Use powders anytime they satisfy specifications and application requirements when compounding and mixing rubber. Powders provide the least expensive approach to rubber compounding. Additives are not needed when they don't bring value or provide clear benefits.
However, the least expensive raw material doesn't always translate to the lowest cost compound. There are times when performance additives bring value and provide clear benefits. Examples of these benefits include reducing manufacturing time, providing a safe means of handling difficult raw materials, and improved product and process uniformity.
But how do compounders and plant chemists and the right performance additives for their applications? With so many options, the choices can be overwhelming. To start, desired outcomes must be carefully defined. A systematic approach is necessary that defines objectives clearly, such as: better throughput and/or precise control of critical ingredients, lower costs with shortened mixing cycles, timely and complete dispersion, minimized airborne dust, ease of handling and incorporation, worker safety, and color control.
To meet these objectives there are multiple performance additive types to be considered and evaluated for each application, including pre-weighed materials, dust-suppressed powders, encapsulations, absorbed liquids, partitioned solids, polymer-based dispersions, paste dispersions, and color dispersions. (Definitions of each of these additive types are provided in the following Power of Performance Additives article.)
A typical formulation starts with a base rubber polymer, but may have 10 to 20 additional ingredients that influence each other, as well as the end product (See the Recipe Chart). It's true that performance additives shouldn't be used unless they bring value, but nearly 78% of all formulations require some sort of additive.
Designers and plant chemists sometimes have limited experience with rubber and often rely on the analytical and resource capabilities of polymer compound service providers. They need assistance making selections for their applications. Chemists and technicians from polymer service providers, such as those on the HEXPOL Compounding team, ask the right questions about the application to ensure selection of the right performance additives meet defined compounding objectives.