SBS Compound

Additional Details

SBS is a block polymer with highly elastomeric features. It is not comparable with other additives used in this sector such as: PP, PE, EVA, EPDM, SBr, Ebr etc. Another family similar to SBS is SIS, Styrene-Isoprene-Styrene block copolymer. It is like SBS except that the central block is composed of an Isoprene polyolefin instead of Butadiene. These products are very similar, but SIS costs more than SBS and therefore we will not deal with this material.

Both materials have double bonds in the elastomeric segment and this makes them not very stable to heat (maximum processing temperature 180-200°C) and to light. Versions are available free of unsaturations (SEBS, SEPS etc.) which are very resistant both to heat and to light, but they are much more expensive.

Use in Asphalts.

SBS, is a concentrate lower than 3%, regardless of the type of bitumen, represents the discontinuous polymeric phase, namely the material dispersed in the bitumen itself. In this case, the SBS endows the bitumen with some essential features, though limited, for their valid use, such as: Ring and Ball increased up to + 30 °C, Penetration reduced by at least 20 tenths of a millimetre, Brookfield Viscosity at 160° of approximately 400 cP , Fraass of at least œ15°C besides a certain Elasticity and Tension Set.

Use in Roofing and Waterproofing.

In these materials, the SBS is used in concentrates varying from 10- 15% . Therefore since the threshold of 3% (approximately) is overcome, the continuous phase of the material will be represented by the SBS itself. It is as if the SBS acts as an enormous sponge which, after having been squeezed, absorbs a large amount of water. Except in our case bitumen is absorbed instead of water.

The advantage is that the sheathing will be mainly made up of SBS and the bitumen will be the "guest". Therefore all the main thermo-mechanical features will depend on the SBS. The main features are: Ring and Ball increased more than + 60°C, Penetration reduced by at least 70 tenths of a millimetre, Brookfield Viscosity at 160° beyond 3000 cP, Bending Test of at least 18°C, besides optimum Elasticity and Tension Set. This data refers to Bitumen with penetration of 80-100 dmm.Until now we have described the SBS block copolymer as a unique product. However there are actually various versions of it, each one designed for a specific use. The first division is the micro-molecular conformation, namely the radial and linear conformation. The second, just as important, is the molecular weight and its distribution. 

We can say in general that in bitumen:

The linear shape can be dispersed more easily, it performs better at low temperature and low work viscosity, and endows the modified product with optimum stability.

The radial shape can be dispersed less easily, it is less stable for storage, but mechanically more resistant to high temperatures, giving it important mechanical features.

The molecular weight inside of the two aforementioned families plays an important support role for the characteristics described.

A higher molecular weight increases the thermo-mechanical features of the product, both radial and linear, and often provides a valid replacement, for example of a radial with a linear, as long as it has adequate molecular weight.

In this latter case, there will be the advantage of good storage stability without excessively losing inmechanical features at high temperatures.