Launched onto the market three years ago, shrink films based on Styrolux® HS 70 have now become well-established in the European sleeve market. Compared to conventional mixtures of SBC (styrene butadiene block copolymer) and PS (polystyrene), this material stands out for its very high final shrinkage of more than 70 percent.
BASF researchers have now developed even further improved Styrolux grades with an eye towards expanding the product line for this application. They have done so in response to the industry’s desire for stiffer films that allow even larger, more complex objects to be shrink-labeled and the thickness of the sleeve film to be further reduced.
A two-component concept that differs from Styrolux HS 70 is being implemented for the first time: with Styrolux T (T = toughness) and Styrolux S (S = stiffness), this concept offers two new Styrolux grades with which the desired property profile of the shrink film can be set when the processor blends them, and only once they are put together do they yield the film material “Styrolux T/S”.
This concept has already received very positive first feedback from film manufacturers. The combination of the two newly developed Styrolux grades now allows manufacturers themselves to adapt the film properties to their specific requirements – a first in the realm of shrink sleeves. BASF experts provide the requisite assistance so that film manufacturers can fully exploit the potential of this development.
In the blended T/S products, the T component provides basic properties such as toughness and good stretchability, while the S component improves the stiffness of the film as well as its storage stability. The latter is determined by the so-called natural shrinkage that the material undergoes after the stretching procedure. This value is ascertained in a 21-day storage test at 40 degrees Celsius [104 degrees Fahrenheit]. A one-to-one mixture of Styrolux T and Styrolux S, for instance, yields a film that is 25 to 30 percent stiffer and that exhibits a natural shrinkage that is about 50 percent less than a corresponding film made of Styrolux HS 70.
