CONICET | Buscador de Institutos y Recursos Humanos

Weld lines occur when two melt streams are combined.They may result in purely cosmetic imperfections, butalso may represent part failure if placed in an area on theplastic highly subjected to stress during service. Qualitativeassessment of these structural and cosmetics defectsis usually accomplished by conventional mechanical characterization,destructive by nature, such as tensile testingor dynamic mechanical analysis (DMA). Nanoindentationoffers the possibility for quick quasi-nondestructive in situtesting, allowing for monitoring the changes that occur inthe surface layer of a plastic micropart. In this study, amethodology for the assessment of the superficial properties:hardness (H) and reduced Young?s modulus (Er)of micromolded parts was developed. The microparts,molded from Polyoxymethylene with two different sets ofprocessing conditions were tested throughout the entirelength and in the vicinity of the welding line. The observedhardness (H) and reduced Young?s modulus (Er) suggestthat there is a steady increase in both values along theweld line from the adjoining flow front point at the innerside of the micropart towards the outer edge. In addition,H and Er were found out to vary consistently with thealterations induced by the processing conditions.