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.

Bamboo Pulp Toughening Poly (Lactic Acid) Composite Using Reactive Epoxy Resin.

A novel poly (lactic acid) (PLA) composite with excellent mechanical properties, toughness, thermal stability, and water resistance was developed using a reactive melt-blending technique. PLA was melt mixed with epoxy resin (EPOXY) and bamboo pulp (PULP) to improve its reaction and mechanical properties. FTIR analysis confirmed the successful reaction of the PLA/EPOXY/PULP composites; the epoxy groups of EPOXY reacted with the -COOH groups of PLA and the -OH groups of PULP. The PLA/EPOXY/PULP5 composite showed a high tensile strength (67 MPa) and high toughness of 762 folding cycles, whereas the highest tensile strength was 77 MPa in the PLA/EPOXY5/PULP20 sample. SEM images presented a gap between the PLA and PULP; gap size decreased with the addition of EPOXY. The Tg of the PLA decreased with the EPOXY plasticizer effect, whereas the Tm did not significantly change. PULP induced crystallinity and increased Vicat softening of the PLA/PULP and PLA/EPOXY/PULP composites. The EPOXY reaction of the PLA/PULP composites improved their tensile properties, toughness, thermal stability, and water resistance.

Property Improvements of Silica-Filled Styrene Butadiene Rubber/Butadiene Rubber Blend Incorporated with Fatty-Acid-Containing Palm Oil.

Using vegetable oils as a plasticizer or processing aid in green rubber products is becoming popular due to environmental concerns. However, differences in vegetable oil processing result in varying amounts of low-molecular-weight (low-MW) free fatty acids (FFAs) in their composition, which range from 2% to 30%. This research investigated how the properties of silica-filled styrene butadiene rubber (SBR) and butadiene rubber (BR) blends were affected by the presence of FFAs in palm oil (PO). The rubber compounds containing a 70/30 SBR/BR blend, 30 phr of silica, and 2 phr of bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT), and the vulcanizing agents were prepared and tested. The PO content was kept constant at 20 phr, while the number of FFAs, i.e., lauric acid (LA), palmitic acid (PA), and oleic acid (OA), in PO varied from 10-30%. The viscosity, dynamic mechanical properties, morphology, cure characteristics, and mechanical properties of the rubber blend were then measured. Regardless of the FFA types, increasing FFA content in PO decreased scorch time, cure time, minimum torque, and viscosity. As the FFA content increased, the torque difference and crosslink density also increased, which led to higher hardness, modulus, tensile strength, and abrasion resistance. The FFA types had a slight effect on the vulcanizate properties, even though LA showed slightly better mechanical properties than PA and OA. The results reveal that FFAs in PO not only improve processability but also function as a co-activator in silica-filled sulfur-vulcanized SBR/BR blend compounds.

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.

Preparation and Characterization of Cellulose Nanocrystals from Bamboos and Their Application in Cassava Starch-Based Film.

Cellulose from different species of bamboo (Thyrsostachys siamesi Gamble, Dendrocalamus sericeus Munro (DSM), Bambusa logispatha, and Bambusa sp.) was converted to cellulose nanocrystals (CNCs) by a chemical-mechanical method. First, bamboo fibers were pre-treated (removal of lignin and hemicellulose) to obtain cellulose. Next, the cellulose was hydrolyzed with sulfuric acid using ultrasonication to obtain CNCs. The diameters of CNCs are in the range of 11-375 nm. The CNCs from DSM showed the highest yield and crystallinity, which was chosen in the film fabrication. The plasticized cassava starch-based films with various amounts (0-0.6 g) of CNCs (from DSM) were prepared and characterized. As the number of CNCs in cassava starch-based films increased, water solubility and the water vapor permeability of CNCs decreased. In addition, the atomic force microscope of the nanocomposite films showed that CNC particles were dispersed uniformly on the surface of cassava starch-based film at 0.2 and 0.4 g content. However, the number of CNCs at 0.6 g resulted in more CNC agglomeration in cassava starch-based films. The 0.4 g CNC in cassava starch-based film was found to have the highest tensile strength (4.2 MPa). Cassava starch-incorporated CNCs from bamboo film can be applied as a biodegradable packaging material.

Role of Microbial Volatile Organic Compounds in Promoting Plant Growth and Disease Resistance in Horticultural Production.

