Oxidized microcrystalline cellulose improve thermoplastic starch-based composite films: Thermal, mechanical and water-solubility properties

The effect of agar from the seaweed Gracilaria fisheri on properties of biodegradable starch foam

This work focuses on the potential of agar from the seaweed Gracilaria fisheri to modify the properties of starch foam. The effects of different ratios of glycerol and agar on the properties of starch foams were investigated. All formulations used in this study produced easy-to-handle, smooth, single-use foam trays with no visible cracks. The addition of agar slightly affected the off-white color of the foam but red and yellow color values significantly decreased with increments of agar content. As the agar content was increased, the foam became less dense. A foam produced at a glycerol:agar ratio of 3:7 exhibited the highest values of flexural stress at maximum load (3.23 MPa), modulus (194.46 MPa) and hardness (97.50), and the highest temperature at maximum weight loss (Tmax) (337 °C). Therefore, starch foam modified with agar from Gracilaria fisheri showed suitable physical, mechanical and thermal properties for food packaging, and could possibly be used in the place of expanded polystyrene (EPS) foam.

Development of starch-rich thermoplastic polymers based on mango kernel flour and different plasticizers

This work reports on the development of starch-rich thermoplastic based formulations produced by using mango kernel flour, avoiding the extraction process of starch from mango kernel to produce these materials. Glycerol, sorbitol and urea at 15 wt% are used as plasticizers to obtain thermoplastic starch (TPS) formulations by extrusion and injection-moulding processes. Mechanical results show that sorbitol and urea allowed to obtain samples with tensile strength and elongation at break higher than the glycerol-plasticized sample, achieving values of 2.9 MPa of tensile strength and 42 % of elongation at break at 53 % RH. These results are supported by field emission scanning electron microscopy (FESEM) micrographs, where a limited concentration of voids was observed in the samples with sorbitol and urea, indicating a better interaction between starch and the plasticizers. Thermogravimetric analysis (TGA) shows that urea and sorbitol increase the thermal stability of TPS in comparison to the glycerol-plasticized sample. Differential scanning calorimetry (DSC) and dynamic-mechanical-thermal analysis (DMTA) verify the increase in stiffness of the sorbitol and urea plasticized TPS and also illustrate an increase in the glass transition temperature of both samples in comparison to the glycerol-plasticized sample. Glass transition temperatures of 45 °C were achieved for the sample with sorbitol.

Green interconnected network structure of chitosan-microcrystalline cellulose-lignin biopolymer film for active packaging applications

As an excellent alternative to petroleum-based food packaging materials, a novel green hybrid composite film with an excellent interconnected network structure was successfully fabricated by integrating chitosan (chi), microcrystalline cellulose (MCC), and lignin nanoparticles (LNP), including the desired amount of plasticizer glycerol (gly). Overall, 36 combinations were developed and investigated for superior biocomposite film formation. Among the various concentration ratios, the 40:35:25 chi-MCC-gly film provided well-organized film formation, good physicochemical properties, mechanical stability, efficient water contact angle, reduced water solubility, and lower water vapor permeability (11.43 ± 0.55 × 10-11 g.m-1.s-1.Pa-1). The performance of the chi-MCC-gly film further enhanced by the homogeneous incorporation of ∼100 nm LNP. With 1 % LNP addition, the tensile strength of the film increased (28.09 MPa, 47.10 % increase) and the water vapor permeability reached a minimum of 11.43 × 10-11 g.m-1.s-1.Pa-1, which proved the impact of LNP in composite films. Moreover, the films showed excellent resistance to thermal shrinkage even at 100 °C and exhibited nearly 100 % UV blocking efficiency at higher LNP concentrations. Interestingly, the green composite films extended the shelf life of freshly cut cherry tomatoes to seven days without spoilage. Overall, the facile synthesis of strong, insoluble, UV-blocking, and thermally stable green composite films realized for food packaging applications.

On the Use of OPEFB-Derived Microcrystalline Cellulose and Nano-Bentonite for Development of Thermoplastic Starch Hybrid Bio-Composites with Improved Performance

Thermoplastic starch (TPS) hybrid bio-composite films containing microcrystalline cellulose (C) and nano-bentonite (B) as hybrid fillers were studied to replace the conventional non-degradable plastic in packaging applications. Raw oil palm empty fruit bunch (OPEFB) was subjected to chemical treatment and acid hydrolysis to obtain C filler. B filler was ultra-sonicated for better dispersion in the TPS films to improve the filler–matrix interactions. The morphology and structure of fillers were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). TPS hybrid bio-composite films were produced by the casting method with different ratios of B and C fillers. The best ratio of B/C was determined through the data of the tensile test. FTIR analysis proved the molecular interactions between the TPS and the hybrid fillers due to the presence of polar groups in their structure. XRD analysis confirmed the intercalation of the TPS chains between the B inter-platelets as a result of well-developed interactions between the TPS and hybrid fillers. SEM images suggested that more plastic deformation occurred in the fractured surface of the TPS hybrid bio-composite film due to the higher degree of stretching after being subjected to tensile loading. Overall, the results indicate that incorporating the hybrid B/C fillers could tremendously improve the mechanical properties of the films. The best ratio of B/C in the TPS was found to be 4:1, in which the tensile strength (8.52MPa), Young’s modulus (42.0 MPa), elongation at break (116.4%) and tensile toughness of the film were increased by 92%, 146%, 156% and 338%, respectively. The significantly improved strength, modulus, flexibility and toughness of the film indicate the benefits of using the hybrid fillers, since these features are useful for the development of sustainable flexible packaging film.

