Herbert Shin-I Chao

Phase behavior and morphology of poly(phenylene ether)/epoxy blends

Abstract The miscibility of diglycidyl ether of bisphenol-A (DGEBA) based epoxies with a series of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) resins was measured and the effects of PPE molecular weight, end-capped or grafted functionality, and blend composition were explored. Interpretation of phase behavior was aided by the use of the Flory–Huggins theory. Miscibility behavior in the unreacted blends was found to correlate with trends in phase separation during the curing reaction. The cured morphologies of these blend systems were also studied. The compatibilization effect of PPE-epoxy copolymer formation was found to play a dominant role in determining the final size of the dispersed phase, while temperature control of reaction and mass transfer kinetics were identified as a possible means of further affecting the cured morphology.

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) redistribution and its significance in the preparation of PPE/epoxy laminate

Abstract To facilitate the PPE /epoxy copolymer formation, PPE was redistributed with phenolic compounds to increase the reactive functional groups per PPE chain. Moreover, the resulting PPE with lower molecular weight improved the resin flow during lamination. An optimized process for producing low molecular weight PPE has been developed. The process was accomplished by redistributing regular PPE (0.46 or 0.40 intrinsic viscosity) with benzoyl peroxide and 4,4′-isopropylidenediphenol (BPA) in toluene. The benzoate group was found to be predominantly incorporated at the PPE chain end and the α carbon of the PPE repeating unit. A portion of the amine-containing phenolic end group, the quinone methide precursor, was oxidized to form a dihydro-1,3-benzoxazine derivative during the redistribution process. However, no dienone structural moiety, a proposed PPE redistribution intermediate, could be identified in the redistributed PPE. Two Tg values representing epoxy and PPE phases were usually observed in the PPE /epoxy laminates. Interestingly, the T8 of the PPE phase was equal to, or higher than, that of the PPE powder from which the laminate was made.

Poly(2,6-dimethyl-1,4-phenylene ether) (PPO®) capping and its significance in the preparation of PPO®/epoxy laminate

The thermal expansion property at 288°C of poly(2,6-dimethyl-1,4-phenylene ether) (PPO®)/epoxy laminate was found to be affected by the PPO/epoxy copolymer content in the laminate. Capping of redistributed PPO with epoxide-containing reagents such as Araldite® EPN 1138 and an “upstaged” resin was readily accomplished with tetraethylammonium hydroxide or N, N-dimethylaminopyridine as the catalyst during the varnish preparation step. The resulting PPO/epoxy laminate maintained the nonlofting property despite the presence of phenolic hardener (curing accelerator) and antimony pentoxide (flame retardant) in the formulation.

A31P NMR study of poly(phenylene oxide) (PPO)(1) resin's hydroxyl end groups

SummaryThe hydroxyl end groups of PPO resin, made from Cu/di-n-butylamine, 2,6-xylenol and oxygen, were capped with diphenyl chlorophosphate. A31P n.m.r. method was developed to distinguish the 2,6-xylenol and 2-methyl-6-(N,N-di-n-butylamino)methyl phenol end groups, which are directly related to the resins thermal stability.

The Reduction of Mannich Bases and Their Derivatives by Tri-N-Butyltin Hydride

Abstract Overall nuclear methylation of phenols was achieved by deamination of their Mannich bases and related derivatives with tri-n-butyltin hydride. The α-methylation of ketones was also similarly achieved.

Detection of Nylon‐6,6 Cyclic Monomers on Polymer Surfaces using Static SIMS

The characteristic static SIMS spectra of the cyclic monomer of Nylon-6,6 have been obtained from the isolated and purified material. The spectra are sufficiently different from those obtained from bulk Nylon-6,6 polymer. Intense fragment ions corresponding to (M+H)+ and (M-H)− are observed in the positive and negative ion spectra, respectively. Results from both quadrupole and ToF-SIMS measurements are presented.

Improved Synthesis of Trans-4-Diethylaminocinnamaldehyde

Abstract The title compound was prepared from diisobuty1 aluminum hydride reduction of 4-diethylaminocinnamonitrile, which in turn was obtained by condensing 4-diethylaminobenzaldehyde and cyanoacetic acid.

Tri-n-butyltin hydride reduction of the end group of a polyphenylene ether

SummaryA method using tri-n-butyltin hydride to reduce the 2-methyl-6-(N,N-di-n-butylamino)methyl phenol end group on PPO®(4) was developed. It generated a polyphenylene ether (PPE) with 2,6-xylenol as the only phenolic end group without causing any significant increase in molecular weight.

Preparation and characterization of a polyphenylene ether and Nylon-6 block copolymer

SummaryA block copolymer of PPO®(1) and Nylon-6 was prepared through modification of the hydroxyl end group of the polyphenylene ether (PPE) with cyanuric chloride or 4,4′-difluorobenzophenone and subsequent anionic polymerization of ɛ-caprolactam using the modified PPE as the promoter. The pure copolymer was isolated by selective solvent extraction, using chloroform to remove PPE homopolymer and unreacted ɛ-caprolactam, and formic acid to remove Nylon-6 homopolymer. The copolymer has two melting points indicative of the Nylon and PPE segments. Its composition has been determined by carbon-13 NMR and elemental analysis.