Microbial volatile organic compounds (MVOCs) are a diverse group of volatile organic compounds that microorganisms may produce and release into the environment. These compounds have both positive and negative effects on plants, as they have been shown to be effective at mitigating stresses and functioning as immune stimulants. Furthermore, MVOCs modulate plant growth and systemic plant resistance, while also serving as attractants or repellents for insects and other stressors that pose threats to plants. Considering the economic value of strawberries as one of the most popular and consumed fruits worldwide, harnessing the benefits of MVOCs becomes particularly significant. MVOCs offer cost-effective and efficient solutions for disease control and pest management in horticultural production, as they can be utilized at low concentrations. This paper provides a comprehensive review of the current knowledge on microorganisms that contribute to the production of beneficial volatile organic compounds for enhancing disease resistance in fruit products, with a specific emphasis on broad horticultural production. The review also identifies research gaps and highlights the functions of MVOCs in horticulture, along with the different types of MVOCs that impact plant disease resistance in strawberry production. By offering a novel perspective on the application and utilization of volatile organic compounds in sustainable horticulture, this review presents an innovative approach to maximizing the efficiency of horticultural production through the use of natural products.

Packaging materials and technologies for microwave applications: a review1.

Packaging materials for microwave application should be generally designed based on products properties and processing conditions such as microwavability, susceptibility, processing condition, barrier properties, mechanical properties, storage condition, sustainability, convenience, and so on. Ready-to-eat products are packed in materials that can sustain thermal processing in an industrial oven and warming process in a household oven. In this context, high barrier polymers are versatile microwave packaging materials due to the microwave transparency (unlike metalized film) and high barrier. Additionally, microwave packaging materials used for ready-to-cook are intended to facilitate the microwave heating of the products in a domestic oven. The introduction of a functional feather to microwave packaging tends to improve the microwaving efficiency such as susceptor and shielding in the household oven or self-venting microwave packaging to safely release the internal steam. Furthermore, microwave-assisted thermal processing intends to control microbial contamination, requiring materials with adequate stability during processing and storage. The features of these materials are addressed in this review along with details on the basic requirements and advanced technologies for microwave packaging, microwave processing of prepackaged food, and migration testing. The prospects of microwave packaging materials in the near future are also discussed.

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.

Sparking Nano-Metals on a Surface of Polyethylene Terephthalate and Its Application: Anti-Coronavirus and Anti-Fogging Properties.

The nano-metal-treated PET films with anti-virus and anti-fogging ability were developed using sparking nano-metal particles of Ag, Zn, and Ti wires on polyethylene terephthalate (PET) films. Ag nanoparticles were detected on the PET surface, while a continuous aggregate morphology was observed with Zn and Ti sparking. The color of the Ag-PET films changed to brown with increasing repeat sparking times, but not with the Zn-PET and Ti-PET films. The water contact angle of the nano-metal-treated PET films decreased with increasing repeat sparking times. The RT-PCR anti-virus test confirmed the high anti-virus efficiency of the nano-metal-treated PET films due to the fine particle distribution, high polarity, and binding of the nano-metal ions to the coronavirus, which was destroyed by heat after UV irradiation. A highly transparent, anti-fogging, and anti-virus face shield was prepared using the Zn-PET film. Sparking was an effective technique to prepare the alternative anti-virus and anti-fogging films for medical biomaterial applications because of their low cost, convenience, and fast processing.

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.

Morphology, Mechanical, and Water Barrier Properties of Carboxymethyl Rice Starch Films: Sodium Hydroxide Effect.

Carboxymethyl rice starch films were prepared from carboxymethyl rice starch (CMSr) treated with sodium hydroxide (NaOH) at 10-50% w/v. The objective of this research was to determine the effect of NaOH concentrations on morphology, mechanical properties, and water barrier properties of the CMSr films. The degree of substitution (DS) and morphology of native rice starch and CMSr powders were examined. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to investigate the chemical structure, crystallinity, and thermal properties of the CMSr films. As the NaOH concentrations increased, the DS of CMSr powders increased, which affected the morphology of CMSr powders; a polyhedral shape of the native rice starch was deformed. In addition, the increase in NaOH concentrations of the synthesis of CMSr resulted in an increase in water solubility, elongation at break, and water vapor permeability (WVP) of CMSr films. On the other hand, the water contact angle, melting temperature, and the tensile strength of the CMSr films decreased with increasing NaOH concentrations. However, the tensile strength of the CMSr films was relatively low. Therefore, such a property needs to be improved and the application of the developed films should be investigated in the future work.

