Characterization of Epoxy Composites Reinforced with Wax Encapsulated Microcrystalline Cellulose

Influence of Biochar and Bio-Oil Loading on the Properties of Epoxy Resin Composites

In this study, we evaluated the use of bio-oil and biochar on epoxy resin. Bio-oil and biochar were obtained from the pyrolysis of wheat straw and hazelnut hull biomass. A range of bio-oil and biochar proportions on the epoxy resin properties and the effect of their substitution were investigated. TGA curves showed improved thermal stability for degradation temperature at the 5% (T5%), 10% (T10%), and 50% (T50%) weight losses on bioepoxy blends with the incorporation of bio-oil and biochar with respect to neat resin. However, decreases in the maximum mass loss rate temperature (T_max) and the onset of thermal degradation (T_onset) were obtained. Raman characterization showed that the degree of reticulation with the addition of bio-oil and biochar does not significantly affect chemical curing. The mechanical properties were improved when bio-oil and biochar were incorporated into the epoxy resin. All bio-based epoxy blends showed a large increase in Young's modulus and tensile strength with respect to neat resin. Young's modulus was approximately 1955.90 to 3982.05 MPa, and the tensile strength was between 8.73 and 13.58 MPa for bio-based blends of wheat straw. Instead, in bio-based blends of hazelnut hulls, Young´s modulus was 3060.02 to 3957.84 MPa, and tensile strength was 4.11 to 18.11 Mpa.

Soybean-based polymers and composites

Development and evaluation of new bio-based sustainable plastics to replace the petroleum-based materials in different industrial applications has both environmental and economic benefits. Bio-based polymers can be widely used in biomedical and agriculture applications due to their excellent biodegradability and biocompatibility. Soy protein is a natural material that can be isolated from soybean, which is a major agricultural crop in the U.S. The viability of soybean-based polymers and composites is questioned due to their high-water absorption and poor mechanical properties. There have been many environmentally friendly attempts to improve the properties of soybean polymers as soybeans and their extracts are widely available worldwide. Soy protein, hulls, and oils all find use in the development of different biodegradable polymers. While the development looks promising, there is still more work to do to make the soybean polymers useful and economically viable. Blending soy protein with other biodegradable polymers, such as polylactide (PLA) and polyurethane dispersion is a valid approach to improve the mechanical properties of soy protein and reduce its water sensitivity.

Production of fatty acid methyl esters and bioactive compounds from citrus wax

Citrus wax is a waste generated during the purification process of the citrus essential oil. A lot of citrus wax wastes are globally produced, despite this, its composition and properties are not well known. Here we present comprehensive results proving the chemical composition and the physical properties of citrus wax. Additionally, our study provides the basis for obtaining value-added products from citrus wax wastes. The qualitative/quantitative analysis revealed the presence of different compounds, which range from flavonoids, saponins, carbohydrates, unsaturated compounds, phenolic hydroxyls, and long-chain fatty acid esters. Given that citrus wax is a source of many bioactive compounds, they were preferably extracted with ethanol. The ethanolic extracts demonstrated the presence in citrus wax of different bioactives, such as 5-5'-dehydrodiferulic acid, 3,7-dimethylquercetin, 5,6-dihydroxy-7,8,3',4'-tetramethoxyflavone, tangeretin, and limonene. After the extraction of bioactives from citrus wax, a washed waxy material with high content of long-chain fatty acid esters was obtained. It was shown that this washed wax can be used for the production of biodiesel. The transesterification reactions in acid media was the preferred process because higher content of fatty acid methyl esters (such as hexadecanoic acid methyl ester and 9,12-octadecadienoic acid (Z,Z)-, methyl ester) were obtained. Currently, citrus wax does not have any industrial application, here we shown that under the concept of waste biorefinery, the citrus wax wastes are useful sources for producing value-added products such as bioactive compounds and biodiesel.

