A novel cured polyphenylene ether resin is disclosed comprising a chloroform nonextractable polyphenylene ether and a chloroform extractable polyphenylene ether. By subjecting the resin to pyrolysis gas chromatography, the resin is decomposed to form 3,5- dimethylphenol specifically. The chloroform extractable polyphenylene ether is contained in the resin in an amount of 0.01 to 20% by weight and comprises polyphenylene ether units substituted by an alkenyl group and/or an alkynyl group. The novel cured polyphenylene ether resin has excellent mechanical properties, electrical properties, heat resistance and chemical resistance. The cured polyphexylene ether resin is prepared by curing a novel curable polyphenylene ether resin comprising polyphenylene ether units substituted with an alkenyl groups and/or an alkynyl groups at a specific average substitution degree. The novel curable polyphenylene ether resin has not only excellent mechanical properties and desired electric properties such as a low dielectric constant and a low dielectric dissipation factor, but also excellent melt processability and storage properties.
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