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The Challenges of Mixing Polymers

Jan 16

In many applications  Mixing Polymers with EvenMix is an important step in the manufacturing process, and mixing polymers is no different. Using different polymers together in a melt mixing process allows manufacturers to improve the strength and other properties of their final product. However, there are many challenges when it comes to mixing polymers, particularly immiscible blends.

Immiscible polymer blends are mixtures of two or more different chemical types of polymers, and can be either homologous or heterogeneous in nature. The morphology of an immiscible polymer blend is highly dependent on the morphologies of the individual components, and can have significant implications for the overall material properties.

Mixing polymers is a complex process because they are non-polar and have a high molecular weight. This makes them difficult to mix compared to smaller molecules, because the free energy of mixing which normally drives mixing for low molecular weight materials becomes a much lower contributor at higher molecular weights.

The entropy of mixing also increases with increasing molecular size, making it even more unfavorable for high molecular weight polymers. This combined with their large molecular weights and low viscosity, means that the thermodynamic behaviour of polymer mixtures is very difficult to predict and control.

Many immiscible polymer blends are useful despite their asymmetric structure. For example, the popular plastics PET and PVA are often used in combination to produce a wide range of consumer goods, from beverage bottles to carpet fibres. This is because of the high mechanical properties of PET, complemented by the good chemical resistance of PVA. The reason they are able to combine is because these two polymers have glass transition temperatures close enough for them to coexist in a partially phase-separated state.

The challenge for a manufacturer is to find a way of maintaining this state indefinitely, as it will provide the best balance of material properties. The most common approach is to use compatibilizers in the blend, which are additives designed to change the morphology of the system and so promote mixing or demixing. However, this is expensive and limits the ability to introduce new polymers into the market.

Another way to achieve this is by using a polymer mixer, which will mix the polymers at a microscopic level and create a single phase. A polymer mixer is a key tool for manufacturers, particularly because it allows them to mix a wide range of immiscible polymer blends.

A polymer mixer can also be used for emulsion polymers, which tend to stratify during storage and need to be mixed before being fed into the activation equipment. EvenMix has developed the Integrated Tote Mixer, which is ideal for addressing these unique mixing needs and is designed to ensure your tote is a true processing vessel.