Kraton polymers are blended with plastics such as styrenics, polyolefins and engineering thermoplastics to improve performance, particularly impact, by toughening these plastics at low or room temperatures. Depending on the application needs, either transparent or non-transparent solutions can be offered. These polymers help compatibilize different plastics to bring out the best in each material, revive the impact of scrap or regrind materials, and improve processability to allow for higher filler or reinforcement loadings.
Kraton polystyrene end blocks provide good compatibility with crystal polystyrene and high impact polystyrene (HIPS), making it good impact modifiers, especially for low temperature applications like food packaging.
For non-transparent applications, USBC polymers may be used (Kraton™ D1101, Kraton™ D1102, Kraton™ D1155 or Kraton™ D1157). Kraton D1101 is the most effective grade given its impact strength, while Kraton D1102 is easy to process and is often used when only mild shear rate compounding equipment (e.g. single screw) is available. Kraton D1155 and Kraton D1157 are the preferred products for upgrading recycled polystyrene and high impact polystyrene from the waste stream.
Unmodified polypropylene homopolymer (hPP) has high rigidity and good heat resistance but has poor impact resistance, especially at low temperatures. Combining Kraton polymers with hPP can improve toughness at both room and low temperatures.
Many applications for impact modified PP require a balance of high flow, high stiffness (modulus) and excellent impact performance, but PP only offers high melt flow (> 30g/10 min.). Often talc, silica or other natural fillers are used to increase stiffness (modulus). Kraton polymers help to increase significantly impact for effective use in thin-walled part designs such as automotive instrument panels and exterior bumper systems.
For non-transparent applications, low molecular weight grades supplied in dense pellet form, offer optimal results since it forms a homogenously dispersed blend composition. Kraton™ G1657 provides best-in-class balance of flow, modulus and impact strength in combination with talc-filled PP copolymer blends. Kraton HSBC polymers can deliver good weatherability and heat aging performance.
To improve transparency, Kraton enhanced rubber segment (ERS) polymers (Kraton™ G1643, Kraton™ G1645 or Kraton™ MD1648) are used to modify random copolymer PP (rPP). The products are delivered as dense pellets, allowing for easy handling and mixing. Kraton HSBC polymers, in combination with rPP, can be sterilized by steam, EO, EB or gamma radiation; it meets most stringent food and medical regulations. These grades can be used in tubing, film, sheet and injection molded products.
Kraton offers a series of functionalized hydrogenated styrenic block copolymers (HSBC) to improve compatibility with polar engineering thermoplastics (ETP), such as polyamides (PA) and high temperature polyamides (HTPA). These functionalized block copolymers, produced by the maleation of an SEBS product, are effective modifiers for toughening a variety of polyamide chemistry. The saturated rubber midblock allows it to withstand ETP processing conditions with heat aging performance and good weatherability.
Kraton polymers are compatible and effective impact modifiers for polyphenylene ether (PPE). Similar to polystyrene, the higher molecular weight styrenic block copolymers (SBC) are more efficient in toughening PPE, providing a unique micro-structure. If heat aging performance, weatherability and limited degradation during processing is critical, Kraton™ G1651, Kraton™ G1654, Kraton™ G1650, Kraton™ G1701, and Kraton™ A1536 or a blend hereof, are recommended.
Polycarbonate is very tough material. Thinner parts (3.2 mm) can achieve a notched Izod at room temperature in the 950 J/m range, but thicker parts (6.4 mm) can become brittle with notched Izod of only 125 J/m range. To toughen thick polycarbonate parts, Kraton™ G 1651 polymer can be added to the material at 5 percent to increase the notched Izod (6.4 mm) by a factor of six at room temperature.
Thermoplastic Polyester Elastomer
Thermoplastic polyester elastomer (TPE-E), also known as COPE or TPC-ET, has excellent low temperature impact strength, very good chemical resistance and heat aging performance, but its major drawbacks is hardness limitation. Kraton™ A polymers were developed to overcome such limitation. These polymers are compatible with TPE-E and offer improved isotropic properties, which enable very thin part injection molding. Compared to traditional Kraton HSBC, Kraton A polymers exhibit more polarity, allowing for excellent dispersion of fillers and color concentrates in such compositions. Ultra-high flow Kraton™ MD6951 is the most efficient grade to achieve lower hardness of TPE-E formulation.