DSpace Repository :: Browsing by Subject "BIOPOLIMEROS"

Browsing by Subject "BIOPOLIMEROS"

Now showing 1 - 8 of 8

Arapey sweet potato peel waste as renewable source of antioxidant: extraction, nanoencapsulation and nanoadditive potential in films
(2021-01) Guerrero-León, Beatriz; Corbino, Graciela; Dufresne, Alain; Errea, María Inés; D'Accorso, Norma Beatriz; García, Nancy L.
"In this work, the peel of Arapey Sweet Potato (Ipomoea batatas), a vegetable waste, was used as a source of phenolic compounds which are widely recognized as beneficial antioxidants for human health. The extract obtained from Ipomoea batatas exhibited an antioxidant activity significantly higher than many antioxidant agents reported in literature (476.96 mg of TROLOX mL-1), as well as good thermal stability. Nanocapsules of the extract coated with low molecular weight polylactic acid were prepared by the emulsification-solvent evaporation method and the nanoparticles obtained were characterized physical; thermal; and morphologically. An analysis of the variables that were investigated to increase the encapsulation efficiency is presented here. Besides, PLA films prepared via the solution-casting method exhibited good compatibility with the nanoparticles loaded with the antioxidant extract, as was evidenced by the uniform and stable dispersion of these particles in the films. Furthermore, an improvement of the mechanical properties of the PLA films due to the presence of the nanoparticles were clearly observed. Results reported here are encourage enough to propose the nanocapsules described in this work as additives or to be used immersed in films for controlled release of antioxidants, putting in value a vegetable waste."
Chitosan: from organic pollutants to high-value polymeric materials
(2017) Errea, María Inés; Rossi, Ezequiel; Goyanes, Silvia Nair; D'Accorso, Norma Beatriz
"...chitosan has proved to be versatile for so many industrial applications and its versatility is the main value of this polymer. However, the lability at acidic pH of chitosan is a limiting factor that affects mainly its industrial implementation for the removal of metallic anions from water. In addition, the physical and mechanical properties may vary between two manufacturing batches due to the characteristic polydispersity of chitosan with respect to molecular weight and degree of acetylation. This variation could affect the industrial process and in some cases, when strict specifications are requested (e.g., drug delivery), increase the final cost of the product because a purification step prior to use is required. Briefly, despite of the disadvantages mentioned before, due to its great versatility, its nontoxicity, its biodegradability, and the fact that it has a renewable resource, the industrial interest in chitosan and its application has been increasing remarkably in the last years."
Compressive behavior of rigid polyurethane foams nanostructured with bacterial nanocellulose at low and intermediate strain rates
(2019-05) Chiacchiarelli, Leonel Matías; Cerrutti, Patricia; Flores-Johnson, Emmanuel A.
"Nanocellulose reinforced foams are lightweight with improved mechanical properties; however, the strain-rate effect on their mechanical response is not yet fully understood. In this work, rigid polyurethane foams (PUFs) nanostructured with bacterial nanocellulose at 0.2 wt % (BNCF) and without it (PUF) are synthesized and subjected to compression tests at different strain rates. The BNC acts as a nucleation agent, reducing the cell size but maintaining a similar apparent density of 40.4 3.3 kg m −3 Both BNCF and PUF exhibit strain-rate effect on yield stress and densification strain. The BNCF exhibits localized progressive crushing and reduced friability, causing a remarkable recovery in the transverse direction. Numerical simulations show that functionally graded foams subjected to impact could be designed using different layers of PUF and BNCF to vary energy absorption and acceleration rate. The results presented herein warrant further research of the mechanical properties of nanostructured foams for impact applications."
Highly functional lactic acid ring-opened soybean polyols applied to rigid polyurethane foams
(2019-10) Herrán, Rodrigo; Amalvy, Javier Ignacio; Chiacchiarelli, Leonel Matías
"We synthesized polyols with high hydroxyl functionalities (FOHs), between 9.0 and 12.6, and characterized them with differential scanning calorimetry, thermogravimetric analysis, and size exclusion chromatography after we parametrically studied the ring-opening reaction of epoxidized soybean oil with lactic acid (LA) as a function of the reaction temperature and lactic acid equivalent frac-tion (fLA). An increase of only 20C in the reaction temperature (from 80 to 100C) caused changes in the hydroxyl number (+17.8%), FOH (–25%), viscosity (–14.0%), and oligomeric content (–24.1%). fLA mostly affected the ring-opening yield, and only for fLA values above 0.4 was possible to achieve values higher than 80%. Rigid polyurethane foams (rPUFs) were synthesized and characterized with scanning electron microscopy, dynamic mechanical analysis (DMA), and compressive mechanical tests. rPUFs with a very high specific compres-sive strength (7.8 kPa kg–1 m3) were synthesized solely with biobased soybean oil. DMA revealed a compromised relationship between the specific compressive strength and its temperature dependence. To increase the first one, the most relevant method was to increase FOH. Instead, to increase the latter one, the OH number had to be maximized."
In-situ thermal aging of biobased and conventional rigid polyurethane foams nanostructured with bacterial nanocellulose
(2021-11-02) Diaz, Tomás Joaquin; Cerrutti, Patricia; Chiacchiarelli, Leonel Matías
