German speciality chemicals firm Lanxess will be showcasing new masterbatches for manufacturing reinforced rubber parts at K2019, which is taking place in Düsseldorf from October 16 to 23, The pre-dispersed additives from the Rhenogran product series are said to be easy to handle, dust free, simple to dose, and also exhibit outstanding processing properties.
“The short-fibre aramid pulp in the Rhenogran P91-40 types provide exceptional reinforcement. They improve dimensional stability and extend the service life of the end products that use them,” explained Dr. Benjamin Bechem, head of Global Marketing for Technical Rubber Goods at Lanxess’ Rhein Chemie (RCH) business unit.
Aramide fibre masterbatches have previously been available in natural rubber, EPDM, NBR and CR matrices. These can also be used in IR, BR, SBR and HNBR, making them virtual all-rounders. New additives pre-dispersed in silicone rubber (Q) and fluorinated rubber (FKM) are filling in the remaining gaps.
“For our next step, we are planning to develop masterbatches of this kind for use beyond rubber as well, such as for thermoplastic polymers,” added Bechem.
Rhenogran P91-40/Q is particularly suited to the manufacture of high temperature resistant, durable, wear-resistant silicone items such as washers and seals. The silicone matrix and the aromatic polyamides in the fibres form a perfectly matched pair, especially when exposed to high thermal stress.
The type dispersed in fluorinated rubber, Rhenogran P91-40/FKM, can be used to manufacture such products as high-performance rubber items for aviation, which withstand high operating temperatures, require good chemical resistance and outstanding dynamic properties. Each of the new additives has above 40% highly fibrillated pulp content, consisting of Twaron 1091 aramid fibres from Teijin Aramid B.V., based in Arnhem in the Netherlands.
The range of products offered by the business unit also includes reinforcing additives based on cellulose fibres (Rhenogran WP – wood pulp) in polymers such as SBR, EPDM and PVC. The native cellulose used comes from various types of hardwood. The renewable fibre material is biodegradable and is a contributing factor in the additive’s cost-effectiveness.
Rhenogran CNT types are currently being developed as further reinforcing additives for special applications that involve withstanding even higher mechanical stresses. Owing to concentrations of 1-2% for single-wall carbon nanotubes (CNTs) and more than 10% for multi-wall CNTs, these masterbatches can be diluted up to 20 times again in compounds. Exceptional thermal and electrical conductivity of the CNTs are additional attractive characteristics. The latter can be used, for example, to make a significant contribution to the anti-static properties of natural rubber compounds and synthetic rubber items.
Rhenogran CNT masterbatches are intended to expand the range of water dispersed CNT latex additives and initially available only in relatively highly diluted states. The water-free systems are produced from the aqueous Rhenofit CNT dispersions by coagulation.
“The special challenge in manufacturing CNT dispersions lies in finding a suitable dispersion method. For that, we use a particularly gentle process that does not destroy the nanostructures. Despite that, the process reliably unfolds and disentangles agglomerates formed during the production of the CNTs and would otherwise impair their homogeneous distribution in the rubber compound later on,” explained Bechem.
Homogeneous mixing in particular is a key prerequisite for achieving an optimized property profile in the end product. This is not usually possible with CNTs added as powders and thus in an agglomerated state. The development of CNT-based additives began at the Rhein Chemie business unit years ago as part of the Inno.cnt innovation alliance sponsored by the Federal Ministry of Education and Research.