Os revestimentos orgânicos de embreagem são compostos basicamente por matriz orgânica, cargas, lubrificantes sólidos e fibras de reforço. A matriz orgânica possui função estrutural e tem grande influência nas propriedades tribológicas do sistema, isto é, no coeficiente de atrito e taxa de desgaste tanto do material de atrito, quanto do contra-corpo metálico. Baseado nas normas ambientais para indústria automobilística, o presente trabalho estuda a viabilidade de substituir a resina fenólica, utilizada como matriz estrutural na composição de revestimentos de embreagem, por termoplásticos de engenharia especiais. O principal objetivo da substituição é a eliminação do fenol livre no produto final, e conseqüentemente a geração de um refugo classificado, de acordo com a norma NBR 10004, como não perigoso. Plásticos de engenharia especiais apresentam alta temperatura de uso contínuo e manutenção das propriedades mecânicas em altas temperaturas e são, geralmente, empregados em materiais que suportam alta pressão, tais como engrenagens, freios, rolamentos e embreagens. Avaliou-se a influência da velocidade de deslizamento e da carga normal no comportamento tribológico tanto do compósito de resina fenólica (base de comparação) como dos compósitos de resina poli (amida imida) e resina poli (éter éter cetona) quando estes deslizavam a seco em um contra-corpo usinado de ferro fundido cinzento, mesmo material utilizado nas placas de pressão. Foram avaliadas características térmicas e mecânicas dos compósitos, por meio de análises termogravimétricas, dinâmicomecânica e dureza. Após os ensaios tribológicos, as superfícies desgastadas dos corpos poliméricos e dos contra-corpos metálicos foram avaliadas por meio de microscopia ótica, microscopia eletrônica de varredura e composição química. Embora os compósitos de resina PAI e resina PEEK sejam classificados como produtos não perigosos, a substituição não é viável pois, nas condições de velocidade de deslizamento e carga normal estudadas, os compósitos de resina PAI e resina PEEK apresentaram menor resistência ao desgaste em comparação ao compósito de resina fenólica. / Organic clutch friction facings are basicly composed of an organic matrix, fillers, solid lubricants and reinforcing fibers. An organic matrix has a structural function and has a large influence over the tribological properties of the system (coefficient of friction and wear rate in both, friction material as for the metal counterpart). Based on the automotive industry environmental standards, this analysis studies the viability of substituting the phenolic resin, used as the structural matrix in the clutch facing composition by high performance polymers. The principle objective for this substitution is to eliminate the free phenol in the final product and consequently produce a classified non-dangerous waste in accordance to the NBR 10004 norm. High performance polymers have high temperature working resistance when in continuous use and also maintain their mechanical properties and are normally used in products that support high pressures, such as gears, brakes, bearings and clutches. The influence of the sliding speed and the normal load under tribological behaviour was evaluated for phenolic composites (comparative basis) and for poly (amide imide) composites and poly (ether ether ketone) composites when these slip under dry conditions against a grey iron machined counterpart, the same material as used for pressure plates. Thermal and mechanical characteristics of the composites, obtained by thermogravimetric analysis, dynamic-mechanical and hardness were analysed. After the tribological tests the worn surfaces of the composites samples and of the metallic counterparts were evaluated with optical microscopy, electro scanning microscopy and chemical composition. The environmental characteristics of these materials classify both materials as not being dangerous, but under the sliding speed and load studied the PAI and PEEK composites showed lower wear resistance than the phenolic composites.

Os revestimentos orgânicos de embreagem são compostos basicamente por matriz orgânica, cargas, lubrificantes sólidos e fibras de reforço. A matriz orgânica possui função estrutural e tem grande influência nas propriedades tribológicas do sistema, isto é, no coeficiente de atrito e taxa de desgaste tanto do material de atrito, quanto do contra-corpo metálico. Baseado nas normas ambientais para indústria automobilística, o presente trabalho estuda a viabilidade de substituir a resina fenólica, utilizada como matriz estrutural na composição de revestimentos de embreagem, por termoplásticos de engenharia especiais. O principal objetivo da substituição é a eliminação do fenol livre no produto final, e conseqüentemente a geração de um refugo classificado, de acordo com a norma NBR 10004, como não perigoso. Plásticos de engenharia especiais apresentam alta temperatura de uso contínuo e manutenção das propriedades mecânicas em altas temperaturas e são, geralmente, empregados em materiais que suportam alta pressão, tais como engrenagens, freios, rolamentos e embreagens. Avaliou-se a influência da velocidade de deslizamento e da carga normal no comportamento tribológico tanto do compósito de resina fenólica (base de comparação) como dos compósitos de resina poli (amida imida) e resina poli (éter éter cetona) quando estes deslizavam a seco em um contra-corpo usinado de ferro fundido cinzento, mesmo material utilizado nas placas de pressão. Foram avaliadas características térmicas e mecânicas dos compósitos, por meio de análises termogravimétricas, dinâmicomecânica e dureza. Após os ensaios tribológicos, as superfícies desgastadas dos corpos poliméricos e dos contra-corpos