CNF-reinforced thermoplastics are composite products that combine Asahi Kasei’s highly heat-resistant cellulose nanofibers (CNFs) with various types of engineering plastics—such as polyamide (PA) and polyacetal (POM)—to yield lightweight materials boasting excellent recycling properties.
What is CNF-reinforced thermoplastics?
CNF-reinforced thermoplastics are composite products that combine Asahi Kasei’s highly heat-resistant CNFs with various types of engineering plastics to yield lightweight materials boasting excellent recycling properties.
To date, Asahi Kasei has developed two families of CNF-reinforced thermoplastics: PA/CNF composite materials combining highly heat-resistant CNFs with various PA, and POM/CNF composite materials combining highly heat-resistant CNFs with POM. These materials are ideal for fabricating sliding components, where the unique properties of CNF composites allow components to be made with smaller sizes, thinner walls, and lighter weights.
Key features of Asahi Kasei’s CNFs
■ High heat resistance ■ Low environmental footprint (Biomass fiber with good material recycling properties) ■ Low specific gravity ■ Low friction coefficient and low abrasion ■ High elasticity ■ Low linear expansion coefficient ■ High gas-barrier strength
The CNFs developed by Asahi Kasei are biomass fibers containing cotton-linter constituents that are miniaturized via sophisticated techniques to sizes as small as nanometer scales.
As indicated by the figure on the right, Asahi Kasei’s CNFs can reinforce resins by serving as biomass fillers with higher heat resistance than conventional CNFs. These materials have good recycling properties—they can be recycled for use as ingredients in the same products—and boast low specific gravity (1.5 g/cm3). Other superior properties of these materials include high elasticity, a low linear expansion coefficient, a low friction coefficient, low abrasion, and high gas-barrier strength.
Heat resistance of CNFs (Asahi Kasei’s CNFs vs. conventional CNFs)
Asahi Kasei’s technologies for nanodispersing CNFs
Because CNFs are extremely hydrophilic, they tend to clump together when blended into resins. This has often prevented CNFs from achieving their full potential as reinforcing additives.
Asahi Kasei is developing technologies for nanodispersing CNFs in a variety of resins, ensuring a single, consistent manufacturing process from CNF production to CNF composites.
PA/CNF composite materials
PA/CNF composite materials combine Asahi Kasei’s highly heat-resistant CNFs with various types of PA. Key features of these materials include good sliding properties, good rigidity at both low and high temperatures, low specific gravity, and good material recycling properties compared to non-reinforced PA or PA/GF. PA/CNF composites are well-suited for use in fabricating sliding components with smaller sizes, thinner walls, and lighter weights.
■ Key features of PA/CNF composite materials
【Feature 1: High heat resistance and good material recycling properties】
Asahi Kasei’s highly heat-resistant CNFs exhibit relatively low thermal degradation and fiber rupture during the material-recycling process. This ensures minimal degradation of the physical properties of injection-molded composite resins even after crushing and remolding multiple times. In addition, these composites are more resistant to color change during injection molding than composites made with conventional CNFs, yielding molded products with superior appearance (see figure below).
【Feature 2: High rigidity and good dimensional stability】
In comparison to non-reinforced polyamides or polyamides reinforced by glass fibers (GFs), Asahi Kasei’s PA/CNF composite materials offer significantly higher rigidity and exhibit high elasticity and a low linear expansion coefficient from low to high temperatures.
【Feature 3: Good sliding properties】
Asahi Kasei’s PA/CNF composite materials have low friction coefficients, exhibit low abrasion, and are less likely to abrade friction partners (such as metals).
Because CNF nanocomposite materials are less likely than glass-fiber-reinforced materials to abrade the metal surfaces over which they slide, these materials eliminate the need to treat those metal surfaces with special surface-processing steps.
■Biomass plastic PA610/CNF composite helps reduce environmental footprint
PA610 is a biomass plastic containing polymers that are 60% plant-derived. Blending PA610 with 10% CNF reinforcers yields a composite with 65% biomaterial content, helping to reduce environmental footprints even more. The use of biomaterials and the high mechanical recyclability of this substance yields parts with lighter weights, helping to reduce the environmental footprint of product components.
⇒For more information on the plant-derived polyamide (PA) 610 LEONA™ BG series of products, click here.
POM/CNF composite materials
POM/CNF composite materials combine Asahi Kasei’s highly heat-resistant CNFs with POM. Key features of these materials include good sliding properties, good rigidity at high temperature, minimal shrinkage, a low coefficient of thermal expansion, and good creep properties at high temperature as compared to general POM. POM/CNF composite materials are well-suited for use in fabricating sliding components with smaller sizes, thinner walls, and lighter weights.
■Key features of POM/CNF composite materials
【Feature 1: Superior sliding properties against surfaces made of metal or of the same material】
POM has good mechanical properties, and exhibits superior friction and abrasion characteristics, making it a popular choice for fabricating gears and other sliding components. Also, CNFs are less likely than glass-fiber-reinforced materials to abrade metal partner surfaces in sliding components. Thus, POM/CNF composite materials combine good mechanical properties with improved sliding behavior.
Moreover, even when used as sliding components against surfaces of the same material—a situation that is commonly understood to yield poor performance—POM/CNF components have low friction and low abrasion and operate silently, as indicated in the figure below. For this reason, choosing POM/CNF materials not only downsizes product, but also allows multiple materials to be replaced by a single material.
【Feature 2: High rigidity and good dimensional stability】
In CNF nanocomposite materials, Asahi Kasei’s highly heat-resistant CNFs—which are based on cotton-linter constituents—are thoroughly dispersed within POM to form high-strength CNF networks throughout the resin, yielding superior rigidity and dimensional stability. POM/CNF composite materials, made with Asahi Kasei’s proprietary CNF dispersion technology, can retain their high rigidity even at high temperatures, where the rigidity of typical resins deteriorates.
【Feature 3: Creep resistance】
Asahi Kasei’s POM/CNF composite materials exhibit outstanding creep resistance, helping to meet the needs for component miniaturization and durability.