Preparation of high solid content glass particle-polymethacrylate composite by an advance wetting method
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Preparation of high solid content glass particle-polymethacrylate composite by an advance wetting method Yi Hong Wu, Siva Jada, and Ren Xu Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (Received 9 January 1997; accepted 28 April 1997)
An advanced wetting method is used to prepare a composite with a high content of ceramic particles in a matrix of photocured polymethylmethacrylate. The method allows for the preparation at minimum stirring of high quality samples with up to 59% solid in volume. The samples present reasonable flow characteristics prior to curing, with high hardness and fracture toughness in the fully cured state. Practical implications of the preparation method for dental restorative applications are studied. The method is also useful in the preparation of similar composites for other practical applications.
I. INTRODUCTION
Ceramic particle-polymer matrix composites are routinely used for dental restorative applications. A typical preform paste of such composites consists of barium-sodium, alumino-borosilicate, glass-ceramic (ionomer glass) particles in liquid methylmethacrylate. A small amount of polymerization inhibitor such as hydroquinone is usually present for desired shelf time, and a small amount of coupling agent methacrylated siloxane such as a 3-(trimethoxysilyl)propyl methacrylate (g-MPS) is used for better particle-matrix bonding.1–3 Recently, some interest was shown in the elastic and fracture behavior of particulate composites,4,5 as well as electrical conduction of coatings of semiconducting particles-polyacrylic acid composite.6 A kinetic model was developed to account for the particle aggregation in a liquid medium.7 In practice, it is advantageous to incorporate a high volume of ceramic particles for higher hardness and lower shrinkage in the composite. A coupling agent enhances the fracture toughness of the composite. High solid composites with good interfacial coupling, however, are difficult to prepare. Agglomeration of particles is usually observed during mixing even with the best silanated powder. Air bubbles tend to be trapped between particles. Capillary forces further stabilize the bubbles and increase the difficulty in their removal even in vacuum. Consequently, due to the high viscosity of the paste at high solid content, breaking up the agglomerates becomes extremely difficult. On one hand such difficulty limits weight percent solid incorporated in the paste; on the other hand, it puts high demands on the power and capacity of the mixing equipment, and ultimately raises the production cost. On a laboratory scale, such preparation of higher solid content preforms has been reported, where a prewet emulsion is diluted on-site for the subsequent application to the cavity.8 There has not been, however, a systematic 1204
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 5, May 1998
Downloaded: 31 Mar 2015
investigation of the preparation of preform mixtures with a wide
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