| Nowadays,compared with the tranditional emulsion products,researchers have shown great interests to investigate and develop high-performance emulsions and emulsion products with superior properties,novel structures or special functions,which is mainly attributed that high-performance emulsions can improve the drawbacks of tranditional emulsions,achieve specific properties that tranditional emulsions don't have,and extend the application fields of emulsion products.Two common methods,emulsion polymerization and emulsifying method,are usually used to produce emulsions.Due to the fact that both of the emulsion polymerization and emulsifying method have their own advantages and disadvantages,therefore,the high-performance emulsions prepared by each of them are also different.The main purpose of this thesis is,based on these emulsion preparation mehods,to design new formula and develop new synthetic techniques for manufacturing high-performance emulsions.In this thesis,the influence of direct core/shell structured emulsion polymerization on the preparation of poly(styene-acrylate)latex particles with direct core/shell morphology was studied.Also,the effect of inverted core/shell structured emulsion polymerization method on the manufacture and properties of poly(vinyl acetate-styrene)latex particles with inverted core/shell morphology was explored,which disclosed the controlling mechanism of transition layer for regulating and controlling the preparation of thermodynamically non-equlibrium but kinetically achievable inverted core/shell structured emulsions.Utilizing single-channel microfluidization method,bio-mass based emulsifier-stabilized nanoemulsions or emulsions were prepared,optimizing the preparation processes for high-performance environmental emulsions.On the basis of the signle-channel method,a new dual-channel microfluidization method was developed.The influence of dual-channel microfluidization method on the preparation of bio-mass based emulsifier-stabilized nanoemulsions was also investigated,extending the preparing approaches for manufacture high-performance emulsions.The main research contents are as follows:(1)Using direct core/shell structured emulsion polymerization method,direct core/shell poly(styrene-acrylate)emulsions with polystyrene cores and polyacrylate shells were prepared.The influence of different core and shell monomer compositions as well as different core-to-shell ratios on the preparation and properties of core/shell structured PS/PA emulsions was studied.The experimental results showed that the properties of emulsions and latex films were significantly affected by the core/shell morphology,especially for controllably adjusting the flim-forming ability and latxe film performances.The thermal properties of latex film were also investigated,showing that there existed an interfacial layer or transition layer with certain thickness between core polymers and shell polymers.The mechanical properties of prepared latex films were studied,which showed that the tensile property was mainly controlled by synergistic function of core polymers and shell polymers that caused by the honeycomb-like latex film microstructure.The properties of the glued wood blocks by core/shell structured poly(styrene-acrylate)emulsions were explored.The results showed that after constructing core/shell morphological latex particles,the shear strength and the boiling water separation time of poly(styrene-acrylate)emulsions were increased and greatly extended,respectively.(2)Combining particle designing method and inverted core/shell structured emulsion polymerization approach,with the kinetically controlling mechanism of transition layer,a thermodynamically non-equilibrium PVAc/PS inverted core/shell structured emulsion was prepared,within which hydrophilic PVAc was used as cores and hydrophobic PS was used as shells.The design,verification and controlling mechanism of transition layer structure was studied.The results showed that the main function of transition layer on achieving inverted core/shell poly(VAc-St)was as follows:First,the transition layer mediated the difference between polymers,which increased the compatibility of PVAc-based polymer and PS-based polymer,thereby restricting the phase reversion;Second,the diffusion,rearrangement,entanglement and grafting process of polymer chains could be occurred in the interior of transition layer,which could form interpenetration network structure and increase the internal viscosity,restrictin the polymer chain further diffusion within the transition layer;Finally,after constructing the transition layer,the mobility of PVAc chains towards aqueous phase was also restricted,inhibiting the possible phase reversion.The latex particle morphologies mediated by the transition layer was studied,showing that the micro-morphologies of inverted core/shell poly(VAc-St)varied from that of broken egg shell-like structure with PS-based coating,over intermediate structures in which uniform PS protuberances surrounded PVAc cores,to core/shell structure with single PVAc core.The properties of the glued wood blocks by inverted core/shell structured poly(VAc-St)emulsions were explored.The experimental results showed that compared with the PVAc emulsions,the shear strength and the boiling water separation time of poly(VAc-St)emulsions were dramatically increased and extended,respectively.(3)Using signle-channel microfluidization emulsifying method,various of environmental nanoemulsions stabilized by different bio-mass based emulsifiers were prepared.Using bio-mass small molecular rhamnolipids(R90)as emulsifier,the influence of single-channel microfluidization method on the droplet diameter and its distribution was studied.It has been shown that the environmental nanoemulsions with smaller droplet diameter and high stability were produced.The preparation processes of microfluidization method was also studied,showing that the fine nanoemulsions could be prepared under different homogenization pressures.In this study,the applicability of single-channel microfluidization method was also studied.The experimental results showed that many kinds of oil types could be used to make namoemulsions that stabilized by R90.The stability of R90-stabilized nanoemulsions under different environmental stresses was studied.The results showed that the R90-stabilized nanoemulsions were not sensitive to the thermal process and storage,but very sensitive to the change of pH values and ionic strength in the system.Using bio-mass large molecular gum arabic(GA),beet pectin(BP)and corn fiber gum(CFG)as polysaccharide-based emulsifiers,environmental emulsions with different droplet diameters and stabilities were produced by single-channel microfluidization.The preparation of emulsions with different oil types which were stabilized by polysaccharide-based emulsifiers were studied.The results showed that single-channel microfluidization method could be used to produce polysaccharide-based emulsifier-stabilized emulsions with various oil types.The storage stability of polysaccharide-based emulsifier-stabilized emulsions was studied,which showed that the storage stability of GA-and BP-stabilized emulsions had better stability,however,the emulsion stabilized by CFG could be separated shortly,forming a creaming layer.(4)Based on the progress of single-channel microfluidization method,a new dual-channel microfluidization emulsifying approach was developed.The droplet diameter and its distribution of nanoemulsions were analyzed to compare the single-and dual-channel microfluidization methods.The experimental results pointed out that the advantages of dual-channel microfluidization method were more efficient,simple and controllable.Under similar homogenization pressures and emulsifier concentrations,nanoemulsions with samller droplet diameter,narrower distribution and more homogenious composition could be produced by only single microfluidization pass.The droplet diameter and its distribution of nanoemulsions with different oil concentrations were studied,which showed that using dual-channe microfluidization method,the high oil-loaded nanoemulsions could be produced,namely even with 50 wt%oil concentration,the emulsion still belonged to nanosized emulsion.Using bio-mass large molecular emulsifiers(Whey protein isolate and gum arabic)and small molecular emulsifiers(Q-Naturaleand Soy lecithin)as research subjects,the droplet diameter and its distribution of bio-mass based emulsifier-stabilized nanoemulsions were investigated.The results showed that bio-mass emulsifier-stabilized environmental nanoemulsions with different size and stability could be prepared by dual-channel microfluidization method by single microfluidization pass,which extended the selectivity of emulsion preparation process,providing new synthetic technique for manufacturing high-performance emulsions. |
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