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.
In this study, we prepared cellulose acetate membranes, by means of casting mold, incorporated with two additives, sodium carboxymethyl lignin and calcium glycerophosphate, in order to improve ...properties for periodontal applications. The membranes were characterized from the morphological, structural, thermal and mechanical point of view, as well as by physiological pH tests. The results showed that membranes with additives improve the physical-chemical and mechanical properties, especially when the two additives are present in the same membrane, which can be attributed to the important synergy between them. The most significant effects occur in increasing the thickness and decreasing the density, which reflects in the porosity of the membranes, although the added amounts do not exceed 1.4%. A 1% increase in lignin concentration does not change the thickness and density of the membrane, but that amount of lignin plus 0.4% calcium glycerophosphate increases the thickness of the membrane by 42% and decreases the density by about 6%. Although there is a decrease in mechanical properties, as observed in Young's modulus and crystallinity, the significant and intermittent increase in sample weight loss with both additives in physiological solution indicates that, in the long run, it can be used as a degradable barrier.
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.
Poly(butylene terephthalate) (PBT)/ acrylonitrile-butadiene-sty rene (ABS) terpolymer blends were prepared in a twin screw extruder and the use of methyl methacrylate-glycidyl methacrylate-ethyl ...acrylate (MGE) terpolymer as compatibilization additive was evaluated. The effect of different screw profiles and mixing conditions were evaluated on the crystallization of the blends. Differential scanning calorimetry (DSC) was used to evaluate melting and crystallization behaviors of the PBT/ABS blends. The binary PBT/ABS blend has shown a double melting peak when cooled at lower cooling rates, mainly due to its melt-recrystallization during the heating up step. ABS has not affected the melting characteristics of neat PBT. The presence of MGE, as a reactive compatibilizer, in the PBT/ABS blends has reduced its heat of fusion and has partially inhibited its melt-recrystallization under heating. As result, it has prevented the occurrence of double melting peak. The epoxy functional groups of the MGE may react in situ to the carbonyls and hydroxyls end groups of the PBT molecules, thereby hindering the mobility of PBT molecules during the crystallization process due to its grafting to the compatibilizer molecules. The melt mixed blends prepared at lower feeding rate have shown a higher degree of crystallinity for the PBT/ABS blend, probably due to degradation of PBT caused by longer residence time in the extruder. The highest shear stress imposed to the blends at higher screw speed increased the degree of crystallinity of PBT, also due to its degradation.
•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.
Cellulose nanocrystals (CNCs) were produced from eucalyptus wood pulp using three different methods: (i) classical sulphuric acid hydrolysis (CN-I), (ii) acid hydrolysis of cellulose previously ...mercerized by alkaline treatment (MCN-II), and (iii) solubilization of cellulose in sulphuric acid and subsequent recrystallization in water (RCN-II). The three types of CNCs exhibited different morphologies and crystalline structures that were characterized using complementary imaging, diffraction and spectroscopic techniques. CN-I corresponded to the type I allomorph of cellulose while MCN-II and RCN-II corresponded to cellulose II. CN-I and MCN-II CNCs were acicular particles composed of a few laterally-bound elementary crystallites. In both cases, the cellulose chains were oriented parallel to the long axis of the particle, although they were parallel in CN-I and antiparallel in MCN-II. RCN-II particles exhibited a slightly tortuous ribbon-like shape and it was shown that the chains lay perpendicular to the particle long axis and parallel to their basal plane. The unique molecular and crystal structure of the RCN-II particles implies that a higher number of reducing chain ends are located at the surface of the particles, which may be important for subsequent chemical modification. While other authors have described nanoparticles prepared by regeneration of short-chain cellulose solutions, no detailed description was proposed in terms of particle morphology, crystal structure and chain orientation. We provide such a description in the present paper.
In this work, the luminescent β-diketonate europium complex, Eu(TTA)3, was incorporated into the polymer cellulose acetate butyrate in different concentrations in the form of composite films. The ...photoluminescence analysis showed that the composites improved the internal transition of the europium ion, 5D0 → 7F2, mainly responsible for the emission of red light from the complex, by providing a highly asymmetric chemical environment around the europium ion and by reducing non-radiative decays. The composite matrix also contributed to the quantum efficiency of the luminescence, reaching 38 %, by reducing the excited state deactivation rates. The luminescence lifetime of the composite linearly decayed with increasing temperature, while the luminescence intensity displayed an exponential decrease by increasing temperature, both behaviors proved to be appropriate for use in optical thermometry. The analysis of Raman spectra, Judd-Ofelt parameters, decay rates, and lifetime showed that the characteristics of the isolated complex were mostly maintained after being added to the polymeric matrix.
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•Composites were obtained by incorporating the europium complex into cellulose butyrate acetate.•The characteristics of the isolated complex were mostly maintained in the composite.•The emission intensity of Eu3+ ions was discussed in function of the temperature.•The composite reached an absolute sensitivity of 0.036 K-1 in temperature sensing.
•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.
Abrasive wear of HDPE/UHMWPE blends Lucas, Alessandra de A.; Ambrósio, José D.; Otaguro, Harumi ...
Wear,
04/2011, Letnik:
270, Številka:
9
Journal Article
Recenzirano
► Increase of UHMWPE (10–30%) content improves HDPE abrasion resistance (DIN53516) ► Presence of UHMWPE improves HDPE mechanical properties under impact and tensile ► Volumetric loss and a function ...of fitted by Ratner and Lancaster equation ► Two-phase separation: HDPE (matrix) and UHMWPE (10–30%, dispersed phase).
Blends of high density polyethylene (HDPE) with ultra-high molecular weight polyethylene (UHMWPE) were obtained by mixing in a melted state at concentrations ranging from 10 to 30% by weight in an intermeshing co-rotating twin screw extruder (ICTSE). The abrasive resistance of the blends was evaluated according to the DIN53516 standard, and it was observed that the volumetric loss of the blends decreased with increasing concentration of UHMWPE. The mechanical properties of the samples were analyzed in terms of flexural, tensile, and impact strength; in general, the HDPE/UHMWPE blends had a good set of properties, most of which were better than the properties of pure HDPE. Thermal analysis of samples was made by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and no significant difference was observed between the blends and pure HDPE. The morphological analysis conducted by scanning electron microscopy (SEM) showed that the UHMWPE is present in the HDPE matrix as a second phase, but there is a good interface between the two. We found an inverse relationship between the volumetric loss in the abrasive wear of the samples and the product between the tensile strength at yielding and strain at yielding,
σ
y
ɛ
y
, as proposed by Lancaster and Ratner (Sinha and Briscoe, 2009
1).
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