Study On Preparation, Structure And Properties Of Modified Organic Glass

Organic- glass is widely used due to its excellent optical propery. But organic glass exhibits drawbacks, such as low heat-resistance and toughness, which limits its use areas. Chemical crosslinking, orientational draw and compositing with nanomaterials are important approaches to improve the thermal and mechanical properties of organic glass, but the researches on the synthesis of crosslinked organic glass, the structure and property of crosslinked and orientational crosslinked organic glass were seldom reported. The synthesis rule of crosslinked organic glass and the structure and property of crosslinked and orientational crosslinked organic glass were investigated in this thesis. Moreover, the structure and thermal property of crosslinked organic glass modified by nano-silica particles prepared by in-situ polymerization were also studied.The studies on the free-radical crosslinking copolymerization rule of methyl methacrylate(MMA)/multi-vinyls monomers showed that the polymerization kinetic process and the evolution of gel formation was obvious different for different MMA/crosslinking agent systems. For MMA/crosslinking agent (A) system, the gel point appeared at about 10-20% conversion, but it appeared at about 60-80% conversion for MMA/crosslinking agent (B) system. With the increase of the concentration of crosslinking agent, the sol conversion increased before the gel point, and decreased after the gel point, while the gel fraction increased and the equilibrium degree of swelling decreased at the same conversion after the gel point. With the increase of polymerization temperature, the gel point was postponed and the gel fraction decreased at the same conversion. The effect of initiator concentration on the gel fraction and equilibrium degree of swelling was not obvious. With the increase of conversion, the molecular weight of sol fraction increased before the gel point and decreased after the gel point.In order to decrease the influence of crosslinking agent on the gel effect in MMA polymerization, crosslinking agent (B) was selected as the crosslinking agent to prepare crosslinked organic glass plates, and the structure and property of crosslinked organic glass were studied. It was found that the gel fraction increased, the equilibrium degree of swelling decreased as the concentration of crosslinking agent (B) increase. The impact strength increased slowly, and the tensile strength and the glass transition temperatureincreased firstly and then decreased as the crosslinking density of organic glass increase.In order to illustrate the orientation on the properties of organic glass, the structure and properties of orientational crosslinked organic glass were measured. The results showed that the structure and properties of the samples of orientational crosslinked organic glass with different thickness and sampled from different location were different in some way. Comparing with common organic glass, the tensile strength, impact strength and glass transition temperature of orientational crosslinked organic glass were obviously enhanced. But comparing with the self-prepared crosslinked organic glass, the improvement on impact strength and the glass transition temperature was not obvious, but the thensile strength improved by 20MPa.Moreover, the preparation, structure and thermal property of crosslinked organic glass modified by nano-silica particles were discussed. It was found that the surface grafting of nano-silica with 3-(trimethoxysilyl)propyl methacrylate (MPS) could enhance its lipophilicity and made the MMA/nano-silica in-situ polymerization available. The results of FT-IR and extraction proved that PMMA was grafted onto nano-silica, and the grafting percent could approach above 90%. The nano-silica particles dispersed very well in crosslinked organic glass prepared by in-situ bulk polymerization, and the glass transition temperature and thermal stability of organic glass nanocomposite were enhanced as nano-silica incorporated.The results of this thesis are helpful to instruct the production and improve the properties of crosslinked organic glass and orientational crosslinked organic glass.