A thermoset material containing β-hydroxyesters wherein said thermoset material is subject to a mechano-chemical process to regenerate an epoxide and a carboxylic acid functionality. A curative for epoxidized plant-based oils and epoxidized natural rubber is created from the reaction between a naturally occurring polyfunctional acid and an epoxidized plant-based oil is disclosed. The curative may be used to produce porosity-free castable resins and vulcanize rubber formulations based on epoxidized natural rubber. Materials made from disclosed materials may be advantageously used as leather substitutes.