- Published: Friday, 14 October 2011 08:11
Synthetic polymer moulds are made from porous poly(methyl methacrylate) (PMMA), produced by polymerising methyl methacrylate (MMA) from an MMA-in-water emulsion into which pre-formed PMMA beads are dispersed. The present PhD project has shown that the composition of the emulsion dramatically affects the final properties of the material. Control of the emulsion stage of the reaction allows for tuning of the porous PMMA properties, enabling porosity and strength to be tailored. The overall objective of the PhD research is to probe the fundamental chemistry underlying the preparation of porous PMMA materials in order to facilitate a scientifically-based rationale for their design.
Pore Size: about 50 microns upwards with overall porosity of 30–35 %. PMMA Bead size: about 90 microns in diameter. We estimate that the ligaments will be about 10–40 microns in diameter and 1–10 microns in thickness.
Sample & Safety
Samples of porous PMMA were X-rayed using the Nikon Custom Bay scanner (45 kV, 171 ?m) to aid in the visualisation of the internal bridging ligaments.
Samples of porous PMMA were X-rayed using the Nikon Custom Bay scanner (45 kV, 171 ?m). The differences in the formulation from the standard blend are detailed below:
- Linear alkyl ethoxylate surfactant at high and low levels of MMA
- Octyl phenol surfactant at high and low level of MMA
- Octyl phenol surfactant at high and low surfactant concentrations
- Linear alkyl ethoxylate surfactant at high and low surfactant concentrations
- Increase in bead molar mass to 2.5MW.
- Substitution of MMA monomer by styrene in polymerisation
Once reconstructed and analysed, the porosity of the materials was determined using segmentation. In all cases the porosity value obtained from x-ray tomography differed from those previous obtained using water uptake techniques. As X-ray tomography includes both open and closed pores, further analysis is now being undertaken to segment the samples to segregate the different pore types within the material.
The results enabled the 3D visualisation of the materials indicating higher porosity than previous though and a number of features only partially visible with alternative techniques, including large holes in the samples and variation of porosity through the layers.
However, visualisation of the ligaments and calculation of the volume of ligaments has not yet been achieved due to considerable difficultly in segmenting the materials without crude assumptions. It is hoped further analysis of the scans may lead to further output from the initial data including modelling the flow rate through the pores as well as the continuation of work on porosity and ligament analysis.