over-vulcanize
/ˌəʊvəˈvʌlkənʌɪz/(also overvulcanise, overvulcanize)
verb
[with object] To subject to over-vulcanization; to make (rubber) hard or brittle by excessive vulcanizing; to overcure (rubber).
Origin
Early 20th century. From over- + vulcanize. Compare earlier over-vulcanization.