| 摘要: | 本研究以二階段溶脹法(Two-Step Swelling)來製備粒徑大於6 μm且具有高交聯結構之均一粒徑微米球。3.30 μm均一粒徑聚苯乙烯(PS)微米球種子可從分散聚合法(Dispersion Polymerization)來合成。
首先探討在二階段溶脹聚合法中，添加單體苯乙烯(Styrene)或甲基丙烯酸甲酯(MMA)來製備PS/PS或PS/PMMA的可行性，由結果得知只有MMA能溶脹成均一粒徑之大粒子。當添加5.0 wt% 穩定劑 (PVA)、1.0 wt% 起始劑(BPO)、0.1 g助溶脹劑(環己烷)、0.2 g水相抑制劑(亞硝酸鈉)及8 g單體可得到均一粒徑且粒徑大小為6.67 μm之PS/PMMA微米球。
接下來在二階段溶脹聚合法中添加單體與交聯劑來製備PS/P(MMA-co-EGDMA)微米球，探討穩定劑(聚乙烯醇
PVA)、起始劑(過氧化二苯甲醯
BPO)、助溶脹劑(環己烷)、水相抑制劑(亞硝酸鈉)、單體(MMA)與交聯劑(二甲基丙烯酸乙二醇酯
EGDMA)之含量對微米球之均一性、型態、粒徑大小、耐溶劑性與耐熱性之影響。
結果顯示添加適量PVA(2.5 wt%)、環己烷(0~0.1 g)、亞硝酸鈉(0.2 g)有助於微米球之均一性。而當1.0 wt% BPO時，所得粒子因轉化率不完全造成表面凹陷，當BPO濃度增加為1.5 wt%時，可改善粒子表面凹陷問題，同時調整反應速率，可得平滑表面之微米球。
當EGDMA濃度為20 wt%時，隨著總單體(MMA+EGDMA)添加量增加能使溶脹微米球粒徑隨之增加。在總單體添加量為 5 g時，可得到均一粒徑且粒徑脹大(7.07 μm)為原始種子2倍以上之PS/P(MMA-co-EGDMA)微米球。另一方面，當EGDMA濃度增加也能使溶脹之微米球粒徑隨之增加，在EGDMA濃度為50 wt%而總單體添加量為6 g時，可得到粒徑將近原始種子三倍(9.48 μm)之PS/P(MMA-co-EGDMA)微米球。
經過耐THF溶劑的測試，可發現本研究所製備之EGDMA濃度大於20wt%之PS/P(MMA-co-EGDMA)高分子微米球確實具有良好的耐THF溶劑性質。由TGA結果顯示導入MMA與EGDMA之交聯高分子微米球之耐熱性質不如PS種子，但是微米球之10 wt%熱重損失下溫度(Td10)為255℃，遠大於其加工溫度。
Highly cross-linked and more than 6 ?m monodisperse microspheres have been fabricated by two-step swelling polymerization. Polystyrene (PS) seed particle (3.30 ?m and Cv 2.50 %) was prepared by dispersion polymerization.
At first, styrene (St) or methyl methacrylate (MMA) were added in the PS solution to investigate whether monodisperse PS/PS and PS/PMMA were prepared or not. The result showed only monodisperse PS/PMMA could be prepared in the two-step polymerization. The monodisperse 6.67 μm PS/PMMA microsphere could be prepared by adding 5.0 wt% stabilizer (polyvinyl alcohol
PVA), 1.0 wt% initiator (benzoyl peroxide
BPO), 0.1 g swelling agent (cyclohexane), 0.2 g inhibitor (NaNO2) and 8 g monomer (MMA) in the 0.1 g PS seed solution.
Then the effects of amount of PVA, BPO, cyclohexane, NaNO2, MMA and ethylene glycol dimethylacrylate (EGDMA) on the particle size, particle size distribution, solvent resistance, and thermal stability of PS/P(MMA-co-EGDMA) microsphere were discussed.
The results showed that the monodisperse PS/P(MMA-co-EGDMA) microsphere could be obtained by adding suitable amount of PVA (2.5 wt%), cyclohexane (0 or 0.1g), and NaNO2 (0.2 g) in 0.1 g PS seed solution. And these microspheres had uniform shape when the weight fraction of BPO was increased to 1.5 wt%.
When the weight fraction of EGDMA was fixed to 20 wt%, with increasing total amount of MMA and EGDMA, the particle size was increased. PS/P(MMA-co-EGDMA) monodisperse microsphere with 7.07 ?m size was obtained by adding 5 g total amount of MMA and EGDMA. On the other hand, when the total amount of MMA and EGDMA was fixed to 6 g, with increasing the weight fraction of EGDMA, the particle size was increased. The PS/P(MMA-co-EGDMA) monodisperse microsphere with 9.48 ?m was prepared by adding 50 wt% EGDMA.
The PS/P(MMA-co-EGDMA) particles with more 20 wt% EGDMA had excellent performance on solvent resistance. TGA results showed PS/P(MMA-co-EGDMA) suppressed the thermal stability of PS. So, introducing MMA or EGDMA to the system decreased the thermal stability of PS. But the temperature of 10 wt% loss (Td10) for PS/P(MMA-co-EGDMA) is 255 ℃, above the processing temperature. |
