Design of Next Generation of Plastics with Cellulose Filaments

H. Lentzakis
Kruger Biomaterials Inc.,
Canada

Keywords: cellulose filaments, natural fibers, sustainable, pulp fibers

Summary:

Cellulose is the most abundant bio-sourced polymer on earth. The need for sustainable materials derived from cellulose is increasingly important due to the environmental impacts of the use of oil-based polymers. FiloCell™ cellulose filaments (CFs) are unique natural fibers, with extremely high length to width aspect ratio and surface area obtained by mechanical peeling of softwood pulp fibers, which are semi-crystalline and have a low density. The 100% yield, fully mechanical process “peels” wood fibers longitudinally, thus preserving their initial length as much as possible, while reducing their diameter by approximately 1,000-fold. The result is extremely fine and smooth filaments made solely of cellulose. CFs are bio-sourced from renewable Kraft pulp fibers and are compostable, biodegradable, and recyclable and a green alternative to glass fibers (GFs). Despite the low cost and availability of GFs, there are key disadvantages to incorporating them into polymer matrices. Handling GFs may lead to damage to upstream and downstream machinery through abrasion and repurposing and recycling GFRPs poses a difficult challenge. CFs-reinforced polymers have similar stiffness properties to GFRPs with a reduction in mass that can reach up to 25% based on substitution rates. CFs can also substitute oil-based polyolefins allowing for a more sustainable and lower carbon emission product. Moreover, CFs can act as a reinforcing agent to post-consumer recycled plastic; thus, improving their viability. CFs were tested with success in polyolefins, biopolymers, thermoplastic elastomers and engineering resins that are widely used in industry such as HDPE, PP, PLA, TPU, EVA and Nylon-6. Their addition to thermoplastics, at relatively low loading levels, results in enhanced mechanical properties if a good dispersion, and a good adhesion between the fibers and the matrix are achieved. CFs cannot be dried using conventional methods such as flash drying, oven-drying or spray drying without provoking agglomeration of the filaments into clumps. Freeze-drying gives a better technical result but is not economically feasible. Kruger Biomaterials have developed a chemical surface-active treatment, whereby an organic solvent is added to the wet CFs and then evaporated to produce free flowing dried filaments that are easily dispersible in thermoplastics. The treatment physically blocks hydroxyl groups in the cellulose fiber, thus weakening hydrogen bonding in the CFs. Other than in thermoplastics, CFs are ideal property enhancers in many industrial applications, such as adhesives, foams, paint and concrete mixtures. In each of these, the addition of CFs imparts strength to the product and allows for the substitution of a more Energy intensive input. In concrete production, CFs also reduces shrinkage and adds strength as the trapped moisture is time released to provide a better cure.