Bitumen Modification Unit. Modified Bitumen Production
The application of polymers makes original bitumen available for application under unfavourable climatic conditions and heavy loads. Often, the so-called SBS-polymers (styrene-butadiene-styrene) are used for bitumen modification. By nature, they are caoutchouc (rubber). Interacting with bitumen, SBS-polymers increase its flexibility, elasticity and strength. Such polymers reduce the binder’s sensitivity to extreme temperatures and allow for significant improvement of its performance characteristics compared with unmodified bitumen. The compatibility of bitumen and polymers is essential to obtain a high-quality final product. In such case, the polymer is able to absorb oil components of the binder, preserving the structure. Due to the modification process, bitumen is turned into an elastomer that possesses better elasticity. Modern petrochemical industry professionals attempt to maximize the yield of light oil products and extract most of the paraffin-naphthenic fractions from bitumen. This reduces its flexibility at low temperatures and reduces the softening point at high temperatures. Most modern bitumen will lose elasticity at approximately twenty degrees (20oC) and begin to soften at between +45oC to 48oС. The use of non-modified bitumen therefore, in both road construction, which requires a binder with a temperature range from -40oC to +70oC, and for roofing materials, which are often subjected to temperatures up to 90oC, is not efficient. Fortunately, there are ways to change and improve the properties of bitumen by mixing it with various additives. This is best achieved in special bitumen modification units such as the GlobeCore UVB bitumen modification system. The least expensive method of improving bitumen’s useful temperature range is to add a large amount (15% or more) of mineral filler such as chalk or talc. The result is a very thick product mostly used as a mastic. It is far more popular to modify bitumen using byproducts of other processes, such as rubber pellets from used tire processing or rubber resin ataxic foam propylene. Unfortunately, the technology of mixing such filler with bitumen requires temperatures above 180oC. Such high temperatures will disintegrate the structure of the rubber resin and oxidize the bitumen. The result is a modified bitumen with a high softening point, but with low ductility, elasticity and high brittleness at low temperatures. This makes it difficult to use in road construction. The alternative to high heat is to introduce more components (swelling accelerators, plasticizers, and adhesives), thus significantly increasing the cost of the modified bitumen.