Rubber Accelerators

Robac SRM102, a New Safe and Effective Replacement for ETU in Polychloroprene

Abstract
Polychloroprene rubber (CR) is used in a diverse range of applications from automotive (hoses, belts and windscreen wiper blades), engineering (bridge and railway mounts), sporting goods (footwear and wetsuits) to cable sheaths. The most effective curative for CR is ethylene thiourea (ETU) in combination with zinc oxide (ZnO). ETU however, is a reprotoxin and suspected endocrine disruptor and has recently been included in the Candidate list of Substances of Very High Concern (SVHC) by the European Chemical Agency (ECHA). As a consequence, ETU is expected to be phased out of use through regulation in the European Union and an alternative agent must be sourced. This will have implications for the Global market as a whole.

This paper introduces Robac SRM102 as a new safe and effective replacement accelerator for ETU in polychloroprene. We provide data comparing a commercial CR masterbatch cured with Robac SRM102 with the same masterbatch cured with ETU, and show that the rheology and mechanical properties of vulcanisates cured with Robac SRM102 are comparable or better than those using ETU.

In recent years, concern in the industry about the impact of heavy metals in the environment as a result of using inorganic activators such as ZnO has also grown. To address this issue, SRM102 was designed specifically with dual functionality in mind to behave as both an accelerator and an activator, i.e. as a multifunctional accelerator. We show that by using Robac SRM102, the standard level of ZnO (5phr) can be reduced in CR to 1phr without affecting the physical properties of the vulcanisates even after thermal ageing.

In this paper, we also provide preliminary data to show that Robac SRM102 can be used as an effective curative in epichlorohydrin (ECO) and VAMAC polymers.