Latest Research from a Highly Cited Scholar: Recovery of epoxy resin using nitric acid | OAJRC Material Science

"When carbon fiber reinforced polymer (CFRP) becomes the darling of cutting-edge industries, is the resulting epoxy resin waste an unavoidable environmental cost or a hidden treasure trove of resources?" "In the wave of the circular economy, have we found the key to unlocking the 'recycling deadlock' of thermosetting plastics?" These questions not only point to the forefront challenges of materials science but also interrogate the sustainability conscience of modern industrial civilization.

Scholars including Naoki Mori and Masatoshi Kubouchi from the Tokyo Institute of Technology, in their paper Recycling of Epoxy Resin in CFRP Prepreg Using Nitric Acid Decomposition Method published in OAJRC Material Science, reveal an innovative pathway for efficiently recovering epoxy resin from CFRP prepreg using the nitric acid decomposition method.

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Waste Epoxy Resin: The "Stubborn Fortress" Blocking the Path to a Circular Economy

CFRP has become a core material in fields such as aerospace and high-end automotive due to its lightweight and high-strength properties. However, its essential component—thermosetting epoxy resin—forms a permanent three-dimensional network upon curing, making it difficult to melt and insoluble in common solvents. This renders its recycling exceptionally challenging. The vast majority of discarded CFRP ultimately ends up as "immortal garbage" in landfills or as black smoke from incinerators. Like a solid "stubborn fortress," it blocks the road to closed-loop material cycling, becoming a glaring flaw in the era of green manufacturing.

Nitric Acid Decomposition Method: A Precise "Chemical Key"

Faced with this "stubborn fortress," traditional mechanical recycling yields only low-value filler, while pyrolysis often damages fiber performance and generates harmful gases. The research by the Tokyo Tech team is like finding a precise "chemical key." They innovatively employ the nitric acid decomposition method to launch a "precision strike" against the epoxy resin within CFRP prepreg. Nitric acid can effectively break the cross-linked network of the epoxy resin under relatively mild conditions, decomposing it into soluble low-molecular-weight compounds. This process not only achieves efficient depolymerization of the epoxy resin matrix but also maximizes the preservation of the original structure and strength of the carbon fibers, opening a new channel for the high-value recovery of both.

From Lab Breakthrough to Industrial Dawn: The Dual Challenges of Efficiency and Purity

Despite its great potential in principle, the journey of the nitric acid decomposition method from laboratory flasks to scaled-up recycling plants remains fraught with thorns. How can we precisely optimize nitric acid concentration, reaction temperature, and time to find the optimal point balancing decomposition efficiency against equipment corrosion and energy consumption? How can we efficiently separate and purify the decomposition products, transforming them into reusable chemical feedstocks instead of creating new wastewater challenges? Every fine-tuning of process parameters relates to the economic viability and environmental friendliness of the entire technological route, requiring deep integration and continuous innovation across materials science, chemical engineering, and environmental science.

The Future of Green Recycling: Reshaping the Circular DNA of the Advanced Materials Industry Chain

The significance of recycling epoxy resin via nitric acid decomposition extends far beyond solving the disposal problem of a single waste stream. It foreshadows a viable path from a linear "extract-manufacture-dispose" model towards a closed-loop "design-use-recycle-regenerate" model. In the future, recovered high-performance carbon fibers could re-enter high-end manufacturing, while regenerated epoxy resin monomers or derivatives could be infused into new product life cycles. This could not only significantly reduce the consumption of virgin resources and environmental impact but also hold the potential to reshape the underlying logic of the advanced composite materials industry, endowing it with a genuine circular DNA.

"The most advanced technology is not about extracting the strongest materials from nature, but about endowing materials with ceaseless, circular life." On the long journey towards sustainable development, advanced recycling technologies represented by the nitric acid decomposition method are like the first light of dawn, attempting to unravel the longstanding predicament of thermosetting plastics. Let us jointly focus on and promote this tale of green revival for waste epoxy resin, to alleviate the burden on our planet and store energy for the future.

The study was published in OAJRC Material Science

How to cite this paper

Naoki Mori, Winarto Kurniawan, Masatoshi Kubouchi, Saiko Aoki. (2026) Recycling of Epoxy Resin in CFRP Prepreg Using Nitric Acid Decomposition Method. OAJRC Material Science, 8(1), 12-20.

DOI: http://dx.doi.org/10.26855/oajrcms.2026.06.002

Scholar Introduction

Masatoshi Kubouchi, Professor Emeritus, Institute of Science Tokyo (formerly Tokyo Institute of Technology), Japan

Dr. Masatoshi Kubouchi is Professor Emeritus at the School of Materials and Chemical Technology, Institute of Science Tokyo (formerly Tokyo Institute of Technology). He received his B.Eng. (1984) and M.Eng. (1986) from Tokyo Institute of Technology, and obtained his D.Eng. from the same institution in 1995. He joined the Department of Chemical Engineering at Tokyo Institute of Technology as a Research Associate in 1986, was promoted to Associate Professor in 1996, and served as Full Professor until his retirement. He also served as Associate Dean of the School of Materials and Chemical Technology from 2016 to 2018. Professor Kubouchi's research focuses on the durability, degradation, and recycling of polymeric materials and composites, particularly in corrosive environments. He is internationally recognized for his pioneering work on the chemical recycling of thermosetting resins, developing nitric acid-based decomposition methods for amine-cured epoxy resins and glass fiber-reinforced composites. His research interests also encompass corrosion behavior of polymers in acidic and alkaline solutions, development of functional composite materials, smart materials for corrosive environments, fracture and erosion of polymer composites, and production of few-layer graphene. He has published extensively in high-impact journals including Polymer, Carbon, Composites Part B: Engineering, ACS Sustainable Chemistry & Engineering, and Polymer Degradation and Stability. Throughout his career, Professor Kubouchi has mentored numerous graduate students and collaborated with researchers across Japan, the Philippines, Iran, and other countries. He has served on multiple academic committees, including as a board member of the Materials Science Society of Japan. His work on epoxy resin recycling and composite durability has been widely cited, with over 2,600 citations to his name, reflecting the significant impact of his contributions to sustainable materials and corrosion science.

Screenshot of Masatoshi Kubouchi's Scopus Author Profile

The author has established broad international academic recognition, as reflected by the following scholarly metrics:

• Google Scholar: 2669 citations, h-index of 25, and an i10-index of 49.
• Scopus: 108 indexed publications, 1970 citations, and an h-index of 22.

These consistently strong citation metrics demonstrate the author's sustained research impact, long-term scholarly contributions, and broad recognition within the international scientific community.

He has published numerous papers in leading international peer-reviewed journals and has engaged in interdisciplinary collaborations with researchers from multiple countries in the fields of materials science, functional materials, and materials physical chemistry. His research findings have become important references in advanced materials design, nanomaterial preparation, materials performance regulation, and functional applications. Through continuous research and academic collaboration, he has made significant contributions to advancing materials science and promoting innovation in new materials technologies, the development of high-performance materials, and the research and development of sustainable materials applications.