Plasticised: Innovation inbiopolymerapplication by using optimized plasticisers and new processingtechniques  (PLAsticised)

Goals

Both textile extrusion (fiber, monofilaments, multi-filaments, tapes) and plastics companies (foil, profile, injection molding) can implement the extrusion formulations in their productions. The newly to be developed coating formulations will become available for companies active in coating, finishing, impregnating and printing on various raw materials. Not only textiles but also applications on metal, plastic, paper or cardboard are eligible. An important input and valorization potential is also provided for companies from the preliminary stage, namely producers of biopolymers, potential (bio) plasticizers, other additives, formulators. Targeted demonstration cases will demonstrate industrial usability for company-specific applications. PLA is a bio-based polymer that has been rising sharply in production volumes and applications in which it is used in recent years. PLA, however, also exhibits negative properties of which the high rigidity and especially brittleness at temperatures below the glass temperature (Tg) is one of the most important. For certain applications, this brittleness is an important obstacle to achieving a broadening of employability. Plasticizers in particular have the potential to absorb the brittleness of PLA. The core objective within PLAsticized is to develop optimized plasticizer formulations in function of the application and to apply them in both existing PLA applications and in newly developed applications within the coating, printing and hot-melt technology. Both an improvement in the user characteristics and a far-reaching broadening of the usability of the renewable PLA raw materials are targeted. Within PLAsticized, the selection and usability of optimized plasticisers for PLA is mapped for extrusion of yarns, films, coatings on textiles and injection molded products as well as their effects on Tg, flexibility and related properties. The impact on the processing and all quality and use parameters such as paintability, maintenance options, migration parameters, UV stability, fire resistance is determined and this in function of the specific targeted applications. This forms the basis for providing specific advice on implementation in the broad domain of the melt processing applications for PLA Applications where TPS or mainly PO are currently being used are also being targeted New extrusion applications for the plasticized PLA such as for extrusion coating on yarn or fabric level or on metal wires are being targeted, for which PLA offers a potential alternative for some PVC as PO applications In addition, new application techniques and application domains are being developed, in which the use of plasticizers is crucial.Dispersions of PLA powders in water and plastisol will be evaluated in various coating techniques (dip coating, squeegee coating, possibly foam coating). ing). The addition of plasticizers will lead to easier and more homogeneous blending (gelling) to a dense coating layer. Such formulations are also eligible for use via printing technology. Such PLA applications offer a potential alternative to some PVC, PU or acrylic coatings. Flexible low-melting plasticized formulations are also evaluated for their usability for hot-melt applications that can be used as an adhesive layer or a finishing layer.

Activities and results

During the first project years, the focus was primarily on identifying plasticizers for PLA. Because the project studied different product types, this was realized for different PLA grades. These were semi-crystalline PLA types for application extrusion and amorphous types for coating applications. Important differences can also be found in the process parameters. For extrusion, for example, more attention was paid to validating the thermal stability, so that process processing during compounding and extrusion was guaranteed for a longer period of time at high temperatures, while for coating applications the stability of the coating pastes was also mainly considered. A compatibility study with PLA was also conducted for the identified plasticizers, followed by migration tests. This provided an overview of which types of plasticizer are better suited for which processes and about the stability of the products.

Specific attention has been paid to the characterization of the obtained plasticized materials. For yarn applications, these were mainly dimensional stability, elongation at break and tensile strength, while for coating applications, an evaluation of flexibility and durability (washing, abrasion) was studied. This was done on the basis of cyclical flexibility tests and microscopy. These techniques are complementary because sometimes flexible PLA coatings with good visual scoring showed microscopic micro-cracks.

The coating component of the project was very ambitious. At the start of the project, there was no worldwide example of PLA coated textile articles. Only extrusion coating for cardboard (drinking cups) was available. All possible processing routes were therefore tested during the project. These were hot melt coating, water-based emulsions, solvent-based coatings and plastisol coatings. From thorough characterization it was decided that mainly hot melt coating and plastisol coatings showed promising results. The choice for this is obvious. Hot melt coatings are an environmentally friendly alternative to coating processes, but had the disadvantage that prior compounding with plasticizers is required and the viscosity during processing is on the high side for conventional hot melt installations. For future projects we therefore look with interest at the extrusion coating application. This is currently not yet applied in the Belgian textile industry, but can be a promising addition. The plastisol coatings are further elaborated for various applications ranging from composite, via inks to flat coatings.

During the last project years, the focus shifted mainly to application-oriented research. Demonstrators were developed for different markets, studies were made on which parameters they meet and where improvements are still required. The improved yarn level properties were further characterized for monofilament, multifilament and staple fiber. As a result, applications ranging from clothing to packaging to technical textiles come to the possibilities. For coating applications, plastisol inks are mainly considered because they can be processed with the current equipment. Because this application is very new, product-specific developments are currently being studied further at companies.

Specific focus has also gone to foaming PLA. Foaming is a common technique for a variety of reasons, ranging from insulation, through price efficiency to lightweight applications. Many different methods of foaming are possible and the different methods (chemical, physical) have been optimized with and without the use of plasticizers.

All research has shown that the choice of plasticizer has a very strong influence on the properties of the final product. An important factor here is biodegradability. PLA in itself is industrially biodegradable, meaning that it has a temperature of at least 60 ° C before it is degraded. Biodegradability could be accelerated through the use of specific plasticizers, which is important for many applications. The biggest disadvantage of plasticized PLA remains the limited choice of bio-based plasticizers. The usual choices are highly susceptible to migration, which of course hinders their applications. A number of plasticizers were identified during the project where little to no migration was observed. These plasticizers are of course an interesting choice and can also be used in blends to meet various requirements. One of the most important conclusions of the project is that the development of products based on PLA is very product-specific. The most important parameters that have an influence on the choice of PLA grade, plasticizer and processing process are therefore the desired strength, biodegradability and stability of the product. This weakness is immediately a strength because PLA lends itself to the manufacture of products that have to break down quickly in nature and at the same time it can also be used to manufacture products with a long service life.