Percolating Behavior of Solid Bimodal (Polymethylmethacrylate + Inert) Particle Packings during Polymerization
✍ Scribed by Stefano A. Mezzasalma
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 190 KB
- Volume
- 195
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
chains have been the subject of interesting analyses (1-4, 8-A percolation-based thermodynamical model was able to predict 14) in which relationships between physics/chemistry and the break-down of bimodal PMMA / I solid particle packings geometry seem to be evident. (P-MMA, polymethylmethacrylate; I, solid phase inert to MMA In this paper it is shown that the application of percolation polymerization) due to the polymerization process of the MMA theory is a powerful method for predicting the breakdown monomers. By slip casting of biphasic PMMA / I aqueous suspenof biphasic solid particle packings-involving agglomerates sions, homogeneous samples of polymethylmethacrylate and variof polymethylmethacrylate (PMMA) and of another solid ous inert solid aggregates (I Å Ca 3 (PO 4 ) 2 , ZrO 2 , Si 3 N 4 , and Al 2 O 3 )
were prepared and embedded in liquid methylmethacrylate to start constituent inert to MMA polymerization-due to the conthe kinetics of the network formation. For any I component, breakversion of prepolymerized aggregates into a polymeric netdown of samples did not occur in well defined PMMA mass conwork, namely, due to the polymerization process. Instead of centration ranges, which were strongly related to the signs of following all dynamical evolution, one can deal (thermody-PMMA and I surface charges (i.e., isoelectric points) of the aquenamically) with a percolation state in the bimodal system, ous solid monodispersed systems. As application of percolation which can be assumed on the basis of experimental results.
theory in composite materials suggest, when the samples resisted
In fact, for certain values of the solid PMMA mass/volthe polymerization kinetics the occurrence of a percolative behavume concentration, samples of the aforesaid particle packior was expected. Accordingly, the model was performed by dealing thermodynamically with the physicochemical features of the ings (prepared with slip casting techniques) were so strongly starting aqueous suspensions (e.g., adsorption from solution at the connected that the polymerization-induced breakdown did solid/liquid interface and solid agglomeration) at the percolation not occur. Therefore, (a) interpreting the point of maximum threshold in bicontinuous PMMA / I systems during the progress rigidity in the framework of the percolation theory and (b) in the polymerization reaction. Thresholds have been regarded as expressing the implied geometrical quantities according to percolation of cubic units and related to the sign of the solid known scaling laws, it was sufficient to focus the percolation PMMA and I surface charge in aqueous monodispersed systems, threshold only for describing the observed critical behavior.
namely, to the attractive, neutral, repulsive character of the elec-On the other hand, it is not evident if the processing of trostatic interparticle forces. Once site percolation thresholds were correctly estimated it was shown that the assumption of percola-the starting solid powders, here employed to prepare and to tion is compatible with the theoretical model when the solid slip-cast aqueous dispersions, can influence the network/ PMMA mass concentration values are ranging just in the critical particle packings kinetics (3). To deal with this question is ranges experimentally obtained. ᭧ 1997 Academic Press a tough task strongly ruled by the effect of complex solid Key Words: solid bimodal packing; percolation theory; particle agglomeration/deagglomeration mechanisms (3, 15-24) on surface charge; thermodynamics; PMMA; tricalcium phosphate; polymerization in an array of obstacles (25), and it is not silicon nitride; alumina; zirconia; isoelectric point. the purpose of this paper to answer exhaustively. Nevertheless, from a heuristic point of view, a qualitative relationship between starting powder processing and percolating behav-