Why Is Calcium Carbonate Powder Added To Flexible PU Foam?

In the manufacturing of flexible PU Foam, the use of inorganic filler to balance cost and performance is a common yet highly controversial practice. Behind this approach lies a complex trade-off between raw material economics and the physical properties of the final product.

From an economic perspective, the introduction of filler directly replaces part of the expensive core raw materials such as polyether polyol. This substitution is not simply a mass-for-mass replacement; it fundamentally alters the stoichiometric ratio of the entire reaction system and triggers a series of chain reactions. More concerning is that certain marketing strategies exploit the density increase caused by filler addition, selling low-grade formulations at higher density classifications to gain excess profits.

The cost advantage comes at the expense of product performance. The incorporation of filler introduces defects into the microcellular structure of the foam, directly affecting breathability and rebound feel. In terms of mechanical properties, all indicators show a downward trend, with tensile strength loss being the most critical. Even at low filler ratios, its role as a stress concentrator significantly reduces foam durability and tear resistance.

The root of these performance declines lies in the physical hindrance effect of filler during chemical reactions. Tiny inorganic particles suspended in the reaction system non-selectively interfere with several key processes, including gas generation, molecular chain extension, and three-dimensional network formation. The extent of this interference is not uniform; it highly depends on the physical characteristics of the filler, among which particle size distribution (fineness) is the most critical variable. The smaller the particle size, the larger the specific surface area, and the stronger the obstruction effect on the reaction system. This not only delays reaction speed but also intensifies the disruption of the final network structure. To mitigate these negative effects, advanced manufacturing processes adopt high-shear pre-dispersion technology, fully homogenizing the filler in the polyol to form a stable slurry. This minimizes localized reaction hindrance caused by filler agglomeration and prevents severe defects such as localized foam collapse.

Despite its drawbacks, filler technology still plays a role in meeting specific market testing standards (such as thermogravimetric analysis) and fine-tuning product density. Looking back at industry history, mainstream formulations in the 1990s generally avoided the use of such filler. Today, the market landscape has been reshaped: filler-based formulations dominate, while pure foams without filler have become a special choice for high-end niche markets. This cycle seems like a microcosm of industry development, constantly swinging on the eternal balance between cost and quality.

We cannot help but ask: Is this cost-performance trade-off, at the expense of certain properties, the ultimate state of the industry? Do you believe a revolutionary technology or material will emerge in the future to truly break the shackles between cost and performance?