NEW ASPECTS OF THE EFFECT OF SIZE AND SIZE DISTRIBUTION ON THE SETTING PARAMETERS AND MECHANICAL-PROPERTIES OF ACRYLIC BONE CEMENTS

The effect of the size and the size distribution of poly(methyl methac rylate) (PMMA) beads on the classical kinetic parameters, peak tempera ture and setting time, for acrylic bone cement formulations prepared w ith PMMA particles in the range 10-60 mu m of average diameter and a r elatively wide size distribution is analysed. In addition, the combine d effects of the concentration of the free radical initiator benzoyl p eroxide and the activator N,N-dimethyl-4-toluidine for the different p article sizes are studied and compared with those of commercially avai lable formulations like CMW or Rostal. The results obtained indicate t hat the use of PMMA particles with average diameter of 50-60 mu m, and a relatively wide size distribution (10-140 mu m diameter), significa ntly changes the curing parameters (peak temperature and setting time) of the cement formulations in comparison with the classical behaviour of the commercial systems CMW and Rostal, without any noticeable loss in the mechanical properties, such as tensile strength, elastic modul i, compressive strength and plastic strain.