Abstract
Objectives The aim of the study was to evaluate the mechanical properties and impact absorption
capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different
hardness reinforced using different amounts of glass fibers (GFs), considering a buffer
space.
Materials and Methods Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl
acetate (VA) contents of 9.4 wt% (“hard” or HA) and 27.5 wt% (“soft” or SO). Durometer
hardness and tensile strength tests were performed to evaluate the mechanical properties
of the materials. Moreover, an impact test was conducted using a customized pendulum
impact tester to assess the impact absorption capacity (with or without a buffer space)
of the specimens.
Results The mechanical properties of the prototypes, namely, durometer hardness, Young's
modulus, and tensile strength, were significantly higher in the HA group than in the
SO group, regardless of the presence or added amount of GFs. The addition of GFs,
particularly in a large amount (10 wt%), significantly increased these values. In
terms of the impact absorption capacity, the original hardness of the EVA material,
that is, its VA content, had a more substantial effect than the presence or absence
of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer
space exhibited significantly higher impact absorption capacities than the SO specimens.
Meanwhile, the SO specimens without the buffer space exhibited significantly higher
impact absorption capacities than the HA specimens. Moreover, regardless of the sample
material and impact distance, the buffer space significantly improved impact absorption.
In particular, with the buffer space, the impact absorption capacity increased with
the added amount of GFs.
Conclusion The basic mechanical properties, including durometer hardness, Young's modulus, and
tensile strength, of the EVA prototype were significantly increased by reducing the
amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly
in large amounts, significantly increased the values of aforementioned mechanical
properties. Impact absorption was significantly affected by the hardness of the original
EVA material and enhanced by the addition of the buffer space. The HA specimen had
a high shock absorption capacity with the buffer space, and the SO specimen had a
high shock absorption capacity without the buffer space. With the buffer space, impact
absorption improved with the amount of added GFs.
Keywords
sports dentistry - mouthguard material - orofacial injuries - composite materials
- materials testing
