Feng-Chih Chang

Characterization and properties of new silicone-containing epoxy resin

A new epoxy monomer, triglycidyloxy phenyl silane (TGPS) has been synthesized. By curing of TGPS, Epon 828 and DER 732, with 4,4diaminodiphenyl methane (DDM), the curing rate and conversion efficiency of these epoxy resins are in the order of TGPS. Epon 828 . DER 732: In the mixed epoxy system of TGPS/Epon 828/DDM, homogenous products are obtained from all proportions. In addition, the glass transition temperature of the blend decreases with increasing amount of TGPS from 140 to 1008C. By using TGA in a N2 environment, the onset decomposition temperature of silicone-containing epoxy resin system of TGPS is 808C lower than that of Epon 828, and the decomposition of TGPS is a two-stage process with maxima weight loss rates at 330 and 4308C, respectively. The first stage involves the breaking of the silicone-containing group in TGPS and the second-stage is carbonization. In the second stage of carbonization, the temperature for maximum weight loss rate is 158C higher than that of the Epon 828 in the first stage. This result indicates that the siliconecontaining group is in favor of the carbonization mechanism and the solid char yield at 8008C for TGPS is 40 wt%. Based on EDX analysis on the surface elements, the presence of Si and C is indicative of the above observation. In addition, the result by using TGA in an air environment shows that the silicon-containing carbon residue is superior in preventing oxidative burning. The high limiting oxygen index (LOI) of TGPS at 35 is considered as an excellent flame retardant in the epoxy system. q 2000 Elsevier Science Ltd. All rights reserved.

The novel polymer electrolyte nanocomposite composed of poly(ethylene oxide), lithium triflate and mineral clay

This work has demonstrated that the addition of optimum content of D-2000 modified montmorillonite enhances the ionic conductivity of the poly(ethyl oxide) (PEO) based electrolyte by nearly sixteen times more than the plain system. Specific interactions among silicate layer, ethyl oxide and lithium cation have been investigated using alternating current impedance (A.C. impedance), differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the initial addition of clay is able to enhance the PEO crystallinity due to the interaction between the negative charge from the clay and the lithium cation. Three types of complexes are present; complex I is present in the PEO phase, complex II resides at the interphase, and complex III is located within the clay domain. Complex II plays the key role in stabilizing these two microstructure phases. FT-IR spectra confirm that the existence of clay is able to dissolve the lithium salts, easier than the plain electrolyte system and thus increases the fraction of free ions.

Crystallization kinetics of poly(trimethylene terephthalate)

The isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) have been investigated using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Enthalpy data of exotherm from isothermal crystallization were analyzed using the Avrami theory. The average value of the Avrami exponent, n, is about 2.8. From the melt, PTT crystallizes according to a spherulite morphology. The spherulite growth rate and the overall crystallization rate depend on crystallization temperature. The increase in the spherulitic radius was examined by polarized light microscopy. Using values of transport parameters common to many polymers (U* = 1500 cal/mol, T∞= Tg − 30 °C) together with experimentally determined values of T (248 °C) and Tg (44 °C), the nucleation parameter, kg, for PTT was determined. On the basis of secondary nucleation analyses, a transition between regimes III and II was found in the vicinity of 194 °C (ΔT ≅ 54 K). The ratio of kg of these two regimes is 2.1, which is very close to 2.0 as predicted by the Lauritzen–Hoffman theory. The lateral surface-free energy, σ = 10.89 erg/cm2 and the fold surface-free energy, σe = 56.64 erg/cm2 were determined. The latter leads to a work of chain-folding, q = 4.80 kcal/mol folds, which is comparable to PET and PBT previously reported.