Preparation and Characterization of Starch/Empty Fruit Bunch-Based Bioplastic Composites Reinforced with Epoxidized Oils

This study examined the development of starch/oil palm empty fruit bunch-based bioplastic composites reinforced with either epoxidized palm oil (EPO) or epoxidized soybean oil (ESO), at various concentrations, in order to improve the mechanical and water-resistance properties of the bio-composites. The SEM micrographs showed that low content (0.75 wt%) of epoxidized oils (EOs), especially ESO, improved the compatibility of the composites, while high content (3 wt%) of EO induced many voids. The melting temperature of the composites was increased by the incorporation of both EOs. Thermal stability of the bioplastics was increased by the introduction of ESO. Low contents of EO led to a huge enhancement of tensile strength, while higher contents of EO showed a negative effect, due to the phase separation. The tensile strength increased from 0.83 MPa of the control sample to 3.92 and 5.42 MPa for the composites with 1.5 wt% EPO and 0.75 wt% ESO, respectively. EOs reduced the composites' water uptake and solubility but increased the water vapor permeability. Overall, the reinforcing effect of ESO was better than EPO. These results suggested that both EOs can be utilized as modifiers to prepare starch/empty-fruit-bunch-based bioplastic composites with enhanced properties.

Ordered long polyvinyl alcohol fiber-reinforced thermoplastic starch composite having comparable mechanical properties with polyethylene and polypropylene

A novel strategy is proposed to fabricate ordered long polyvinyl alcohol fiber (PVAF)-reinforced thermoplastic starch (TPS) composites with significantly improved mechanical properties. The PVAFs were uniformly fixed on two rods first; then sandwich-like TPS/fibers/TPS composite films were prepared by hot pressing, and PVAFs (0-4.08 wt%) with the same orientation were added to the composite films. The tensile test demonstrated that the tensile strength of the PVAF/TPS composite film improved from 2.13 MPa for TPS to 20.98 MPa with 4.08 wt% PVAFs, which is higher than the tensile strength of polyethylene (PE) (11.88 MPa) and polypropylene (PP) (19.29 MPa) and ten times higher than that of TPS. The sandwich-like cross-section of the composite film was observed by scanning electron microscopy to prove the better compatibility between PVAF and TPS. The nanoindentation test revealed that the addition of fibers improved the elastic modulus and hardness of the surface of the material. The strengthening mechanism for different PVAF contents was simulated by finite element analysis and attributed to the reduced maximum von Mises stress at the interface between the fiber and the TPS matrix, avoiding the stress concentration and corresponding fracture. This study provides a new way to prepare degradable composite films with suitable mechanical properties to replace PE or PP.

Insights into the production and physicochemical properties of oxycellulose microcrystalline with coexisting crystalline forms

Oxycellulose microcrystalline (Oxy-MCC) was prepared utilizing nonwood agro-industrial residue, rice husk (RH), via consecutive soda delignification and non-acidic catalytic oxidation. The resultant Oxy-MCC, with a 31 wt% yield, has granular microstructured particles with an average diameter of 41.66 ± 4.11 μm. The porous morphology has been observed in Oxy-MCC micrographs, using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and TGA/DTG thermal analysis indicated the presence of typical cellulose characteristics, while the presence of carbonyl spectral peak signalized the efficacy of D-RH oxidation process. The x-ray diffraction (XRD) confirmed the coexistence of cellulosic crystalline forms of cellulose I and cellulose II with 84.8% crystallinity index. Significant growth of crystallite size was observed from 1.7 nm (RH) to 9.4 nm (Oxy-MCC). The maximum decomposition temperature (T_max) was found to be 324 °C, thus indicating good thermal stability. Oxy-MCC showed, overall, attractive thermal and physicochemical properties for oxycellulose nanocrystalline (Oxy-NCC) production.

A novel method to produce sustainable biocomposites based on thermoplastic corn-starch reinforced by polyvinyl alcohol fibers

Adding reinforced fiber or cross-linking agent into thermoplastic starch (TPS) is an effective method to improve its performance. Herein, biodegradable polyvinyl alcohol fiber (PVAF) and sodium hexametaphosphate (SHMP) were not added into TPS directly; the PVAFs were preliminary treated (pre-soaking) by an SHMP solution, and then mixed with starch and glycerol to prepare 2 wt% PVAF/TPS composites through extrusion and injection molding. This process promoted crosslinking action between PVAFs and starch, and as a consequence enhanced the mechanic and dynamic mechanic behavior. The PVAFs with different immersion times were characterized by SEM, FTIR, and WAXD. The results confirmed that the SHMP coating was formed by a chemical bond connection on the surface of the PVAFs, particularly for the PVAFs soaked for 1.5 h, which produced a corresponding PVAF/TPS composite with a maximum tensile strength of 9.18 MPa and an impact strength of 21.29 kJ m⁻². The corresponding tensile fractured cross-section images were shown by SEM. The DMA curves indicated that the pre-soaked PVAFs effectively improved the energy storage modulus and transition temperature of composites, and the activation energy of the starch macromolecules reached a maximum of 349.9 kJ mol⁻¹ during the dynamic mechanic process. The contact angle attained a maximum of 66.25°. Compared with TPS, the pre-soaked PVAF-reinforced PVAF/TPS composites had better mechanical properties, good processability through traditional extrusion and injection molding, reduced water wettability, and potential applications for packaging and catering.

Adding reinforced polyvinyl alcohol fiber (PVAF) pre-soaked in an SHMP solution into thermoplastic starch (TPS) is an effective method to improve its performance.

Rheological, Thermal, Superficial, and Morphological Properties of Thermoplastic Achira Starch Modified with Lactic Acid and Oleic Acid

The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes.