| Summary: | 碩士 === 國立勤益科技大學 === 化工與材料工程系 === 95 === Micro-size optical particles of Poly (methyl methacrylate) were produced at size range of the 1-10μm by dispersion polymerization in an methanol /water mixed-dispersion medium with poly(vinylpyrrolidone) as a steric stabilizer and 2,2'-azobisisobutyronitrile as a radical initiator.
The effects of the reaction parameters on the particle size, size distribution, thermal properties and optical properties, such as the cross-linking agent concentration, media solvency (controlled by varying the amount of methanol addition), the concentration of initiator and
stabilizer were investigated.
The particle size increased with the decrease of the system’s initial solubility parameter and monomer concentration (MeOH/H2O=70/30 wt%). The appropriate increase in stabilizer concentration was a prerequisite for prepared particles without coagulated and/or odd-shaped particles. When concentration of initiator was added into the system, a notably increasingly the particle size and widely particle size distribution. Particle size and size
distribution were found to increase with increasing polymerization temperature. On the other hand, the surfeit amount of the cross-linking agent in the reaction leads to agglomerate particles itself. The investigation
of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with the particles size and distribution.
In this study, the Tg of the synthesized PMMA is about 116-121°C,which is fairly higher than that of commercial PMMA (Tg=105°C). The synthesized PMMA of 0.005-0.02wt% cross-linking agent (EGDMA) is greater than 120℃, but the higher 0.025wt% of EGDMA shall not measured with Tg. The optical property of particles was characterized employing the UV-Vis and ABBE refractometer. The macro-size optical particles the refractive index of increased with increasing concentration of optical macro-size particles at the 546nm or 589nm. However, the scatter index decreased with increasing amount of macro-size optical particles.
When 10mg of macro-size optical particles was dispersed in the methanol, the refractive index at 546nm was found to decrease from 1.3265 to 1.3283 with increasing the particles size from 1.61 to 3.97. In this research, result
shows higher of scatter index (550nm) and refractive index (546nm), when the particle size is 1.79um.
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