Novel activator for DPG replacement and property improvement
This paper demonstrates the properties of a novel ionic liquid activator as a DPG replacement and cure additive. The novel activator shows good cure time yet demonstrates scorch safety and some accelerator and zinc efficiency. This paper will focus on the DPG replacement for tyre and conveyor belt segments of rubber manufacturing.
The role of DPG (diphenylguanidine) as co-activator (and co-accelerator) with a sulfenamide is well established in the tyre manufacturing industry. The use of the DPG boosts the cure speed whilst also offering advantages in dynamic properties due to its interaction with silicic acid as it is an organic base. This effect is often seen as improved tan δ results that are lower than for many other cure combinations and boosters. The effects of cure boosting and rolling resistance improvement are conventionally superior when using a sulfenamide and DPG.
The automotive industry is driving the trend to eliminate DPG as it is a potential precursor for aniline. This makes a potentially hazardous chemical compound inside rubber articles. This paper demonstrates the application of a novel activator comprising an ionic liquid, which is capable of replacing DPG and yielding matching or improved product behaviour. The novel activator shows good cure time yet demonstrates scorch safety and some accelerator and zinc efficiency. This paper focuses on the DPG replacement for tyre and conveyor belt segments in rubber manufacturing. The study is conducted on two main rubber compounds, a carbon black filled NR and a highly silica filled SBR which has been silanized. The different effects of varying zinc oxide content, addition of extra silica, removal of DPG content, addition of the DPG replacements Premix Acti 8 and Activ8 on cure characteristics and mechanical properties of the materials are evaluated.
The NR compounds are faster in curing with the Activ8 than with the silica containing Premix Acti 8. This is evidence of the scorch delaying impact of the silica content of the Premix. This is also apparent in the SBR compounds. The SBR compounds have superior aging to the control material while the NR is inferior. The SBR compounds (which are silica filled) showed good aging and property retention. With some of the SBR compounds excellent property retention and dynamics were achieved. The dynamics were good for all compounds.
R. Bosch, RFP Rubber Fibres Plastics, 01 2020, 32-37.