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Novel Siloxane-Modified Epoxy Resins as Promising Encapsulant for LEDs
(2020-01-01)
Lin, Chih-Hao
;
Whang, Wha-Tzong
;
Chen, Chun-Hua
;
Huang, Shu-Chen
;
Chen, Kai-Chi
This study investigated a new category of transparent encapsulant materials for light-emitting diodes (LEDs). It comprised a phenyl group that contained siloxane-modified epoxy (SEP-Ph) hybridized with a cyclic tetrafunctional siloxane-modified epoxy (SEP-D4) with methylhexahydrophthalic anhydride (MHHPA) as a curing agent. The SEP-Ph/SEP-D4 = 0.5/0.5 (sample 3) and SEP-D4 (sample 4) could provide notably high optical transmittance (over 90% in the visible region), high-temperature discoloration resistance, low stress, and more crucially, noteworthy sulfurization resistance. The lumen flux retention of the SEP encapsulated surface mounted device LEDs remained between approximately 97% and 99% after a sulfurization test for 240 h. The obtained comprehensive optical, mechanical, and sulfurization resistance proved the validity and uniqueness of the present design concept with complementary physical and chemical characteristics.
Poly(vinyl alcohol)-controlled synthesis of monodispersed crosslinked poly(methyl methacrylate) microparticles with significantly improved mechanical properties
(2019-07-01)
Kao, Yu-Chen
;
Chen, Chun-Hua
;
Whang, Wha-Tzong
;
Chen, Yi-Chun
;
Chen, Kai-Chi
A facile synthesis concept focusing on the poly(vinyl alcohol) (PVA) concentration induced interfacial energy effects in seed swelling polymerization was realized for the successful fabrication of a series of monodispersed poly(methyl methacrylate) (PMMA) microparticles with four crosslinking agents, 2,2-bis[(methacryloyloxy)methyl]butyl methacrylate, 1,2-ethanediyl bis(2-methylacrylate), 1,3-divinylbenzene and 1,2-ethanediyl diacetate. We revealed a special role of PVA in regulating the diffusion of crosslinking agents as well as the swelling degree of latex seeds and, more noticeably, the consequent improved mechanical properties of the crosslinked PMMA microparticles formed. The highest recovery rate obtained from the PMMA microparticles with 0.6 wt% PVA approached 67%, which is higher than or comparable to reported values. This work not only developed a new facile synthesis approach for producing highly uniform tough crosslinked PMMA microparticles for more potential applications but also provided valuable insights into fundamental aspects of seed swelling polymerization. (c) 2019 Society of Chemical Industry
Effect of doping metal ion on holographic storage characteristics of PQ/poly(hydroxyethyl methacrylate-co-methyl methacrylate) hybrids
(2007-01-01)
Cheng, Wei-Sheng
;
Whang, Wha-Tzong
;
Chang, Yu-Chia
;
Chen, Po-Lin
;
Hsiao, Yi-Nan
Holographic Storage Characteristics of PQ/poly(methyl methacrylate) have been significantly improved by doping metallic ion Yb+3 and Er+3. The hybrid materials display significant enhancement in the holographic 13 +3 characteristics. The diffraction efficiency promote to 59% with Yb+3, to 47% with Er from the undoped sample is 40%. The increment is up to 47% in Yb+3 sample; the dynamic range enhance to 2.12 and 1.58 on Yb+3 and Er+3 containing sample individually in comparison to 1.16 for the undoped copolymer. The increment of dynamic range is up to 82% for Yb+3 containing sample. The related mechanism of these changes is preliminary discussed with the analysis of UV-vis, FT-IR and Photoluminescence spectroscopy.
Zr-MOF/Polyaniline Composite Films with Exceptional Seebeck Coefficient for Thermoelectric Material Applications
(2019-01-23)
Lin, Chih-Chien
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Huang, Yi-Chia
;
Usman, Muhammad
;
Chao, Wen-Hsuan
;
Lin, Wei-Keng
Controlling the polymerization of aniline in the presence of zirconium-based metal-organic frameworks (Zr-MOFs) using polystyrene sulfonic acid as a dopant resulted in the formation of a new type of freestanding thermoelectric composite film. Polyaniline chains interpenetrate into the Zr-MOFs to enhance the crystallinity of polyaniline, resulting in an improved degree of electrical conductivity. In addition, the inherent porosity of the Zr-MOFs functions to suppress the increase in thermal conductivity, thus dramatically promoting a negative Seebeck coefficient. When 20 wt % Zr-MOF was used, a power factor of up to 664 mu W/(m K-2) was obtained, which was accompanied by a surprisingly large, negative Seebeck coefficient. The new class of MOF-based composites offers a new direction for developing new types of efficient thermoelectric materials.