Composites of Unsaturated Polyester Resins with Microcrystalline Cellulose and Its Derivatives

The paper investigates the properties of unsaturated polyester resins and microcrystalline cellulose (MCC) composites. The influence of MCC modification on mechanical, thermomechanical, and thermal properties of obtained materials was discussed. In order to reduce the hydrophilic character of the MCC surface, it was subjected to esterification with the methacrylic anhydride. This resulted in hydroxyl groups blocking and, additionally, the introduction of unsaturated bonds into its structure, which could participate in copolymerization with the curing resin. Composites of varying amounts of cellulose as a filler were obtained from modified MCC and unmodified (comparative) MCC. The modification of MCC resulted in obtaining composites characterized by greater flexural strength and strain at break compared with the analogous composites based on the unmodified MCC.

Preparation and Evaluation of Green Composites from Microcrystalline Cellulose and a Soybean-Oil Derivative

The present work aimed at developing fully green composites from renewable materials, i.e., acrylated epoxidized soybean oil (AESO) and microcrystalline cellulose (MCC) by a solution casting method. The reinforcing effect of MCC on AESO resins was optimized by adjusting MCC loading from 20 to 40 wt % in terms of physical, mechanical, and thermal properties as well as water absorption of the resulting MCC/AESO composites. The interaction between MCC and AESO was characterized by Fourier transform infrared (FTIR) analysis, which revealed possible hydrogen bonds between the ⁻OH groups of MCC along with the polar components of AESO including C=O, ⁻OH, and epoxy groups. This was further evidenced by a benign interfacial adhesion between MCC and AESO resins as revealed by scanning electron microscope (SEM) analysis. The incorporation of MCC into AESO resins significantly increased the density, hardness, flexural strength, and flexural modulus of the MCC/AESO composites, indicative of a significant reinforcing effect of MCC on AESO resins. The composite with 30 wt % MCC obtained the highest physical and mechanical properties due to the good dispersion and interfacial interaction between MCC and AESO matrix; the density, hardness, flexural strength, and flexural modulus of the composite were 15.7%, 25.0%, 57.2%, and 129.7% higher than those of pure AESO resin, respectively. However, the water resistance at room temperature and 100 °C of the composites were dramatically decreased due to the inherent hydrophilicity of MCC.

Preparation and Characterization of Epoxy Resin Cross-Linked with High Wood Pyrolysis Bio-Oil Substitution by Acetone Pretreatment

The use of cost effective solvents may be necessary to store wood pyrolysis bio-oil in order to stabilize and control its viscosity, but this part of the production system has not been explored. Conversely, any rise in viscosity during storage, that would occur without a solvent, will add variance to the production system and render it cost ineffective. The purpose of this study was to modify bio-oil with a common solvent and then react the bio-oil with an epoxy for bonding of wood without any loss in properties. The acetone pretreatment of the bio-oil/epoxy mixture was found to improve the cross-linking potential and substitution rate based on its mechanical, chemical, and thermal properties. Specifically, the bio-oil was blended with epoxy resin at weight ratios ranging from 2:1 to 1:5 and were then cured. A higher bio-oil substitution rate was found to lower the shear bond strength of the bio-oil/epoxy resins. However, when an acetone pretreatment was used, it was possible to replace the bio-oil by as much as 50% while satisfying usage requirements. Extraction of the bio-oil/epoxy mixture with four different solvents demonstrated an improvement in cross-linking after acetone pretreatment. ATR-FTIR analysis confirmed that the polymer achieved a higher cross-linked structure. DSC and TGA curves showed improved thermal stability with the addition of the acetone pretreatment. UV-Vis characterization showed that some functional groups of the bio-oil to epoxy system were unreacted. Finally, when the resin mixture was utilized to bond wood, the acetone pretreatment coupled with precise tuning of the bio-oil:epoxy ratio was an effective method to control cross-linking while ensuring acceptable bond strength.