Glass transition temperatures of poly(hydroxystyrene-co- vinylpyrrolidone-co-isobutylstyryl polyhedral oligosilsesquioxanes)

A series of poly(hydroxystyrene-co-vinylpyrrolidone-co-isobutylstyryl polyhedral oligosilsesquioxanes) (PHS–PVP–POSS) hybrid polymers with various POSS contents was prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with styrylisobutylpolyhedral oligosilsesquioxanes (POSS), followed by selective removal of the acetyl protective group. The POSS content of a hybrid polymer can be effectively controlled by varying the feed ratios of reactants. The Tg of the POSS hybrid increases with the POSS content of PHS–PVP–POSS hybrids. The mechanism of Tg enhancement in these PHS–PVP–POSS hybrids was investigated using DSC, FTIR and GPC. The formation of the physically cross-linked POSS in these hybrid polymers trends to restrict polymer chain motion and results in significant Tg increase.

Thermal properties and hydrogen bonding in polymer blend of polybenzoxazine/poly(N-vinyl-2-pyrrolidone)

Abstract The thermal properties and hydrogen bonding behavior of B-a type polybenzoxazine (PBZZ)/PVP blends were investigated by DSC and FTIR. The DSC result shows a single Tg over the entire compositions and a large positive deviation based on Kwei equation was observed in the Tg versus composition diagram, implying that strong hydrogen bonding interaction exists between PBZZ and PVP segments. The strength of hydrogen bonding interaction is in the order of inter-association between the hydroxyl group of PBZZ and the carbonyl group of PVP (K A =594 L mol −1 ) >self-association between the hydroxyl group of pure PBZZ (K B =72.6 L mol −1 ) >inter-association between the hydroxyl and the Mannich-based bridge of pure PBZZ (K C L mol −1 ). Good correlation between DSC and FTIR analysis were observed.

Ionic conductivity enhancement of the plasticized PMMA/LiClO4 polymer nanocomposite electrolyte containing clay

Abstract This work has demonstrated that the addition of an optimum content of dimethyldioctadecylammonium chloride (DDAC)-modified montmorillonite clay (Dclay) enhances the ionic conductivity of the plasticized poly(methyl methacrylate)-based electrolyte by nearly 40 times higher than the plain system. Specific interactions among silicate layer, carbonyl group (CO) and lithium cation have been investigated using Fourier-transform infrared (FTIR), solid-state NMR, alternating current impedance. The FTIR characterization confirms that both of the relative fractions of ‘complexed’ CO sites and ‘free’ anions increase with the increase of the Dclay content, indicating that strong interaction exists between the CO group and the lithium salt. In addition, the solid-state NMR demonstrates that the interaction between the PMMA and the clay mineral is insignificant. The addition of clay mineral promotes the dissociation of the lithium salt and thus, the specific interaction can be enhanced between the CO and the free lithium cation. However, the balanced attractive forces among silicate layers, CO groups, lithium cations and anions is critical to result in the higher ionic conductivity.

Synthesis and Characterization of Copolyesters Containing the Phosphorus Linking Pendent Groups

Poly(ethylene terephthalate)-co-poly(ethylene DDP)s (PET-co-poly(ethyl- ene DDP)s), were synthesized by charging 9,10-dihydro-9-oxa-10-phosphaphenan- threne-10-oxide (DOP), itaconic acid, terephthalic acid, and ethylene glycol in one reactor to conduct the microaddition reaction (using H2PtCl6 as catalyst), esterification reaction, and polycondensation reaction. H2PtCl6 has demonstrated to be a highly efficient microaddition catalyst to improve the DDP conversion. The microaddition reaction of the phosphorus compound (DOP) with the itaconic acid can be proceeded at a significantly lower temperature (110°C) and results in higher conversion (. 98%). The use of the H2PtCl6 catalyst makes it possible to charge all the reactants in one reactor to produce high molecular weight phosphorus-containing copolyesters without requir- ing the presynthesis of the DDP. These resulting copolyesters are identified by Fourier transform infrared spectroscopy, 1 H-NMR, and differential scanning calorimetric anal- ysis. Thermal characteristics, thermal stability, intrinsic viscosity, acid value, and rheological and mechanical properties of these copolyesters were also characterized. The presence of the bulky pendent phosphorus side groups in the copolyester tends to decrease the structural regularity and retards its crystallization. The formation of a protected char layer for the phosphorus-containing copolyester raises the decomposi- tion temperature of the copolyester under an oxygen atmosphere higher than that of PET. The limiting oxygen index values of all phosphorus-containing copolyesters are all higher than 33. Higher phosphorus content results in decreasing crystallinity, lower melting temperature, lower decomposition temperature, as well as lower tensile strength, but increasing residual char after thermal degradation and higher limiting oxygen index value. The rheological behaviors of copolyesters remain similar to that of PET. The glass temperatures of copolyesters are all ; 77°C (76.8°-77.2°C). Incorpora- tion of phosphorus moieties into its molecular chain has a significant effect on thermal and flame retardancy behavior. However, the crystal lattice of all copolyesters do not change with incorporation of the pendent phosphorus side group in the backbone of the copolyester.

