Microencapsulation technology based on Pickering emulsion-spray drying method

doi:10.16085/j.issn.1000-6613.2024-1449

Abstract

Abstract:

In order to reduce the potential risks in the recrystallization refining process of energetic materials in actual production, a new technology combining confined crystallization and microencapsulation was proposed. Constructing the confined structure of Pickering emulsion in cyclohexane/acetonitrile anhydrous system with SiO₂ as emulsifier, the optimal emulsion ratio to adjust the particle size of emulsion droplets was obtained. The rotational speed of the centrifugal atomizer was adjusted to maintain the confined structure of the droplets, the drying temperature was determined by the solvent volatilization rate curve, and microcapsules with different polyethylene wax content were prepared. The process mechanism was proposed according to the experimental results of low temperature drying. The best parameters of the emulsion were as follows: the content of SiO₂ was 0.5g/120mL cyclohexane, and the volume ratio of cyclohexane and acetonitrile was 6∶1. The optimum conditions for the formation of microcapsules were as follows: the drying temperature was 135℃, the feed rate was 4mL/min, the centrifugal atomizer speed was 12000r/min, and the polyethylene wax content was 5% (mass fraction). The characterization data of FTIR and ¹H NMR verified the existence of the o-chlorobenzoic acid, which was the substitute materials of energetic materials in the microcapsule, and the amount of encapsuled core material was up to 84% (mass fraction). The results showed that the polyethylene wax/SiO₂ shell was first molded to isolate the recrystallization process from the surrounding environment, reduce the potential risk in this process, and limit the crystal growth with confined space to obtain sub micrometer scale core material, completing the coupling of recrystallization and coating process.

Key words: process control, emulsions, drying, microcapsules, composites, safety

摘要：

为降低实际生产中含能材料重结晶精制过程的潜在风险，本文提出一种乳液限域与微囊化相结合的新技术。以SiO₂为乳化剂在环己烷/乙腈无水体系中构筑Pickering乳液限域结构，通过调整乳滴粒径得到最优乳液配比；调节离心雾化器转速使雾滴维持乳液限域结构，通过溶剂挥发速率曲线确定干燥温度，制备不同聚乙烯蜡含量的微胶囊，并根据低温干燥实验结果提出过程机理。得出乳液最佳参数：SiO₂含量为0.5g/120mL环己烷，环己烷与乙腈体积比为6∶1；当干燥温度为135℃、进料量为4mL/min、离心雾化器转速为12000r/min、聚乙烯蜡质量分数为5%时，微胶囊成型效果最佳；FTIR和¹H NMR分析验证了微胶囊含能材料的代替材料邻氯苯甲酸的存在，且包覆量最高为84%（质量分数）。研究结果表明：本工艺中聚乙烯蜡/SiO₂壳材首先成型，将重结晶过程与周围环境相隔绝，降低其过程的潜在风险，并以限域空间限制晶体生长得到亚微米尺度的芯材，完成重结晶与包覆过程的耦合。

关键词: 过程控制, 乳液, 干燥, 微胶囊, 复合材料, 安全

CLC Number:

TQ560.6

QIN Biming, NIE Xinyao, LIU Yang, WANG Zihan, XIA Liangzhi. Microencapsulation technology based on Pickering emulsion-spray drying method[J]. Chemical Industry and Engineering Progress, 2025, 44(10): 5609-5618.

覃必铭, 聂鑫垚, 刘洋, 王梓涵, 夏良志. 基于Pickering乳液-喷雾干燥法的微囊化技术[J]. 化工进展, 2025, 44(10): 5609-5618.

Figures/Tables 18

References 27

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组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm	组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm	组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm
a	100	0.1	80.32	f	120	0.1	92.11	k	140	0.1	94.04
b		0.3	52.42	g		0.3	35.19	l		0.3	33.30
c		0.5	30.93	h		0.5	19.91	m		0.5	22.80
d		0.7	17.84	i		0.7	16.09	n		0.7	19.47
e		0.9	13.88	j		0.9	21.66	o		0.9	23.99

组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm	组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm	组序	环己烷体积/mL	SiO₂质量/g	平均粒径/μm
a	100	0.1	80.32	f	120	0.1	92.11	k	140	0.1	94.04
b		0.3	52.42	g		0.3	35.19	l		0.3	33.30
c		0.5	30.93	h		0.5	19.91	m		0.5	22.80
d		0.7	17.84	i		0.7	16.09	n		0.7	19.47
e		0.9	13.88	j		0.9	21.66	o		0.9	23.99

溶剂	截距	斜率	拟合方程
乙腈	-0.01101	0.01868	Q₁=-0.01101+0.01868T
环己烷	0.8625	0.01698	Q₂=0.8625+0.01698T

溶剂	截距	斜率	拟合方程
乙腈	-0.01101	0.01868	Q₁=-0.01101+0.01868T
环己烷	0.8625	0.01698	Q₂=0.8625+0.01698T

聚乙烯蜡质量分数/%	m_A/mg	m_B/mg	S_A	S_B	ω_B/%
2	9.0	10.1	3.35	0.50	27
3	26.5	14.5	5.18	0.50	32
4	12.6	11.7	2.59	0.50	33
5	27.4	16.0	1.84	0.50	84