Biomedical subjects

A G Andreopoulos

Publications and source records attributed to A G Andreopoulos.

6 recordsLinked to original sources

PubMed1991

Surface treated polyethylene fibres as reinforcement for acrylic resins.

The use of poly(methyl methacrylate) as a bone and dental cement material over several decades has provided us with experience related to processing and performance. A recognized disadvantage of such cements is their mechanical behaviour, expressed by low crack propagation resistance, impact strength, fatigue resistance and reduced fracture toughness. Many attempts have been made to resolve these problems either by modifying the poly(methyl methacrylate) chemical structure via copolymerization or incorporating reinforcing additives. The latter is of great importance, because it can lead to the preparation of composite materials with considerably improved performance. Besides reinforcement, the incorporation of additives, such as fibres, results in better processing characteristics, e.g. lowers polymerization exotherm. In this work, poly(methyl methacrylate) reinforced with Tekmilon ultra high modulus polyethylene fibres was studied, focussing on the interfacial bonding between matrix and reinforcement. Some finishing agents were used to treat the fibres and their efficiency was mainly evaluated through the effect on the mechanical properties of the composite material prepared.

Acrylic Resins↗

PubMed1991

Repairs with visible light-curing denture base materials.

Visible light-curing interpenetrating networks are newly developed materials suitable for several dental applications. These materials have several advantages, including versatility and good physicomechanical properties, but also present some weaknesses, such as increased water sorption and poor adhesion to plastic teeth. The suitability of a visible light-curing resin as a repair material, ie, its bending strength, was examined. Results were compared to those obtained with a self-curing acrylic resin. The visible light-curing resin led to repairs with lower strength.

Acrylic Resins↗

PubMed1989

Gel content determination in cross-linked polyethylene.

Gel content is the dominating parameter which affects properties and prescribes the behaviour of a given type of cross-linked polyethylene. Researchers have determined the gel content by several methods based on solvent extraction, a process which dissolves the linear thermoplastic polymer but swells only the cross-linked fraction. In this work, a comparative evaluation was made using model samples to select the most effective solvents and the suitable extraction conditions leading to increased reliability.

Gels↗

PubMed1989

Properties of poly(2-hydroxyethyl acrylate) networks.

Hydrogels, based on poly(2-hydroxyethyl acrylate) cross-linked with 1,4 butanediol dimethacrylate, were studied in respect to their swelling and mechanical behaviour. The determination of Young's modulus at r.t. permitted the calculation of average molecular weight between cross-links. This value could, in turn, be correlated with water-swelling data to give indicative values of the interaction parameter for the system poly(2-hydroxyethyl acrylate)-water.

Absorption↗

PubMed1987

Diffusion characteristics of alginate membranes.

The diffusive properties of alginate membranes prepared by the interfacial reaction of sodium alginate solution with gypsum substrates were studied. The penetrants of primary importance for the above study were methyl methacrylate (MMA) and water, since alginate membranes are used as mould release agents, during the casting of poly(methyl methacrylate) (PMMA) in gypsum moulds in a water bath. Vapour sorption measurements were carried out at various temperatures. The effect of temperature and the combined action of water and MMA on the swelling behaviour of the membrane was also investigated. The results indicate that the water sorption of alginate membranes is non-Fickian, in spite of the linearity of the curves obtained by plotting Mt/M infinity versus t 1/2, at least for a short time period. The membrane treatment with methyl methacrylate, leads to considerably lower equilibrium sorption, possibly because of the formation of a thin film of poly(methyl methacrylate) on the membrane surface.

Alginates↗

PubMedDate not supplied

The effect of bonding agents on the bond strengths of facial silicone elastomers to a visible light-activated resin.

Three bonding agents were evaluated to determine their effect on the strength of the bond when Silskin II and Cosmesil SM4 silicone facial elastomers were polymerized to a light-activated denture resin. A silane bonding agent proved to be superior, whereas a light-activated bonding agent had inferior bonding characteristics. Intensive heat aging had no significant effect on bond strength.

Acrylic Resins↗