Owens Corning (NYSE: OC), a leading global producer of glass fiber reinforcements for composite systems and residential and commercial building materials, today reported results of a new study that shows how the company's boron-free Advantex® E-CR glass fiber outperforms standard E-glass reinforcements in stressed laminates in a corrosive environment.
The study combined corrosion and stress testing and later examined the composite laminates using SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray) spectroscopy. Advantex® glass fibers demonstrated superior corrosion resistance compared to E-glass in composite structures exposed to a solution of 10 percent sulfuric acid. The study also confirmed previous findings on the leaching mechanism of Eglass in acidic environments.
"The outcome of this study provides a compelling reason for using Advantex® glass fiber reinforcements throughout a composite structure," says Ashish Diwanji, vice president of innovation for the Owens Corning Composite Solutions Business.
"Some application designs require E-CR glass in a corrosion barrier and allow standard E-glass in the rest of the laminate," continues Diwanji. "These results argue for reducing the risk of laminate failure by using ECR glass throughout the structure."
Diwanji says previous testing examined the impact of corrosive chemicals on bare glass.
"While those tests were helpful in understanding the performance of Advantex® glass, our customers also wanted studies comparing Advantex® glass and standard E-glass fibers in composite laminates. Stress-corrosion testing was developed to check laminates under load in a corrosive environment to more closely simulate conditions an application may encounter in the field. Looking at the results under advanced optical and X-ray equipment allows us to easily see the results of the tests."
Diwanji says the study used glass fiber-reinforced composite rods that were exposed to a 1 percent strain for only 72 hours and then immersed in a 10 percent sulfuric acid solution under no load and at room temperature for an extended period of time. At regular intervals, rods were removed and examined for the effects of corrosion. After one month, the comparison found substantial differences between the non-corroded Advantex® glass fibers and corroded E-glass fibers. With E-glass fibers, studies have noted a disappearance of boron and reduction in alumina and calcium, indicating that most of the glass components (except silica) were leached from the strands. This study confirms those results in a different way.
While the corrosion resistance of Advantex® glass compared to E-glass was dramatic at one month, researchers decided to continue the study to see if new information could be obtained from a longer exposure.
After a three-month exposure in 10 percent sulfuric acid, the E-glass samples showed corroded fibers along the entire perimeter of the composite rod and considerable damage on one side of the rod. Deformation of the rod occurred as the E-glass deteriorated. There was also de-bonding and subsequent fracturing, which was clearly visible in the enlarged images.
"The technique of coupling SEM with EDX answered a number of questions about the corrosion mechanism not easily answered by other techniques," added Diwanji.
The patented boron- and fluorine-free Advantex® glass production process also results in a higher performing fiber and a significantly smaller environmental footprint compared with standard E-glass processes.
Other advantages of Advantex® E-CR glass fibers include:
- Qualification as E-CR glass under ASTM D578, ISO 2078 and DIN 1259-01
- Proven technology for fiber production, fabrication and end-use applications
Advantex® glass reinforcements are increasingly being used to reduce the risk of catastrophic failure because they provide excellent corrosion resistance in any liquid or wet environment, including water and acidic or weakly alkaline solutions.
Fast-growing applications include flue-gas desulphurization equipment used in coal-fired power plants, underground water and sewage pipe, desalination plants and a variety of salt water marine applications including tidal energy installations.
Eric Carlier, innovation and application development leader, OCV® Reinforcements, will present results of the study at 10:30 a.m. Thursday, April 15, at JEC Composites 2010 in Paris, the world's largest trade show for composite materials.