Styrene Block Copolymers as Impact Modifiers

Unpublished work at BASF has shown that using these S-EB-S block copolymers the highest notched impact strength is obtained with a high molecular weight product. Thus for the S-EB-S block copolymers of the Kraton 

Volume average Izod notched impact Modulus in SPS (wt%) Impact modifier particle size (pm) strength (kgcm/cm) tension (kg/cm2) 

The use of olefin rubbers [18] as good impact modifiers for sPS when used in conjunction with S-B or S-B-S block copolymers, which may be hydrogenated in the butadiene phase, has also been described. Instead of butadiene, isoprene can be used. Examples of the olefinic polymers are polyethylene, ethylene-propylene rubbers (EPR) and polypropylene-(ethylene propylene rubber) block copolymers. Here the styrene block copolymers presumably function as 

Similar blends and also blends containing additionally polyphenylene ether and glass fibres are described in EP 767 211 [19]. 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

---

Blends with styrene-butadiene-styrene block copolymers as impact-modified molding materials W. Germany 2,713,455 1977 General Electric... 

---