In this work, three composites with different contents (5, 10, and 15% w/w) of kraft pulp fibre were produced as reinforcing elements for natural latex matrix and the mechanical properties were ...evaluated. In order to improve the interfacial adhesion between the matrix and the reinforcing element, chemical modifications were carried out on the surface of the fibres using octanoyl and benzoyl chlorides as modifying agents. The extension of chemical modification of the fibres was visualized by the presence of absorption bands in the spectroscopy analyzes of the modified fibre in relation to the crude fibre (ester carbonyl 1700–1740 cm
−1
); in addition, the hydroxyl band was preserved, which indicates a modification of surface character. The modified fibres became more hydrophobic due to the decrease in surface energy and the change in the dispersive and polar components. An increase in the storage modulus was observed for the composites with surface-modified fibres, which agrees with the improved dispersion between the surface-modified fibres and the matrix verified by means of scanning electron microscopy images. The incorporation of fibres did not cause changes in the thermal properties of the composites.
•Additives used directly impact mechanical and thermal properties of films.•All formulation of blend films had a high antioxidant activity by DPPH method.•Potential uses as packaging for food ...products.•Compatible and miscible blends.•The best formulations was (36:24:22:18) due to mechanical, antioxidant properties.
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The aim of this study was to investigate the antioxidant, mechanical and physical properties of a new film-based polymeric blend of hydrocolloids obtained from the aqueous extraction of chia seeds (source antioxidants) and apple pectin. The individual matrices films were brittle and rigid with poor mechanical properties. The blends formulations contributed to improved mechanical properties regarding workability and resistance. The antioxidant results showed the potential hydrocolloid from chia seeds as natural source of antioxidant in these polymeric films. The formulation 3 (14(hydrocolloid):41(pectin):25(glycerol):20(glutaraldehyde) displayed well thermal, mechanical, morphological and antioxidant properties, suggesting their great potential for food packaging.
Flaxseed gum (FG)-based films were developed with the addition of glycerol as a plasticizer and glutaraldehyde as a crosslinking agent. HCl was added to improve crosslinking and decrease the ...hydrophilicity of the matrix. Different cellulose nanocrystal (CN) amounts were used as reinforcements in the optimum FG formulation. The crosslinking process at pH 3.5 led to a lower solubility of FG in water (from 100% to 53%) and an increase in thermal stability (from 160 ºC to 209 ºC). FTIR analysis confirmed a reduction in the -OH band due to crosslinking between the hydroxyl groups of FG. A diffuse diffraction pattern was observed for all FG films. The addition of 4% w/w of CN contributed to reduction of water solubility (from 53% to 20.8%) and absorption (from 21.9% to 6.8%). Finally, an improvement was observed in the tensile mechanical properties in the nanocomposites, showing satisfactory results for the proposed formulations, mainly with 8% w/w of CN added to the matrix. Overall, this study demonstrated that FG/CN nanocomposites are promising materials to be use as a sustainable biopolymer for application as bioplastics.
In this work, nine different types of edible coating based on pectin, cellulose nanocrystals, glycerol, and essential oil of lemongrass were prepared and used to coat strawberries with a film formed ...directly on the surface of the coated fruit. The effects of the different edible coatings
on refrigerated fruits in terms of weight loss, titratable acidity, total soluble solids, pH, and anthocyanin content was evaluated after 2 days, 4 days, 6 days, and 8 days of storage. Application of the edible coatings reduced the weight loss of the coated strawberries and the anthocyanin
content. The total soluble solids content of or uncoated fruit increase more markedly than that of coated fruit. In contrast, pH was maintained for both coated and uncoated strawberries. The edible coatings were effective in minimizing of the weight loss, without worsening the physical chemistry
attributes. The treatments T5 and T9 presented the best results.
•High aspect ratio CNC was extracted from soy hulls.•Mild acid hydrolysis conditions are preferable to improve yield and preserve crystallinity.•CNC reinforced NR nanocomposites were prepared.•High ...mechanical performance nanocomposites were obtained.•Sedimentation of CNC plays a major role in the mechanical properties.
