Evolution of Plastic Compounding Technology: From Rubber to Twin Screw Extruders


Plastic compounding technology has a rich history that traces its origins back to rubber compounding. The development of machinery for rubber compounding in the late 1800s and early 1900s set the foundation for advancements in the field. However, it was during World War II that significant progress was made, as companies like Union Carbide spearheaded research on synthetic rubbers and thermoplastics to support the war effort. This blog post explores the evolution of plastic compounding technology, focusing on the pivotal role played by twin screw extruders and the integration of scientific advancements and artistry in the process.

 Origins of Plastic Compounding Technology 

The development of plastic compounding technology can be traced back to work done in the late 1800s and early 1900s by machine builders in Germany and England. Companies like Werner & Pfleiderer Inc. and Banbury played a crucial role in developing machinery for rubber compounding. However, it was during World War II that significant breakthroughs occurred. Companies like Union Carbide conducted extensive research, leading to the development of new synthetic rubbers and thermoplastics that were vital for the war effort.

 The Emergence of Twin Screw Extruders 

In the early 1950s, Paul Erdminger of Bayer Corp. revolutionized the field with his development of a special three-lobe co-rotating twin screw design. This breakthrough paved the way for modern compounding technology. The Werner & Pfeiderer Corp. (now Coperion) played a key role in commercializing Erdminger's design. The main advantage of twin screw extruders over single screw and Banbury type extruders was their flexibility, thanks to the self-wiping elements and a more efficient design.

 Understanding the Material Flow 

DuPont made significant contributions to the understanding of twin screw extruders in the 1970s by developing a mechanical description of their geometry. This work proved fundamental in comprehending the material flow in co-rotating twin screw extruders. W&P engineers further enhanced the design by introducing a two-lobe configuration that increased the surface area. These developments allowed for improved control over the compounding process and enhanced product quality.

 Advancements in Twin Screw Extruders 

Twin screw extruders are characterized by two variables: Do/Di (outer diameter to inner diameter) and Md/A3 (specific torque over centerline distance cubed). Over the years, the value of Md/A3 has increased from 3 to 20, while machines are now capable of running at much higher RPM, depending on the application. This progress has significantly increased the throughput capacity of modern twin screw extruders compared to their 1970s counterparts. For instance, a 45-mm latest-generation twin screw extruder can achieve the same throughput as a 160-mm twin screw extruder from the 1970s.

 The Role of Single Screw Extruders 

Single screw extruders, although less flexible compared to twin screw extruders, played a vital role in early polymer processing. These extruders primarily focused on melting and homogenizing polymers, and they were often used in conjunction with powder discharge from polymer reactors. While single screw extruders were drag and pressure building devices, their limitations in terms of feed rate and cooling methods spurred the development and adoption of twin screw extruders.

 Combining Science and Art in Compounding 

In the 1990s, advanced modelling techniques were developed to understand the fluid mechanics of the flow in twin screw extruders. Engineers at Krupp Werner & Pfliederer (Coperion) led by Arash Kiani made significant contributions in this area. These simulation tools allowed process engineers to optimize machine conditions for specific compounding tasks. However, despite the advancements in simulation, the setup of compounding extruders remains an art that is augmented by scientific principles. The wide range of possibilities in configuring twin screw extruders presents both opportunities and challenges, requiring expertise and experience to achieve optimal results.

 The evolution of plastic compounding technology from its origins in rubber compounding to the modern era of twin screw extruders has revolutionized the industry. Advancements in machine design, scientific understanding, and simulation tools have enhanced the efficiency and flexibility of the compounding process. However, the artistry and expertise of process engineers continue to play a crucial role in achieving optimal results.

 It is worth mentioning that Niche Polymer, a leading company in the field of plastics compounding, offers custom compounding as one of its main services. With their expertise and state-of-the-art facilities, Niche Polymer specializes in tailoring compounds to meet the specific requirements and performance criteria of their clients. Their dedication to customization and quality further highlights the ongoing advancements and specialization within the field of plastics compounding.

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