Navegando por Palavras-chave "mechanical properties"
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- ItemSomente MetadadadosApplication of chitosan emulsion as a coating on Kraft paper(Wiley-Blackwell, 2011-06-01) Reis, Arlete B.; Yoshida, Cristiana M. P. [UNIFESP]; Reis, Ana Paula C.; Franco, Telma T.; Universidade Estadual de Campinas (UNICAMP); Fed Univ Vale Jequitinhonha & Mucuri; Universidade Federal de São Paulo (UNIFESP); Packaging Technol CtrKraft paper was coated with chitosan emulsion film. the novelty of this paper is the formation of a packaging bilayer system in only one drying step, which combines a biodegradable polymer emulsion (chitosan and palmitic acid) with Kraft paper. This system is described in detail and characterized for barrier properties (water vapor permeability rate (WVPR), air permeability and water absorption capacity (Cobb test)), mechanical properties (tensile properties, Taber stiffness and tear strength) and structural properties. the application of chitosan coating (3.5 gm(-2), wet basis) on Kraft paper sheets provides a significantly lower WVPR (by ca 43%) and water absorption capacity (by ca 35%) as compared to uncoated Kraft paper. the incorporation of palmitic acid into the chitosan film solutions at 1.8 gm(-2) improves the properties of Kraft paper even more by further reducing the WVPR and water absorption capacity by 51 and 41%, respectively. the air resistance of the coated Kraft systems is lower by 8- and 11-fold compared to uncoated Kraft paper, which could be associated with the chitosan film acting as a gas barrier and as a coating agent that fills the pores between cellulose fibers. (C) 2011 Society of Chemical Industry
- ItemSomente MetadadadosCarbon Nanotube-Reinforced Aluminum Matrix Composites Produced by High-Energy Ball Milling(Springer, 2017) Travessa, Dilermando N. [UNIFESP]; da Rocha, Geovana V. B. [UNIFESP]; Cardoso, Katia R. [UNIFESP]; Lieblich, MarcelaAlthough multiwall carbon nanotubes (MWCNT) are promising materials to strengthen lightweight aluminum matrix composites, their dispersion into the metallic matrix is challenge. In the present work, MWCNT were dispersed into age-hardenable AA6061 aluminum alloy by high-energy ball milling and the blend was subsequently hot-extruded. The composite bars obtained were heat-treated by solution heat treatment at 520 A degrees C and artificially aged at 177 A degrees C for 8 h, in order to reach the T6 temper. Special attention was given to the integrity of the MWCNT along the entire composite production. The microstructure of the obtained bars was evaluated by optical and scanning electron microscopy, and the mechanical properties were evaluated by Vickers microhardness tests. Raman spectroscopy, x-ray diffraction and transmission electron microscopy were employed to evaluate the structural integrity of MWCNT. It was found that milling time is critical to reach a proper dispersion of the reinforcing phase. The composite hardness increased up to 67% with the dispersion of 2% in weight of MWCNT, when comparing with un-reinforced bars produced by similar route. However, age hardening was not observed in composite bars after heat treatment. It was also found that MWCNT continuously degraded along the process, being partially converted into Al4C3 in the final composite.
- ItemAcesso aberto (Open Access)Desenvolvimento de compósitos de resina epóxi/não tecido utilizando refugo da indústria de não tecido(Universidade Federal de São Paulo (UNIFESP), 2016-06-20) Leite, Jose Rodolfo Vieira [UNIFESP]; Passador, Fabio Roberto [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Non-wovens are formed by extrusion processes and may be produced in an economical manner which are used in disposable products. Medical and hospital sector and packaging sectors are the largest consumers of non-wovens. The non-woven industry generates a large content of solid waste from the production. The wastes of non-wovem are fibers of various polymers, including polyamide, polyethylene, polypropylene, polyester and polystyrene. These materials have great interest for use as a reinforcing agent in thermosetting matrix, contributing to an improvement in the mechanical properties of these matrices, and also collaborating with the decrease of the solid residue of the non-woven industry. In this work, epoxy/nom-woven composites were prepared using two different types of waste of non-wovenssupplied fromParaíba´s Valley industries. The composites were prepared by hand lay-up thecnique and characterized by thermal, mechanical and morphological properties. The addition of 0.6 to 1.2 phr of fibers of PE/PP non-woven increased the glass transition temperature of the epoxy resin in the composite, besides improving the mechanical properties, as evidenced by the increase in elastic modulus and flexural modulus of the composites. For composite reinforced with laminated of PE/PP/PET non-woven, which presents a preferred direction of the fibers, resulting from the consolidation of these laminates, the mechanical properties of the composite are influenced by the direction of the fibers. Composites whit laminates arranged longitudinally to the direction of consolidation had superior mechanical properties. Thus, residues of the non-woven industry can be used as fillers for preparation of composites materials and can be an alternative for decreasing the amount of discharge of the product, using a low cost and simple method.
- ItemSomente MetadadadosProcessing, thermal and mechanical behaviour of PEI/MWCNT/carbon fiber nanostructured laminate(Iop Publishing Ltd, 2017) Santos, L. F. P.; Ribeiro, B. [UNIFESP]; Hein, L. R. O.; Botelho, E. C.; Costa, M. L.In this work, nanostructured composites of polyetherimide (PEI) with addition of functionalized multiwall carbon nanotube (MWCNT) were processed via solution mixing. After processing, these nanocomposites were evaluated by thermogravimetry (TGA), dynamic-mechanical analysis (DMA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Subsequently, the nanocomposite was processed with carbon fibers by using hot compression molding. In order to evaluate interlaminar fracture strength, the processed laminates were mechanically evaluated by interlaminar shear strength (ILSS) and compression shear test (CST). Also, the Weibull distribution was employed to help in the statistical treatment of the data obtained from the mechanical tests. With regards to the fracture of the specimens, optical microscopy was used for the evaluation of the material. The addition of 1 wt% of MWCNT in the polymer matrix increased both thermal stability and viscoelastic behavior of the material. These improvements positively impacted the mechanical properties, generating a 16% and 58% increase in the short-beam strength and apparent interlaminar shear, respectively. In addition, it can be verified from morphological analysis of the fracture a change in the failure mode of the laminate by the incorporation of MWCNT. This behavior can be proven from CST test where there was no presence of the shear force by compression.