Polymer(Korea), Vol.21, No.5, 745-754, September, 1997
SBS Triblock Copolymer/Polybutadiene/Methyl Isobutyl Ketone 3성분계에서의 상거동 연구
The study of Phase Behavior in SBS Triblock Copolymer/Polybutadiene/Methly Isobutyl Ketone Ternary System
초록
SBS trlblock 공중합체와 polybutadiene (PBD) 및 methyl Isobutyl ketone (MIK)으로이루어지는 3성분계의 상분리 거동을 관찰하였다. Turbidimetry로 cloud point curve를 얻었고, 분리된 각 회박상과 농후상에서의 성분 고분자들의 조성을 1H-NMR로 분석하여 binodal curve를 얻었다. Cloud point 실험에서 성분 고분자 혼합물의 농도가 0∼4wt%, 그리고 PBD에 대한 SBS의 조성이 0.7에서 1 무게분율이 되는 5∼9 wt% 고분자 흔합 용액에서는 turbidity가 관찰되지 않았다. 저농도의 고분자 혼합물 용액에서 PBD에 대한 SBS의 조성이 증가할수록 cloud point 온도(Tp)는 낮아지는 경향이었고, 농도가 증가할구록 7.5∼16 ℃범위로 상승하였다. 3성분계의 phase diagram에서 상분리 온도가 증가할수록 안정 영역이 확장되었고, conjugate phase를 연결한 tie line의 기울기들이 상분리 온도와는 관계없이 PBD와 MIK가 이루는 축 방향으로 급격하게 기우는 경향을 나타내어 성분 고분자들의 MIK에 대한 친화력이 서로 다른 것임을 확인하였다. 3성분계의 Flory-Huggins 상호작용 Parameter(χ)를 온도, 농도, 고분자 혼합물의 조성및 분자량의 함수로 유도한 Einaga식을 이용하여 SBS와 PBD간의 상호작용 parameter χt23를 산출, 그 값이 0.8∼1.3의 범위에 있음을 밝혔다. 이를 근거로 SBS와 PBD는 상용성이 없는 것으로 추정하였다.
The phase separation behavior of a ternary system consisted with SBS, PBD, and MIK was studied. The cloud Point (Tp) was determined by turbidimetry and binomial curves were drawn by the data obtained from the 1H-NMR analysis for those components of the phases obtained from the phase separation experiments. The cloud point test yielded that there was no turbidity generated in the polymer concentration range 0 to 4 wt% of the solution of polymer mixture. No turbidity was observed in the polymer concentration range 5 to 9 wt% as well where the weight fraction of SBS to PBD varies from 0.7 to 1.0. The ternary system shows a lowering trend of Tp as the amounts of SBS added increased in the lower limit of concentration range of polymer mixture, but at higher concentration range the Tps are found to be elevated to the temperature range of 7.5 ∼ 16 ℃ The phase diagram obtained by the phase separation experiment reveals that the stable region is expanded as the temperature is elevated. The steep slope of the tie line inclined to the PBD/MIK axes implies that the two polymers used have different affinities to the solvent. The polymer-polymer interaction parameter χt23 found by Einaga equation lies in the range of 0.8 to 1.3, which indicates SBS and PBD are incompatible.
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