The Self-organization Process Study Of Fluorinated/Non-fluorinated Polyacrylate Gradient Emulsion Blend Film

Based on the concept of gradient polymer blend films and self-stratification mechanisms, a gradient blend film with surface property of fluorinated polyacrylate on one side and good adhesion on another side is possible by blending fluorinated polyacrylate latices and other latices. If achieved, the incompatibility of the fluorinated film with substrate could be avoided. The self-organization process over a heterophase liquid applied a driving force during the film-forming process so as to distribute the phases between the air and substrate is simple and tractable. However, the self-stratification mechanism was mainly applied in solution system which usually uses poisonous organic solvents and melts systems which usually need high temperature and is energy consuming. With regard to the latex blends system which is environmentally friendly and energy saving, the polymers are covered by emulsifier such that the surface free energies of different latex particles in the system are of little differences. Unfortunately, the differences of surface free energies between different latex particles have been a main provider of the driving force during the self-organization process in the blends system. So the formation of gradient structures by self-organization in latex blends system is difficult due to the lack of driving forces. In this paper, the self-organization process of gradient structure in latex blends system were discussed in detail, the effect factors on gradient, such as temperature, Tg, particle size, substrates and so on were studied.The effects of film-formation temperature (FFT), heat treatment and Tg on the self-organized film-formation of fluorinated/non-fluorinated polyacrylate latex blends were studied. To this end, six kinds of fluorinated polyacrylate latices with different Tg and same content of fluorine were prepared and mixed with the same non-fluorinated polyacrylate latex, respectively. All the blends latices were dried at 15℃; 30℃; 45℃and 60℃. The surface properties and morphologies were characterized by contact angle measurement and AFM. The element composition and structure of films across the section was analyzed by XPS, SEM-EDX and ATR-FTIR. The results showed that, drying at temperatures above the MFFT of fluorinated component is necessary for the enrichment of fluorinated component on film-air interface (F-A) of the film and formation of gradient structure. Moreover, when the Tg of fluorinated component is higher than that of the non-fluorinated polyacrylate, the big difference of Tg of the two components and the low FFT are in favor of the formation of gradient structures of the films. Compared with that of sample whose two components can film-formation at room temperature, the two components of sample which only one component can film-formation at room temperature were easier to self-organize to the different surface of the film during film-formation and anneal process because of their different Tg. Increasing the heat treatment temperature above the Tf of polymers make for the phase separation but the formation of gradient structure.The effects of particle size of the components and content of PF6MBA on the gradient structure of films were discussed. The content of fluorine in film-thickness direction was analyzed by XPS depth profiling, SEM-EDX and ATR-FTIR. The surface properties and morphology were characterized by contact angle measurement and AFM. It was found that, after film-formation at room temperature and anneal 2h at 110℃, the fluorine content increased from F-G to F-A gradually in the blends film whose fluorinated polyacrylate latex with smaller particle size and higher Tg than that of fluorine-free polyacrylate latex. Moreover, the content of PF6MBA in the system was above 30%is necessary for the gradient structure and the pure fluorinated polyacrylate surface of F-A.The effects of substrates of film on the gradient structure were discussed. The blend latex was film-formed on Al, Steel, Glass, and PTFE. The content of fluorine in film-thickness direction was analyzed by XPS depth profiling, SEM-EDX and ATR-FTIR. The surface properties and morphology were characterized by contact angle measurement and AFM. The result shows that increasing the surface free energy of substrate and decreasing the thickness of film would promote the formation of perfect gradient structure(the fluorinated polymer content increased from 0%on F-G to 100%on F-A gradually) after anneal above the Tf of polymer.The effects of adding the fluorinated acrylate copolymer in fluorinated/non-fluorinated polyacrylate latex blend on the surface property, gradient structure and compatibility of the blend film were studied by surface free energy testing, adhesion test, DSC and SEM-EDX. The results showed that the compatibility of the blend system was improved after adding the copolymers. The increasing of the fluorine content of copolymer was beneficial to the formation of gradient structure. The copolymer had little influence on the surface property of the films. Blending fluorinated polyacrylate copolymer and non-fluorinated polyacrylate copolymer latexes, the gradient structure film was abtained while film-formation at room temperature, the gradient structure was obviouse after annealing at 110℃, the lengthening of the fluorinated chain segment was in favour of the gradient structure and surface property.