Japanese Paper Firms take New Approaches to Cellulose Fiber Reinforcement

 

A few weeks ago the online publication of Plastics Today (Santa Monica, Calif., USA) featured an article that explained how in addition to Rengo (featured in OTW Nanotechnology section this past week - 8/2 edition - for their work with cellulose nanofiber) Mitsubishi Paper is also working to develop low-cost micro-cellulosic CNF product as well as traditional CNF, which currently costs around $90/kg, using a different approach than Rengo.

The article by Stephen Moore explained that Yasuyuki Oku, group leader at the company’s Marketing & Incubation Group, said that lower cost cellulose microfibers, or even millifibers, can adequately reinforce thermoplastics for many applications and they can be incorporated into the polymer matrix much more easily than traditional CNF, particularly when exploiting the company's papermaking expertise. Japan’s Ministry of Economy, Trade and Industry (METI) has set a target of reducing the cost of CNF to JPY400–500/kg ($1.60–2.00/lb.) by 2030 but there are some in the industry that think this goal is challenging. Adoption of cellulose microfibers might be a good alternative (or supplement).

Mitsubishi Paper already offers cellulose fiber-reinforced polypropylene (PP) compounds on a commercial basis with its Cellulomix series. Its high purity cellulose fiber PCV30-F PP compound offers reinforcement levels of 10%, 20% and 30% with tensile strengths of 36, 45, and 56 MPa, respectively, versus 32 MPa for neat PP resin. Heat distortion temperatures are substantially improved from 110°C (at 0.45 MPa) to 127°C, 145°C and 154°C, respectively. Compared with a standard PP grade’s MFR of 60, MFRs of the three grades are 14, 2 and 1, respectively. Mitsubishi Paper also offers wood pulp-filled PP grades that are lower in cost with mechanical properties that are slightly down on the other grades.

Mitsubishi Paper is also active in the application of recycled carbon fiber in PP thermoplastic compounds. PP reinforced with virgin carbon fiber is expensive and can find it hard to compete with carbon fiber-reinforced polyamide (CF-PA) compounds on a cost versus performance basis.

Mitsubishi Paper is recovering carbon fiber waste such as trimming from thermoset composite manufacture and fiber extracted from discarded composite parts, and press-forming it with PP film layers into multi-layer CF-PP roll stock that can be further processed into three-dimensional press-formed parts or even used in insert molding or back molding processes. The company’s Carboplus  Repro roll product has a base weight of 30–100 g/m2 (thickness: 450–1500 µm and CF content of 50–90wt%). The product using recycled CF retains 90% of the mechanical attributes of CF-PP roll stock incorporating virgin CF.

More information about Mitsubishi Paper Mills, Ltd. is available online.