High Substitution Synthesis of Carboxymethyl Chitosan for Properties Improvement of Carboxymethyl Chitosan Films Depending on Particle Sizes.

This study investigated the effect of chitosan particle sizes on the properties of carboxymethyl chitosan (CMCh) powders and films. Chitosan powders with different particle sizes (75, 125, 250, 450 and 850 µm) were used to synthesize the CMCh powders. The yield, degree of substitution (DS), and water solubility of the CMCh powders were then determined. The CMCh films prepared with CMCh based on chitosan with different particle sizes were fabricated by a solution casting technique. The water solubility, mechanical properties, and water vapor transmission rate (WVTR) of the CMCh films were measured. As the chitosan particle size decreased, the yield, DS, and water solubility of the synthesized CMCh powders increased. The increase in water solubility was due to an increase in the polarity of the CMCh powder, from a higher conversion of chitosan into CMCh. In addition, the higher conversion of chitosan was also related to a higher surface area in the substitution reaction provided by chitosan powder with a smaller particle size. As the particle size of chitosan decreased, the tensile strength, elongation at break, and WVTR of the CMCh films increased. This study demonstrated that a greater improvement in water solubility of the CMCh powders and films can be achieved by using chitosan powder with a smaller size.

Corn starch reactive blending with latex from natural rubber using Na+ ions augmented carboxymethyl cellulose as a crosslinking agent.

A mixture of corn starch and glycerol plasticizer (CSG) was blended with latex natural rubber (LNR) and carboxymethyl cellulose (CMC). The addition of 10 phr of CMC improved the Young's modulus (6.7 MPa), tensile strength (8 MPa), and elongation at break (80%) of the CSG/LNR blend. The morphology of the CSG/LNR/CMC blends showed a uniform distribution of LNR particles (1-3 µm) in the CSG matrix. The addition of CMC enhanced the swelling ability and water droplet contact angle of the blends owing to the swelling properties, interfacial crosslinking, and amphiphilic structure of CMC. Fourier transform infrared spectroscopy confirmed the reaction between the C=C bond of LNR and the carboxyl groups (-COO-) of CMC, in which the Na+ ions in CMC acted as a catalyst. Notably, the mechanical properties of the CSG/LNR/CMC blend were improved owing to the miscibility of CSG/CMC and the CMC/LNR interfacial reaction. The CSG/LNR/CMC biodegradable polymer with high mechanical properties and interfacial tension can be used for packaging, agriculture, and medical applications.

PET/Bio-Based Terpolyester Blends with High Dimensional Thermal Stability.

To improve the dimensional thermal stability of polyethylene terephthalate (PET), a poly(ethylene glycol 1,4-cyclohexane dimethylene (CHDM) isosorbide (ISB) terephthalate) (PEICT) known as ECOZEN®T110 (EZT) was introduced into PET using a melt blending technique. The miscibility, morphology, and thermal properties of the PET/EZT samples were investigated. The introduction of amorphous EZT into semi-crystalline PET increased the glass transition temperature (Tg) but decreased the crystallinity, which could be related to the transesterification reaction. By adding EZT contents up to 20%, the PET/EZT samples showed a single Tg, which indicated the miscibility between PET and EZT. However, two Tg values were observed in the PET/EZT samples with higher EZT contents (30-70%), indicating partial miscibility. This may have been due to the slightly different rheological and thermodynamic parameters that were affected by a higher ratio of bulky (rigid ISB and ductile CHDM) groups in EZT. However, the heat distortion temperature of the PET/EZT samples remarkably increased, which indicated that the dimensional stability was truly enhanced. Although the crystallinity of the PET/EZT samples decreased with increasing EZT content, the tensile strength and Young's modulus decreased slightly. Based on these results, the as-prepared PET/EZT samples with high dimensional stability can be used as a high-temperature polymeric material in various applications.

Preparation and characterization of positively surface charged zinc oxide nanoparticles against bacterial pathogens.

