Thixotropic Behavior of Hydrophobically Modified Ethoxylated Urethane-thickened Waterborne Latex †

doi:10.7503/cjcu20190606

Abstract

Abstract:

Hydrophobically modified ethoxylated urethanes(HEURs) were synthesized by preparing the prepolymers from the reaction between polyethylene glycol(PEG, M_n=4000, 6000, 8000) and isophorone diisocyanate(IPDI), and then end-capping the polymers with liner alkanols(C12, C14, C16, C18). The structure, molecular weight and polymer dispersity index(PDI) of HEUR were characterized by proton nuclear magnetic resonance( ¹H NMR), Fourier transform infrared spectroscopy(FTIR) and gel permeation chromatography(GPC) respectively, and the rheology behaviors of the HEUR-thickened latex were also studied. It was found that the rheological curve of the HEUR-thickened latex(Latex/HEUR) showed thixotropic loops when HEUR were substituted by C14, C16 and C18 and the mass fraction was more than 1.0%, indicating that these Latex/HEUR were thixotropic fluids. The location of thixotropic loops moved to low shear rate and the viscosity of Latex/HEUR dropped sharply with an increase of the ratio between the molecular weight of hydrophilic segment and that of the hydrophobic end. As the amount of HEUR increased, the thixotropic loop area(S_loop) showed the upward trend. These rheological behavior were attributed to the association, hydrogen bonding and chain entanglement of HEUR in latex. Scanning electron microscope(SEM) and atomic force microscope(AFM) were used to characterize the aggregation state and surface morphology of Latex/HEUR. The results showed that the size of Latex/HEUR particles increased and the surface became rough with the increase of the HEUR end group length.

Key words: Hydrophobically modified ethoxylated urethane, Associative thickener, Aqueous dispersion, Thixotropy, Micro morphology

CLC Number:

O631

TrendMD:

LU Man,SONG Chunmei,WAN Bo. Thixotropic Behavior of Hydrophobically Modified Ethoxylated Urethane-thickened Waterborne Latex ^†[J]. Chem. J. Chinese Universities, 2020, 41(5): 1108.

Figures/Tables 14

HEUR-P(x)	$M n, G b$	PDI	$M n, T b$	$M n, N b$
PEG4000	6900	1.05	—	—
HEUR-4(12)	9700	1.21	4816	4780
HEUR-4(14)	10000	1.15	4872	4906
HEUR-4(16)	11100	1.16	4928	4915
HEUR-4(18)	11200	1.15	4984	5042
PEG6000	10400	1.04	—	—
HEUR-6(12)	12800	1.17	6816	6563
HEUR-6(14)	13200	1.15	6872	6807
HEUR-6(16)	13500	1.14	6928	6961
HEUR-6(18)	14600	1.15	6984	7223
PEG8000	14000	1.04	—	—
HEUR-8(12)	15700	1.19	8816	8817
HEUR-8(14)	16000	1.12	8872	8848
HEUR-8(16)	17200	1.14	8928	9067
HEUR-8(18)	18100	1.15	8984	9274

HEUR-P(x)	$M n, G b$	PDI	$M n, T b$	$M n, N b$
PEG4000	6900	1.05	—	—
HEUR-4(12)	9700	1.21	4816	4780
HEUR-4(14)	10000	1.15	4872	4906
HEUR-4(16)	11100	1.16	4928	4915
HEUR-4(18)	11200	1.15	4984	5042
PEG6000	10400	1.04	—	—
HEUR-6(12)	12800	1.17	6816	6563
HEUR-6(14)	13200	1.15	6872	6807
HEUR-6(16)	13500	1.14	6928	6961
HEUR-6(18)	14600	1.15	6984	7223
PEG8000	14000	1.04	—	—
HEUR-8(12)	15700	1.19	8816	8817
HEUR-8(14)	16000	1.12	8872	8848
HEUR-8(16)	17200	1.14	8928	9067
HEUR-8(18)	18100	1.15	8984	9274

L/H-P(x)	w[HEUR-P(x)](%)	W_loop/s^-1	S_loop/(MPa·s^-1)	η₁(4 s^-1)/(mPa·s)	η₂(200 s^-1)/(mPa·s)	Δη ^b(%)
Latex	0	—	—	3.34	3.27	7
L/H-8(14)	1.5	—	—	7400	4580	38.1
	2.0	147	0.72	13600	7310	46.2
	2.5	131	3.93	20500	10400	49.3
	2.8	127	6.20	24500	12100	50.6
L/H-8(16)	1.5	61	3.56	15700	4180	73.4
	2.0	41	5.36	29100	6190	78.7
	2.5	28	12.04	47400	8030	83.1
L/H-8(18)	1.0	49	0.94	10600	2220	79.1
	1.3	24	2.04	23800	3480	85.4
	1.5	16	3.28	35100	4260	87.9

L/H-P(x)	R_h	w[HEUR-P(x)](%)	W_loop/s^-1	S_loop/ (MPa·s^-1)	η₁(4 s^-1)/ (mPa·s)	η₂(200 s^-1)/ (mPa·s)	Δη(%)
Latex	—	0	—	—	3.34	3.27	7
L/H-8(14)	18.7	2.5	131	3.93	20500	10400	49.3
L/H-6(14)	14.0	2.5	94	15.03	19300	7890	59.1
L/H-4(14)	9.3	2.5	57	7.99	12200	4460	63.4
L/H-8(16)	16.5	1.5	61	3.56	15700	4180	73.4
L/H-6(16)	12.4	1.5	53	3.69	13000	3380	74.0
L/H-4(16)	8.3	1.5	52	4.35	17400	2380	86.3
L/H-8(18)	14.8	1.5	16	3.28	35100	4260	87.9
L/H-6(18)	11.1	1.5	16	3.95	31500	3650	88.4
L/H-4(18)	7.4	1.5	8	4.08	22900	2370	89.6

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