Preparation and characterization of microencapsulated polythiol

Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, OFCM Institute, School of Chemistry and Chemical Engineering, Zhongshan University, Guangzhou 510275, PR China; Materials Science Institute, Zhongshan University, Guangzhou 510275, PR China
Polymer 01/2008; DOI: 10.1016/j.polymer.2008.03.044

ABSTRACT Microcapsules containing curing agent for epoxy were successfully prepared by in situ polymerization with poly(melamine–formaldehyde) (PMF) as the shell material and high-activity polythiol (pentaerythritol tetrakis (3-mercaptopropionate), PETMP) as the core substance. Having been encapsulated, the core material PETMP had the same activity as its raw version. The synthesis approach was so improved that the consumption of polythiol was reduced to a low level. By carefully analyzing the influencing factors including catalyst concentration, reaction time, reaction temperature, feeding weight ratio of core/shell monomers, dispersion rate and emulsifier content, the optimum synthetic conditions were found out. The results indicated that not only core content and size of the microcapsules but also thickness and strength of the shell wall can be readily adjusted by the proposed technical route. The relatively thin shell wall (∼0.2 μm) assured sufficient core content even if the microcapsules were very small (1–10 μm). The polythiol-loaded microcapsules proved to be qualified for acting as the mate of epoxy in making two-part microencapsulated healing agent of self-healing composites.

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    ABSTRACT: Two types of healing agent carriers (microcapsules containing epoxy solution, referred to as EP-capsules, and etched hollow glass bubbles (HGBs) loaded with amine solution, referred to as AM-HGBs) used in self-healing epoxy systems were prepared and characterized in this study. The core percentages were measured at about 80 wt% and 33 wt% for EP-capsules and AM-HGBs, respectively. The loaded amine in AM-HGB, after incorporation into the epoxy matrix, showed high stability at ambient temperature, but diffused out gradually during heat treatment at 80 °C. The amount and the mass ratio of the two released healants at the crack plane were correlated with the size, concentration, and core percentage of the healing agent carriers. A simplified cubic array model for randomly distributed healing agent carriers was adopted to depict the longest diffusion distance of the released healants, which is inversely proportional to the cubic root of the carrier concentration.
    Smart Materials and Structures 04/2014; 23(6):065003. · 2.02 Impact Factor
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    ABSTRACT: Part I of this study (H Zhang and J Yang 2014 Smart Mater. Struct. 23 065003) reported the preparation and characterization of epoxy microcapsules (EP-capsules) and amine loaded hollow glass bubbles (AM-HGBs), and the modeling of a two-part self-healing system. In part II, the self-healing performance of this material system is systematically investigated. Various factors including the ratio, the total concentration and the size of the two carriers are studied as well as the healing temperature and the post heat treatment process. The best healing performance is obtained at a ratio of 1:3 of EP-capsules to AM-HGBs. It is observed that a higher concentration of larger carriers, together with a higher healing temperature, enables better healing behavior. Healing efficiency of up to 93% is obtained in these systems. In addition, post heat treatment decreases the healing efficiency due to stoichiometric mismatch of healing agents caused by leakage of amine in the HGBs at elevated temperature.
    Smart Materials and Structures 04/2014; 23(6):065004. · 2.02 Impact Factor
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    ABSTRACT: Abstract Microcapsules containing a liquid metal alloy core of gallium-indium (Ga-In) are prepared via in situ urea-formaldehyde (UF) microencapsulation. The capsule size, shape, thermal properties, and shell wall thickness are investigated. We prepare ellipsoidal capsules with major and minor diameter aspect ratios ranging from 1.64 to 1.08 and with major diameters ranging from 245 µm to 3 µm. We observe that as the capsule major diameter decreases, the aspect ratio approaches 1. The thermal properties of the prepared microcapsules are investigated by thermogravimetric (TGA) and differential scanning calorimetry (DSC). Microcapsules are shown to survive incorporation into an epoxy matrix and to trigger via mechanical damage to the cured matrix. Microcapsules containing liquid metal cores may have diverse applications ranging from self-healing to contrast enhancement or the demonstration of mechano-adaptive circuitry.
    Journal of Microencapsulation 02/2014; · 1.57 Impact Factor


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May 31, 2014