Strategies and techniques for improving heat resistance and mechanical performances of poly(lactic acid) (PLA) biodegradable materials.

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13-19°C to 23-25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review.

The flame-retardant modification of rice straw fibers (RSFs) was carried out to solve the technical problem of poor fire-proof performance of RSFs. The physical and mechanical properties and thermal insulation properties of rice straw fiber cement-based composites (RSFCC) at high temperatures were characterized. The results show that the three flame retardants affected the chemical structure of RSFs. The thermal stability and flame retardancy of flame-retardant RSFs were significantly higher than that of non-flame-retardant RSFs. The crystallinity of several groups of modified RSFs increased in varying degrees compared to untreated fibers. The mass-loss rate of RSFCC increased with the increase of temperatures. The strength and thermal conductivity of RSFCC decreased with the rise of temperatures. The strength and thermal conductivity of the composite flame-retardant modified fiber RSFCC at high temperatures were significantly higher than those of the non-flame retardant modified fiber or the single flame retardant modified fiber RSFCC.

Effect of flame-retardant rice straw fibers on properties of fiber cement-based composites at high temperatures

Poly (butylene adipate) terephthalate (PBAT) and corn stalk (CS) are both biodegradable materials. The high cost of PBAT limits its range of applications. In this paper, a biodegradable composite was prepared by melt-blending PBAT with CS as a filler. PBAT and different amounts of CS were melted in an internal mixer. The compatibility of CS with PBAT or with a modified PBAT (MPBAT) and its dispersion in either of them were studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and other test methods. The properties of PBAT/CS or MPBAT/CS composites were investigated by evaluating the following: mechanical properties, contact angle, water absorption, oxygen permeability, and water vapor permeability. It was found that CS and MPBAT had good compatibility. The results from soil burial experiment results showed that the biodegradability of the two composites increased with CS. CS showed great potential in biomass composites. Compared with PBAT/CS composites, MPBAT/CS composites had higher tensile properties and better barrier ability. The introduction of biomass fillers in MPBAT would promote the application of biodegradable materials in the field of environmentally friendly packaging materials. 

The preparation and performance of poly(butylene adipate) terephthalate/corn stalk composites

PLA composites reinforced with rice residues or glass fiber—a review of mechanical properties, thermal properties, and biodegradation properties

Utilizing four kinds of straw fibers (sorghum, rice, corn, and soybean) as filling fibers, polylactic acid (PLA) and poly (adipic acid)/polybutylene terephthalate (PBAT) in a mixture (7:3) were used as matrix to prepare composite materials by a hot pressing molding process. The mechanical properties, and thermal stability of the four fiber-filled composites were evaluated. The composites had high interfacial quality and no obvious voids. The soybean straw/PLA/PBAT composite had the best interfacial quality. PLA/PBAT-based composite materials were examined. The experimental results show that the soybean straw/PLA/PBAT composite had the best tensile strength, bending strength, and impact strength (14.3 MPa, 19.5 MPa and 3.23 KJ·m-2, respectively), which was 25.3%, 14.6%, and 27.8% higher than that of the corn straw/PLA/PBAT composite. The thermal stability of the corn straw/PLA/PBAT composite was the best, with an initial decomposition temperature of 286 °C, and the residual amount was 7.3%.

https://bioresources.cnr.ncsu.edu/wp-content/uploads/2020/02/BioRes_15_2_2596_Feng_ZWH_Performance_Comparison_Four_Straw_PLA_PBAT_WPCs_16737-2.pdf

Performance Comparison of Four Kinds of Straw/PLA/PBAT Wood Plastic Composites

The focus of this work was to analyze the influence of leaf treatments on mechanical, physical and chemical properties and thermal stability of the gelatin/lotus leaf composites. Lotus leaves were treated with drinking water at 95 °C for 5 min. The gelatin/untreated lotus leaf (referred to as GUL) and the gelatin/hot water treated lotus leaf (referred to as GHL) composites have been prepared by the compression molding technique. The composites have been investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TAG), Scanning electron microscopy (SEM). Effect of the lotus leaf hand lay-up fiber orientation was studied for longitudinal, transverse and random orientation of the fibers. The tensile strength of gelatin/lotus leaf composites were influenced by the orientation of the fibers. It was found that longitudinal orientation delivered higher mechanical properties than that of the transverse and random orientation whether untreated or treated. The hot water modification of the lotus leaf was employed to improve the interfacial adhesion of the composites in order to improve the tensile properties. By using TGA analysis data and Ozawa-Flynn-Wall (OFW) method, the thermal stability and degradation temperature of the lotus leaves treated with hot water were higher than those of untreated leaves. In addition, the properties of the novel bio-composites were potential in further development of biodegradable packaging materials.

