EFEITO DA TERMORRETIFICAÇÃO NA QUALIDADE DE COLAGEM DE LÂMINAS DE MADEIRA PARA A PRODUÇÃO DE COMPENSADO

Plywood is a wood panel that can be used both in the furniture industry and in construction due to its structural use. However, to be used in construction, it needs to be resistant against wood decay agents and water, without compromising its mechanical properties. The heat treatment is an alternative treatment which improves the wood resistance to fungi and improves its dimensional stability. Thus, the objective of this study is to evaluate the influence of the heat treatment with three different temperatures, 160, 180 and 200°C in the wettability of wood veneers and the shear strength in the bond line of the plywood produced with them. To do so, it was carried out the wettability testing using digital goniometer in the treated veneers at three temperatures and for the control specimen. Besides, it was carried out the shear strength in the bond line test, for testing the quality of bonding according to ABNT NBR ISO 12466-1 (2006). Because of the results obtained, it could be seen that the surface of the treated wood became more hydrophobic with increasing temperature, and this also resulted in a decrease in shear strength in the bond line, once the adhesive used (phenol-formaldehyde) is water based, however, the regulatory requirements have been met.O compensado é um painel de madeira que pode ser utilizado tanto na indústria moveleira quanto na construção civil, devido ao seu uso estrutural. Entretanto, para ser utilizado na construção civil, o compensado necessita ser resistente aos agentes xilófagos e à umidade, sem comprometer suas propriedades mecânicas. Nesse aspecto, a termorretificação surge como uma alternativa de tratamento, que aumenta a resistência da madeira ao ataque de fungos e a sua estabilidade dimensional.  Desse modo, o objetivo deste trabalho foi avaliar o efeito da termorretificação na qualidade de colagem de lâminas de madeira para a produção de compensado. Para isso, foram realizados os testes de molhabilidade utilizando o goniômetro digital, para lâminas tratadas nas três temperaturas e na amostra de controle. Além disso, foi realizado, o ensaio de cisalhamento na linha de cola, para testar a qualidade da colagem segundo a ABNT NBR ISO 12466-1 (2006). Com os resultados obtidos pode-se perceber que a superfície da madeira tratada se tornou mais hidrofóbica com o aumento da temperatura, e isso resultou também na diminuição da resistência ao cisalhamento na linha de cola, pois o adesivo utilizado (fenol-formaldeído) é à base de água, contudo, os requisitos normativos foram atendidos

Hydroxyapatite coating deposited on grade 4 Titanium by Plasma Electrolytic Oxidation

The present study reports the deposition of coating using Plasma Electrolytic Oxidation (PEO) onto grade 4 titanium to produce novel surface features. Samples were treated in an electrolytic solution of calcium acetate and sodium glycerolphosphate. The temporal evolution of hydroxyapatite coatings with high Ra roughness and a maximum thickness of 120 μm was obtained. X-ray spectra revealed the presence of hydroxyapatite, rutile and calcium phosphate. Cell growth measurement by MTT assay showed that the coatings were not toxic because cells grew on all samples17614271433CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informaçã

Electrochemical characterization of samples of commercial steel treated with acetylene plasma

104-111Cutting tools have been employed in wood processing must be corrosion and wear resistant due to the acidic composition of wood and the wear generated during cutting, which lead to the deterioration of steel saws. Hydrogenated amorphous carbon films possess mechanical, tribological and barrier properties that can increase the hardness, wear and corrosion resistance of this type of tool. This work has involved an investigation of the effectiveness of plasma-deposited amorphous carbon thin films in protecting commercial carbon steel saws. Before deposition, the substrates were sputter-cleaned in argon plasma (19.27 Pa; 50 W) for 180 s. The films have been deposited using acetylene and argon mixtures excited by a radio frequency power supply (13.56 MHz, 70 W). The concentration of acetylene in the mixture has been varied in the inverse proportion to that of argon so as to maintain a constant total gas pressure of 1.8 Pa. The deposition time was 3600 s. The chemical behavior of the coated saws have been evaluated by electrochemical impedance spectroscopy (EIS) and polarization curves.Surface images of the plasma-coated samples have been recorded by scanning electron microscopy (SEM). The results have indicated that the plasma treatment has increased the corrosion resistance of carbon steel samples in acidic solutions

Polylactic acid scaffolds obtained by 3D printing and modified by oxygen plasma

The purpose of tissue engineering is to repair, replace, and regenerate tissues and organs. For this aim, materials supports, as polylactic acid (PLA) are used. PLA is a thermoplastic polymer that presents biodegradability, biocompatibility and good processability. PLA scaffolds can accurately constructed by 3D printing. Then, the objectives of this work were to modify the hydrophobic surface of PLA scaffolds using oxygen plasma and to study the cell viability and proliferation. The characterization was done by AFM, contact angle, FTIR and studies of proliferation and cell viability. Results showed that the material acquired hydrophilic properties by the presence of oxygen reactive species and by contact angle decrease. It was also observed an increase in the surface roughness. We can conclude that although the surface modifications were effective and the PLA scaffolds were not cytotoxic, there were no improvements in the proliferation process with the studied osteo-1 lineage cells.