Polymer blends of polyamide-6 (PA6) and poly(phenylene oxide) (PPO) compatibilized by styrene-maleic anhydride (SMA) copolymer

Abstract The commercially available styrene—maleic anhydride copolymer (SMA—8% MA) has been demonstrated to be a highly effective compatibilizer for polymer blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). SMA is miscible with PPO and tends to be dissolved in the PPO phase during the earlier stages of melt blending. The dissolved SMA has the chance to make contact and reacts with PA6 at the interface to form the desirable SMA- g -PA6 copolymer. This in situ -formed SMA- g -PA6 graft copolymer tends to anchor along the interface to reduce the interfacial tension and results in finer phase domains. The overall mechanical property improvement of the compatibilized blends over the uncompatibilized counterparts is drastic, especially for these PPO-rich blends. The mechanism of this conventional reactive compatibilization system has been discussed in detail.

Poly(oxypropylene)-amide grafted polypropylene as novel compatibilizer for PP and PA6 blends

Poly(oxypropylene)-amide grafted polypropylene (PP) was prepared in an extruder by the reaction of poly(oxypropylene) (POP)diamines and maleated PP (PP-g-MA). The resulting POP-grafted PP copolymers are confirmed by the FTIR analysis, and used as compatibilizers for polyamide 6 (PA6) and polypropylene blends. These compatibilizers, POP-functionalized PPs (PP-g-MA-co-POPs), have different amphiphilic properties depending on the content of MA in the starting PP-g-MA and the molar ratio of MA/amine. The compatibilization effect is examined in terms of morphologies, thermal and mechanical properties. The morphologies, affected by the molecular weight of POP diamine in PP-g-MA-co-POP copolymer, show a decreasing size of the dispersed PA6 particles as the molecular weight of POP diamine increasing from 230 to 400 to 2000. Using these PP-g-MA-co-POP copolymers, the compatibilized blends show improvements in mechanical properties, including Izod impact strength and tensile toughness, over a conventional compatibilizer. The POP and amide functionalities in the compatibilizers can facilitate the formation of hydrogen bonding with PA6 and, therefore, the compatibilizing effect. During the compounding process, the compatibilizers further react with PA6 in situ to afford the mixture of PP-g-MA-co-POP-PA6, PP-g-MA-co-POP-co-PA6 and PP-g-MA-co-PA6 copolymers, which further improves the compatibilizing effect.

Reactive compatibilization of polymer blends of poly(butylene terephthalate) (PBT) and polyamide-6,6 (PA66) .1. Rheological and thermal properties

Abstract Epoxy resin (EEW = 2060) has been demonstrated to be an efficient reactive compatibilizer for the incompatible polymer blends of polyamide-6,6 (PA66) and poly(butylene terephthalate) (PBT). Processability improvement has been achieved by reducing die swell and melt fracture during blending extrusion. Reactions involved in this three-component system are very complex but only the coupling reactions between epoxy and PBT and PA66 endgroups are considered essential. This epoxy resin is more compatible with PBT than with PA66 but the reactivity of the former is slower than that of the latter. Additionally, PBT has a lower melting temperature than that of PA66; this epoxy resin therefore has the first chance to react with PBT, then with PA66, at the interface. Certain mixed copolymers, epoxy-co-PBT-co-PA66, are expected to be frmed and to anchor at the interface. These mixed copolymers are believed to be the major contributor in improving the compatibility of incompatible PA66/PBT blends.