Abstract: An aramid particle containing a peroxide radical initiator wherein the particle contains 3-40 wt % peroxide radical initiator based on the weight of the aramid particle. Also, disclosed is a particle-elastomer composition having 100 parts by weight of at least one natural or synthetic elastomer, such as rubber; 0.1 to 20 parts by weight of a peroxide or 0.1 to 25 parts by weight of sulfur, an amount of a sulfur donor providing the equivalent of 0.1 to 25 parts by weight of sulfur, or a mixture of sulfur and a sulfur donor to an equivalent total of 0.1 to 25 parts by weight of sulfur; and 0.1 to 20 parts by weight of the aramid particle.

Abstract: The invention pertains to a composition comprising a particle and a matrix, the particle being at least partially coated with a composition comprising: a) a Bunte salt (A); b) a polysulfide (B) comprising the moiety —[S]n— or —[S]0—Zn—[S]p, wherein each of o and p is 1-5, o+p=n, and n=2-6; and c) sulfur or a sulfur donor (C). Preferably, the matrix contains a wax. Most preferred polysulfide (B) has the formula: wherein each of o and p is 1-5, o+p=n, and n=2-6; and R is independently selected from hydrogen, halogen, nitro, hydroxy, C1-C12 alkyl, C1-C12 alkoxy, and C1-C12 aralkyl; and d) sulfur or a sulfur donor (C). The invention further relates to a vulcanization process comprising the use of said composition, the elastomer composition thus obtained, and a skim composition, tire, tire tread, undertread, or belt containing the same.