Bioplastics

Everyday life without plastics has become unthinkable. The vast majority of plastics used today incorporate fossil-based resources. However, bio-based plastics from renewable raw materials are a viable forward-looking alternative. 

Primarily sugar, starch, proteins, cellulose, lignin, fats or oils harvested from plants such as corn, sugarcane, sugar beets or lumber are used as source materials for manufacturing bio-based plastics.

Compared to the use of fossil-based resources, renewable raw materials lead to a reduced carbon footprint and increased sustainability of the plastic products.

Fewer fossilized hydrocarbons are used, resulting in less multimillion-year-old CO₂ being released into the atmosphere. Moreover, it promotes independence from increasingly scarce and costly fossil-based resources. Bio-based plastics can be comprised entirely or partially of sustainable raw materials. They can be biodegradable, though some are only partially so. Conversely, biodegradable plastics are not necessarily bio-based.

When filling and mixing biopolymers, we achieve throughputs with our systems that are comparable to those of fossil-based engineering plastics. A wide range of feeding technologies allows us to provide an optimized feeding system for any bulk material. Using patented FET technology, the extruder’s intake section is equipped with a porous, gas-permeable wall to which a vacuum is externally applied. The resulting gas vacuum markedly increases the material intake capacity and throughput when processing feed-limited  products. Due to the intensive mixing and devolatilization in the extruder, very high product quality is achieved.

Since native starch cannot be melted using heat, it must be converted into thermoplastic starch (TPS). In this process, the starch powder (i.e. from corn, potatoes, or tapioca) is gelatinized (cooked) in the extruder. While adding liquid, heat and shearing energy, the starch's partially crystalline structure is transformed into a completely amorphous structure. This process is irreversible. To give the TPS more flexibility, plasticizers, such as glycerin, can be added to the process. Gravimetric liquid feeders ensure that additives are  added with very high accuracy, even at low feed rates.

Starch blends are mixtures of thermoplastic starch (TPS) and plastics made from fossil-based or sustainable raw materials. Manufacturing of this type of bioplastic, currently comprising the largest share of all bioplastics, can be accomplished within the twin screw extruder in a single process step. The biopolymer is fed directly into the extruder along with components for TPS. The recipes and properties of starch blends vary greatly depending upon the purpose of the end product. Using high-accuracy feeders, raw materials are introduced into the twin screw extruder. With the smart flow aid device ActiFlow, gravimetric twin screw feeders can reliably feed even difficultflowing starches with high accuracy. Within the ZSK extruder the raw materials are modified by means of intensive energy
introduction and homogeneously mixed. The melt is reliably devolatilized and, depending upon product properties, can be processed into compounds using strand or underwater pelletizing.