Polymer bound dispersions or chemical masterbatches are names given to rubber chemicals that are suspended on a binder system to improve dispersability and to reduce health, safety, and housekeeping issues. Polymer bound dispersions have been around for a long time; however, they have grown in popularity due to the desire for improved product performance and scrap reduction. A variety of rubber chemicals can be suspended on polymer binder systems but the most common are curatives, accelerators, and antioxidants. Polymer bound dispersions of the before mentioned rubber chemicals are used because they reduce fly loss and improve dispersability leading to improved compound consistency. Other common polymer bound rubber chemicals include zinc oxide, magnesium oxide, and antimony oxide which can cause dispersion issues when used in the raw powder state.
Initially, the most common polymer used in polymer bound dispersions was ethylene propylene rubber (EPR). EPR is ideal for polymer bound dispersions because it is not curable with sulfur or standard rubber accelerators increasing the shelf life 100%. EPR can also incorporate high amounts of chemical additives leading to increased activity levels. Although EPR is the most common polymer, polymer bound dispersions can be made with a variety of different polymers including SBR, EPDM, NR, and NBR.
Due to improvements in dispersion technology many new polymer binder systems are being used today to help reduce the melt point of the bound chemical to improve its dispersability. Melt point of rubber accelerators plays a key role in how well they disperse in the rubber compound; because the addition of polymer raises the melt point of the raw powder. This occurs because polymers do not melt until much higher temperatures then standard rubber accelerators.. This is why new polymer technology is so important. Now polymer binder systems rely on polymers with lower melt points that act more like a plastic then polymer. They are hard at room temperature and have very low melt points to ensure excellent dispersability. Curative and accelerator dispersion is very important because poor dispersion of these chemicals can cause inconsistency in the crosslink density through out the cured part leading to the initiation of a failure event; such as inconsistent modulus, tensile rupture, inconsistent tear, and fatigue failure. Poor dispersion of accelerators can be seen as undispersed streaks or particles of powder and they can leave convex flaws on the surface of the rubber part referred to as pebbling.
Although Polymer bound dispersions are primarily used to improve the raw powder dispersion they have a variety of other positive impacts as well. They reduce fly loss associated with dusty chemicals, improve housekeeping, and are easier to weigh. However, the greatest impact polymer bound dispersions offer is in regards to heath and safety initiatives. Once the powder chemical is polymer bound it renders the hazardous liquid or powder inert. This reduces employee safety hazards immensely. Another benefit of polymer bound dispersions is they can be color coded to offer visual cues to help eliminate any handling errors.
Polymer bound dispersions can be produced in either slab or pellet form depending on the customers specific needs. Binder systems themselves can also be tailored to the individual process as well. Mill mixing operations require slab forms with soft binder systems. Operations with automatic feed systems require a pellet form with a binder system that is hard at room temperature to increase out put and to reduce clogging when feeding. Even though the binder system is hard at room temperature it can be designed to soften at low elevated temperatures to ensure dispersability.
Polymerics Inc. offers many proprietary polymer bound dispersion binder system that will fit all of your dispersion needs and can be tailored to your process and your product. For further information please contact customer service at 330-928-2210 x 232 or by e-mail email@example.com