Yufeng Huang,Yakai Feng,Xujun Sun,Ying Han,Dongshun Liu,Xiaohua Tan
Organic silicones have been used as encapsulant materials for light-emitting diodes (LEDs) for many years, while their performances need to be improved in order to satisfy the requirements of high-power LEDs. A ZrO 2 /silicone hybrid resin (ZHR) was synthesized for LEDs encapsulation by in situ sol-gel reactions. The oligosiloxane was synthesized as polymeric matrix by nonaqueous sol-gel condensation using diphenylsilanediol (DPSD), vinyltrimethoxysilane (VTMS), and 3-methacryloxy propyl trimethoxysilane (MPTMS) as monomers. Then zirconium propoxide was added into this polymeric matrix to be hydrolyzed to obtain the hybrid resin with a uniform dispersion of ZrO 2 nanoparticles. The Si–O–Zr covalent bond was detected and benefited for excellent dispersibility of the ZrO 2 nanoparticles and the well compatibility between organic and inorganic phases. The cured ZHR with 5 wt% ZrO 2 content showed high light transmittance (greater than 80% in visible light range), high refractive index (=1.56), and high thermal stability (no yellowing at 150°C for 240 hours). The luminous flux of the LED chip with ZHR encapsulant was 10% higher than that of the pure silicone resin, suggesting that ZHR has great application potential in the field of LED packaging.
A UV-curable poly(butyl fumarate) (PBF)/poly(propylene fumarate)-diacrylate (PPF-DA) hybrid material with good performance for LED encapsulation is introduced in the paper. They have been prepared by radical polymerization using PBF and PPF-DA macromers with a UV curing system. PBF and PPF-DA were characterized by Fourier-transform infrared (FT-IR) and H-nuclear magnetic resonance (1H NMR). The thermal behavior, optical and mechanical properties of the material were examined by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), ultraviolet-visible spectroscopy (UV–vis), and a material testing system mechanical testing machine, respectively. The results indicated that the hybrid material has a suitable refractive index (n= 1.537) and high transmittance (99.64% in visible range) before/after thermal aging. With the increasing of the double bond ratio from 0.5 to 2, the water absorption ratios of the prepared encapsulation material were 1.22%, 1.87% and 2.88%, respectively. The mechanical property experiments showed that bonding strength was in the range of 1.86–3.40 MPa, tensile-shear strength ranged from 0.84 MPa to 1.57 MPa, and compression strength was in the range of 5.10–27.65 MPa. The cured PBF/PPF-DA hybrid material can be used as a light-emitting diode (LED) encapsulant, owing to its suitable refractive index, high transparency, excellent thermal stability, lower water absorption, and good mechanical properties.Keywords:poly(butyl fumarate)-based polymer;composites;characterization;UV-curing;LED encapsulant
Vinyl-containing titanium-silphenylene-siloxane oligomers ( O1 , O2 , O3 , and O4 ) with different molar ratios of titanium to silicon were successfully synthesized in high yields by nonhydrolytic sol-gel reaction, and the obtained four oligomers were further crosslinked with methylphenyl hydro-silicone oil ( 4 ) to form corresponding polymers ( P1 , P2 , P3 , and P4 ) by hydrosilylation reaction. Their structures were characterized with spectroscopic characterization techniques including FTIR, 1 H-NMR, and Raman spectroscopy. The effect of titanium element on crosslinking behavior, thermal resistance, refractive index, transparency, thermal aging stability, glass transition temperature, and surface properties of the polymers were studied. Compared with titanium-free polymer P1 , the thermal resistance, refractive index, and thermal aging stability of titanium-silphenylene-siloxane polymers ( P2 , P3 , and P4 ) were significantly improved. The titanium-silphenylene-siloxane polymers achieved a high refractive index ( n = 1.580–1.584) and thermostability ( T 5d > 500 °C). In thermal aging, the polymers exhibited superior performances with high optical transparency (~90% at 450 nm) and exhibited high thermal stability (~84% at 450 nm after thermal aging at 150 °C for 120 h). These data indicate that the polymers have potential application in optical materials such as LED encapsulants.
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