There has been much discussion about the environmental benefits of using pultruded materials, but what about the products at the end of their useful life? Can such materials be reused?
Fiber-reinforced polymer (FRP) composites can be recycled through pultrusion, by grinding and thermal reclaiming of fibers. However, current practices can produce dense components that nearly double the strength of plastic lumber and are on par with oak planks.
This post will examine current efforts to recycle, reuse, and recover.
The American Composites Manufacturers Association (ACMA) has partnered with the Institute for Advanced Composites Manufacturing Innovation (IACMI) to develop an effective, scalable method of composite recycling. In collaboration with Owens Corning, Ashland ─ a global specialty materials company ─ and with support from the University of Tennessee, the coalition devised a process to keep scrap and used composites out of landfills.
Another effort comes from the American Chemistry Council, which has a vision for a sustainable planet. In 2017, the council established two ambitious goals to achieve:
- By 2030, 100% of U.S. plastic packaging will be recyclable or recoverable.
- By 2040, 100% of U.S. plastics packaging will be reused, recovered, or recycled.
Recent sustainability efforts are all the more urgent as the growth of composite materials is expected to follow a sharp upward trajectory. Attendees at ACMA’s first conference in 2018 first learned about its dedication to the recycling of composites. The process has potential applications in wind turbine blades, electronic circuit boards, and other items that have so far lagged behind in the recycling effort.
To help achieve these goals, a set of principles was developed to guide its efforts. In this respect, the council developed the Road Map to Reuse, a plan to achieve these goals and a push toward a circular economy for plastics, in which these materials are kept in use for as long as possible and then repurposed rather than disposed of.
To compound matters, the global composites industry is growing amid rising demand for high-performance materials. According to a Markets and Markets Report, the global composites market size is projected to grow at a compound annual growth rate (CAGR) of 8.8% from 2020 to 2025, reaching $112.8 billion from $74.0 billion in 2020. A further breakdown from its Glass Fiber Market Forecast, Research and Markets, pegs the growth of the glass fiber market at a compound annual growth rate (CAGR) of 4.27%, valued at $ 14,193.55 million in 2019, growing to $19,837.62 million in 2027.
The growth in demand is understandable as glass fibers tout excellent corrosion resistance, higher stiffness and strength, and high tensile strength, along with durability and high-temperature tolerance. These fibers find applications across a broad range of end-use industries, including automotive, construction, marine, wind energy, aerospace & defense, and others.
Many recycling methods for composites work by burning off (pyrolysis) or chemically dissolving (solvolysis) the resins from a composite part, allowing the fibers to be reclaimed and reused. Other recycling and research efforts are looking into methods for repurposing end-of-life (EoL) composite parts in their entirety, to achieve different goals so as to:
- retain as much of the original fiber and resin’s mechanical properties as possible;
- to minimize the cost of processing; and
- to reduce the carbon footprint of the recycling process
The following is a summary of such efforts:
Energy Recycling (incineration method). The method seeks to convert waste (FRP material) into cement raw materials through a comprehensive method of crushing and burning. In this process, the FRP waste is first crushed into a powder with a particle size of 10 mm, then blown into a cement kiln to be combusted as fuel. What's left behind can be used as raw material for cement. This method can completely handle the FRP waste.
A portion of the FRP waste is converted into energy, which can reduce fuel consumption and reduce carbon dioxide emissions. Due to the high heat in the kiln, there are very few harmful gases. There is no danger of harmful gases polluting the air.
Physical Recycling. FRP waste is crushed into powders of different particle sizes and used as fillers in composites such as building materials and thermoplastics. This is a low-cost, simple process and does not pollute the environment with secondary pollution. But when manufacturing micro powder, the cost to crush materials is relatively high. The disadvantage of adding micro powder to FRP products is that the more micro powder is added, the lower the resulting product's strength.
Chemical Recycling. This method is to pyrolyze the FRP waste in an oxygen-free or even ultra-high vacuum environment and to decompose the waste into unsaturated polyester raw materials, glass fibers, and fillers. Unsaturated polyester raw materials and fiberglass can be used to remake FRP profiles; fillers can be used as agricultural fertilizers to balance the acidity and alkalinity of the soil, and can also be used as raw materials for composite materials. In this way, FRP waste can be renewed and greatly reduces environmental pollution. So far, the chemical recovery method is considered to be the most promising recycling technology.
Repurposing and pyrolysis. Anmet in Poland provides manufacturing companies with metal recycling solutions. Andrzej Adamcio, Anmet's CEO, found a niche in providing solutions for recycling composite wind turbine blades at the end of their life spans. Leveraging his experience in metals recycling, he worked on methods to recycle glass and carbon-fiber composite blades. Currently, wind blade recycling is one of the company’s main areas of focus and a major growth area going forward.
Meanwhile, in the Netherlands, experts at Van Wees (manufacturer) and Crossply Technology have discovered that reusing excess thermoplastic trimmings can be achieved by creating a chips-based laminate. With this process, the sustainability gains are significant. Chip-based recycled material can offer half the bending strength of continuous-fiber cross-ply panels made of similar fiber and resin.
The new products from this zero-waste manufacturing process include parts useful to the construction and auto industries, such as interior panels and door handles. This discovery may have little direct effect on pultrusion or other thermoset composites, but it does demonstrate that work in the area is underway and that discoveries from one material may lead to findings in another.
As technology continues to advance, pultruded products are developing a positive performance record and eco-profile. As awareness of the benefits of recycling products grows, so will the industry.
Contact Tencom to discuss FRPs for your specific needs.
