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.

Reactive Blending of Modified Thermoplastic Starch Chlorhexidine Gluconate and Poly(butylene succinate) Blending with Epoxy Compatibilizer.

Biodegradable starch-based polymers were developed by melt-blending modified thermoplastic starch (MTPS) with poly(butylene succinate) (PBS) blended with epoxy resin (Er). A modified thermoplastic starch blend with chlorhexidine gluconate (MTPSCh) was prepared by melt-blending cassava starch with glycerol and chlorhexidine gluconate (CHG) 1.0% wt. The Er was melt-blended with PBS (PBSE) at concentrations of 0.50%, 1.0%, 2.5%, and 5.0% (wt%/wt%). The mechanical properties, water resistance, and morphology of the MTPSCh/PBSE blends were investigated. The MTPSCh/PBSE2.5% blend showed an improvement in tensile strength (8.1 MPa) and elongation at break (86%) compared to the TPSCh/PBS blend (2.6 MPa and 53%, respectively). In addition, water contact angle measurements indicated an increase in the hydrophobicity of the MTPSCh/PBSE blends. Thermogravimetric analysis showed an improvement in thermal stability when PBS was added to the MTPSCh blends. Fourier transform infrared spectroscopy data confirmed a new reaction between the amino groups of CHG in MTPSCh and the epoxy groups of Er in PBSE, which improved the interfacial adhesion of the MTPSCh/PBSE blends. This reaction improved the mechanical properties, water resistance, morphology, and thermal stability of the TPSCh/PBSE blends.

Enhancement in mechanical and antimicrobial properties of epoxidized natural rubber via reactive blending with chlorhexidine gluconate.

An epoxidized natural rubber (ENR) blend with chlorhexidine gluconate (CHG) was prepared using a two-roll mill at 130 °C. CHG was added at concentrations of 0.2, 0.5, 1, 2, 5, and 10% (w/w) as an antimicrobial additive. The ENR blend with 10% (w/w) CHG showed the best tensile strength, elastic recovery, and Shore A hardness. The ENR/CHG blend exhibited a smooth fracture surface. The appearance of a new peak in the Fourier transform infrared spectrum confirmed that the amino groups of CHG reacted with the epoxy groups of ENR. The ENR with 10% CHG exhibited an inhibition zone against Staphylococcus aureus. The proposed blending improved the mechanical properties, elasticity, morphology, and antimicrobial properties of the ENR.

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.

Modified Poly(Lactic Acid) Epoxy Resin Using Chitosan for Reactive Blending with Epoxidized Natural Rubber: Analysis of Annealing Time.

Poly(lactic acid) was melt-blended with epoxy resin without hardener and chitosan (CTS) to prepare modified PLA (PLAEC). Epoxy resin 5% and CTS 1-20% (wt/wt) were incorporated into PLA during melt mixing. PLAEC was melt-blended with an epoxidized natural rubber (ENR) 80/20 wt. The PLAEC CTS 1% blended with ENR (PLAEC1/ENR) showed a high tensile strength (30 MPa) and elongation at break (7%). The annealing process at 80 °C for 0-15 min maintained a tensile strength of approximately 30 MPa. SEM images of the PLAE/ENR blend showed phase inversion from co-continuous to ENR particle dispersion in the PLA matrix with the addition of CTS, whereas the annealing time reduced the hole sizes of the extracted ENR phase due to the shrinkage of PLA by crystallization. Thermal properties were observed by DSC and a Vicat softening test. The annealing process increased the crystallinity and Vicat softening temperature of the PLAEC1/ENR blend. Reactions of -COOH/epoxy groups and epoxy/-NH2 groups occurred during PLAE and PLAEC preparation, respectively. FTIR confirmed the reaction between the -NH2 groups of CTS in PLAEC and the epoxy groups of ENR. This reaction increased the mechanical properties, while the annealing process improved the morphology and thermal properties of the blend.

Effect of chlorhexidine gluconate on mechanical and anti-microbial properties of thermoplastic cassava starch.

Antimicrobial thermoplastic starch (TPS) was developed using cassava starch, glycerol, and chlorhexidine gluconate (CHG) blend. CHG was added at concentrations of 1%, 5%, 10%, and 20% (wt./wt.) as an antimicrobial additive. The tensile strength and hardness of the blended samples increased with the chlorhexidine gluconate content, especially for 1% CHG. wt./wt. (12.6 MPa and 94, respectively). The TPS/CHG20 blend exhibited a large phase of CHG and recrystallization of TPS. The water solubility decreased with the addition of CHG. Nuclear magnetic resonance data confirmed a reaction between the hydroxyl groups of TPS and the amino groups of CHG. The TPS/CHG20% exhibited an inhibition zone for three bacterial types (Staphylococcus aureus, Escherichia coli, and Bacillus cereus) and three fungal types (Rhizopus oligosporus, Aspergillus oryzae, and Candida albicans). CHG acted simultaneously as a chain extender and an antimicrobial additive for TPS, improving its tensile strength, hardness, and anti-microbial properties.

Sericin cocoon bio-compatibilizer for reactive blending of thermoplastic cassava starch.

Cassava starch was blended with glycerol to prepare thermoplastic starch (TPS). Thermoplastic starch was premixed with sericin (TPSS) by solution mixing and then melt-blended with polyethylene grafted maleic anhydride (PEMAH). The effect of sericin on the mechanical properties, morphology, thermal properties, rheology, and reaction mechanism was investigated. The tensile strength and elongation at break of the TPSS10/PEMAH blend were improved to 12.2 MPa and 100.4%, respectively. The TPS/PEMAH morphology presented polyethylene grafted maleic anhydride particles (2 µm) dispersed in the thermoplastic starch matrix, which decreased in size to approximately 200 nm when 5% sericin was used. The melting temperature of polyethylene grafted maleic anhydride (121 °C) decreased to 111 °C because of the small crystal size of the polyethylene grafted maleic anhydride phase. The viscosity of TPS/PEMAH increased with increasing sericin content because of the chain extension. Fourier-transform infrared spectroscopy confirmed the reaction between the amino groups of sericin and the maleic anhydride groups of polyethylene grafted maleic anhydride. This reaction reduced the interfacial tension between thermoplastic starch and polyethylene grafted maleic anhydride, which improved the compatibility, mechanical properties, and morphology of the blend.

Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin.

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.