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The Pultruded Composite Window Profile

The development of composite material windows has undergone significant changes over the past two decades, evolving from traditional unsaturated resins to modern polyurethane windows. This transformation has largely been driven by advancements in resin technology, propelling the entire window industry forward.

However, due to the cost of raw materials, production efficiency issues, post-production surface treatments, and UV resistance considerations, composite materials are generally 20% to 30% more expensive than standard steel windows. The manufacturing process is not highly efficient due to the intricacies of the craft, limiting the use of these windows primarily to colder regions like Canada. Since the 1990s, and especially in recent years, the development of polyurethane materials has significantly altered the landscape of the window industry.

I will discuss composite material windows from two aspects: fiberglass yarn and resin systems.

Fiberglass Untwisted Coarse Yarn: Fiberglass products are a new type of composite material made from a resin matrix and reinforced fibers. Initially, the imported fiberglass window profiles used non-alkaline fiberglass as reinforcement. In contrast, the most commonly used in China are high-alkali and C-grade fiberglass untwisted coarse yarns, with only a few companies using E-grade fiberglass reinforcement. In the past decade, national industrial policies have encouraged the development and application of E-glass fibers and introduced high-alkali fibers, limiting the growth of the medium-alkali fiber industry. Research indicates that during the production of fiberglass windows, stress caused by different cooling speeds on the fiber surface and inside can create micro-cracks on the surface. Studies show that water can erode fiberglass, and in humid environments, the strength of fiberglass is significantly lower than that of new fibers. Over time, the strength of fiberglass in humid conditions gradually decreases, accompanied by alkalization and mold growth. In reality, during the installation of pultruded windows, it’s challenging to avoid scratches on the resin surface, leading to erosion over time. This inevitably causes mutations in the fibers and resin, reducing the lifespan of fiberglass windows. Therefore, enhancing the application of E-glass untwisted coarse yarn is essential. E-glass is now extensively used in the window industry. For smaller grooves, we can use finer yarns like 1200 tex to optimize the process.

Polyurethane Resin: Polyurethane resin, a common resin in the rubber industry, is divided into two components: isocyanate and polyol. UV-resistant additives are generally mixed into the polyol. In recent years, polyurethane resins specifically designed for windows have simplified production compared to previous polyester windows. Their advantages include light weight and high strength, with a density of about 1.8 and strength comparable to ordinary carbon steel, eliminating the need for felt wrapping to enhance strength. Polyurethane resin boasts excellent dimensional stability, high lateral mechanical properties, high specific strength and rigidity, and good thermal insulation. This resin allows for the production of thin yet strong profiles, and is gradually being adopted in industries like wind power and solar panel framing. Additionally, polyurethane resin features low thermal expansion, corrosion resistance, and good electrical properties.

Composite material windows have their advantages and cannot completely replace traditional windows. Their outstanding corrosion resistance can withstand acids, alkalis, salts, oils, and other corrosive media, and they are rust-resistant. Their lifespan can reach up to 50 years, matching that of buildings, and they offer excellent thermal insulation, soundproofing, and can be painted in various colors to suit different decorative styles. However, these materials also have drawbacks, such as susceptibility to aging and cracking, especially under high temperatures and sunlight exposure, potentially leading to yellowing within 2 to 3 years. Their complex assembly process and low production efficiency require skilled labor, and they are prone to damage during installation and difficult to repair. Moreover, variations in quality due to imperfect technology in some factories can leave a negative impression on customers. Overall, while fiberglass windows have many advantages, it’s important to consider their potential drawbacks and specific application environments when making a selection.

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