Effect of polymer microspheres on selected properties of injection-molded shapes based on thermoplastic starch

Changes in the mechanical properties of thermoplastic potato starch in relation with changes in B-type crystallinity

The poor mechanical properties and high water solubility of biodegradable thermoplastic starch (TPS) represent the main disadvantages of TPS in many applications. In this work, TPS film was prepared from a water solution of corn starch modified by 5 wt% dialdehyde starch (DAS) as crosslinking agent and 3 wt% montmorillonite (MMT) as reinforcing additive. Interactions occurring in the TPS films were investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, XRD, DSC, dynamic mechanical thermal analysis (DMTA) and TGA. The results obtained fom FTIR spectroscopy and DSC suggest the formation of hydrogen bond interactions between the hydroxyl group of starch, DAS, the MMT layers and glycerol. DMTA indicated that the relaxation of films with DAS and MMT appears in a higher and broader temperature range due to the starch backbone stiffness; the extreme increase in the storage modulus confirmed the suggested interactions. The determination of the weight loss of the films in water indicated a significant increase of the water resistance of TPS due to incorporation of DAS and MMT. Changes in mechanical properties of the films containing DAS and clay were determined, showing a substantial increase in tensile strength from 2.7 to 6.7 MPa, while Young's modulus increased by 15 times for TPS modified with 5% DAS and 3% MMT. Therefore, the outcomes of this study confirmed that DAS is a suitable biomacromolecule crosslinker for starch and can significantly enhance TPS and TPS/MMT properties. © 2019 Society of Chemical Industry

Starch is a biopolymer that is abundant in nature, low-cost, biodegradable, and can be transformed into a thermoplastic material. This work evaluates the films’ physicochemical, thermal, and mechanical properties based on low-density polyethylene (LDPE) and thermoplastic starch (TPS) from beans. Films of four formulations of LDPE with TPS (0, 5, 10, and 15%) were formulated by the extrusion process. The films were evaluated for thickness, color, mechanical properties (tensile strength, Young’s modulus, elongation at break), barrier, and morphological properties. The barrier properties (WVTR and WVP) significantly increased when TPS was incorporated into the films. While the tensile strength and Young’s modulus did not present changes with the addition of TPS, the elongation at break increased from 204.14 to 343.81% with the addition of TPS. Adding TPS to an LDPE matrix modifies its physico-mechanical properties favorably so that it can be applied as a material for flexible packaging.

A new biodegradable composite with open cell by combining modified starch and plant fibers

The aim of this research is to investigate the effects of different thermoplastic starches and starch contents on the physico-mechanical and morphological properties of new polymeric-based composites from low density polyethylene (LDPE) and thermoplastic starches. Different compositions of thermoplastic starches (5–40 wt%) and LDPE were melt blended by extrusion and injection molding. The resultant materials were characterized with respect to the following parameters, i.e., melt flow index (MFI), mechanical properties (tensile, flexural, stiffness and impact strength) and water absorption. Scanning electron microscopy (SEM) was also used in this study for evaluating blend miscibility. MFI values of all blends decreased as the starch content increased, while the sago starch formulation showed a higher MFI value than others. The incorporation of fillers into LDPE matrix resulted in an increased in tensile modulus, flexural strength, flexural modulus and slightly decreased tensile strength and impact strength. However, sago starch filled composites exhibited better mechanical properties as compared to other starches. The SEM results revealed that the miscibility of such blends is dependent on the type of starch used. The water absorption increased with immersion time and the thermoplastic sago starch samples showed the lowest percentage of water absorption compared with other thermoplastic starches.

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.

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

Poly[(butylene adipate)‐ co ‐terephthalate] (PBAT) is currently the most widely used and versatile petroleum‐based fully biodegradable polyester, drawing extensive attention from researchers. However, the high production cost of PBAT restricts its widespread application. Currently, incorporating fillers into PBAT materials is considered the most effective approach to reduce production costs, with thermoplastic starch recognized as the optimal filler for PBAT base materials. Nevertheless, the low mechanical strength of thermoplastic starch significantly compromises the performance of PBAT base materials. In this study, thermoplastic starch with higher mechanical strength was prepared by partially substituting commonly used glycerol with a higher molecular weight sorbitol as the plasticizer. The enhanced thermoplastic starch was then used as a filler for PBAT materials, leading to the fabrication of PBAT‐based blend films with high starch content. Mechanical property tests revealed a 52.2% and 65.3% increase of tensile strength in the transverse and longitudinal directions, respectively, when sorbitol partially replaced glycerol as the plasticizer for thermoplastic starch. Scanning electron microscopy results demonstrated improved dispersion of thermoplastic starch particles in PBAT when sorbitol and glycerol were used together. Meanwhile, the thermal performance and stability of PBAT were not significantly affected by the thermoplastic starch filling. © 2024 Society of Chemical Industry.

