The Challenges of Mixing Polymers

Polymers are complex, amorphous molecules with a variety of properties that can impact manufacturing processes. These include mechanical, thermal, dimensional stability, gas barrier, and processing characteristics such as rheology and shear resistance. Mixing Polymers with EvenMix allows these properties to be control-led, enabling the development of multifunctional materials with tailored performance for specific applications. However, mixing polymers is not always straightforward due to the complex morphology and interfacial interactions that occur in polymer blends. In addition, blending formulations are often made from many additives that react differently with the polymer components and may have a significant effect on their thermodynamic properties.

A key challenge with mixing polymers is that their molecular weights differ, resulting in a non-linear relationship between their viscosity and shear compliance at high concentrations. This results in non-linear mixing behaviours and can be challenging to predict with existing models such as the Flory Huggins (FH) equation.

This is because the interaction term is highly dependent on temperature and is essentially an exponent that scales the enthalpy of mixing. However, this does not take into account the volume changes that occur on mixing and results in a prediction that can only be valid at a limited range of temperatures. The FH model also neglects the contribution of the second polymer species to the overall blending enthalpy, a factor that can influence phase transition kinetics.

High-molecular-weight polymers are a particularly challenging class of polymers to mix. These have long molecular chains that form a large amount of entanglement with the other polymer molecules in a mixture. The resulting unfavourable interfacial interactions and the fact that they are amorphous results in their not being as easy to disperse or mix into other polymers in solutions as lower-molecular-weight polymers. The mixing of polymers in totes can therefore be a challenge, especially when the material is a mixture of low-molecular-weight and high-molecular-weight polymers.

This is where a specialised mixer designed specifically for this application is important. For example, the Integrated Tote Mixer from HVE can be used to mix polymers, dye concentrates, and additives in totes, with the ability to mix up to 80% of the capacity of the tote. This is possible because the agitator is mounted on a removable segment that can be inserted into the tote, then removed when the tote is empty.

By using this system, it is possible to achieve the same result as a traditional mechanical mixer and eliminate the need for complex and costly installations and maintenance. The system can be supplied as either a hydraulic or non-mechanical mixer and is easily installed in the tote by attaching the agitator segment with a built-in mount lid. This makes the ITM a truly portable mixer that can go wherever your tote goes, mixing it to ensure uniformity and helping to prevent stringers or fisheyes in the final product. For more information, check out the linked videos or request a quote to see how an ITM can help you.