Effects of coupling agents on the properties of poly (methyl methacrylate) /hydroxyapatite composites for denture base application
Loading...
Date
2011
Authors
Wei Ling, Tham
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Poly( methyl methcrylate) (PMMA) composites containing 5 wt% hydroxyapatite
(HA) was prepared by using heat-processing polymers powder and liquid method. In
phase 1, both PMMA and HA powder were grounded using planetary ball milling.
The effects of the grinding time and particle size of the PMMA/HA powder on the
flexural properties and morphology of the composites was investigated. The suitable
grinding time is 90 min. For the planetary ball mill-ground PMMA/HA powder, the
flexural modulus of the respective PMMA composites was slightly increased.
Planetary milling is capable of increasing the surface area of fine particles in the
composites specimens, which resulted in a more homogeneous distribution of HA
and a reduction of void contents in PMMA matrix. This phenomenon was evidenced
by field emission scanning electron microscopy (FESEM). In phase 2, HA was
surface treated with three types of coupling agent, i.e., silane coupling agent, titanate
coupling agent and zirconate coupling agent with different concentrations based on
HA (2, 4, 6, and 8%). The chemical treatment of HA was examined using fourier
transform infrared spectroscopy (FTIR). The mechanical properties of PMMA/5HA
composites were characterized using tensile, 3-point bending flexural and fracture
toughness tests. The improvement of the mechanical properties could be related to
the enhancement of interfacial interaction between PMMA and HA by the surface
treatment of coupling agents which can be evidenced by FESEM and energy
dispersive X-ray (EDX). The thermal properties of PMMA/5HA composites were
evaluated using dynamic mechanical thermal analysis (DMT A), differential scanning
calorimetry (DSC) and thermogravimetry analysis (TGA). The thermal properties of
PMMA/HA composite was increased significantly by the y-MPS treatment. In phase
3, the kinetics of water absorption and simulated body fluid (SBF) absorption and
their effects on the flexural properties for PMMA/HA composites was studied for an
immersion period of 2 months. The mathematical treatment used in analyzing the
data was the single free phase model of diffusion, which assumed Fickian diffusion
and utilized Fick's second law of diffusion. The kinetics of water absorption and
SBF absorption of the PMMA/HA composites conformed to Fickian law behavior,
whereby the initial moisture absorption follows a linear relationship between the
percentage weight gain at any time t and tl/2, followed by saturation. For X-ray
evaluation test, it was found that the radiopacity behaviour of the PMMA/HA was
improved by the coupling agent treatment. In overall, PMMAJHA composite treated
with y-MPS can achieved a balance of properties in term of mechanical, thermal,
water barrier and radiopacity behavior in which make it suita.ble for denture base
application.
Description
Keywords
Poly (methyl methcrylate) , Denture base , Coupling agents