Solvothermal synthesis was used to investigate the formation of zinc oxide (ZnO) nanoparticles (NPs). A series of ZnO NPs was synthesized with different relative ratios of didodecyldimethylammonium bromide (DDAB) and zinc nitrate (ZN). The variation in the molarity influenced the crystallinity, size, and morphology of the obtained ZnO NPs. X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and zeta potential analysis were used to study the characteristic features of the ZnO NPs. The ZnO surface charge, size, and morphological structure were highly reliant on the concentrations of DDAB and ZN. With increasing relative ratio of DDAB to ZN, the particle size of ZnO NPs decreased and the surface charge increased to higher positive value. The ZnO NPs synthesized with cationic liquid DDAB presented enhanced performance in preventing the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) strains. The antibacterial activity of ZnO NPs have direct contact with the microbial cell wall resulting in destruction of bacterial cell integrity, release of antimicrobial Zn2+ ions, and induce cell death. This is due to the positively charged smaller ZnO NPs, prepared with DDAB cationic surfactant, effectively acting as an antimicrobial agent against food-borne pathogenic bacteria.

Effects of incorporating calcined corals as natural antimicrobial agent into active packaging system for milk storage.

A series of nylon (NY)/linear low-density polyethylene (LLDPE) containing calcined corals (NY/LL-CORALS) composite films were prepared using the cast extrusion method. We investigated the effect of different contents of incorporated calcined corals on the physical properties and antimicrobial activity of the composite films as well as their feasibility for milk storage applications. The results indicated that the main compound in calcined corals was calcium oxide (CaO). As the calcined corals content increased, the crystallinity of the composite films slightly decreased, but no significant changes in their thermal stability and permeability were observed. The NY/LL-CORALS composite films exhibited excellent antimicrobial performance against Escherichia coli and Staphylococcus aureus. Notably, the NY/LL-CORALS packaging significantly extended the lag time of bacteria and delayed the bacterial growth cycle in milk during storage. Thus, the NY/LL-CORALS composite films could be a potential food packaging material that could prolong the shelf life of fresh food.

Calcined marine coral powders as a novel ecofriendly antimicrobial agent.

In this study, natural waste of marine corals was calcined to prepare an antimicrobial agent. Energy-dispersive X-ray fluorescence spectroscopy showed that the major element and compound of calcined corals were Ca and CaO, respectively, while X-ray photoelectron spectroscopy revealed the occurrence of more than one oxygen species (O1s) on the surface of calcined corals, which was ascribed to the presence of MgO. Scanning electron microscopy imaging showed that calcined corals had a rough surface and an irregular shape, and the particle size distribution indicated that the average particle size of the calcined corals was 7.3 µm. The calcined corals exhibited large zones of inhibition against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria as well as a fungus (Penicillium sp.), in the antimicrobial tests using well diffusion method. Notably, as a membrane-active and species-specific agent, pronounced antimicrobial activity for calcined corals was observed against S. aureus. Our newly developed bioactive calcined corals could be the potential antimicrobial agents in medical, biological, and food packaging applications.

Poly(Lactic Acid)/Zno Bionanocomposite Films with Positively Charged Zno as Potential Antimicrobial Food Packaging Materials.

A series of PLA/ZnO bionanocomposite films were prepared by introducing positively surface charged zinc oxide nanoparticles (ZnO NPs) into biodegradable poly(lactic acid) (PLA) by the solvent casting method, and their physical properties and antibacterial activities were evaluated. The physical properties and antibacterial efficiencies of the bionanocomposite films were strongly dependent on the ZnO NPs content. The bionanocomposite films with over 3% ZnO NPs exhibited a rough surface, poor dispersion, hard agglomerates, and voids, leading to a reduction in the crystallinity and morphological defects. With the increasing ZnO NPs content, the thermal stability and barrier properties of the PLA/ZnO bionanocomposite films were decreased while their hydrophobicity increased. The bionanocomposite films showed appreciable antimicrobial activity against Staphylococcus aureus and Escherichia coli. Especially, the films with over 3% of ZnO NPs exhibited a complete growth inhibition of E. coli. The strong interactions between the positively charged surface ZnO NPs and negatively charged surface of the bacterial membrane led to the production of reactive oxygen species (ROS) and eventually bacterial cell death. Consequently, these PLA/ZnO bionanocomposite films can potentially be used as a food packaging material with excellent UV protective and antibacterial properties.