Impact of Hot Water Treated Lotus Leaves on Interfacial and Physico-Mechanical of Gelatin/Lotus Leaf Composites

Polylactic acid has good biodegradability and it is dosage is increasing. Therefore, the degradation of PLA has become a new problem that needs serious management. In this study, the spores of Aspergillus niger were inoculated onto wheat straw/PLA composites containing different contents of sodium alginate, and the mass loss and characterization (microstructure, fourier transform infrared spectroscopy, thermal properties, and X-ray diffraction) of the composites were detected. The objective was to explore the possibility of degradation of PLA composites by A. niger and the effect of sodium alginate on the degradability of PLA composites. The results showed that when the amount of sodium alginate was 3% and 6%, the mass loss rate of the composites only increased at the initial stage of degradation. However, when the amount of sodium alginate was 9%, the mass loss rate of the composites was significantly increased. It was found that A. niger could colonize the surface of the composites and cause cracks and depressions on the surface by morphological observation. The infrared spectral curve showed that the number of hydroxyl and carbonyl groups in the composites increased after degradation. According to the thermogravimetric curve of the composites, the pyrolysis temperature of the composites with sodium alginate content of 9% increased and the residual mass decreased after degradation. When the amount of sodium alginate was 9%, the crystallinity of the composites was greatly reduced, and it is crystallization zone was easier to degrade compared with other treatments. The results would provide a theoretical support for the rapid degradation of PLA composites. 

Degradation of wheat straw/polylactic acid composites by
 Aspergillus niger

The main objective of this work was to estimate the usefulness of response surface methodology (RSM) and genetic algorithm (GA) in modeling and predicting the strength of jute/poly(lactic acid) (PLA) composite laminates. Firstly, the impact of the hot water treatment on the thermal, molecular structure, and morphological characterizations as well as kinetic analysis of jute fibers were performed by Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM). The FTIR results showed that the hot water treatments reduced the content of lignin, hemicellulose, and impurities of the fibers. Hot water treated fibers exhibited higher thermal stabilities compared with untreated fibers as shown with TGA results. The SEM results showed effect contact surface area improved after the hot water treatment, leading to better mechanical properties of bio-composites. Secondly, the influences of the ply orientation, plies and fiber content on the tensile strength and flexural strength of the hot water treated fibers composites were evaluated by RSM. RSM with the Box Behnken Design was utilized to establish the quadratic models of two objectives in response to input parameters. Analysis of variance (ANOVA) was used to determine percentage contribution of various parameters on two quality objectives. According to the ANOVA results, ply orientation had the most important impact on tensile strength while the ply orientation-fiber content interaction had the most important impact on flexural strength. Finally, multi-objective optimization was carried out to maximize tensile strength and flexural strength using the desirability function and GA. The optimized results both showed an acceptable relative error between experimental and optimized values. 

Investigation and prediction of mechanical properties of hot water treated jute/poly(lactic acid) composite laminates using response surface methodology and genetic algorithm

With the exponential growth of the computing power, machine learning techniques have been successfully used in various applications. This paper intended to predict and optimize the shear strength of single lap cassava starchbased adhesive joints for comparison with the application of artificial intelligence (AI) methods. The shear strength was firstly determined by the experiment with three independent experimental variables (starch content, NaOH concentration and reaction temperature). The analysis of range (ANORA) and analysis of variance (ANOVA) were applied to investigate the optimal combination and the significance of each factor for the shear strength based on the orthogonal experiment. The performance of all AI models was characterized by mean absolute error (MAE), root mean square error (RMSE) and regression coefficient (R2 ) compared with the experimental ones. The GA-optimized ANN model was combined with the genetic algorithm (GA) to find the optimal combination of factors for the finalized optimized cassava starch adhesives (CSA-OP). The physicochemical properties of the cassava starch and CSA-OP were determined by the FTIR, TGA and SEM-EDS, respectively. The results showed that the numerical optimized condition of the GA-optimized ANN model was superior to the orthogonal experimental optimized condition. The sensitivity analysis revealed that the relative importance of variables was consistent with the results from ANOVA. FTIR results showed that there were high hydroxyl groups in cassava starch. TGA results showed that the residue of CSA-OP was higher than the cassava starch. SEM-EDS results showed that both the cassava starch and CSA-OP had abundant carbon and oxygen functional groups. Consequently, the obtained results revealed that the use of AI methods was an adequate approach to model and optimize the experimental variables of the shear strength of single lap cassava starch-based adhesive joints. 

Weixing Zhang

Papers

Performance Comparison of Four Kinds of Straw/PLA/PBAT Wood Plastic Composites

Impact of Hot Water Treated Lotus Leaves on Interfacial and Physico-Mechanical of Gelatin/Lotus Leaf Composites

Degradation of wheat straw/polylactic acid composites by Aspergillus niger

Investigation and prediction of mechanical properties of hot water treated jute/poly(lactic acid) composite laminates using response surface methodology and genetic algorithm

Modeling and Optimization of the Shear Strength of Cassava Starch-Based Adhesives Using Artificial Intelligence Methods