水性乳液/聚氨酯模型缔合增稠剂的触变性机理

doi:10.7503/cjcu20190606

摘要/Abstract

摘要：

以异佛尔酮二异氰酸酯(IPDI)与聚乙二醇(PEG, 分子量为4000, 6000和8000)为原料, 以直链醇(C12, C14, C16和C18)为封端剂, 合成了疏水改性乙氧基化氨基甲酸酯(HEUR), 并将其应用于乳液增稠. 采用核磁共振波谱(¹H NMR)、傅里叶变换红外光谱(FTIR)及凝胶渗透色谱(GPC)表征了HEUR的结构、分子量及其分布, 研究了其在水性乳液中的流变行为. 研究结果表明, 当HEUR封端基团为C14, C16和C18, 且质量分数增加到1.0%以上时, 增稠的乳液(Latex/HEUR)的流变曲线出现触变环, 为触变性流体. 当HEUR亲疏水比值(R_h)减小时, 疏水性增强, 触变环向低剪切速率( $γ ˙$ )方向移动, 黏度下降率(Δη)增大; 当HEUR用量增加时, 触变环面积(S_loop)也增大. 这些触变性特点归因于HEUR在乳液中的缔合作用、氢键作用及链缠结. 利用扫描电子显微镜(SEM)和原子力显微镜(AFM)对Latex/HEUR的聚集态和表面形貌进行了表征. 结果表明, 随着HEUR封端基团链长增加, Latex/HEUR颗粒粒径增大, 表面变粗糙.

关键词: 疏水改性乙氧基化氨基甲酸酯, 缔合增稠剂, 水分散液, 触变性, 微观形貌

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

中图分类号:

O631

TrendMD:

陆曼,宋春梅,万波. 水性乳液/聚氨酯模型缔合增稠剂的触变性机理. 高等学校化学学报, 2020, 41(5): 1108.

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

图/表 14

Scheme 1 Synthetic route of HEUR-P(x) polymers

Table 1 GPC characterization of HEUR-P(x) polymersa

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

Table 1 GPC characterization of HEUR-P(x) polymersa

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

Fig.1 FTIR spectra of HEUR-P(x) polymers with different hydrophilic length(A) and different hydrophobic length(B) (A) a. HEUR-4(12); b. HEUR-6(12); c. HEUR-8(12); (B) a. HEUR-8(14); b. HEUR-8(16); c. HEUR-8(18).

Fig.2 1H NMR spectrum of HEUR-8(16) Inset: Zoom in on the chemical shift of —NH— labeled as i.

Table 2 Rheological properties of Latex/HEUR under different hydrophobicity

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

Scheme 2 Schematic diagram of thickened mechanism in Latex/HEUR(A) and the break and rebuild processes of Latex/HEUR under the shear press(B)

Fig.3 Storage modulus(G', a) and loss modulus(G″, b) dependence on strain for L/H8-(12)(A), L/H-8(14)(B), L/H-8(16)(C) and L/H-8(18)(D) under the concentrations of 4.0%(A), 2.8%(B), 2.5%(C) and 1.5%(D) at 23 ℃

Fig.4 Rheology hysteresis up(a—e) and down(a'—e') curves of L/H-8(x) under the concentrations of 0.5%(A) and 1.0%(B) a, a'. L/H-8(12); b, b'. L/H-8(14); c, c'. L/H-8(16); d, d'. L/H-8(18); e, e'. Latex.

Fig.5 A model diagram of thickened mechanism of HEUR-P(x) at different mass fractions (A) w<0.5%; (B) 1.0%<w<1.5%; (C) w>1.5%.

Fig.6 Rheology hysteresis up(a—c) and down a'—c') curves of L/H-P(x) under different concentrations(w) of L/H-8(12)(A), L/H-8(14)(B), L/H-8(16)(C), L/H-8(18)(D)

Fig.7 Rheology hysteresis up(a—c) and down a'—c') curves of L/H-P(x) with x=12(A), 14(B), 16(C), 18(D) under the concentration of 3.0%(A), 2.5%(B), 1.5%(C) and 1.5%(D)

Table 3 Rheological properties of Latex/HEUR under different hydrophilicity

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

Fig.8 SEM images of Latex and L/H-P(x) at the concentration of 1.5% (A) Latex; (B) L/H-8(12); (C) L/H-8(16); (D) L/H-8(18).

Fig.9 AFM images(A—D) and particle sizes(A'—D') of Latex(A, A') and L/H-8(x)(B—D, B'—D') at the concentration of 1.5% (A, A') L/H-8(12); (B, B') L/H-8(12); (C, C') L/H-8(16); (D, D') L/H-8(18).

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