Preparation And Performances Of UV-curable Organic/Inorganic Flame-resistant Hybrid Coating Materials

How to introduce sols containing silicon and/or phosphorus prepared by using the sol-gel method into UV-curable coatings to improve the flame retardant of coatings is the main theme of this thesis. In order to meet the rapid prototyping need of UV curing technique, volatile solvents in the sols were extracted. Distilled sols were transferred to tripropylene glycol diacrylate (TPGDA, a reactive diluent) to form sol dispersions, and then added to the UV-curable coating recipe to form the hybrid coating system. Moreover, the effects of several modified powders on performances of UV-cured hybrid films were also discussed. The main results could be drawn as follows.1) A series of silica sols were synthesized using the acid-hydrolysis sol-gel method from tetraethoxysilane (TEOS) and y-methacryloxypropyl trimethoxy silane (MPS). The properties of hybrid coating materials consisted of silica sols, bisphenol A type epoxy acry late (product name:SM6104) and TPGDA were investigated in detail. The results showed that:(1) After optimizing the structure of sols and the extraction process of solvents, the stability of sol dispersions was improved, so stabilization period of the optimal sample is more than180days.(2) Compared to UV-curable pure organic coatings, conversions of C=C double bonds of the hybrid coating materials go down, but these thermal stability, flame retardancy, physical and mechanical properties (elastic modulus, hardness, abrasive resistance and scratch resistance, etc) were greatly improved.2) Silicon/phosphorus-containing binary sols were prepared by the reaction of TEOS, TMP and MPS, and their solvents were extracted. The performances of hybrid coating materials consisted of Si-P binary sols, SM6104and TPGDA were investigated. The results showed that:(1) The storage stability of Si-P binary sols was less than that of silica sols.(2) With the content increase of phosphorus in sols, abrasive resistance of hybrid coatings is further improved.(3) Silicon and phosphorus in sols have a synergetic effect for the flame retardancy of hybrid coatings. Compared with organic-silica system, thermal stability and flame retardancy (time to igniation and total heat release) of Si-P/organic system improved further.3) Starting with silica sol and Si-P binary sol, low-hydroxyl (a rare content of hydroxy) sols were synthesized using an anhydrous sol-gel method. The properties of hybrid coatings consisted of low-hydroxyl sols, SM6104and TPGDA were investigated. The results showed that:(1) Due to the bigger matrix of low-hydroxyl sols, their deposited stabilitiy is worse than that of two sols (silica sols and Si-P binary sols).(2) Compared with silica/organic system and Si-P/organic system, their flame retardancy still improved further, which was shown as the longer ignited time and the lower total heat release.(3) Due to the less hydroxyl groups, scratch resistance and abrasive resistance of hybrid coatings are weaken, and their visible light transmittance also declines because of adding Ti-containing component.4) SiO2nanoparticles were modified by MPS, and then added to TPGDA to form SiO2/TPGDA dispersions. The performances of hybrid coatings consisted of SiO2/TPGDA dispersions, silica sols, SM6104and TPGDA were investigated. The results showed that:(1) MPS-modified SiO2nanoparticles resulted in increase of viscosity of coatings, but could improve conversions of C=C double bonds of coatings, and abrasive resistance of UV-cured coatings. Their glossiness slightly decreases.(2) Time to igniation of coatings containing MPS-modified SiO2nanoparticles was longer, but total heat release is essentially equal to coatings without MPS-modified SiO2nanoparticles.5) ATO nano powder (or dispersions), low melting point glass powder (LMPGP) and ammonium polyphosphate (APP) were modified by MPS, and then used for fillers of organic/Si-P hybrid coating system. The results show that:compared to organic/Si-P hybrid coating without these powders,(1) their thermal stability got the improvement, their amount of residual carbon wholly increased to>40%, their ignited time lengthened and the total heat release significantly decreased.(2) Their physical and mechanical properties were all affected to varying degrees. They include the lower hardness of APP-containing coating, and the better abrasive resistance of the LMPGP-containing coatings, and the decreased visible light transmittance of ATO-containing coatings.6) Deposited stability of silica sol dispersions and the deposited stability failure of coatings were researched by computer simulation using the Monte Carlo method based on the percolation model. It can be found that:(1) On three premises,1) the more molecular numbers of TPGDA the sol/TPGDA dispersions,2) the less functional groups (Si-OH) of MPS compared with TEOS,3) the hypothesis that the reactive activity between MPS and MPS (MPS-MPS) was lower than that of TEOS-TOES, to add the content of MPS could also improve the deposited stability of silica sol dispersions.(2) The time to add SM6104to sol was earlier, the gelation time of sol was shorter. On the premise that the same time to add SM6104to sols, the content of MPS was more, deposited stability time of coatings was longer. Moreover, the time to add SM6104to sols was later, the content effect of sol precursor MPS on the gelation time of sol was weaker. These results were completely consistent with the results of experiments. It could be concluded that the active hydroxyl in the molecular structure of SM6104might react with clusters in sol to accelerate the gelation process, which caused the worse deposited stability of hybrid coatings.