纳米木质素/二氧化硅基微胶囊的制备及在自愈合涂层中的应用

doi:10.7503/cjcu20190045

摘要/Abstract

摘要：

利用磷酸化改性木质素/二氧化硅复合纳米颗粒(PAL/SiO₂)作为壁材包埋活性组分异佛尔酮二异氰酸酯(IPDI)制备微胶囊(PAL/SiO₂-IPDI). 通过加入少量反应活性更高的聚合多甲基多二异氰酸酯(PMDI), 与水反应形成聚脲, 以增加微胶囊的壁厚. 采用光学显微镜、扫描电子显微镜(SEM)和激光粒度分析仪(DLS)研究了PAL/SiO₂复合纳米粒子掺杂量, 水油比和剪切速率对微胶囊表面形貌、粒径和壁厚的影响. 结果表明, 所制备的微胶囊呈现规整球形, 壁厚为2.36~3.50 μm, 平均粒径为40.3~201.5 μm. IPDI作为芯材包埋在微胶囊中, 芯材含量约为82.8%. 将制备的PAL/SiO₂-IPDI微胶囊添加到环氧树脂中得到自愈合环氧树脂涂层. 其在高盐浓度溶液中的抗侵蚀测试结果显示, 添加质量分数4%的PAL/SiO₂-IPDI微胶囊的环氧树脂涂层在划破后能够快速愈合, 显著降低基底的腐蚀电流和腐蚀速率. 纳米压痕实验表明, 环氧涂层的硬度为249.99 MPa, 而添加PAL/SiO₂-IPDI微胶囊后硬度增加到302.98 MPa, 弹性模量也有提高.

关键词: 木质素, 二氧化硅, 复合纳米颗粒, 微胶囊, 自愈合涂层

Abstract:

Phosphorylated lignin/silica nano composites(PAL/SiO₂) were used as shell material to encapsulate active isophorone diisocyanate(IPDI) to prepare microcapsules(PAL/SiO₂-IPDI). A small amount of polymeric methane diisocyanate(PMDI) with more reactivity was added to react with residual water to form polyurea, which could effectively increase the wall thickness of the microcapsules and improve the stability of the system. The effects of PAL/SiO₂ nano composite content, water-oil ratio and shearing rate on the morphology, particle size and wall thickness of microcapsules were studied by optical microscopy(OM), scanning electron microscopy(SEM) and dynamic light scattering(DLS). The results show that the prepared PAL/SiO₂-IPDI microcapsules were spherical with a wall thickness of 2.36—3.50 μm and an average diameter of 40.3—201.5 μm under optimum preparation conditions. Fourier transformed infrared spectroscopy(FTIR) and thermogravimetric analysis(TGA) revealed that the healing agent IPDI was successfully embedded as a core material in the microcapsules with a content of approximately 82.8%. The PAL/SiO₂-IPDI microcapsules were blended with epoxy resin to prepare self-healing coatings. The anti-corrosion tests in the high salt concentration solution show that the epoxy resin coating containing 4%(mass fraction) PAL/SiO₂-IPDI microcapsules could heal quickly after scratching, which significantly reduced the corrosion current and corrosion rate of the iron substrate. SEM images demonstrate that the pure epoxy coating had no sign of healing at the scratching area, while that in the self-healing epoxy coating was filled with cross-linking polymer. In addition, the nano indentation tests show that the hardness value of the epoxy coating increased from 249.99 MPa to 302.98 MPa after adding PAL/SiO₂-IPDI microcapsules, and the elastic modulus was also improved.

Key words: Lignin, Silica, Composite nanoparticles, Microcapsule, Self-healing coating

中图分类号:

O636
O646.21

TrendMD:

李岚, 钱勇, 杨东杰, 邱学青. 纳米木质素/二氧化硅基微胶囊的制备及在自愈合涂层中的应用. 高等学校化学学报, 2019, 40(6): 1293.

LI Lan,QIAN Yong,YANG Dongjie,QIU Xueqing. Preparation of Lignin/silica Nanoparticle Based Microcapsules and Their Application in Self-healing Coatings^†. Chem. J. Chinese Universities, 2019, 40(6): 1293.

图/表 11

Scheme 1 Preparation of microcapsule process schematic diagram

Table 1 Parameters of PAL/SiO2 emulsion with different water/oil ratios and PAL/SiO2 contents

Sample	Water phase		Oil phase		O/W volume ratio	Mean diameter/μm
Sample	V(Water)/mL	Mass fraction of PAL/SiO₂(%)	V(IPDI)/mL	V(PMDI)/mL	O/W volume ratio	Mean diameter/μm
a	12	0.5	3	1	1∶3	40.3
b	12	0.5	5	1	1∶2	49.3
c	6	0.5	3	1	1∶1.5	56.6
d	5	0.5	4	1	1∶1	49.5
e	3	0.5	5	1	0.5∶1	152.4
f	5	0.1	4	1	1∶1	201.5
g	5	1.0	4	1	1∶1	46.7
h	5	2.0	4	1	1∶1	43.6

Fig.1 Optical images of PAL/SiO2 emulsion with different water/oil ratios and PAL/SiO2 content —(H) are samples a—h of Table 1.

Table 2 Parameters of PAL/SiO2 emulsion with different speeds

Speed/ (r·min^-1)	Water phase		Oil phase		O/W volume ratio	Mean diameter/μm
Speed/ (r·min^-1)	V(Water)/mL	Mass fraction of PAL/SiO₂(%)	V(IPDI)/mL	V(PMDI)/mL	O/W volume ratio	Mean diameter/μm
11000	6	0.5	3	1	1∶1.5	73.1
13000	6	0.5	3	1	1∶1.5	56.7
16000	6	0.5	3	1	1∶1.5	56.4
19000	6	0.5	3	1	1∶1.5	55.4
22000	6	0.5	3	1	1∶1.5	43.7

Fig.2 Size distribution and optical microscope(inset)(A) and SEM images of PAL/SiO2 micocapsules(B, C) and the shell(D)

Fig.3 FTIR spectra(A) and TGA curves(B) of PAL/SiO2 shell(a), IPDI(b) and the IPDI-loaded microcapsules(c)

Fig.4 Corrosion performance of steel panels coated with pure(A1, A2) and self-healing(B1, B2) epoxy coatings before(A1, B1) and after(A2, B2) in 10% NaCl solution for 24 h

Fig.5 SEM images of pure(A)and self-healing epoxy(B) coating and its anti-corrosion performance fter being scratched

Fig.6 Tafel plots of pure and self-healing epoxy coatings containing 4% PAL/SiO2 microcapsules coated on steels

Table 3 Tafel parameters of pure and self-healing epoxy coatings containing 4% PAL/SiO2 microcapsules coated on steels

Sample	Current, I/A	Corrosion rate/(mm·a^-1)
Steel	2.29×10^-5	3.35×10^-1
Epoxy	3.69×10^-7	5.39×10^-3
Self-healing epoxy	5.27×10^-8	7.70×10^-4
Epoxy after rupture	3.63×10^-5	5.31×10^-1
Self-healing epoxy after rupture	6.48×10^-6	0.95×10^-3

Fig.7 Nanoindentation load-displacement curves of different PAL/SiO2 content coatings

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