Properties of athletic mouth protectors and materials.
The properties of a variety of mouth protectors and sheet materials used to fabricate custom mouth protectors were determined in order to recommend limits for a specification. Hardness, water sorption, water solubility, impact absorption, and tear strength were measured, and limits for these properties were suggested.
Use of Polyolefin as Mouthguard Material as Compared to Ethylene Vinyl Acetate
A new mouthguard material, polyolefin, was recently developed. To date, no studies have compared ethylene vinyl acetate (EVA) and polyolefin mouthguards. The aim of this study was to evaluate the physical properties of polyolefin, relative to those of EVA. Two polyolefin materials, hard and regular, were used, in addition to EVA. Hardness, tensile strength, tear strength, elongation, and water absorption were analyzed, as well as the adhesive strength of the materials in laminated mouthguards. Hard polyolefin (MG-H) and EVA were significantly harder than regular polyolefin (MG-R) (p<0.01). Regular polyolefin had significantly lower tensile and tear strengths than MG-H and EVA (p<0.01), while MG-H had significantly higher tensile and tear strengths than EVA (p<0.01). Both polyolefin materials had significantly lower water absorption and higher adhesive strength than EVA (p<0.01). In this study, polyolefin exhibited satisfactory physical properties when compared with EVA. This suggests that polyolefin is suitable for use as a mouthguard material.
Determination of Optimal Ball-Burnishing Parameters for Plastic Injection Moulding Steel
The objective of this study is to determine the optimal plane ball-burnishing parameters for plastic injection moulding steel PDS5 on a machining centre by utilising the Taguchi’s orthogonal array method. The design and manufacture of a burnishing tool are described. Four burnishing parameters, namely the ball material, burnishing speed, burnishing force and feed, were selected as the experimental factors in Taguchi’s design of experiments to determine the optimal burnishing parameters which have the dominant influence on surface roughness. The optimal burnishing parameters were found after carrying out the experiments specified by Taguchi’s L18 orthogonal table, by the analysis of variation, and by a full factorial experiment. The optimal plane burnishing parameters for the plastic injection moulding steel PDS5 were a combination of a tungsten carbide ball, a burnishing speed of 200 mm/min, a burnishing force of 300 N and a feed of 40 μm. The surface roughness Ra of the specimen can be improved from about 1 μm to 0.07 μm by using the optimal burnishing parameters for plane burnishing.