Bioresorbable and degradable glass fiber compostable composite parts

Bioresorbable and degradable glass fiber, compostable composite parts
China Glass Fiber 2024-05-08 17:58 Jiangxi
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Bioresorbable bone fixation implants made by ABM Composite (above left) and automotive brake pedals (right) made with ArcBiox BGF30-B1 long fiber technology (LFT) compound, which is polylactic acid (PLA) reinforced with ArcBiox X4 degradable glass fiber. ArcBiox BGF30-B1 passed the industrial composting test conducted by DIN CERTCO/TUV in Germany according to EN 13432 (Image source: ABM Composite)

What if glass fiber reinforced polymer (GFRP) composites can be composted at the end of their service life in addition to providing decades of proven advantages in weight reduction, strength and stiffness, corrosion resistance and durability? This is the appeal of ABM Composite's technology.

Bioactive glass, high-strength fibers

Founded in 2014, Arctic Biomaterials Oy (Tampere, Finland) has developed a degradable glass fiber made of so-called bioactive glass. “This is a special formula developed in the 1960s that allows the glass to degrade under physiological conditions,” says Ari Rosling, R&D Director at ABM Composite. “When it enters the body, the glass breaks down into its component mineral salts, releasing sodium, magnesium, phosphates, etc., which creates a condition that stimulates bone growth.”

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Typical properties (Image source: ABM Composite)

“Its properties are similar to those of E-glass,” says Rosling. “But this bioactive glass is difficult to manufacture and draw into fibers. Previously, it was only available as a powder or putty. As far as we know, ABM Composite is the first company to use it to manufacture high-strength glass fibers on an industrial level. We are now using these ArcBiox X4/5 glass fibers to reinforce different types of plastics, including biodegradable polymers.”

Medical implants

The Tampere region, two hours north of Helsinki, Finland, has been a hub for bio-based, biodegradable polymers for medical applications since the 1980s. “One of the first commercial implants made from these materials was made in Tampere, and that’s how ABM Composite, now our medical business unit, got its start,” says Rosling.

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Image credit: ABM Composite

“There are a lot of biodegradable, bioresorbable polymers used in implants,” he continues, “but their mechanical properties are far from natural bone. We are able to reinforce these biodegradable polymers so that the implants have the same strength as natural bone.” Rosling notes that the addition of ABM’s medical-grade ArcBiox glass fibers can increase the mechanical properties of biodegradable poly-L-lactic acid (PLLA) polymers by 200-500 percent.
As a result, ABM Composite’s implants have higher performance than implants made from unreinforced polymers, while also being bioresorbable and promoting bone formation and growth. ABM Composite also uses automated fiber/strand placement technology to ensure optimal fiber orientation, including placement of fibers along the entire length of the implant and placement of additional fibers at potential weak points.

Home and Technical Applications

As its medical business unit grew, ABM Composite recognized that bio-based and biodegradable polymers could also be used in cookware, tableware, and other household items. “In this regard, these biodegradable polymers typically have inferior mechanical properties compared to petroleum-based plastics,” Rosling said, “but we can reinforce these materials with our biodegradable glass fibers, making them actually good alternatives to fossil-based commercial plastics for a wide range of technical applications.”

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Image source: ABM Composite

As a result, ABM Composite has increased its technical business unit, which now has 60 employees. “We offer a more sustainable end-of-life (EOL) solution,” Rosling said. “Our value proposition is that these biodegradable composites can be put into industrial composting operations, where they become soil.” Traditional E-glass is inert and does not degrade in these composting facilities.

ArcBiox Fiber Composites

ABM Composite has developed ArcBiox X4/5 glass fiber in various forms for composite applications, from chopped fibers and injection molding compounds to continuous fibers for processes such as weaving and pultrusion. Its ArcBiox BSGF series combines biodegradable glass fibers with bio-based polyester resins, offering general purpose technical grades and ArcBiox 5 grades, which are approved for use in food contact products.

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ArcBiox X4/5 glass fiber is available in chopped and continuous forms, the latter of which can be used in processes such as weaving and pultrusion, as shown below right in combination with a bio-based polyester resin (Image credit: ABM Composite)

ABM Composite has also investigated various biodegradable and bio-based polymers, including polylactic acid (PLA), PLLA, and polybutylene succinate (PBS). The figure below shows how X4/5 glass fiber improves performance to compete with standard glass-reinforced polymers such as polypropylene (PP) and even polyamide 6 (PA6).

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Image source: ABM Composite

Bio-based PP and PA, whose production is increasing rapidly, do not degrade, Rosling said. “While bio-based PLA and PBS do degrade, their mechanical properties and heat resistance are typically very low. Our biodegradable glass fibers are a big step forward, fully improving their properties to enable new applications.”

Durability and compostability

If these composites are biodegradable, how can they last? "Our X4/5 glass fibers do not dissolve in 5 minutes or overnight like sugar does, and while their properties do degrade over time, it is not as dramatic," said Rosling. "To degrade effectively, we need prolonged elevated temperatures and humidity, like those found in the body or in an industrial compost pile. For example, we have tested cups and bowls made from our ArcBiox BSGF material and they can withstand up to 200 dishwashing cycles without losing functionality. Although the mechanical properties degrade to some extent, they do not degrade to the point where the cups are no longer safe to use."

