SEBS對聚苯乙烯超臨界發泡之影響

The Influence of Styrene-Ethylene-Butylene-Styrene Block Copolymer on the Foaming of Polystyrene under CO2 Supercritical Conditions

陳佳瑜(Chia-Yu Chen)

指導教授 ： 王賢達 ； 翁彰明

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2008年)

摘要

本研究利用超臨界二氧化碳為發泡劑來探討四種聚苯乙烯（PS）與不同比例之苯乙烯-乙烯-丁烯-苯乙烯團塊共聚物（SEBS）之混合物，在不同的發泡溫度及不同的發泡壓力下，對於發泡體密度、發泡體外觀與發泡體結構之影響。此四種PS樹脂包括了三種一般性PS（GPPS）和一種耐衝擊性PS（HIPS）。實驗結果顯示四種PS含SEBS會造成PS的玻璃轉化溫度（Tg）下降，尤其PS含2phr SEBS時下降最明顯。但隨著SEBS含量的增加，在本研究中添加5phr、7phr和10phr SEBS時，對四種PS的Tg沒有再明顯的下降，反而有持平的現象。
在低的發泡溫度與發泡壓力下，例如低於發泡溫度120℃和低於發泡壓力2000psi時，可使四種PS/SEBS發泡體具有良好的外觀；而高的發泡溫度與發泡壓力，會使四種PS/SEBS發泡體的外觀變差和表面破裂，例如發泡溫度135℃以上和發泡壓力4000psi時。四種PS/SEBS發泡體的最低發泡密度則發生在發泡壓力為2000~3000 psi、發泡溫度為130~135℃左右，其最低發泡密度約為0.03g/cm3左右。而HIPS/SEBS發泡體比GPPS/SEBS發泡體對發泡溫度與發泡壓力較敏感，且能獲得發泡體最低發泡密度的範圍較狹窄。發泡壓力越大時，發泡體的氣泡平均泡徑會越小。當四種PS中添加SEBS可增強PS的韌性，降低四種PS/SEBS發泡體表面的破裂現象，且由於SEBS的添加可獲得開孔性氣泡結構之發泡體。分子量大的GPPS含SEBS比分子量小的GPPS含SEBS較容易得到表面良好且平坦的發泡體。

關鍵字

聚苯乙烯 ； 苯乙烯-乙烯-丁烯-苯乙烯團塊共聚物 ； 超臨界發泡 ； 二氧化碳

並列摘要

This work studied the foam density, foam appearances and foam structure of four polystyrene（PS）resins blended with styrene-ethylene-butylene-styrene block copolymer（SEBS）at various ratios under different foaming temperatures and foaming pressure. Carbon dioxide was used as a foaming agent. The four PS resins contained three general- purpose PS（GPPS）resins and one high-impact PS（HIPS）resins. When four PS resins were blended with SEBS, the glass transition temperatures（Tgs）of four PS/SEBS apparently decreased, especially the Tgs of four PS resins with 2phr（per hundred resin）SEBS. As the content of SEBS increased in four PS resins such as PS/5phr, 7phr and 10phr SEBS, the Tgs of four PS/SEBS did not further reduce and were similar to the Tgs of four PS/2phr SEBS.
Four PS/SEBS foams had a good appearance at the low foaming temperatures such as below 120℃ and low foaming pressure such as below 2000psi . Four PS/SEBS foams displayed a poor appearance and many cracks on the surface at the high foaming pressure and the high foaming temperature, for example, the foaming temperature above 135℃ and the foaming pressure at 4000psi. The lowest foam density of four PS/SEBS foams occurred at the foaming pressures between 2000 psi and 3000 psi and the foaming temperatures ranging from 130 to 135℃. The lowest foam density was about 0.03g/cm3 under the aforementioned foaming conditions. HIPS/SEBS foams were more sensitive to foaming temperature and foaming pressure than GPPS/SEBS foams. The range of the low foam density for HIPS/SEBS foams was much narrower than that for GPPS/SEBS foams. Small cell size could be obtained for four PS/SEBS foams at the high foaming pressure. When SEBS was added to four PS resins, open-cells structures for four PS/SEBS foams are obtained and the enhancement of toughness in four PS/SEBS resins were observed with the reduction in cracks of four PS/SEBS foams. GPPS with a high weight average molecular weight（Mw） exhibited a better foam surface appearance after foaming than PS with a low Mw.

並列關鍵字

Polystyrene ； Styrene-Ethylene-Butylene-Styrene block Copolymer ； Supercritical foam ； Carbon dioxide

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