Styrenic block copolymer solutions enhance sustainability and the circular economy

Kraton's Expertise in SBC Technology:

Kraton Corporation, a leader in styrenic block copolymers (SBCs) and sustainable pine chemical solutions, employs anionic polymerization for precise molecular structures tailored to various applications. This technology ensures high monomer conversion and minimal residuals.

Architecture of Kraton SBCs:

Kraton's SBCs consist of polystyrene end blocks covalently bonded to rubbery midblocks like butadiene or isoprene. This structure forms hard and soft phases, providing excellent elastic properties and strength due to physical crosslinking points.

Types of SBCs:

Kraton offers SBCs with unsaturated rubber midblocks (USBC) or selectively hydrogenated midblocks (HSBC). HSBCs provide better resistance to high temperatures, mechanical properties, and resistance to degradation, suitable for various polymer blends.

Innovation and Sustainability:

Kraton focuses on sustainable solutions like plasticizer-free polymers, natural fiber fillers, and enhancing bioplastics properties, aligning with the push for a circular economy. Key challenges include designing recyclable products and improving recycled content performance.

Introduction of CirKular+ Product Line:

In 2020, Kraton introduced the CirKular+ product line, designed for use with recycled plastics, approved by plastic recyclers' associations in North America and Europe. It includes compatibilization and performance enhancement additives.

Experimental Data and Analysis:

Data comparing CirKular+ compatibilizers with polyolefinic compatibilizers demonstrate improved performance. The impact strength and other key properties of compounds modified with CirKular+ additives are evaluated through various tests.

Recyclability of CirKular+ Additives:

Compounds modified with CirKular+ additives maintain or improve their properties through multiple extrusion cycles. Spiral flow measurements indicate consistent flow behavior, enhancing recyclability.

Practical Applications:

CirKular+ additives are successfully used in flexible and rigid applications, improving impact and tear strength while maximizing recycled content. Examples include blown film production and injection molding of trash containers.

Compatibilization of Mixed Plastic Streams:

Functionalized SBC polymers act as compatibilizers for mixed plastic streams, enhancing compatibility between different polymer types and improving morphology for more efficient recycling.


CirKular+ additives enable product design for recyclability, enhance recycled content performance, and improve the reusability of contaminated or mixed plastic streams. They offer a promising solution for the transition to a more sustainable, circular economy in the plastics industry.


This article is an edited and abridged version of source material provided by Aparajita Bhattacharya, Freddy Vervoort, Eduardo Goncalves and Yuliya Streen, Kraton.