Avaliação e comparação de propriedades físicas e mecânicas de materiais de moldagem experimentais / Assessment and comparison of mechanical and physical properties of commercial and experimental gypsums

RESUMO

OBJETIVO: O objetivo deste estudo foi avaliar e comparar in vitro propriedades fisicas e mecanicas (resistencias a compressao e a tracao diametral, tempo de presa, fidelidade de copia e dureza) de gessos comerciais, cujas composicoes foram alteradas. MATERIAL E METODO: Foram confeccionados 40 corpos-de-prova para cada tipo de gesso e submetidos aos testes citados (n=10). Os corpos-de-prova obtidos para verificacao da resistencia a tracao foram antes submetidos a analise de dureza. Os tempos de presa foram analisados imediatamente apos a manipulacao dos materiais e os demais ensaios propostos foram realizados apos 7 dias da obtencao das amostras. RESULTADOS: Os valores obtidos nos testes foram analisados estatisticamente (1-way ANOVA, Tukey, p<0.05); observou-se que Exp1 apresentou melhor reproducao de detalhes e Exp2 o menor tempo de presa em relacao aos materiais comerciais (p<0.05). Nas demais propriedades, os gessos experimentais apresentaram comportamentos semelhantes aos comerciais. CONCLUSOES: Concluiu-se que as alteracoes na composicao dos gessos contribuiram para a melhoria na reproducao de detalhes no grupo Exp1, e diminuicao no tempo de presa no grupo Exp2.

ABSTRACT

OBJECTIVE: The purpose of this study was to evaluate and to compare in vitro mechanical and physical properties (compression and diametral tensile strength, setting time, loyalty to copy and hardness) of commercial and experimental gypsums (Exp1 and Exp2), whose compositions were altered. MATERIAL AND METHOD: Forty specimens were obtained for each type of gypsum (n=10). The specimens obtained to verify tensile strength were submitted to hardness analysis before. The setting time were analysed immediately after the manipulation of materials and the other tests were conducted 7 days after the specimens were obtained. RESULTS: The values were analyzed statistically (1-way ANOVA, Tukey, p <0.05) and it was observed that Exp1 showed better reproduction of details and Exp2 presented lesser setting time than commercial materials (p <0.05). As regards to other properties, experimental gypsums showed similar behavior to commercial gypsums. CONCLUSION: It was concluded that alterations in gypsum composition contributed to the improvement in reproduction of details in Exp1 group, and promoted a decrease in setting time in Exp2.