Innovative low temperature plasma approach for deposition of alumina films

Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O2%) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen ( 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Estadual Paulista Laboratório de Plasmas TecnológicosUniversidade Federal de São Paulo (UNIFESP) Departamento de Ciências Exatas e da TerraUniversidade de São Paulo Departamento de Física NuclearUniversidade de São Paulo Departamento de Física AplicadaUNIFESP, Depto. de Ciências Exatas e da TerraSciEL

Electrochemical characterization of samples of commercial steel treated with acetylene plasma

Cutting tools have been employed in wood processing must be corrosion and wear resistant due to the acidic compositionof wood and the wear generated during cutting, which lead to the deterioration of steel saws. Hydrogenated amorphouscarbon films possess mechanical, tribological and barrier properties that can increase the hardness, wear and corrosionresistance of this type of tool. This work has involved an investigation of the effectiveness of plasma-deposited amorphouscarbon thin films in protecting commercial carbon steel saws. Before deposition, the substrates were sputter-cleaned inargon plasma (19.27 Pa; 50 W) for 180 s. The films have been deposited using acetylene and argon mixtures excited by aradio frequency power supply (13.56 MHz, 70 W). The concentration of acetylene in the mixture has been varied in theinverse proportion to that of argon so as to maintain a constant total gas pressure of 1.8 Pa. The deposition time was 3600 s.The chemical behavior of the coated saws have been evaluated by electrochemical impedance spectroscopy (EIS) andpolarization curves.Surface images of the plasma-coated samples have been recorded by scanning electron microscopy(SEM). The results have indicated that the plasma treatment has increased the corrosion resistance of carbon steel samples inacidic solutions

Bond strength of lithium disilicate after cleaning methods of the remaining hydrofluoric acid

Different ceramic surface cleaning methods have been suggested after the acid conditioning. The aim was to evaluate the effect of different protocols used to remove the remaining hydrofluoric acid on the shear bond strength (SBS) between lithium disilicate and resin cement. Forty-four specimens of lithium disilicate (IPS e.max Press) were divided in 4 groups (n=11): group C (control, no treatment); group HF+S (5% hydrofluoric acid + silane); group HF+US+S (5% hydrofluoric acid + ultrasound cleaning + silane); group HF+PH+S (5% hydrofluoric acid + 37% phosphoric acid + silane). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed to characterize the surface morphology. The SBS test was performed on the resin/ceramic interface, and the failure mode was characterized. SBS values were submitted to 1-way ANOVA and the Tukey test (?=.05). The relation between surface treatment and failure modes was analyzed using the chi-squared test (?=.05). The surface treatment type interfered in the shear strength (p<.001) and higher SBS values were observed for the groups HF+US+S (17.87 MPa) and HF+PH+S (16.37 MPa). The surface treatment did not influence the failure mode (p=.713). No fluorsilicate salts were observed after ultrasound cleaning. The utilization of ultrasound cleaning was an effective procedure to remove remaining fluorsilicate salts, promoting the highest SBS values

Synthesis of multifunctional chlorhexidine-doped thin films for titanium-based implant materials

Our goal was to create bio-functional chlorhexidine (CHX)-doped thin films on commercially pure titanium (cpTi) discs using the glow discharge plasma approach. Different plasma deposition times (50, 35 and 20 min) were used to create bio-functional surfaces based on silicon films with CHX that were compared to the control groups [no CHX and bulk cpTi surface (machined)]. Physico-chemical and biological characterizations included: 1. Morphology, roughness, elemental chemical composition, film thickness, contact angle and surface free energy; 2. CHX-release rate; 3. Antibacterial effect on Streptococcus sanguinis biofilms at 24, 48 and 72 h; 4. Cytotoxicity and metabolic activity using fibroblasts cell culture (NIH-F3T3 cells) at 1, 2, 3 and 4 days; 5. Protein expression by NIH-F3T3 cells at 1, 2, 3 and 4 days; and 6. Co-culture assay of fibroblasts cells and S. sanguinis to assess live and dead cells on the confocal laser scanning microscopy, mitochondrial activity (XTT), membrane leakage (LDH release), and metabolic activity (WST-1 assay) at 1, 2 and 3 days of co-incubation. Data analysis showed that silicon films, with or without CHX coated cpTi discs, increased surface wettability and free energy (p 0.05), whereas cell metabolism (MTT assay) was affected by CHX, with the 35 min of plasma deposition time group displaying the lowest values as compared to bulk cpTi (p 0.05). Altogether, the findings of the current study support the conclusion that silicon films added with CHX can be successfully created on titanium discs and have the potential to affect bacterial growth and inflammatory markers without affecting cell viability/proliferation rates