Synthesis And Characterization Of Hollow Polymer Microspheres

Polymer hollow microspheres were widely used in medicine, cosmetics, paint and leather, and other fields. In the process of preparing the polymer hollow microspheres, the requirement of the compound control was high. Therefore, the study related to the synthetic manipulation showed great significance for the theory and application. In this paper, polystyrene and polyurea hollow micropheres were prepared by alkali swelling method and template method respectively. Their main structural properties, such as hollowness, latex particle size and dispersibility were systemetically studied and the optimization method were investigated.Polystyrene hollow microspheres were prepared by seeded emulsion polymerization and alkali swelling method. The preparation process comprised four steps: Firstly, prepared the acidic nuclear latex particles; Secondly, coated the surface of the acidic nuclear with a weak hydrophilic intermediate layer; Thirdly, coated the surface of the intermediate layer with a strong hydrophobic shell containing crosslinking agent; At last, the polystyrene hollow microspheres with average particle size 480-1672 nm, cavity size 8%-38%（concentration） and good dispersion were obtained after alkali swelling. In the process of preparing the hollow microspheres, the monomer conversion rate was more than 97wt%. Polystyrene polymer particles were characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetric and differential scanning calorimeter, infrared spectra etc. Influence of the amount of emulsifier, core-shell ratio, crosslinking agent, the type of alkali and the value of pH on the microspheres morphology were investigated. Finally, summed up the optimal process conditions. The results showed that, the optimal experiment conditions for preparing the polymer hollow microspheres were as follows: the amount of emulsifier was 0.1wt% in the nuclear acidic phase preparation; core-shell ratio was 0.8 and crosslinking agent was 3-6wt% in the shell-nuclear acidic phase preparation; the initial pH value of alkali swelling was 10.78.CaCO₃ particles were adopted as templates and polyureaa shell formed on the surface of the CaCO₃ particles to give the CaCO₃/polyurea composite microspheres.The CaCO₃ templates were removed by hydrochloric acid and polyurea hollow microspheres were obtained. For the preparation of CaCO₃ particles, the effects of the crystal control agent type and amount, surface modifiers, concentration of reactants on the CaCO₃ particles morphology were investigated. CaCO₃ particles were characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering laser particle size analyzer, X-ray diffraction and infrared spectroscopy. The results showed that, CaCO₃ particles prepared by the sodium carboxymethyl cellulose（CMC） or poly styrene sulfonate（PSS） as crystal control agent were mainly vaterite and calcite type. The CaCO₃ particles prepared by the sodium tripolyphosphate（STP） as crystal control agent were amorphous nano-CaCO₃ particles. Modified CaCO₃ particles with oleic acid or sodium stearate did not destroy the crystal form of CaCO₃ particles, the dispersion of the modified CaCO₃ particles was improved. Prepared the polyurea hollow microspheres with the CaCO₃ particles as the template. The influences of template morphology and surfactants on the structure of polyurea hollow micropheres were investivated. By introduction of the triethylenetetramine, the structurally stable polyurea hollow microspheres were obtained.