In the fields of building energy efficiency and industrial insulation, vermiculite insulation boards have gradually become a popular choice in the market due to their outstanding thermal insulation properties, fire-resistant characteristics, and environmental advantages. Their production process involves a series of complex and critical technologies, including raw material processing, binder selection, forming and pressing, as well as drying and curing. These technologies directly determine the products thermal insulation, heat resistance, strength, fire rating, and environmental performance. Below, we provide a brief analysis of the key technologies in vermiculite board production.
Pre-treatment Technology for Vermiculite Raw Materials
The primary raw material for vermiculite boards is expanded vermiculite. The quality of vermiculite directly impacts the performance of the insulation boards. High-quality vermiculite should exhibit excellent expandability and low impurity content. Mined vermiculite contains significant impurities such as soil and mica fragments, which must first be removed through screening and washing. Screening uses sieves with varying mesh sizes to separate large particles, while washing employs water flow to remove fine soil and soluble impurities.
The subsequent expansion process is critical. Pre-treated vermiculite is rapidly heated to 800–1000°C, causing its moisture to vaporize abruptly. This triggers rapid expansion along cleavage planes, increasing volume by 8–20 times. The expanded vermiculite forms a loose, porous structure that significantly enhances thermal insulation properties. Heating methods vary, with gas and electric heating being common. Precise control of heating temperature and duration is essential to ensure uniform and stable expansion results.
Selection and Application Technology of Binders
The selection of binders for vermiculite boards is critical to effectively bonding expanded vermiculite particles into a plate-like structure. An ideal binder must possess strong adhesive strength to ensure secure particle bonding, providing the insulation board with sufficient mechanical strength to resist damage during handling and installation. It must also exhibit excellent high-temperature resistance, matching the elevated operating conditions of vermiculite insulation boards without decomposing or degrading its bonding properties. Additionally, it should be environmentally friendly, avoiding the release of harmful substances during use.
Currently, common binders include inorganic and organic types. Inorganic binders like cement and water glass offer advantages such as high-temperature resistance, non-combustibility, and low cost, but may increase the weight of the insulation board, potentially affecting its thermal performance. Organic binders such as phenolic resin and polyurethane provide high bonding strength and lightweight properties, enhancing the flexibility of the insulation board, but exhibit relatively weaker high-temperature resistance. In actual production, inorganic and organic binders are often blended to leverage their respective strengths and achieve optimal performance. Precise control over binder dosage and mixing uniformity is also critical: insufficient binder leads to poor bonding, while excessive amounts compromise insulation performance and increase costs.
Forming and Pressing Technology
The primary forming methods for vermiculite insulation boards are mold pressing and extrusion. Mold pressing involves placing the mixed vermiculite and binder material into a specific mold, where it is shaped under controlled pressure and temperature. Pressure is typically maintained between 5–15 MPa, while temperature ranges from 100–250°C depending on the binder type. Precise control of pressure and temperature ensures uniform density, accurate dimensions, and excellent mechanical strength and thermal insulation properties in the finished boards.
Extrusion molding employs screw extruders to continuously form materials into specific insulation board shapes. This method offers high production efficiency, making it suitable for large-scale manufacturing. However, it demands sophisticated equipment and requires precise control of material flow rate, pressure, and temperature during extrusion to ensure consistent board quality.
Drying and Curing Technology
Formed vermiculite insulation boards contain significant moisture and require drying treatment. Drying not only removes moisture but also enhances binder curing, improving board strength. Drying temperatures are typically controlled between 100–150°C, with durations ranging from 2–8 hours depending on board thickness and moisture content. Excessively high temperatures may cause cracking or performance degradation, while insufficient heat leads to incomplete drying and compromised quality.
Post-drying curing is essential to stabilize the boards performance. Curing conditions significantly impact board properties, typically requiring 3–7 days at 20–30°C and 40–60% relative humidity. This facilitates complete binder curing, improving durability and stability.
Each critical technology in vermiculite insulation board production is interconnected. Issues in any stage may compromise the final quality and performance of the boards. Only through continuous optimization and innovation of these technologies can vermiculite insulation boards with outstanding performance that meet market demands be produced. This will drive the development of the insulation materials industry and make greater contributions to building energy efficiency and industrial insulation applications. Future advancements in vermiculite insulation boards are anticipated in achieving breakthroughs such as ultra-low thermal conductivity (≤0.08 W/m·K) and high strength with lightweight properties (density ≤250 kg/m³), further solidifying their core position in the green building insulation sector.
