy of the CS/CMC/paraffin (6/1/0.5% w/v) coating was investigated in terms of the Haugh unit (HU), weight loss, pH, and microbial load at the end of storage. The best egg storage temperature was 4°C, which maintained an HU of grade AA in coated and uncoated eggs for 4 wk. Lower weight loss (2.14%) was observed in coated eggs at 4°C storage than at 30°C storage (3.26%). The pH in the albumen of coated and uncoated eggs at 4°C increased from 6.84 to 6.88 and 7.01 to 7.03, respectively, after 4 wk of storage. No microbes were detected in the coated and uncoated eggs at 4°C. The maximum microbial count was 728 ± 35 cfu/mL in uncoated eggs at 30°C storage. Egg coating prevented microbial contamination of eggs stored at 30°C for 4 wk. The freshness of the eggs did not affect the nutrient content. The egg-coating material effectively maintained egg quality, prevented microbial contamination of eggs, and increased the shelf life of eggs at storage temperatures of 25 and 30°C.

Effect of Egg-Coating Material Properties by Blending Cassava Starch with Methyl Celluloses and Waxes on Egg Quality.

An egg-coating material was developed to extend the shelf-life and freshness of eggs by blending cassava starch (CS) with gelling agents and waxes. The effects of the properties of this egg coating on egg quality were investigated. Hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), beeswax, and paraffin wax were used. CS blended with low-molecular-weight paraffin (Paraffin(L)) and CMC coating material displayed a tensile strength of 4 MPa, 34% elongation at break, 0.0039 g day-1 m-2 water vapor permeability, and a water contact angle of 89° at 3 min. Eggs coated with CS/CMC/Paraffin(L) solutions had a Haugh unit value of 72 (AA grade) and exhibited a weight loss of 2.4% in 4 weeks. CMC improved the compatibility of CS and Paraffin(L). This improvement and the hydrophobicity of Paraffin(L) provided suitable mechanical and water-resistance properties to the coating material that helped to maintain the quality of the coated AA-grade eggs with low weight loss for 4 weeks.

Thermoplastic mung bean starch/natural rubber/sericin blends for improved oil resistance.

Oil resistant thermoplastic elastomers (TPE) were prepared using mung bean thermoplastic starch (MTPS) blending with rubbers and sericin. Sericin was incorporated into MTPS as a compatibilizer. MTPS with sericin (MTPSS) was blended with natural rubber (NR) and epoxidized NR (ENR). Sericin at 5% improved the tensile strength (10 MPa), elastic recovery (52%) and morphology of the MTPSS/ENR blend. The mechanical properties, elastic recovery and morphology of the MTPSS5/NR blend were improved by the addition of ENR. The MTPSS/ENR showed palm (28%) and motor oils (8%) swelling resistance because of the hydrophilicity of MTPS and high polarity of ENR. The MTPSS/ENR/NR showed gasoline swelling resistance (104%) because of the hydrophilicity of MTPS and low polarity of NR. FTIR confirmed a reaction between the -NH groups of sericin and the epoxy groups of ENR. This reaction improved the compatibility, mechanical properties, elastic recovery, morphology and oils swelling resistance of the blends.

Effect of sodium benzoate and chlorhexidine gluconate on a bio-thermoplastic elastomer made from thermoplastic starch-chitosan blended with epoxidized natural rubber.

Thermoplastic elastomer (TPE) was developed by blending thermoplastic starch (TPS) with rubber. Thermoplastic starch-chitosan (TPSC) was prepared by the solution mixing of cassava starch, chitosan (CTS) and glycerol in acidified water (lactic acid 1 wt%) at 80 °C follow by melt mixing at 130 °C. Sodium benzoate (BEN) and chlorhexidine gluconate (Cl) were added during the solution mixing as additives for antimicrobial properties. TPSC was melt-mixed with epoxidized natural rubber (ENR) (70/30 wt/wt). The tensile strength and elongation at break of the TPSC/ENR increased with the additive content. Elastic recovery was improved by the addition of Cl. A new peak in the FTIR data confirmed the reaction between the reactive functional groups of the CTS and the additives with the epoxy groups of ENR. These reactions and miscibility of the TPSC/ENR/additives blends improved the mechanical properties, elasticity, morphology, and antimicrobial properties of the blends.