Finding the right grade of Capa™ for your polyurethane elastomers

Plastic Materials, Capa
8 March 2018

Perstorp’s Capa™ range extends to around 60 different grades, making it one of the broadest offer of caprolactones on the market.

Polyurethane elastomers from Perstorp

The range reflects the broad spectrum of products and applications where Capa™ can be used, from encapsulation resins to large industrial rollers. “The different grades we can offer are suitable for polyurethane elastomers that need to provide different types of properties,” says Joel Neale, Capa™ Product Manager, Perstorp. “There are a number of different parameters that you can change with any polyol design, including molecular weight and functionality, and these changes can alter the final urethane quite dramatically.” If you need your elastomer to be longer lasting, more durable or harder, it’s all possible thanks to Capa™.

However to find the right grade for the right application, there are multiple factors that need to be taken into account.

“You need to consider the inherent properties of the polyol itself, and whether the customer will be able to handle it and process it. When it comes to choosing the correct molecular weight and the right grade, you need to consider the final properties you want to achieve.”

Capa™ is the one molecule with millions of opportunities. One of the segments Capa™ is used for is Polyurethane elastomers, it can also be used for improving the performance of Coatings, Bioplastics, Adhesives and Thermoplastics. Elastomers can be split into a number of different sub segments. They are:

Cold cast elastomers

Since cold cast elastomers are generally mixed and cured at room temperature, there is an inherent need for low viscosity liquid grades. There are around six grades of Capa™ for these applications, which are available in diols, triols and tetrols. All of them are low viscosity polyesters that will provide good mechanical properties and excellent outdoor durability including UV- and hydrolytic resistance.

“In general changing the functionality will increase the hardness and the rigidity of the final urethane in these applications,” says Joel Neale. “The diols will provide quite a flexible material whereas the triols, particular the short chain triols, will provide quite a hard material.”

Hot cast elastomers

A wider range of polyols can be used in hot cast elastomers, going from low molecular weights of approximately 500 up to the 4000 molecular weight range. Most grades of Capa™ in this sub segment are di-functional however there as also short-chain triols that can be used as cross-linkers.

As well as offering a broad range of molecular weights, Perstorp can also offer a number of different choices in the base glycol, which can result in differences in the final properties of the urethane such as flexibility or tear strength.

“For example, if you use Diethlyene glycol as the backbone of the of the polyol, then you’ll see greater levels of flexibility. If you use Monoethylene glycol, we see a greater level of tear strength,” explains Joel Neale. “It’s a subtle change but it can be enough to differentiate the final product from its competitors.”

Thermoplastic elastomers (TPU)

The high quality of Capa™ polyols make them a good fit for thermoplastic polyurethane elastomers (TPU) applications, especially when it is important to maintain colour generation at a low level during production and the final article needs to be extremely durable. The range of grades in this sub segment are similar to those for hot cast elastomers – predominantly di-functional materials in the 1000-2000 molecular weight range. However, the range also extends to products for specific applications. Lower molecular weights materials (800, 1000 and 1200) are typically used in TPU film applications, mid-range molecular weights (around 2000) are used in standard TPU injection moulding and extrusion applications and higher molecular weights (3000 – 4000) are used in TPU adhesives.

As with the hot cast product range, different base glycols can be chosen in order to refine the final urethane.

Microcellular urethane foam (MCU)

Capa™ is used in microcellular urethane foam (MCU) due to its good dynamic performance, however it can be used in many different ways. “The range of products offered is quite varied depending on the type of system the customer is designing,” says Joel Neale. “We offer some specialty designed copolymers for these types of applications, where we can see synergies with other high performance polymers.”

As demands on MCU elastomers increase in terms of dynamic performance, dampening performance and being able to withstand higher loads, Capa™ stands out as a good choice as a high-performance polyester.

How we can help?

The breadth of the Capa™ range, allows customers greater choice when it comes to finding the right grade of the caprolactone. If you need support in finding the perfect grade, we’re here to help.

“Our standard products are just the tip of the ice berg in terms of what we can offer,” says Joel Neale. “A standard product will improve performance and might be sufficient but together we can fine tune it and make it perfect for you. These changes, while they seem subtle, can really give an extra few per cent in performance and help differentiate your final product in the market to give you that competitive edge.”

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