The start and end of plaster stiffening can be precisely controlled by additives. Retarders and dihydrate-based accelerators in particular have a much greater influence on nucleation than substances that affect solubility. It is common practice to use stucco plaster in combination with highly effective accelerators, especially finely ground plaster. Gypsum crystal growth begins immediately after contact with water. Modern plasterboard plants require a curing time of less than 10 minutes, which requires high quantities of accelerator, often around 0.5 %. However, this is often not enough to achieve the processing time of just a few seconds until stiffening begins. Premature hardening can lead to problems such as poor fluidity, caking and clumping, which disrupts the manufacturing process and reduces the quality of the panels.

COMBINATION OF RETARDER AND ACCELERATOR FOR IDEAL BINDING CURVE

Because of that, a combination of retarder and accelerator is used in the production of plasterboard to create an ideal setting curve characterised by a slight extension of the dormant phase and then rapid setting. The so-called "snap set" avoids problems in the mixer and ensures a high degree of hydration (95 - 98%) before the boards are cut and dried. In addition, the strength of the board core is improved, which is particularly desirable in the production of lightweight boards. The use of Retardan® enables the targeted incorporation of foam into the liquid gypsum mass, keeps the mixer clean and improves the wet bonding of the board layers. Retardan® products are valued for their well-defined retardation.

ADVANTAGES OF RETARDAN®

  • Postponement of the start of hydration without loss of intensity
  • No inhibition of crystal growth (in contrast to fruit acids)
  • Rapid strength development and higher final strength
  • Unchanging quality and worldwide availability
  • Defined production with synthetic raw materials under controlled conditions

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