Cellulose nanocrystals (CNCs) were isolated from soy hulls by acid sulfuric hydrolysis. The resulting CNCs were characterized using TEM, AFM, WAXS, elemental analysis and TGA. The CNCs have a high crystallinity, specific surface area and aspect ratio. The aspect ratio (around 100) is the largest ever reported in the literature for a plant cellulose source. These CNCs were used as a reinforcing phase to prepare nanocomposite films by casting/evaporation using natural rubber as matrix. The mechanical properties were studied in both the linear and non-linear ranges. The reinforcing effect was higher than the one observed for CNCs extracted from other sources. It may be assigned not only to the high aspect ratio of these CNCs but also to the stiffness of the percolating nanoparticle network formed within the polymer matrix. Moreover, the sedimentation of CNCs during the evaporation step was found to play a crucial role on the mechanical properties.
•Oxypropylation of soybean hulls was successful.•Two products were obtained in a single reaction step.•Viscous polyol formed has adequate characteristics to prepare polyurethanes.•Superficial ...modified soybean hull may be employed in self-reinforced composite preparation.
The present study is aimed at oxypropylating soybean hulls (SH) to obtain two products in a single reaction: a viscous polyol (SHP) and a solid fibrous residue of soybean hulls modified on the surface (SHBM) by a layer of thermoplastic polymer poly (propylene oxide). The oxypropylation reaction was conducted by polymerizing propylene oxide in the presence of the SH in a reaction catalysed by KOH at 150°C. The chemical composition of the SH was determined. The samples before (SH) and after oxypropylation (SHP and SHBM) were characterized by Fourier Transform Infrared Spectroscopy and thermogravimetric analysis. The SH and SHBM were also characterized by scanning electron microscopy and X-ray diffraction. The SHP was characterized with respect to its hydroxyl index value (IOH), intrinsic viscosity η and with respect to the amount of poly (propylene oxide) homopolymer (PPO) formed. These characterizations were carried out in order to assess the effectiveness of the process and verify the applicability of both products: (i) for producing polymer derivatives such as polyurethane foams in the case of polyol; and (ii) to prepare biphasic monocomponent composites in the case of the superficially oxypropylated residue.
The objective of this work was to evaluate the susceptibility of
larvae from different oviposition times to fipronil. The LPT was performed in sextuplicate, at concentrations of 18.75, 37.5, 75, 150 ...and 300 µg.mL
. The LC
found for the egg masses incubated with +7, +14 and +21 days were respectively 105.87, 110.71 and 121.22 µg.mL
. The larvae originating from egg masses from the same group of engorged females, incubated on different days, presented similar mortality rates compared to the evaluated fipronil concentrations, facilitating the maintenance of laboratory colonies of this tick species.
This work was conducted with the objective of improving the physicochemical properties of flaxseed gum with added agar. Three formulations of flaxseed gum/agar (FG/AG) blends (75/25, 50/50 and 25/75) ...were studied in the presence of glutaraldehyde as crosslinking agent and a glycerol plasticizing agent. Cellulose nanocrystals (CNCs) were used as reinforcing agents at different levels (2%, 4% and 8% w/w) to prepare nanocomposite films by casting polymeric blends of flax seed and agar with both additives. The interaction with water (vapor permeability and solubility), scanning electron microscopy and tensile tests were performed for films, blends and nanocomposites. The flaxseed gum, agar and additives showed good homogeneity, as demonstrated by scanning electron microscopy. All the formulations presented tenacity increase between 585 and 811%, and lower values of solubility relative to the control film (FG
control
). The best formulation of nanocomposites was 50/50–4% CNCs, that presented higher modulus of elasticity and increase in tenacity of 130% relative to the 50/50 blend and 1588% relative to the control film. The results showed that AG and CNC can modulate the properties of FG, opening numerous opportunities for investigation. Due to the significant improvement in the mechanical properties, FG/AG blends and nanocomposites have excellent potential in applications as sustainable packaging.
The present work evaluates the partial oxypropylation of dried bacterial cellulose (BC) performed by grafting propylene oxide with potassium hydroxide as the catalyst. Samples were characterized by ...scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Partial transformation of BC was observed, with cellulose fibers being covered by the thermoplastic phase, leading to a new biphasic mono-component composite material. This synthesis can be considered a green chemical process, since it does not require the use of solvents nor the application of any processing operation, given the fact that the final product is ready for further exploitation as it is removed from the reactor. The obtained material can be used in various applications in the polymer field, i.e. composites, reinforced rigid polyurethane foams, and others.
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