| Poly(vinyl butyral)(PVB), prepared from polyvinyl alcohol by the reaction with butyraldehyde in the presence of small amounts of mineral acid, is widely used as the film sandwiched in the laminated glass owing to its merits, such as sturdiness, flexibility and great adhesiveness with glass as well as the high impact strength at low temperature. However, compared with these properties, heat-resistance of PVB is not so outstanding, which could be the main reason leading to PVB mechanical weakness in higher temperature range. Plasticized PVB is widely used for commercial laminated glass. Addition of plasticizer also generates decrease of glass transition temperature of pure PVB. Meanwhile, thermal and mechanical properties of PVB are also determined by the presence of butyral, hydroxyl and acetyl groups. Zirconium dioxide (ZrO2) is a kind of inorganic material which has high heat-resistance and strength, thus this research aims to improve thermal/mechanical properties of four types of PVBs by adding ZrO2 nanoparticles through sol-gel method and produce high-performance laminated glass experimentally using the improved PVBs-ZrO2 hybrid films as an interlayer film. Here four types of PVB, PVB60H, Plasticized PVB60H, PVB60HH and PVB60T, of which H, HH and T indicate the degree of acetalization, T being the lowest while HH being the highest. Hybrid films were tested by DMA (Dynamic Mechanical Analysis), TMA (Thermal Mechanical Analysis), tensile tests and experimental laminated glasses were measured by transmittance test and impact resistance test.DMA results showed that glass transition temperature Tg of PVB edged up monotonically with increasing vinyl alcohol (hydroxyl groups) content:Tg of HHZ-10 containing 12-16 wt% polyvinyl alcohol bottomed out at around 90℃, while Tg of TZ-10 topped at around 98℃, of which the polyvinyl alcohol content doubled than the former one. Plasticizer reduced the Tg of PVBs while both adding certain amount of ZrO2 particles into PVBs and annealing process under high temperature could effectively escalate the Tg and residual storage modulus of PVBs. TMA results showed that the diminishing absolute value of expansion coefficient of hybrid material could be increased by one or two orders of magnitudes as high by adding ZrO2 particles to form stronger crosslinking with the hydroxyl groups of PVBs. Increasing ZrO2 content and annealing temperature (100℃for plasticized PVB60H-ZrO2,130℃for PVB60H-ZrO2, PVB60HH-ZrO2 and PVB60T-ZrO2) contributed to increasing Young's modulus along with simultaneous decline of elongation at break. Better adhesiveness together with appropriate balance between tensile strength and elongation at break could improve the impact resistance of laminated glass. Adding 2.5-10 wt% of ZrO2 at high annealing could maintain even improve the impact resistance of PVBs laminated glass. With great balance between tensile strength and elongation at break, laminated glass sandwiching PVB60HH-ZrO2 (ZrO2 content 2.5/5/10 wt%) exhibited great impact resistance topped by laminated glass with plasticized PVB60H-ZrO2 (ZrO2 content 2.5/5 wt%) annealed at 100℃. Adulterating certain amount of ZrO2 (2.5-10 wt%) doesn't cause optical performance deterioration. The transmittance of plasticized PVB60H-ZrO2 films was 3-5% lower than that of PVB60HH-ZrO2, PVB60T-ZrO2 and PVB60H-ZrO2. In the ultra-violet zone of 200-400nm, PVB60H-ZrO2 and plasticized PVB60H-ZrO2 were UV-resistant while the UV light transmittance of PVB60HH and PVB60T reached to 60-80% which need to be solved by adding functional inorganic particle in further study. |
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