Issue 05/2022

Fibres / Textiles /

Fibres / Textiles / Nonwovens Biobased textile coating PLA and PHA based formulations for textile coating and screen-printing Centexbel (Kortrijk, Belgium) is proud to have won the Techtextil Innovation award 2022 in the category “new approaches to sustainability & circular economy” with a breakthrough innovation in biobased coatings. This invention introduces a novel method of applying PLA or PHA coatings and prints on textiles using a waterborne formulation. The advantage of this approach is that it completely avoids the use of organic solvents or specialized equipment, resulting in a reasonable pricing and decreased environmental impact. Due to its innovative character this development was patented under EP3875545A1. PLA and PHA are not too stiff for coatings Polylactic acid (PLA) and polyhydroxyalkanoates (PHA) are known to be stiff and brittle polymers. Centexbel started its efforts on testing how to process them into coatings more than 5 years ago. Methods like solvent casting, emulsification, hotmelt coating, extrusion coating and plastisols were explored. Especially plastisols are interesting because they are well known in the textiles industry for processing the stiff polymer PVC into highly flexible coatings. The finding that plastisols can also be used for biobased thermoplastic polymers was key for the development. Formulation composition The concept of this award-winning formulation originated from a PVC plastisol, a mixture of PVC powder and plasticizer. However, this approach was impossible with PLA or PHA since only a small fraction of PLA or PHA could be dispersed in plasticizer. To solve this issue Centexbel added water and biobased processing additives to obtain a stable waterborne dispersion. In the end, this dispersion has a solid content of 40 %, is relatively cheap, roughly 4–5 EUR/kg for the PLA-based dispersion and is compatible with a range of fillers and colourants. Depending on the used plasticizer the biobased content ranges from 75 % to 100 %. Plasticizer screening A large part of the innovation was the search for good plasticizers for PLA and PHA, needing to both improve the flexibility and show minimal migration. There is a whole range of biobased plasticizers available that were screened, amongst which esters of citric acid, levulinic acid, glycerol, fatty acids or isosorbides. These can be between 30 % to 100 % biobased. A specific finding was that when plasticizers are used in combination with surfactants, a much lower level of migration could be observed. This is a very important finding as especially PLA is known for its low long-term compatibility with plasticizers. Plasticizers influence polymers in many ways. They impact crystallinity, Tg, flexibility, melting point and viscosities. It is therefore interesting to see that by a smart choice of plasticizer different properties can be achieved. Of course flexibility is the main parameter that is influenced, but another important parameter is biodegradability. The process of biodegrading relies heavily on whether bacteria, chemicals and enzymes can reach the polymer. This is why the speed of biodegradation can be different depending on the crystallinity of a polymer. When the polymer is amorphous, enzymes can reach single polymer strands, which is not the case when crystallinity is increased and polymer chains are packed in stable crystalline structures. It was therefore interesting to see that when crystallinity is decreased, the speed of biodegradation was increased. This trade-off carries on when looking at additives, crosslinkers that improve durability or adding fillers that can increase disintegration rate of the materials. Figure 1: upscaling of the pastes is easy This development was made within the BIONTOP and HEREWEAR projects that have received funding from the Bio Based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 837761 and the Horizon 2020 programme under grant agreement No 101000632. Centexbel promotes the use of biobased coatings through its Biocoat initiative that is a joint project of Sirris and Centexbel. It is part of the COOCK collective R&D and collective knowledge transfer initiative of VLAIO under the grant agreement HBC.2019.2493 10 bioplastics MAGAZINE [05/22] Vol. 17

COMPEO Textiles Properties and first implementations Coatings and prints prepared with this PLA or PHA dispersion need a thermal treatment at 160°C for 3 minutes after which a range of properties was determined: • Excellent abrasion resistance (80,000 cycles on Martindale using wool and a pressure of 9kPa) • Crumple flex (9,000 cycles): Good flexibility if screenprinted but mediocre for coatings. PHA-based products are more flexible than PLA. • Tunable biodegradation • Good UV stability • Mediocre wash resistance The coatings and prints show clear strengths and weaknesses, even though development continues to improve the flexibility, wash resistance and application temperature. The formulation has already been successfully adapted for use on wallpaper (in cooperation with Masureel International) and coated flax fabric used in the production of thermoplastic composites (in cooperation with Flaxco and Finipur). In addition to these industrial processes, Centexbel demonstrated that these dispersions can be used in carpet backing, artificial leather and barrier coatings. On top of that improvements are ongoing for use in fashion and Centexbel is continuously looking for further opportunities for cooperation. Leading compounding technology for heat- and shear-sensitive plastics Join us K 2022, Düsseldorf October 19 – 22, 2022 Hall 16 Booth A59 www.centexbel.be Uniquely efficient. Incredibly versatile. Amazingly flexible. With its new COMPEO Kneader series, BUSS continues to offer continuous compounding solutions that set the standard for heat- and shear-sensitive applications, in all industries, including for biopolymers. Figure 2: Wallpaper print (Masureel), artificial leather (Centexbel) and thermoplastic composite (Flaxco) • Moderate, uniform shear rates • Extremely low temperature profile • Efficient injection of liquid components • Precise temperature control • High filler loadings By: www.busscorp.com Willem Uyttendaele, Brecht Demedts, Myriam Vanneste Centexbel Kortrijk, Belgium bioplastics MAGAZINE [05/22] Vol. 17 11