New Method to Improve Mechanical Properties of Recyclable Nanocomposite

László Szabó and Kenji Takahashi and colleagues at Kanazawa University and Kanazawa Institute of Technology demonstrated that irradiating short carbon fiber thermoplastics with an electron beam can improve their mechanical properties.

The researchers based their study on polymers that are thermoplastic so that the resulting composite could be readily recycled and remolded into other forms. With environmentally friendly concerns in mind they focused the study on the biobased cellulose propionate for the composite matrix.

Their study included investigation of the effects of electron beam irradiation on the strength for polymers functionalized with esters to increase crosslinking, and enhanced with carbon fibers, as well as different forms during irradiation (dumbbells and pellets) and long and short extrusion nozzles.

Findings in the Research

Despite the potential drawbacks of carbon fiber inclusion and irradiation induced crosslinking, the researchers found that irradiating pellets of short-carbon-fiber composite made them stronger.

Further studies suggested that the irradiation strengthened and lengthened the carbon fibers, while irradiating pellets and making dumbbells from the pellets left sufficient uncrosslinked polymer matrix for some carbon fiber mobility to mitigate stresses. The shorter nozzle also diminished effects that shorten carbon fiber during extrusion.

“The composite retains its potential for recyclability (i.e. still thermoplastic) and the treatment is practically chemical-free,” report the researchers.

Polymers reinforced with carbon fibers:

• combine strength and low weight
• boast significant green credentials as they are less resource-intensive during production and use, and
• readily recycled

While the mechanical properties of continuous-fiber laminates are sufficiently competitive for applications in aerospace and automobiles, composites reinforced with short carbon fibers could be attractive for fast-manufacture, and even 3D Printing for applications with more moderate strength requirements.