Effect of crosslinking agents on the dispersive behaviour of polymer particles in seed swelling polymerisation
(2017-07-25)
Kao, Yu-Chen
;
Whang, Wha-Tzong
;
Chen, Yi-Chun
;
Chen, Kai-Chi
;
材料科學與工程學系
This study focused on the effect of crosslinker structure between PMMA on the dispersity of crosslinked particles in seed swelling polymerisation. We used five different crosslinking agents in an assessment of the dispersity of crosslinking monodisperse particles using PMMA seed particles in seed swelling polymerisation. These results show that the structure of the crosslinking agent affects the dispersity during the swelling stage. According to the solubility parameter theory of computation, the departure of similar solubility parameter causes the swollen particles to segregate into more dispersity. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Facile Synthesis of Diamino-Modified Graphene/Polyaniline Semi-Interpenetrating Networks with Practical High Thermoelectric Performance
(2018-02-07)
Lin, Yen-Hao
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Lee, Tsung-Chi
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Hsiao, Yu-Sheng
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Ling, Wei-Keng
;
Whang, Wha-Tzong
p-Phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs not only provide additional pathways by creating chemically bonded PDG and PANI for smoothly transporting carriers but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electrical conductivity, Seebeck coefficient, and thus the thermoelectric (TE) performance. The found optimized TE figure of merit (ZT) of 0.74 approaches a practical high level which is comparable or much higher than previously reported ones for TE polymers.
Humidity-switch chromism of aniline-pentamer in Nafion
(2016-08-19)
Lin, Yen-Hao
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Hsiao, Yu-Sheng
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Lu, Hsiao-Chi
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Chen, Peilin
;
Whang, Wha-Tzong
Aniline-pentamer (AP) in Nafion triggered with humidity content displays an interesting chromism from blue to pink, which is much wider of color shift than general polyaniline. Thermogravimetric analysis confirms the reversal color change related to the moisture content in the sample. IR absorption spectra make known AP having high degree of protonation at lower water content. UV-Vis absorption expose the chromism process having something more than just protonation. The change of electronic energy levels and PL spectra reveal that there must be a complex interaction in NaAP. Raman scattering mapping confirms that drying causes the - SO3- hydrophilic channels transforming to isolated domains dispersed in matrix, which induces heavy protonation and complexation of AP with - SO3- groups. We can infer that the interesting humidity-switch chromism is due to the reversible protonation/deprotonation as well as complexation of AP with - SO3- groups through the reversible change of Nafion\'s morphology.
Anti-corrosion characteristics of polyimide/h-boron nitride composite films with different polymer configurations
(2014-12-15)
Huang, Yi-Chia
;
Lo, Teng-Yuan
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Chao, Cheun-Guang
;
Whang, Wha-Tzong
;
材料科學與工程學系
Anti-corrosive polyimide/hexagonal boron nitride (PI/h-EN) composite films were prepared with different monomers to offer different polymer configurations: rigid and soft. In PI/h-BN composite films, different configurations of polymers show different crystallinity trends of the polymer matrix. In our study, the degree of crystallinity in rigid polymer decreases with the EN content; in flexible polymers it is independent of the BN content. It is worth noting that BN in different PI matrices can effectively enhance the protection of steel from corrosion. With a flexible PI matrix, the PI/h-BN coating exhibited better resistance to water vapor and better anti-corrosion. Only 5 wt.% of h-BN in the composite is enough to offer high anti-corrosion, a positive corrosion voltage. (C) 2014 Elsevier B.V. All rights reserved.
A Facile Surface Treatment Utilizing Binary Mixtures of Ammonium Salts and Polar Solvents for Multiply Enhancing Thermoelectric PEDOT: PSS Films
(2014-12-01)
Tsai, Tsung-Che
;
Chen, Tsung-Han
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Chang, Hsiu-Cheng
;
Chen, Chun-Hua
;
Huang, Yi-Chia
Smart assembling of multi-scaled functional interfaces in thermoelectric Ga2Te3/Te hetero-nanocomposites
(2014-01-01)
Chang, Hsiu-Cheng
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Chiang, Ming-Hsiu
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Tsai, Tsung-Che
;
Chen, Tsung-Han
;
Whang, Wha-Tzong
We describe an innovative concept and facile approach in fabricating laterally assembled Ga2Te3/Te binary nanocomposite films, which comprise two-dimensional quasi-periodic Ga2Te3 nanoassemblies surrounded by interlocking highly-conductive Te single crystals for comprehensively establishing subnanoto micro-scaled multi-style versatile interfaces. The distinct Ga2Te3/Te nanocomposite film exhibits a power factor that is about 60 times higher than the reported conventional Ga2Te3 and Te materials, mainly due to the 2- to 3-order improved electrical conductivity and the comparable Seebeck coefficient.

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