The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

Microparticles of corn starch and chitosan crosslinked with glutaraldehyde, produced by the solvent exchange technique, are studied as reinforcement fillers for thermoplastic corn starch plasticized with glycerol. The presence of 10% w/w chitosan in the microparticles is shown to be essential to guaranteeing effective crosslinking, as demonstrated by water solubility assays. Crosslinked chitosan forms an interpenetrating polymer network with starch chains, producing microparticles with a very low solubility. The thermal stability of the microparticles is in agreement with their polysaccharide composition. An XRD analysis showed that they have crystalline fraction of 32% with Va-type structure, and have no tendency to undergo retrogradation. The tensile strength, Young’s modulus, and toughness of thermoplastic starch increased by the incorporation of the crosslinked starch/chitosan microparticles by melt-mixing. Toughness increased 360% in relation to unfilled thermoplastic starch.

Starch-based biodegradable foams with a high starch content are developed using industrial starch as the base material and supercritical CO2 as blowing or foaming agents. The superior cushioning properties of these foams can lead to competitiveness in the market. Despite this, a weak melting strength property of starch is not sufficient to hold the foaming agents within it. Due to the rapid diffusion of foaming gas into the environment, it is difficult for starch to maintain pore structure in starch foams. Therefore, producing starch foam by using supercritical CO2 foaming gas faces severe challenges. To overcome this, we have synthesized thermoplastic starch (TPS) by dispersing starch into water or glycerin. Consecutively, the TPS surface was modified by compatibilizer silane A (SA) to improve the dispersion with poly(butylene adipate-co-terephthalate) (PBAT) to become (TPS with SA)/PBAT composite foam. Furthermore, the foam-forming process was optimized by varying the ratios of TPS and PBAT under different forming temperatures of 85 °C to 105 °C, and two different pressures, 17 Mpa and 23 Mpa were studied in detail. The obtained results indicate that the SA surface modification on TPS can influence the great compatibility with PBAT blended foams (foam density: 0.16 g/cm3); whereas unmodified TPS and PBAT (foam density: 0.349 g/cm3) exhibit high foam density, rigid foam structure, and poor tensile properties. In addition, we have found that the 80% TPS/20% PBAT foam can be achieved with good flexible properties. Because of this flexibility, lightweight and environment-friendly nature, we have the opportunity to resolve the strong demands from the packing market.

The blends of polylactic acid plasticized with acetyl tributyl citrate (P-PLA) and thermoplastic wheat starch (TPS) were prepared by a co-rotating twin screw extruder and the effect of maleic anhydride grafted PLA (PLA-g-MA) content as reactive compatibilizer on blends compatibility through morphological, rheological and tensile properties of the blends was investigated. Considerable improvement in properties of P-PLA/TPS (70/30 w/w) blend with incorporating the optimum PLA-g-MA content of 4 phr was achieved as this blend exhibited better morphological and rheological properties with an increase by 158 and 276% in tensile strength and elongation at break, respectively, compared to the uncompatibilized blend. Also the thermal stability and moisture sorption properties of the blends as effected by TPS content were studied. Decreasing in thermal stability and increasing in equilibrium moisture content of the blends were observed with progressively increasing of TPS content. For prediction the moisture sorption behaviour of blends with various TPS contents at different relative humidity, the moisture sorption isotherm data were modeled by GAB (Guggenheim–Anderson–de Boer) model.

Aluminum metal foam has become an advanced popular material because it has excellent mechanical and electrical properties and is lightweight. The present work developed the Aluminium metal foam specimen using wax powder as a blowing agent through the powder metallurgy method. The effect of process parameters such as powder size, stirring speed, sintering temperature, and foaming agent content on the mechanical behavior of the developed specimens has been studied experimentally. In the design of experiments, the Taguchi orthogonal L9 array has been implemented. The percentage of porosity was estimated using the Archimedes principle, and mechanical behaviors such as flexural, tensile, and compressive strength were determined. The ANOVA analysis of variance it’s been carried out to check the significant parameters affecting the mechanical behavior of developed specimens. It was observed that the powder size is the highly significant parameter, followed by stirring speed, the content of the foaming agent, and sintering temperature. The Maximum Porosity is 71.30%, Compression strength 12.01 MPa, Tensile strength is 6.16 MPa, and Flexural strength is 5.18 MPa. The microstructure study reveals that there is no adequate composition in the specimen. The novelty in this research work is using a novel foaming agent as a Wax powder to develop aluminium metal foam and attain good properties.

In this study, the effects of foaming agent loading on the physical, mechanical and morphological properties of composites were investigated. Composites based on high-density polyethylene, rice husk flour, foaming agent and coupling agent were melt compounded using twin-screw extruder. The samples were foamed via a batch process using a compression molding machine at180°C. The mass ratio of rice husk flour to high-density polyethylene was controlled at 40:60 for all blends. The concentration was set to vary between 0, 1, 2 and 3 per hundred resins (phr) for foaming agent. The amount of coupling agent was fixed at 2% for all formulations. Results indicated that the cell size and average cell density of samples increased with an increase of foaming agent content. Also, by increasing the chemical foaming agent content the density, tensile modulus and flexural strength of the rice husk flour filled high-density polyethylene composites were decreased. However, the water absorption and thickness swelling of the composites increased by addition of the foaming agent. Scanning electron microscopy confirmed that the chemical foaming agent had a significant effect on the density reduction of foamed composites. This project has shown that the strategy of foaming wood plastic composites can be a good solution to overcome the high density of these composites.

Active meat packaging from thermoplastic cassava starch containing sappan and cinnamon herbal extracts via LLDPE blown-film extrusion