ELISABETH CARVALHO L. CARDOSO

ELISABETH CARVALHO L. CARDOSO

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Influence of particle size of bio-calcium carbonate used as reinforcement of PBAT/PLA bio-based foams compatibilized with ionizing radiation
2019 - CARDOSO, ELISABETH C.L.; PARRA, DUCLERC F.; SCAGLIUSI, SANDRA R.; LUGAO, ADEMAR B.
Bio-filler from eggshells as reinforcement of bio-based polymers are based on their principle benefits such as good strength and stiffness besides being an environmental friendly, degradable and renewable material. Eggshell is an agricultural waste largely considered as garbage and discarded mostly because it contributes to pollution. Biodegradable polymers as PLA (poli-lactic acid) and PBAT (butylene adipate co-terephthalate) are thermoplastics which can be processed using most conventional polymer processing methods. PLA is high in strength and modulus (63 MPa and 3.4 GPa, respectively) but brittle (strain at break 3.8%) while PBAT is flexible and tough (strain at break ~710%). In order to reduce interfacial tension exhibited by PLA/PBAT blend, compatibilization is fundamental: herein it was used as compatibilizing agent PLA previously e-beam irradiated at 150 kGy: ionizing radiation induces compatibilization by free radicals, improving the dispersion and adhesion of blend phases, without the use of chemical additives and at room temperature. PLA/PBAT, 65/35 blend with bio-filler, from avian eggs, of 38 and 75 µm particle size were prior homogenized in a co-rotating twin-screw extruder and further foamed in a mono-screw extruder, by using CO2 as Physical Blowing Agent (PBA). Characterizations involved: Melt Index, DSC, TGA, FTIR, SEM, XRD and mechanical essays.
Nanocomposites foams of polypropilene modified by ionizing radiation containing CaCo3/ag° nanoparticles of bio-calcium carbonate-study of bactericidal effect
2019 - PARRA, DUCLERC F.; SILVA, ORELIO L. da; KOMATSU, LUIZ G.; CARDOSO, ELIZABETH C.L.; LUGAO, ADEMAR B.
This paper presents a study of high melting strengh polypropylene (HMSPP) foams by gamma irradiation with insertion of silver nanoparticles (AgNPs) adsorbed in carrier of CaCO3 (natural source) aiming bactericidal effect. The use of silver (Ag°) gives important antibacterial property since silver is highly toxic against bacterae. The HMSPP matrix was processed in a twin screw extruder under CO2 atmosphere and polypropylene nanocomposites (HMSPP-AgNC) were obtained in different concentrations of silver. The material was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), cytotoxicity assay and reduction colony-forming-unit (CFU). The analyzed foams showed spherical clusters and homogeneous regions with good distribution of the silver nanoparticles. Furthermore, the HMSPP@AgNCs foams exhibited a antibacterial efficiency against E. coli and S. aureus due to the presence of the biocidal silver nanoparticles.
Study of PBAT/PLA bio-based blends reinforced with chicken eggshell nano powder compatibilized with ionizing radiation
2020 - CARDOSO, ELIZABETH C.L.; PARRA, DUCLERC F.; SCAGLIUSI, SANDRA R.; LUGAO, ADEMAR B.
Eggshell is a solid waste, with production of several tons per day and it is mostly sent to landfills at a high management cost. A few used of eggshell include: fertilizing the garden, cleaning pots and pans, seed starter, feeding birds, making bone broth, etc… Nevertheless, chicken eggshell biowaste has recently been used to substitute calcium carbonate (CaCO3), due to its reinforcing property and low price. It is economically viable to transform eggshell waste to acquire new values, transforming it into a bioplastic: a biodegradable polymer made from bio-mass. The surprising strength of eggshells endorses their application for reinforcement of biodegradable polymers herein studied: PLA (poly-lactic acid) and PBAT (butylene adipate co-terephthalate). PLA is derived from renewable sourced: polylactic acid plastics are sturdier and capable to be blend with conventional petroleum polymers; nevertheless, they exhibit a narrow process window and low thermal stability, besides an inherent high cost. PBAT, as PLA, is a biodegradable aliphatic polyester, although a synthetic polymer based on fossil resources. By incorporating PBAT in PLA it is expected to improve flexibility of PBAT/PLA blend. Previous studies using PBAT/PLA, 50/50 blends containing 15% of chicken eggshell 125 µm improved mechanical behavior of net blends: values for both force and strain practically doubled, proving the effective reinforcement action of calcium carbonate extracted from eggshells. Conventional polymer processing methods can be used in both PLA and PBAT compositions. Due to common incompatibility between PLA and PBAT, considering their extreme glass transition temperatures: 62 º C and – 30 º C, respectively, it is required a compatibilizer to accomplish or increase their interaction. Herein it was used PLA previously e-beam radiated at 150 kGy, as compatibilizing agent: ionizing radiation induces compatibilization by free radicals, improving the dispersion and adhesion of blend phases, without the use of chemical additives and at room temperature. Herein there were prepared bio-composite PBAT/PLA 82/18 blends with 2.5, 5.0 and 10.0 % of eggshell nano-powder, 161 nm, in average, and 5.0 % of PLA 150 kGy e-beam radiated were homogeneized in a co-rotating twin-screw extruder. Subsequent investigations included: Differential Scanning Calorimeter (DSC), Thermal Gravimetric Analysis (TGA), Fourier Transmittance Infrared (FTIR), X-Ray Diffraction (XRD), Tensile Strength and Elongation at Break
Butyl rubber recycling by means of gamma radiation followed by mechanical shear
2018 - SCAGLIUSI, SANDRA R.; CARDOSO, ELIZABETH C.L.; LUGAO, ADEMAR B.
Polymeric materials (plastics and rubbers) cover a continuously raising proportion of urban and industrial solid wastes discarded in landfills and consequently their impact on environment are more and more concern. Rubbers exhibit a very slow natural decomposition due to their chemical structure weather resistant as well to enzymatic degradation and to microorganisms. Rubber recovering is hampered by its insolubility caused by crosslinked structures. Besides, this tridimensional structure causes various problems for material recovering and reprocessing. Just 8% to 12% of polymeric residues are thermoplastic polymers; remaining are elastomers especially post consumption tires. It is relevant to emphasize that the crosslinking is essential for practical use of rubber and this process is worldwide known as vulcanizing process, discovered by North American Charles Goodyear. The implementation of new technologies in order to reduce polymeric residues, acceptable from the environmental viewpoint and at an effective cost proved to be a great problem due to inherent complexities for polymers reuse. Ionizing radiation has capacity to change structure and properties of polymeric materials. Butyl rubbers have been used in wide scale within a variety of applications such as tires spare-parts and diverse artifacts. Major effect of high energy photon, such as gamma rays in butyl and halo-butyl rubbers is the creation of free radicals accompanied by changes in mechanical properties. This work aims to the development of processes of controlled degradation (de-vulcanizing) of butyl rubber in order to characterize their availability for modification and changes of their properties. Experimental results obtained showed that butyl rubbers irradiated at 25 kGy and further sheared can be used as the starting point for mixtures with pristine rubber.