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During industrial composting tests, ArcBiox materials with X4 glass fibers met the standard requirements of breaking down into fragments <2 mm in 90 days and biodegradation of 90% (measured by carbon content). * Cold injection molding, ** Hot injection molding for crystalline materials. 1. Complies with UNI EN ISO 20200:2016, MP 2238 rev 0 2017, 2. Oxo-biodegradability testing according to ISO 14855-1:2012 (Image credit: ABM Composite)

However, it is important that when these composites are disposed of at the end of their useful life, they do meet the standards required for composting. ABM Composite carried out a series of tests to demonstrate compliance with these standards. “According to the ISO standard (industrial composting), biodegradation should occur within 6 months and decomposition within 3 months/90 days,” says Rosling. “Decomposition means placing the test sample/product into the biomass or compost. After 90 days, the biomass is tested using a sieve. After 12 weeks, at least 90% of the product should be able to pass through a 2mm x 2mm sieve.”

Biodegradation is determined by grinding the raw material into a powder and measuring the total amount of CO2 released after 90 days. This assesses how much of the carbon content is converted into water, biomass and CO2 during the composting process. “To pass the industrial composting test, 90% of the theoretical 100% CO2 must be achieved during the composting process (calculated based on carbon content).”
Rosling says ABM Composite has passed the decomposition and biodegradation requirements, with tests showing that adding its X4 glass fibers actually improved biodegradability (see table above), with the unreinforced PLA mix only reaching 78%, for example. “But when adding our 30% degradable glass fibers, the biodegradation rate increased to 94%, and the decomposition rate was still very good,” he explains.
As a result, ABM Composite has demonstrated that its materials can be certified as compostable according to the EN 13432 standard. So far, the tests its materials have passed include: the ultimate aerobic biodegradability (biodegradability) test of materials under controlled composting conditions ISO 14855-1, the aerobic controlled decomposition test ISO 16929, the chemical requirements test ISO DIN EN 13432, and the plant test (ecotoxicity test) OECD 208, ISO DIN EN 13432.

CO2 released during composting

CO2 is released during composting, but some of it remains in the soil and is then used by plants. Composting has been studied for decades and both industrial and retroactive processes release less CO2 than other waste disposal alternatives, and is still seen as an environmentally friendly and carbon footprint-reducing process.

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ABM Composite has also demonstrated that its composted materials are non-toxic to plants grown in them (above) and pass aerobic biodegradation requirements under home composting conditions (below) (Image credit: ABM Composite)

Ecotoxicity requires testing both the biomass formed during the composting process and the plants grown using that biomass. “This is to ensure that composting of these products does not cause any harm to growing plants,” Rosling said. In addition, ABM Composite has demonstrated that its materials meet biodegradation requirements under home composting conditions, which also require 90% biodegradability, but within 12 months, compared to the shorter time frame for industrial composting operations.

Industrial applications, production, costs and future growth

ABM Composite’s materials are used in a range of commercial applications, but more cannot be disclosed due to confidentiality agreements. “We tailor our materials to fit the requirements of applications such as cups, plates, cutlery and food storage boxes,” Rosling says, “but they are also used in cosmetic containers and large household items as an alternative to petroleum-based plastics. Recently, our materials have been selected for parts in large industrial machinery that need to be replaced every 2-12 weeks. These companies have realized that due to the reinforcement of our X4 glass fibers, these machine parts actually have the required wear resistance and can be composted after use. This is an attractive solution in the near future as these companies are faced with the challenge of meeting new environmental and CO2 emission regulations.”

“There is also growing interest in using our continuous fibers in different types of fabrics and nonwovens to make structural components for construction. We are also seeing interest in using our degradable fibers with bio-based but non-degradable PA or PP and inert thermoset materials,” adds Rosling.

Currently, X4/5 glass fibers are more expensive than E-glass fibers, but are also produced in relatively small volumes. ABM Composite is pursuing multiple opportunities to expand the range of applications and facilitate the expansion of production to 20,000 tons/year as demand grows, which will also help reduce costs. Even so, Rosling says that in many cases, the costs of meeting sustainability and new regulatory requirements have not been fully considered. Meanwhile, the urgency of saving the planet is growing. “Society is already pushing for more bio-based products,” he explains. “There are a lot of incentives to move circular technologies forward, and the world needs to move faster on this, and I think society will only increase the push for bio-based products in the future.”

LCA and Sustainability Advantages

Rosling says ABM Composite’s materials reduce greenhouse gas emissions and use of non-renewable energy by 50%-60% per kilogram. “We are performing LCA (life cycle analysis) calculations on our products using the Environmental Footprint Database 2.0, the approved GaBi dataset, and the methods outlined in ISO 14040 and ISO 14044.”

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The difference between fossil-based polymers on the left and ABM Composite’s materials on the right. The orange on the left represents the non-renewable CO2 released during the incineration of EOL products, and the green data on the right reflects the renewable CO2 absorbed into the product during the manufacturing process (Image source: ABM Composite)

"Currently, when the composite material's life cycle ends, a lot of energy is required to incinerate or pyrolyze composite waste and EOL products. Shredding and composting is an attractive option, which is definitely one of the important value propositions we provide. We are providing a new type of circularity." Rosling said, "Our glass fiber is made of natural mineral components that are already present in the soil. So why not compost EOL composite parts, or dissolve the fibers in non-degradable composites after incineration and use them as fertilizer? This is a recycling option that is really attracting global interest." (Source: compositesworld, Donghua Jingwei New Materials Research Institute)