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Preparation method and properties of vinyl trifluoride
Polytrifluoroethylene composite emulsions are the main film-forming substance for fluorosilicone coatings. It has a broad application prospect in automotive, aerospace and other fields. Its main contents are as follows:
Synthesis of poly(dimethylsiloxane) microemulsions. Through experiments, CTAB/OP-10 or DBDA/OP-10 was chosen as the emulsification system. The synthesized microemulsions have narrow particle size distribution, good stability and high conversion rate. With a temperature of 70-80°C, pH 11 and an emulsification dosage of 0.7%-0.9%, the synthesised microemulsions had a high solid content of 36% and good stability. The emulsions were characterised by IR, DSC/TG, SEM and solid content analysis.
2. Synthesis of polyvinylidene trifluoride emulsions. Ammonium persulfate and perfluorodiyl peroxide are used as initiating systems, with continuous or intermittent feeding, resulting in emulsions with good stability, small particle size and narrow distribution. The synthesis of PCTFE emulsions using perfluorodiyl peroxide as initiator greatly reduced the polymerisation reaction time. The emulsions were characterised using IR, DSC/TG, SEM and solid content analysis methods.
3. Based on the synthesis of polydimethylsiloxane microemulsions and poly(trifluorovinyl chloride) emulsions, octamethylcyclotetrasiloxane modified poly(trifluorovinyl chloride) emulsions were synthesized using the core-shell technique. The effects of monomer proportioning, dosing method, initiator and stirring speed on the emulsion polymerization were investigated. The monomers were rationed 1.0:1.0, with semi-continuous or continuous controlled feeding and stirring reaction speed of 400-700 r. The synthesized emulsions had good performance, small particle size and narrow distribution, and the use of perfluoroperoxydiacarbonyl as initiator greatly reduced the polymerization time. The emulsions were characterised by infrared and transmission electron microscopy, fluorine content, particle size analysis, solid content and stability.
4. Using vinyltriethoxysilane as the monomer, polyvinyltriethoxysilane as well as silane-trifluorochloroethylene emulsions can be synthesised using some conventional use of emulsion polymerisation methods. The effect of monomer ratios on polymerisation is discussed. The performance aspects of the polymeric nanoemulsions were characterised analytically by means of IR, DSC/TG, particle size, solid content and stability to provide some reference for further research work.
Main properties of polyvinyl chloride trifluoride
(1) Physical properties Polyvinyl chloride trifluoride (PCTFE) is a crystalline polymer with a crystallinity of 85% to 95%. Its structure is characterised by full isostructures and inter-isostructures. It looks like an irregular configuration and therefore the product has a good transparency. PCTFE is almost impermeable to water, has low permeability and low water absorption, and therefore maintains good insulating properties even in water.
(2) Mechanical properties The mechanical properties of PCTFE are related to molecular weight and processing conditions, and are closely related to crystallinity. Tensile strength, modulus of elasticity, bending properties and hardness increase with increasing crystallinity.
(3) Thermal properties The melting process temperature of PCTFE is 212~217℃, the greater the influence of crystallinity, the higher the melting reaction temperature. The glass transition temperature (Tg) varies with the degree of crystallinity, generally between 45 ℃ ~ 90 ℃. The glass transition temperature (Tg) measured with a thermal expansion meter is about 50 °C. If PCTFE is stored at 260 to 280 °C for a long time, the molecular weight will decrease due to thermal decomposition.
(4) Electrical related properties PCTFE molecules have both a certain volume of large electronegativity difference is small chlorine atoms, but also some small volume of electronegativity large fluorine atoms, the arrangement information is not symmetrical, so the knowledge molecular structure has different polarity, its tgδ and dielectric constant electrical constant is obviously not as good as PTFE, tgδ by the temperature and frequency of the impact to a great. However, the body resistivity and dielectric strength of pctfe are very high.
(5) Chemical resistance The chemical resistance of PCTFE is slightly inferior to that of PTFE, but is still better than that of other national plastics in China.
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