High melt strength polypropylenes are tailored to have long chain branching that in turn gives them simultaneously their mechanical strength and elasticity.The current market leader in the field with its HMS PP grade that exhibits a broad foaming range process window. Typical foam density for specific applications are:

High melt strength and extensibility of Borealis HMS PP grades allow tailoring of foam properties by adding linear polymer component while keeping good foamability as shown in the two figures that follow:

Borealis HMS PP Force Versus Drawdown (L), and Tensile Modulus Versus Density (R)

Rheology Curves Comparing Traditional Linear PPs (Green) and Borealis Daploy HMS PP Foaming Grade (Orange)

In the above graphic,there is a rheological, contrast between traditional linear PPs and high melt strength (HMS) PP with its defined high-performance foaming window.

With HMS PP it is even possible to manufacture extremely low 20–50 kg/m3 density foams. These extruded foams have very finely delineated and uniform cell structure. These type foam structures are beyond the capability of standard linear PPs that fall well outside the high-performance HMS foaming window. Additionally, Borealis HMS PP is blendable with standard PP and broader polyethylene extrusion grades, as well as being processable on the vast majority of established foam extrusion equipment. This capability offers endless opportunities to custom tailor foams to very specific end-use applications and that these parts are fully recyclable.