Have you ever wondered why some plastic products outperform others in strength, durability, and cost-effectiveness? The secret often lies not in the base polymer itself, but in the sophisticated world of plastic modification through functional fillers. These mineral powders, when properly selected and incorporated, can dramatically enhance material properties while reducing production costs.
In this first part of our series, we will uncover how ordinary-looking powders transform plastics into high-performance materials. From the widely used calcium carbonate to specialized talc and wollastonite, each filler brings unique advantages to polymer composites. Join us as we explore the science behind these “filler all-stars” and discover how they contribute to creating better, smarter plastic products.
Carbonato de calcio
Calcium carbonate (CaCO₃) is currently the most widely used powdered inorganic filler. It is inexpensive, abundantly available, non-toxic, odorless, offers a whiteness level of up to 96%, can be easily colored, and possesses good chemical stability. It is also easy to dry, making it widely applicable in many plastics. From the perspective of fillers, calcium carbonate can be divided into three categories: heavy calcium carbonate, light calcium carbonate, and activated calcium carbonate.
Carbonato de calcio pesado
Heavy calcium carbonate, abbreviated as heavy calcium, is produced by mechanically crushing, screening, grading, and surface-treating materials such as limestone. Based on the crushing method, it is further classified into dry-process heavy calcium carbonate (commercially known as double-flight powder) and wet-process heavy calcium carbonate. As it is mechanically crushed, the particles are irregular in shape and vary in size, with an average particle diameter of 1–10μm. Among these, 50% are below 3μm. The density ranges from 2.7 to 2.9 g/cm³, and it is almost insoluble in water. In recent years, advancements in crushing (such as jet milling) and grading technologies have enabled the production of even finer products, including ultra-fine heavy calcium carbonate with particles as small as 0.1μm. Heavy calcium carbonate is commonly used in PVC to reduce costs and improve dimensional stability. When used in combination with clay, it enhances elasticity and heat resistance.
Carbonato de calcio ligero
Light calcium carbonate, abbreviated as light calcium, is chemically produced calcium carbonate, also known as precipitated calcium carbonate. Its particles are mostly spindle-shaped, needle-shaped, or columnar, with a diameter of 1–10 μm. Among these, 80% are below 3 μm, and the density is 2.65 g/cm³. Light calcium carbonate is often used in polyolefins, serving the same purpose as heavy calcium carbonate. It offers better reinforcement effects and improved acid resistance.
Activated Calcium Carbonate
Activated calcium carbonate, also known as colloidal calcium carbonate or modified calcium carbonate, is referred to as “Hakuenka” in Japan. It is produced by modifying the surface of light or heavy calcium carbonate powder with a surface treatment agent (such as stearic acid, with a mass fraction of about 3%). It appears as a white, fine, soft powder with a density of 1.99–2.01 g/cm³. Plastic products filled with activated calcium carbonate exhibit certain strength, a smooth surface, good lubricity, and ease of processing.
Calcium carbonate is graded by particle size as follows:
• Particle size of 1–5 μm: fine-particle calcium carbonate
• Particle size of 0.1–1 μm: micro-fine calcium carbonate
• Particle size of 0.02–0.1 μm: ultra-fine calcium carbonate
• Particle size below 0.02 μm: super-micro calcium carbonate
Currently, the production of ultra-fine calcium carbonate mostly employs continuous spray carbonization and spray drying processes (known as the double-spray process). This method refines the apparent agglomerates of calcium carbonate and ensures uniform surface activation. When the particle size ranges from 0.005 to 0.02 μm, its reinforcing effect is comparable to that of silica.
Polvo de talco
Talc powder (3MgO·4SiO₂·H₂O) primarily consists of hydrated magnesium silicate, obtained by crushing and refining natural talc. It is a typical flaky filler with inert chemical properties and a smooth texture. Its density ranges from 2.7 to 2.8 g/cm³. Talc powder is the second most widely used filler after calcium carbonate. As a plastic filler, it enhances product hardness, flame retardancy, acid and alkali resistance, electrical insulation, dimensional stability, and creep resistance. It also provides lubricity, reducing wear on machinery and molds. However, excessive use may affect the weldability of products.
Due to its flaky structure, talc powder imparts high rigidity and low anisotropy to plastic products, making it suitable for large and flat products. Talc powder is primarily used as a crystallization nucleating agent for PP, refining the spherulites of PP, increasing crystallinity, and enhancing rigidity. It can also be used in PVC, PE, PA, PC, and other resins, with a typical addition rate of 10%–40%. The processing conditions and equipment for talc-filled plastics are similar to those for calcium carbonate-filled plastics. Both can be processed by extrusion, compression molding, injection molding, and calendering to produce various types of plastic products. Talc powder is non-toxic and can be used in products that come into contact with alimento.
Wollastonite
Wollastonite (CaSiO₃) is the third most widely used filler after calcium carbonate and talc powder. Natural wollastonite has a β-type calcium silicate chemical structure and is a mixture of acicular, rod-like, and granular particles, with acicular particles being the dominant form. Wollastonite appears as a white crystal, free of crystalline water, with low hygroscopicity, non-toxicity, low thermal expansion coefficient, high thermal stability, resistance to chemical corrosion and weathering, and excellent mechanical and electrical properties.
Wollastonite has a refractive index of 1.62, which is close to that of PVC compounds, making it the preferred filler for transparent PVC products. Due to its acicular structure, wollastonite provides certain reinforcing effects to plastics and can partially replace expensive glass fibers. It can be used in PVC, PP, PE, PA, polyesters, epoxy resins, phenolic resins, and other resins, with an addition rate generally below 40%. Surface treatment with silane coupling agents is commonly applied.
From the versatile calcium carbonate to the reinforcing talc and wollastonite, we’ve seen how these mineral ‘powders’ are the unsung heroes behind stronger and more cost-effective plastics. But the filler lineup doesn’t end here!
To be continued in Part 2…
Acerca de Epic Powder
En Polvo épico, we specialize in developing and supplying high-performance fillers tailored to enhance the properties of your plastic products. Our advanced materials, including the fillers discussed above, are engineered to meet the highest standards of quality and efficiency. Whether you are looking to improve strength, reduce costs, or achieve specific functional characteristics, Epic Powder offers innovative solutions to help you excel in a competitive market. Partner with us to unlock the full potential of your materials.
