Influencia de la adición de cauchos SBS y SEBS en polietilenos de baja densidad para film soplado

Abstract

This project was carried out in the facilities of Dynasol Elastomers in Gajano, Cantabria, Spain, and the main aim was to study the influence of rubber manufactured in Dynasol when they are added to prepare polyethylene films. The low-density polyethylene is one of the most demanded polymers in Europe after polypropylene. Each year, 8,2 million tons of low density polyethylene are sold only in Europe. If these data were extrapolated for all the world, it could be 6 times greater. On the other hand, packaging (films, bags) is the area that demands the highest amount of plastics, about 40 %, and particularly, the most used polymer for packaging is low density polyethylene. For these reasons, for rubber manufacturers like Dynasol Elastomers, it is very important to know how different types of rubber (SBS, SEBS) affect low density polyethylene films. If rubber could improve the mechanical and optical properties of films, its market opportunities would greatly be expanded. In addition, it is necessary to point out that there is a lack of information about SBS or SEBS / LDPE or LLDPE blends. The literature review that was carried out revealed that there were no information published about the influence of SBS or SEBS rubber (in low percentages) in the mechanical and optical properties of low density polyethylene blown films. Therefore, to fill this gap, this work analyses the influence of three types of rubber (linear SBS, linear and decoupled SBS and linear SEBS) manufactured by Dynasol Elastomers in the properties of common low density polyethylene used in the production of blown film. To evaluate the mechanical properties of blown film produced from SBS or SEBS / LDPE or LLDPE blends, four different types of tests were carried out (percent elongation and tensile strength at break, tear strength, tensile set and sealability) following the international standards. The addition of rubber C500 and CH6180X when preparing polyethylene blown film resulted in very successful values of percent elongation and tensile strength at break of 522% and 14,8 MPa, respectively, which clearly improved the values of pure polyethylene (290% and 10,4 MPa, respectively). One of the most successful and relevant results in this work is the significant decrease of tension set under constant elongation, which means a better elastic recovery. Particularly, for blown films from blends with a 10 % of rubber CH6180X, the recovery capacity is increased by 20 % in comparison to pure polyethylene results. To evaluate optical properties three tests were carried out (opacity, haze and gloss) following the international standards. The results reported in this work prove that the optical properties of the films are kept, which is especially noteworthy. Generally, optical properties of films are worsened in these mixing processes. However, rubber CH6180X and LDPE blend is able to keep and even to improve the optical properties of films, specially haze and opacity, while, at the same time, improving mechanical properties. It must be emphasized that this work can provide new market opportunities for types of rubber like CH6180X and, even, C500, since this kind of rubber have improved the low-density polyethylene film mechanical properties as well as the optical properties. This fact confirms that mechanical qualities can be improved without deteriorating the optical properties by adding rubber as main component to modify low density polyethylene. These improvements can become very relevant information for any kind of packaging market, like more resistant bags for heavy stuff where a big amount of polymer is commercialized, but moreover, this can also be important for sanitary instrumentation where very strict properties are required or for specialized packaging like in the food area.