FRACTURE BEHAVIOR OF THE POLYMETHYL METHACRYLATE WITH TWO DIFFERENT CURING PROCESSES

ABSTRACT
The usage of Polymers in different fields is enormous and crucial. Polymethyl
Methacrylate (PMMA) is one of the earliest widely used polymers, and well known
around the world by a variety of trade names; Lucite, Oroglas, Perspex, Plexiglas and
acrylic resin which may vary from country to country. This material is one of the hardest
polymers, rigid and good weather resistance.
The usage of PMMA is widely spread in the medical technologies which reflected from
a good degree of compatibility with human tissue, and can be used for replacement of
intraocular lenses in the eye when the original lens has been removed in the treatment
of cataracts. In orthopaedics, PMMA bone cement is used to affix implants and to
remodel lost bone caused by traffic accident and war injures. In cosmetic surgery, tiny
PMMA microspheres suspended in some biological fluid are injected under the skin to
reduce wrinkles or scars permanently.
Parts made of PMMA have high mechanical strength and good dimensional stability.
Other reported properties include a high Young's modulus and good hardness with low
elongation at break. Therefore, PMMA was used extensively as aircraft windshields for
many aircraft (hitting a bird at 600 mph is dangerous to aircraft as it is deadly for birds).
On the other side, typical working loads during Polymers service are the loads leading
to fracture. Even though this kind of loading resistance in PMMA is important, there is a
deficiency in the literature in this area. Accordingly, covering this area constitutes very
important potential for research and study.
Therefore, the purpose of this research is to investigate the fracture behavior of PMMA.
Two methods of preparing the specimens (method of cure) will be taken into
consideration. As a result of this research, more accurate data about fracture and
mechanical properties about this widely used material in dental applications are
becoming available for dentists. Tensile, compression and fracture tests were carried
out in this study. The results showed that a slight improve in the tensile strength of the
long curing process specimens compared with short curing specimens. However, the
compressive strength of the short curing is better than long curing specimens. The
fracture test results showed that the fracture toughness of the short curing specimens is
higher than that of the long curing specimens.