Preparation of Styrene-isoprene-styrene Thermoplastic Elastomer by Three Times Feeding Method of Reactive Extrusion†

doi:10.7503/cjcu20140776

Abstract

Abstract:

Styrene/isoprene/styrene(SIS) triblock thermoplastic elastomer was polymerized by three times feeding method using a co-rotating intermeshing twin screw extruder as the reactor and n-butyllithium as the initiator. ¹H NMR spectra show that the polyisoprene block of the copolymer is mainly composed of 1,4-polyisoprene structure. The molecule chains of the copolymers were degraded using hydrogen peroxide catalyzed by osmium tetroxide, the segments of polystyrene after oxidization were characterized by gel permeation chromatography(GPC) cooperating with the multi-angle laser light scattering(MALLS) instrument. It was found that the copolymers consisted of polystyrene-polyisoprene-polystyrene(PS-PI-PS) three blocks. Cooperated with the survey of dynamic mechanical analysis(DMA) and transmission electron microscope(TEM) photographs, it was confirmed that styrene/isoprene/styrene(SIS) had two phase separation structure. Tensile testing showed the relationship between tensile strength of the copolymer with styrene content.

Key words: Anionic polymerization, Reactive extrusion, Three times charging method, Thermoplastic elastomer, Styrene/isoprene/styrene triblock copolymer

CLC Number:

O632.1

TrendMD:

SHAN Dong, YANG Long, WANG Jiming, ZHENG Anna. Preparation of Styrene-isoprene-styrene Thermoplastic Elastomer by Three Times Feeding Method of Reactive Extrusion^†[J]. Chem. J. Chinese Universities, 2014, 35(12): 2698.

Figures/Tables 13

Scheme 1 Syntheses routes of the polymerization

Table 1 Protons distribution of SIS

Chemical shift, δ	Relative proton	Chemical shift, δ	Relative proton
7.05	Phenylic meta and para	4.68, 4.76	3,4-Ip
6.55	Phenylic ortho	1.68	cis-1,4 methyl
5.13	1,4-Ip	1.60	trans-1,4 and 3,4 methyl

Fig.1 1H NMR spectra of SIS-0328(a) and SIS-1209(b)

Table 2 Chemical shift(δ) of H and the computing method of the mass fraction

δ	Peak area	Double bond structure	Mass fraction of monomer
6.25—7.15	A₁	Isoprene	$68 × [A 3 + (1 / 2) A 4] 68 × [A 3 + (1 / 2) A 4] + 104 × (1 / 5) A 1$
1.64—1.72	A₂	3,4-Ip	A₄/(2A₃+A₄)
4.97—5.22	A₃
4.63—4.78	A₄	cis-1,4-Ip	A₂/(A₂+A₅)
1.56—1.64	A₅	trans-1,4-Ip	[A₅/(A₂+A₅)]-[A₄/(2A₃+A₄)]
6.25—6.75	A₆	Random-St	(A₁-A₆)/A₁

Table 2 Chemical shift(δ) of H and the computing method of the mass fraction

δ	Peak area	Double bond structure	Mass fraction of monomer
6.25—7.15	A₁	Isoprene	$68 × [A 3 + (1 / 2) A 4] 68 × [A 3 + (1 / 2) A 4] + 104 × (1 / 5) A 1$
1.64—1.72	A₂	3,4-Ip	A₄/(2A₃+A₄)
4.97—5.22	A₃
4.63—4.78	A₄	cis-1,4-Ip	A₂/(A₂+A₅)
1.56—1.64	A₅	trans-1,4-Ip	[A₅/(A₂+A₅)]-[A₄/(2A₃+A₄)]
6.25—6.75	A₆	Random-St	(A₁-A₆)/A₁

Table 3 Microstructure and its content of SIS-0328 and SIS-1209

Compd.	Mass fraction(%)
Compd.	Ip	cis-1,4-Ip	trans-1,4-Ip	3,4-Ip
SIS-0328	60.9	64.6	27.9	7.5
SIS-1209	70.8	65.2	26.0	8.8

Scheme 2 Mechanism of the oxidative reaction

Fig.2 GPC curves of SIS-0328(a) and SIS-1209(b) before(A) and after degradation(B)

Table 4 GPC data for SIS-0328 and SIS-1209 before and after degradation

Sample	Before degradation		After degradation
			First peak		Second peak
	10^-4M_n	M_w/M_n	10^-4M_n	M_w/M_n	10^-3M_n	M_w/M_n
SIS-1209	9.3	1.0	1.4	1.4	4.7	2.2
SIS-0328	11.0	1.8	3.1	2.0	14.6	1.6

Fig.3 TEM images of SIS-0328(A) and SIS-1209(B)

Fig.4 Effect of loss factor of SIS-0328(a) and SIS-1209(b) on temperature

Fig.5 Loss modulus(A) and storage modulus(B) of SIS-0328(a) and SIS-1209(b) on temperature

Fig.6 Tensile strength tests for SIS-0328(a) and SIS-1209(b)

Table 5 Physicomechanical properties of SIS-1209 and SIS-0328

Sample	Maximum tensile strength/MPa	Maximum ultimate elongation(%)	300% Stretching strength/MPa
SIS-1209	13.0	1860	2.2
SIS-0328	12.2	1197	5.8

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