Production process for lignin-reinforced PLA developed by KraussMaffei and partner

KraussMaffei and Cypriot company Synergy Horizon developed a process for producing a 100% bio-based reinforced thermoplastic – lignin-reinforced PLA.

KraussMaffei and Synergy Horizon developed lignin-reinforced PLA.

Transforming waste into filler

Lignin is the second most abundant organic material on Earth. Around 50 million tons of lignin, including hydrolysis lignin, are produced annually worldwide as a waste product from wood processing in the paper and bioethanol industries, 98% of which is incinerated.

Lignin can be extracted from lignocellulosic biomass by various methods. One of the methods is the hydrolysis of biomass for bioethanol production, which generates hydrolysis lignin as a byproduct.

With a focus on hydrolysis lignin valorization, Synergy Horizon transforms lignin into valuable products for various applications. Also, the Cypriot company recently developed a process to produce free-flow lignin powder that can be metered into the extruder as a filler.

Achieving process optimization

In its technical center, KraussMaffei demonstrated incorporating natural raw material lignin into PLA matrix. Both the laboratory extruder – ZE Blue Power 28 and small ZE Blue Power 42 production compounder, successfully incorporated up to 30% lignin.

On the process configuration, the company specially adapted screw configuration to the lignin with heavy-sensitive mixing elements, operate at a low temperature of 160°C maximum, and use both a 6 D-long filling zone and side degassing.

The ZE BluePower generation with its optimum Da/di of 1.65 is perfectly suited for processing these shear- and temperature-sensitive polymers.

Antioxidant, odor-free, biodegradable

Compared to pure PLA, the lignin reinforcement enables flexural and tensile modulus to be increased by around 30%. The bio-reinforced PLA is useful in packaging applications where stiffness is required to hold packaging shape under load.

Lignin also adds sufficient antioxidant capacity that help particularly in food packaging application to prevent oxidation of food and maintain its quality and safety by inhibiting radical oxidation and preventing the formation of off-flavors, odors or toxic compounds.

The novel biocompound can also be applied to biodegradable plastics for agricultural purposes, such as mulch films, to protect them from oxidative degradation.

In addition, unlike other type of lignin, biocompound with lignin has no odor, which makes it more suitable for food packaging.

Last but not least, unlike pure PLA which has limited biodegradability due to its dependence on specific enzymes and industrial conditions, PLA biocompounds own enhanced biodegradation properties with biodegradation rate more than 90% in 99 days.