"The incorporation of nanofillers and the use of biobased polyols might have a deleterious effect on the aging performance of rigid polyurethane foams (RPUFs) applied in the insulation and marine industries. To study this, RPUFs obtained from petroleum based (RPUF) and castor oil (RPUFRIC) polyols were nanostructured with bacterial nanocellulose (BNC) up to 0.3 wt%. Water immersion experiments revealed that the normalized water absorption (NWA) at the steady state was not affected by lower BNC contents (<0.2 wt%). Higher BNC contents caused a complex effect on post-cure and foaming, generating cell size expansion as well as shrinkage. In-situ DMA aging analysis revealed that the specific storage modulus (E'sp) under flexural conditions of the RPUFRIC and RPUF decreased by a maximum amount of 7.27% and 6.19%, respectively. The effect of BNC on the E'sp was negligible, expect for the case of the RPUF, where higher BNC concentrations (>0.2 wt%) caused a decrease of up to 13.69%. The previous results reinforce the hypothesis that the incorporation of BNC in both conventional and biobased polyurethane systems do not cause significant changes on the aging performance of the resulting foams, provided that low BNC concentrations are employed."
Kinetic and chemorheological modeling of thermosetting polyurethanes obtained from an epoxidized soybean oil polyol crosslinked with glycerin
(2022-10) Armanasco, Franco; Chiacchiarelli, Leonel Matías; D'hers, Sebastián
"Thermosetting polyurethanes were obtained using an aromatic isocyanate and a hydrophobic polyol formulation obtained from epoxidized soybean oil (ESO) crosslinked with glycerin. A systematic DSC analysis of the effect of catalyst type, crosslinker concentration, isocyanate index and ESO crystallization on cure kinetics was conducted. The combination of a stannic catalyst at 0.2 wt% and glycerin at 20 wt% produced a cure kinetics governed by an autocatalytic heat flow where vitrification played a key role in the formation of chemical bonds. The evolution of Tg as a function of conversion, which followed Di-Benedetto's predictions, supported the hypothesis that vitrification was a preponderant phenomenon during cure. Dynamic Mechanical Analysis (DMA) of a post-cured sample revealed a Tg centered at 220°C, whereas quasi-static flexural mechanical tests shown a flexural modulus of 2.14 GPa and a flexural strength of 99.4 MPa. Rheological experiments at isothermal conditions supported the hypothesis that vitrification played a key role in the evolution of apparent viscosity. A master model using Kim-Macosko equations was obtained for the proposed formulation. The results presented in this work will serve to further extend the use of biobased polymers applied in the polymer composite industry."
Nanostructured rigid polyurethane foams with improved specific thermo-mechanical properties using bacterial nanocellulose as a hard Segment
(2021-01) Chiacchiarelli, Leonel Matías; Benavides, Sara; Armanasco, Franco; Cerrutti, Patricia
"Bacterial nanocellulose (BNC) was used to synthesize rigid polyurethane foams (RPUFs) based on its reaction with the isocyanate precursor (ISO route) and also by using the conventional procedure (POL route). The results indicated that at only 0.1 wt. % of BNC, drastic improvements of specific elastic compressive modulus (+244.2 %) and strength (+77.5 %) were found. The reaction of BNC with the precursor was corroborated through the measurement of isocyanate number and the BNC caused a significant nucleation effect, decreasing the cell size up to 39.7%. DSC analysis revealed that the BNC had a strong effect on post-cure enthalpy, decreasing its value when the ISO route was implemented. DMA analysis revealed that the RPUFs developed using the ISO route proved to have an improved damping factor, regardless of BNC concentration. These results emphasize the importance of using the ISO route to achieve foamed nanocomposites with improved specific mechanical properties."
Preparation of an environmentally friendly lead adsorbent. A contribution to the rational design of heavy metal adsorbents
(2020-10) Rossi, Ezequiel; Ávila Ramírez, Jhon Alejandro; Errea, María Inés
"This work described the preparation and characterization of water insoluble chitosan derivatives as lead adsorbents. In highly regioselective reactions, N-substituted crosslinked chitosan derivatives were obtained by crosslinking native chitosan with mucic and adipic acid (a polyhydroxylated and a non-functionalized diacid of the same length chains). The crosslinking degree of the chitosan modified with adipic acid was significantly higher than that crosslinked with mucic acid (0.446 and 0.316, respectively), while the degree of substitution was almost the same (approximately 80 %). Lead adsorption isotherms were constructed at different temperatures and adjusted to well-known models, obtaining the best fit to the experimental data with Langmuir model. The lead adsorption capacity of new materials was greater than many of the adsorbents described in literature (76.3 and 69.7 mg g−1 for chitosan modified with mucic and adipic acid, respectively). Moreover, thermodynamic parameters were calculated, and results showed that the lead adsorption on the derivatives was spontaneous, exothermic, and governed by chemical interaction. Besides, kinetic studies were performed and adjusted to well-known models. The pseudo-second order kinetic equation was the one that most appropriately described the lead adsorption on the new materials. Results were consistent with the strong electrostatic attraction established between the lead cations and the free carboxylate groups of the derivatives."

Browsing by Subject "BIOPOLIMEROS"

Results Per Page

Sort Options