metálicos foram avaliadas por meio de microscopia ótica, microscopia eletrônica de varredura e composição química. Embora os compósitos de resina PAI e resina PEEK sejam classificados como produtos não perigosos, a substituição não é viável pois, nas condições de velocidade de deslizamento e carga normal estudadas, os compósitos de resina PAI e resina PEEK apresentaram menor resistência ao desgaste em comparação ao compósito de resina fenólica. / Organic clutch friction facings are basicly composed of an organic matrix, fillers, solid lubricants and reinforcing fibers. An organic matrix has a structural function and has a large influence over the tribological properties of the system (coefficient of friction and wear rate in both, friction material as for the metal counterpart). Based on the automotive industry environmental standards, this analysis studies the viability of substituting the phenolic resin, used as the structural matrix in the clutch facing composition by high performance polymers. The principle objective for this substitution is to eliminate the free phenol in the final product and consequently produce a classified non-dangerous waste in accordance to the NBR 10004 norm. High performance polymers have high temperature working resistance when in continuous use and also maintain their mechanical properties and are normally used in products that support high pressures, such as gears, brakes, bearings and clutches. The influence of the sliding speed and the normal load under tribological behaviour was evaluated for phenolic composites (comparative basis) and for poly (amide imide) composites and poly (ether ether ketone) composites when these slip under dry conditions against a grey iron machined counterpart, the same material as used for pressure plates. Thermal and mechanical characteristics of the composites, obtained by thermogravimetric analysis, dynamic-mechanical and hardness were analysed. After the tribological tests the worn surfaces of the composites samples and of the metallic counterparts were evaluated with optical microscopy, electro scanning microscopy and chemical composition. The environmental characteristics of these materials classify both materials as not being dangerous, but under the sliding speed and load studied the PAI and PEEK composites showed lower wear resistance than the phenolic composites.

OBJECTIVES: To assess the viability of using high-strength polymers as framework materials for full arch implant-supported fixed prostheses, veneered with full-coverage restorations of different materials. The machinability, mechanical performance, and damping capacity of the polymer-based materials was of interest. METHODS: The two framework polymers – a polyetheretherketone (JUVORA™ Dental Disk, Juvora) (PEEK) and a fiber-reinforced composite (TRINIA™ CAD/CAM Disk, Trinia) (TR) – were characterized with Fourier-Transform Infrared (FTIR) Spectroscopy and energy-dispersive X-ray spectroscopy (EDS). Phase 1 consisted of a machinability study involving the merlon fracture test, which tested the milling success of PEEK and TR at 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm. 10 four-walled merlons of each thickness and material were milled out of CAD/CAM Disks (n = 100 merlons, n = 400 walls) using a 5-axis milling machine, inLab MC X5 (Dentsply Sirona, Germany). Milling success rate, fracture height, fracture length, fracture position, fracture direction, and chipping factor were assessed. In phase 2, 20 bars of dimensions 3.3 mm x 10 mm x 40 mm were milled from each of the two framework materials, PEEK and TR, and two veneer materials – a composite resin material (Shofu Disk HC, Shofu, Inc., Kyoto, Japan) (COM), and a high-translucency 3 mol% yttria-stabilized tetragonal zirconia polycrystal material (Cercon® ht, Dentsply Sirona, Bensheim, Germany) (ZR). Framework and veneer bars were bonded to each other in 4 framework/veneer combinations of 10 bilayers each: PEEK/COM (PCB), PEEK/ZR (PZB), TR/COM (TCB), and TR/ZR (TZB). Bilayer bars were loaded to failure in a 3-point bending test. Failure load, biaxial flexural strength, failure pattern and failure mode were documented. In Phase 3, 10 full arch fixed implant-supported frameworks were designed and fabricated in TR material over an epoxy resin model containing 4 implants in the second premolar and lateral incisor positions. 5 frameworks were veneered by COM in the canine to first molar region, while the other 5 were veneered by ZR. Four loading sites were designated per prosthesis in the occlusal surface of the first molars and the first premolars. Prostheses were loaded at the four occlusal sites in 5 cycles of loading and unloading. The damping capacity of the prostheses was calculated based on energy absorbed during loading and unloading. Displacement and permanent deformation values of the prosthesis structures were obtained from the load-displacement data. Prostheses were loaded to failure at the same sites, and failure load and failure mode were observed. RESULTS: The minimum machined thickness of PEEK and TR was 0.5 mm. There was no significant difference between milling success of PEEK and TR, but cumulative success rate was slightly superior in PEEK. PEEK exhibited a ductile response to machining damage, while TR showed a more brittle response. Chipping factor of PEEK was higher than TR eightfold, meaning TR showed an improved marginal integrity at 0.5 mm. Both materials showed concerning signs of machining damage with the milling parameters and tools used in this study. Bilayer bars with a TR framework withstood significantly higher loads at failure compared to bilayers with a PEEK framework. Bilayer bars with a ZR veneer withstood significantly