Elastomers for Bitumen Modification

Bitumen is a complex mixture of inorganic and organic compounds and is what remains after vacuum distillation of crude oil. These compounds can be classified as asphaltenes, which are insoluble in n-heptane, and maltenes, which are soluble in n-heptane. Bitumen binder is essentially a liquid thermoplastic that behaves as an elastic solid at low temperatures and a viscous liquid at high temperatures. Polymer modification of bitumen is used to improve cold temperature flexibility and cracking resistance, while simultaneously improving deformation resistance at high temperatures.

Polymers, or elastomers, are commonly used to modify or improve the properties of bitumen including:

• Cracking Resistance
• Deformation Resistance (tire mark, footprints)
• Flexibility
• Low Temperature Flexibility
• UV Resistance
• Thermal Ageing Resistance (Sun and oxygen)

While SBS is the most common polymeric modifier for bitumen, other elastomers like SBR, EVA, EBA, POEs and TPOs have also been used. In addition, elastomers functionalized with glycidyl methacrylate (GMA) have also been used, alone or in combination with SBS, primarily for bitumen road pavement. In this document we will comment on POEs, TPOs and GMA functionalized elastomers.

Polyolefin elastomers (POEs) have been successfully used to modify bitumen, especially in bitumen roofing shingle applications. While these elastomers are nonpolar and have limited compatibility with bitumen, they can be used to substitute some of the SBS in the formulation. Replacing 30% of the SBS with POE results in a formulation with very similar end properties and processability compared to the straight SBS modified bitumen but with a lower cost.

Thermoplastic Polyolefins (TPOs) are commonly used to modify bitumen formulations used in flexible roofing membranes. These TPOs can provide improvement in high temperature performance (footprint resistance, mechanical integrity), UV and thermal aging resistance, and cost optimization through formulation recipe flexibility. In addition, TPOs can provide improved cold temperature bending performance, even after thermal and UV aging. TPOs can reduce overall bitumen formulation costs as they allow for the use of recycled or wide-spec polyolefins while maintaining property performance.

Glycidyl Methacrylate (GMA) modified elastomers, also called Reactive Terpolymers (RET) are primarily used in bitumen formulations for road pavement applications. The GMA modified elastomer can fully or partially replace SBS in the formulation. If fully replacing SBS, the loading level is generally 50% of the SBS level, up to a maximum 2.5%. The GMA modified elastomer chemically reacts with the asphaltene resulting in improvements in cold temperature cracking resistance, high temperature rutting and stripping resistance, fatigue resistance, and more stable transport and storage of the bitumen.

Entec Polymers offers a wide variety of thermoplastic polymers and elastomers that can be used in bitumen formulations for roofing shingles, roofing membranes and pavement applications

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