Study On Synthesis Of Nanometer Calcium Carbonate And Epoxy Resins Toughening

Nanometer calcium carbonate is an inorganic filler with broad application andmulti-purpose, which is widely used in rubber, plastic, paper, paint industry. Epoxyresin has high crosslinking density with three dimensional network structure aftersolidification and its internal stress is great, so it is very brittle、fatigue and poorimpact resistance. Nanoparticles in epoxy resins can rise the toughening andreinforcing effect for it plays "rivetting" function and "crazing" effect. But nanometercalcium carbonate tends to aggregate and forms the secondary particles. Usually in theproduction process （such as carbonization method）, certain dispersing agent is addedto avoid the aggregation of nanometer particle. In addition, the surface of nanometercalcium carbonate is hydrophilic/oleophobic. It often causes dispersed unequally inthe matrix and difficult to form a good interface combination as filler. So the syntheticnano-CaCO₃should be modified further.In this paper, direct precipitation, microemulsion and hydrothermal method areused for preparation of nanometer calcium carbonate. It can simplify the modificationsteps, and improve the adhension between the modifier and nanopaticles using somesurfactant both as dispersant and modifier, so as to improve the modification effect.Nanometer calcium carbonate is added to the epoxy resin. It can achieve thetoughening effect, for the surfactant can improve the effect of the binding forcebetween nano-CaCO₃and epoxy matrix. The main research work of this paper is asfollows:1、 Nanometer calcium carbonate is prepared respectively by means ofmicroemulsion, hydrothermal, the direct precipitation method. The X-ray diffraction,infrared spectrum and TEM are employed to characterize the products. Test resultsshow that calcium carbonate with good crystallized calcite structure, uniform particle size, modified surface and good dispersion can be got by direct precipitation andhydrothermal method. Not only good dispersion and smaller particle size can be gotby hydrothermal method, but also nano-CaCO₃surface is modified by the chemicaladsorption between surfactant and particle surface.2、 Nano-CaCO₃is prepared by hydrothermal method with SDS as surfactant.Using single factor experiment method, the influence of the SDS additives, reactiontemperature and reaction time on the surface modification effect and size areanalyzed,and the best synthetic process conditions are reached.3、 Nano-CaCO₃is prepared by hydrothermal method respectively withpolyethylene glycol, betaine and the composite agent （SDS+betaine） as modifyingagent. The X-ray diffraction, infrared spectrum and TEM are employed tocharacterize the products. Test results show that calcium carbonate crystal form,morphology and surface modification are affected by different surface active agent.4、Nano calcium carbonate/epoxy resin composite material is prepared by dopingnano-CaCO₃to epoxy resin with casting method. The effect of different nano-CaCO₃amount on the mechanics properties of composite materials is investigated. Theresults show that after appropriate doping of nanometer calcium carbonate, epoxyresin bending strength, bending elastic modulus and impact strength are improved.