higher loads at failure compared to bilayers with a COM veneer. The biaxial flexural strength of the four framework/veneer combinations could not be compared due to the occurrence of delamination in 3 of the 4 groups. The PZB group was the only group with fracture of both the veneer and framework without any delamination and exhibited a mean biaxial flexural strength of 46.15 ± 5.76 MPa. None of the bilayer bars with a TR framework exhibited framework fracture. In delaminated specimens, bilayer bars with a TR framework exhibited mixed adhesive-cohesive failure on both layers, while bilayer bars with a PEEK framework exhibited purely adhesive failure on the PEEK-cement interface. Full arch implant prostheses with a TR framework demonstrated elastic hysteresis in continuous cycles of cyclic loading, which is evidence of viscoelastic damping. Significantly higher energy absorption was observed in prostheses veneered with COM compared to ZR. Energy absorption decreased with increasing cycles of loading-unloading. Significantly higher maximum displacement was observed in prostheses veneered with COM compared to ZR, and in cantilever support compared to bounded support. Maximum displacement was inversely related to the thickness of the veneer and framework materials. Permanent deformation of the prosthesis was negligible after 10 cycles. The failure pattern of all prostheses presented as fracture in the veneer only and partial delamination of the veneer with mixed adhesive-cohesive failure mode. The mean failure load at ZR-veneered bounded sites was significantly higher than that of COM-veneered bounded sites. The mean failure load at bounded loading sites was significantly higher than that of cantilever loading sites. ZR-veneered prostheses demonstrated failure load values above 1000 N at all sites. CONCLUSION: The merlon fracture test is well-complemented by several quantitative and qualitative measures to assess the machinability of materials. Optimized tools and parameters for milling PEEK and TR should be investigated. Full arch implant prostheses with TR framework and ZR veneer are a viable option for fixed implant rehabilitation demonstrating damping capacity, adequate failure load values, and easy repairability.

Le frittage sélectif par laser (ou Selective Laser Sintering, SLS) des poudres polymères thermoplastiques est maintenant une technique répandue de fabrication additive. Néanmoins, ce procédé n'est industriellement mature que pour une seule famille de polymères, les polyamides. Pour que ce procédé soit employé dans la fabrication de pièces subissant des contraintes thermiques au-delà de 50 °C, il est ainsi nécessaire d'étendre la gamme des matériaux utilisables à des polymères hautes performances tels que les poly(aryl-éther-cétone) ou les poly(aryl-imide). Cette étude décrit la fabrication additive, couche par couche, de pièces aérospatiales complexes en polymères hautes performances. Pour cela, sept poudres en polymère ont été sélectionnées afin d'étudier l'influence de celles-ci sur les différentes phases du procédé et sur la qualité de la matière frittée/fondue. Ainsi, la morphologie de leurs particules, leurs microstructures ou encore leurs densités versées et tapées sont analysées, de même que leurs stabilités thermiques, leurs capacités à absorber l'eau ou à s'écouler. Dans un second temps, une étude paramétrique du procédé a été réalisée dans le but d'aboutir à la fabrication de pièces de bonne qualité matière, tout en portant un intérêt vis-à-vis des évolutions de la poudre cycle après cycle de fabrication. De plus, il est important, dans un souci d'optimisation, d'utiliser toutes les possibilités de forme qu'offre cette fabrication additive et d'en évaluer la résistance mécanique. C'est pourquoi une loi de comportement mécanique d'un polyamide 12 consolidé sélectivement par laser a été déterminée et implémentée dans un code de calcul par éléments finis (ZéBuLoN®). Cette loi de comportement, dans le domaine linéaire et non linéaire, représentative de l'anisotropie du matériau, a ensuite été validée expérimentalement sur des éprouvettes d'essais mécaniques et sur un démonstrateur aérospatial. / Selective Laser Sintering (SLS) of thermoplastic polymer powders is now widely used as a additive manufacturing technique. Nevertheless, this process is industrially mature for only one family of polymers : the polyamides. To use this process in manufacturing applications that are used above 50 °C, it is necessary to increase the range of useable powders to high temperature resistant families of thermoplastic such as poly(aryl-ether-ketone) or poly(aryl-imide). This study investigates the layer-by-layer additive manufacturing of complex parts by SLS from high temperature resistant thermoplastic powders. Seven polymers powders were selected to study their influences on the process steps and the quality of sintered/melted materials. To do so, morphology of theirs particles, microstructures or tapped and poured density are analysed, and also theirs thermal stabilities, capacities to absorb water or theirs flow abilities. In a second step, a study of the influence of process parameters has been carried out to obtain parts with good material quality, taking into account the evolution of the powder after each cycle of fabrication. Moreover, it is important to use all the possibilities of this process in terms of geometry. That is why a law for the mechanical behaviour of laser sintered polyamide 12 has been determined and implemented in a finite element code (ZeBuLoN®). This law, in its linear and non-linear domain, is representative of the material anisotropy and has been experimentally validated on tensile samples and one aerospace part.