Self-reinforced Composites – a multi morphological approach to close the loop

The history of modern polymers began in 1907 with the introduction of Bakelite, the first fully synthetic plastic. Since then, polymers have become the backbone of our technological society. Owing to their unique property profiles and ease of processing, they are now embedded in almost every sector—from medicine, electronics, automotive, and food packaging to aerospace. Their service life spans an extraordinary range, from seconds (e.g., packaging films) to decades (e.g., structural components), highlighting both their versatility and the complexity of their lifecycle management.

This success, however, comes with a severe environmental cost. Planet Earth is suffering from the misuse of plastics, insufficient collection and recycling systems, and the lack of robust circular concepts that keep materials in a closed loop. In parallel, many applications - especially those involving motion, such as transport and logistics - are under increasing pressure to reduce weight, energy demand, and secondary emissions. Polymers, with their inherently low density, are ideal candidates for lightweight design, but in their conventional form they often lack the stiffness and strength required for demanding structural applications.

One powerful route to overcome this limitation is to exploit the intrinsic strength of polymer chains through molecular orientation. By reorienting the molecular structure - for example in highly drawn, high-tenacity fibers - the degree of chain alignment can be maximized, allowing us to tap into the high bond dissociation energies of covalent bonds along the backbone. This principle of self-reinforcement was first formulated in 1975 by Capiati and Porter as the “one-polymer composite” concept. Over the past decades, self-reinforced polymers (srP) based on polypropylene have been intensively investigated and brought to market, combining excellent specific strength with enhanced recyclability, since all components are based on the same polymer chemistry.

Nevertheless, despite their superior strength, srP often show limitations in stiffness, which is critical for many lightweight structures. An effective strategy to address this is the sandwich design approach, in which different morphologies of one and the same polymer - high-tenacity fibers, bulk material, and structural foam - are combined within a single component. This “morphology lightweight approach” leverages the specific advantages of each morphology: fibers for strength, bulk for toughness and connectivity, foam for bending stiffness and weight reduction. The result is a high-performance, single-material system that is both structurally efficient and intrinsically more recyclable.

These tailored laminates and sandwich structures can be further processed using established technologies such as thermoforming and co-injection molding, enabling complex geometries and integration into existing manufacturing chains. However, processing such materials poses nontrivial challenges, including fiber relaxation and core crushing, which can compromise performance and recyclability if not properly controlled.

This keynote will introduce the morphology lightweight approach with self-reinforced polymers, outline the underlying structure–property relationships, and discuss current solutions and open challenges in processing. It will point out that the intelligent combination of polymer morphologies within a single-material framework offers a promising pathway toward truly circular, lightweight, and performance plastics. The history of modern polymers began in 1907 with the introduction of Bakelite, the first fully synthetic plastic. Since then, polymers have become the backbone of our technological society. Owing to their unique property profiles and ease of processing, they are now embedded in almost every sector—from medicine, electronics, automotive, and food packaging to aerospace. Their service life spans an extraordinary range, from seconds (e.g., packaging films) to decades (e.g., structural components), highlighting both their versatility and the complexity of their lifecycle management. This success, however, comes with a severe environmental cost. Planet Earth is suffering from the misuse of plastics, insufficient collection and recycling systems, and the lack of robust circular concepts that keep materials in a closed loop. In parallel, many applications - especially those involving motion, such as transport and logistics - are under increasing pressure to reduce weight, energy demand, and secondary emissions. Polymers, with their inherently low density, are ideal candidates for lightweight design, but in their conventional form they often lack the stiffness and strength required for demanding structural applications. One powerful route to overcome this limitation is to exploit the intrinsic strength of polymer chains through molecular orientation. By reorienting the molecular structure - for example in highly drawn, high-tenacity fibers - the degree of chain alignment can be maximized, allowing us to tap into the high bond dissociation energies of covalent bonds along the backbone. This principle of self-reinforcement was first formulated in 1975 by Capiati and Porter as the “one-polymer composite” concept. Over the past decades, self-reinforced polymers (srP) based on polypropylene have been intensively investigated and brought to market, combining excellent specific strength with enhanced recyclability, since all components are based on the same polymer chemistry. Nevertheless, despite their superior strength, srP often show limitations in stiffness, which is critical for many lightweight structures. An effective strategy to address this is the sandwich design approach, in which different morphologies of one and the same polymer - high-tenacity fibers, bulk material, and structural foam - are combined within a single component. This “morphology lightweight approach” leverages the specific advantages of each morphology: fibers for strength, bulk for toughness and connectivity, foam for bending stiffness and weight reduction. The result is a high-performance, single-material system that is both structurally efficient and intrinsically more recyclable. These tailored laminates and sandwich structures can be further processed using established technologies such as thermoforming and co-injection molding, enabling complex geometries and integration into existing manufacturing chains. However, processing such materials poses nontrivial challenges, including fiber relaxation and core crushing, which can compromise performance and recyclability if not properly controlled. This keynote will introduce the morphology lightweight approach with self-reinforced polymers, outline the underlying structure–property relationships, and discuss current solutions and open challenges in processing. It will point out that the intelligent combination of polymer morphologies within a single-material framework offers a promising pathway toward truly circular, lightweight, and performance plastics.