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Thermo-reactive Para-alkyl phenolic resins are commonly used as crosslinkers for natural and synthetic rubber. Hydroxymethyl should be included in the phenolic resin. In actual production, they are mainly used in composite rubber that requires high heat resistance, and for natural rubber, their addition reduces the occurrence of sulfur return in the vulcanization system. The addition of these resins can improve the heat resistance, improve the mechanical properties, good insulation properties and improve the aging resistance of the rubber.