Preparation of Armor Structure Polystyrene@Magnesium Hydroxide Composite Microspheres by Pickering Suspension Polymerization with Nano-magnesium Hydroxide as Pickering Stabilizer †

doi:10.7503/cjcu20190462

Abstract

Abstract:

The unique properties of organic-inorganic composite microspheres with armor structure have aroused great interest. Armor structure organic-inorganic composite microspheres were prepared by Pickering suspension polymerization using styrene as monomer, azobisisobutyronitrile(AIBN) as initiator, magnesium hydroxide nanosheets as Pickering stabilizer. The composite microspheres were characterized by scanning election microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), thermal gravimetric analysis(TGA) and micro-scale combustion calorimetry(MCC). The morphology and structure of the composite microspheres were confirmed. Magnesium hydroxide was tightly coated on the surface of the polystyrene microspheres to form the armor structure composite microspheres with magnesium hydroxide as the outer layer and polystyrene as the inner sphere. When magnesium hydroxide content was 2%, the average particle size of the microspheres was 25 μm, much lower than that of pure PS microspheres, 760 μm. It was also proved that the composite microspheres with armor structure could reduce the heat release rate and inhibit the cracking of polymers. And the acid etching of microspheres could remove completely the outer layer of magnesium hydroxide. This Pickering suspension polymerization is simple to operate, low cost, and the prepared armor composite microspheres have small particle size, narrow distribution and high sphericity. Moreover, the armor structure endows the material with a certain degree of flame retardant performance.

Key words: Armor structure, Magnesium hydroxide nanosheet, Pickering stabilizer, Composite microsphere

CLC Number:

O631
O647

TrendMD:

ZHU Pei,WANG Feng,CHEN Zheming,LI Gen,GAO Chong,LIU Peng,DING Yanfen,ZHANG Shimin,CHEN Juan,YANG Mingshu. Preparation of Armor Structure Polystyrene@Magnesium Hydroxide Composite Microspheres by Pickering Suspension Polymerization with Nano-magnesium Hydroxide as Pickering Stabilizer ^†[J]. Chem. J. Chinese Universities, 2020, 41(3): 556.

Figures/Tables 14

Fig.1 TEM(A), SEM(B) images and size distribution(C) of the synthesized MH nanosheets

Fig.2 XRD patterns of the synthetic synthetic MH(a) and stardard MH(b)

Fig.3 Confocal fluorescence microscope images of Pickering emulsion stabilized by dyed 2% MH

Fig.4 Optical microscopy images of Pickering emulsions stabilized by different content of MH Mass fraction MH(%): (A) 0.5; (B) 1; (C) 2; (D) 4.

Fig.5 FTIR spectra of MH(a), PS(b), PS@MH-0.5%(c), PS@MH-1%(d), PS@MH-2%(e) and PS@MH-4%(f) microspheres

Fig.6 SEM images of PS(A, B), PS@MH-0.5%(C, D), PS@MH-1%(E, F) and PS@MH-4% micropheres(G, H) (B), (D), (F), (H) are high magnification of the rectangles in (A), (C), (E), (G), respectively.

Sample	D/μm	δ/μm	ε	Coverage	Sample	D/μm	δ/μm	ε	Coverage
PS	760	208	0.273	0	PS@MH-2%	25	5	0.215	4.06
PS@MH-0.5%	256	243	0.949	10.40	PS@MH-4%	27	11	0.411	9.10
PS@MH-1%	35	14	0.402	2.84

Fig.7 SEM image(A) and EDS patterns(B—D) of PS@MH-0.5% microspheres (B) C element;(C) Mg element; (D) O element.

Fig.8 XRD patterns of MH(a) and PS@MH microspheres(b—d) b. PS@MH-1%; c. PS@MH-2%; d. PS@MH-4%.

Fig.9 SEM images of PS@MH-2%(A, B) and PS@MH-2%-Etch microspheres(C, D) with different magnifications

Fig.10 TGA curves for PS@MH-2%(a) and PS@MH-2%-Etch(b) microspheres

Sample	HRC/(J·g^-1·K^-1)	HRR/(W·g^-1)	THR/(kJ·g^-1)	T_max/℃
PS	772	822.9	35.2	443.6
PS/MH-2%	781	831.3	35.5	442.3
PS@MH-2%	612	624.1	34.3	436.8

Fig.11 Heat release rate curves of PS(a), PS/MH-2%(b) and PS@MH-2%(c)

Fig.12 Mechanism of armor structure composite microspheres by Pickering suspension polymerizations for emulsion stabilized by MH nanosheets

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