About High-activity Desiccant Filler
The High-activity Grade is our desiccant filler for critical polymer systems. It has a higher available CaO content and a finer, tighter particle size than the CaO-based Filler Grade, so it reacts faster and captures more water per kilogram added. It is intended for formulations in which small amounts of moisture lead to rejected batches, short shelf life or visible defects.
The main users are manufacturers of one-component moisture-curing sealants and adhesives based on polyurethane, silane-modified polymer or silicone, and producers of PVC plastisol sealants and coatings. In moisture-curing products, water carried in by calcium carbonate, plasticisers and pigments starts the cure inside the cartridge, sausage or drum. Adding the High-activity Grade during production scavenges this water, which supports package stability, consistent extrusion rate and reliable skin time in the field. In PVC plastisols it helps prevent bubbles and blisters when the film is gelled in the oven.
Because the grade still functions as part of the filler package, formulators can include it within the total filler loading rather than as an extra additive. Obsidian Minerals produces the High-activity Grade in Gujarat and tests available CaO, particle size and residue on every batch in an NABL-accredited laboratory. It is supplied with an SDS, Technical Data Sheet and Certificate of Analysis. Laboratory samples are available for stability and cure trials.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| Available CaO | ≥ 90 % | Internal method (titration) |
| Particle size, D50 | 3–6 µm | Laser diffraction |
| Residue on 45 µm | ≤ 0.5 % | Sieve |
| Loss on ignition (1000 °C) | ≤ 3.0 % | Internal method |
| Surface treatment | Available on request | — |
| Appearance | White fine powder | Visual |
Typical values for guidance. Guaranteed limits are stated on the Technical Data Sheet and batch CoA. Performance in each sealant or plastisol system should be confirmed by the formulator.
Key features & benefits
Higher available CaO
With available CaO typically at or above 90 %, the High-activity Grade binds more water per kilogram, allowing lower additions or greater protection in formulations with a heavy moisture load.
Fine, tight particle size
A D50 of a few microns and very low coarse residue give fast reaction and smooth dispersion, avoiding grit or surface specks in thin sealant beads, coatings and plastisol films.
Supports package stability
By removing water introduced with fillers and plasticisers, the grade helps moisture-curing sealants and adhesives resist skinning and viscosity rise in cartridges, sausages and drums.
Counts towards filler loading
The grade can be included within the total filler content of a sealant or plastisol, giving moisture control without pushing the formulation beyond its target solids or viscosity.
Applications
Moisture-curing PU and hybrid sealants
Used in one-component polyurethane and silane-modified polymer sealants and adhesives for construction and automotive work, scavenging moisture from fillers and plasticisers to protect shelf life.
PVC plastisol sealants and coatings
Added to plastisol seam sealers, underbody coatings and coated fabrics to reduce bubbles, pinholes and blisters caused by moisture released from fillers and plasticisers during oven gelation.
Silicone and specialty adhesives
Applied in neutral-cure silicone and specialty adhesive formulations where traces of water affect cure profile, adhesion or storage stability. Compatibility should be checked with the chosen cure system.
Critical rubber and cable compounds
Suitable for rubber and cable compounds with strict limits on porosity and electrical defects, where a faster, more complete moisture reaction is needed than the standard filler grade provides.
Usage & handling
- Sealants and adhesives: typically 1–5 % of the formulation, added with the fillers under vacuum mixing.
- PVC plastisols: typically 2–5 % of the formulation, dispersed during the paste preparation stage.
- Allow mixing time for reaction before final de-aeration and filling.
- Store sealed and dry; contact with water releases heat, so follow the SDS for handling.
Packaging & supply
- 25 kg HDPE bags with moisture-barrier liners on request
- 1 MT or 1.2 MT jumbo (FIBC) bags
- Custom pack sizes for sealant producers on request
Frequently asked questions
Why use a High-activity Grade in moisture-curing sealants?
In one-component sealants and adhesives, water from fillers, plasticisers and pigments starts the cure inside the pack. The High-activity Grade reacts quickly with this water, which helps prevent skinning, lumps and viscosity rise during storage. Its fine particle size also keeps sealant beads smooth and free of specks.
How much should I add to a PVC plastisol?
Typical additions are about 2–5 % of the plastisol formulation, depending on how much moisture the fillers and plasticisers contain and on the gelation conditions. The aim is to remove enough water to stop bubbles and blisters in the oven. Trials at two or three levels will show the lowest effective dose.
Can the High-activity Grade affect cure speed or adhesion?
Calcium oxide is alkaline and reacts with water, so it can influence cure speed, skin time and adhesion in some systems, particularly those with acid-sensitive catalysts or primers. Formulators should run stability, cure and adhesion tests before production use. A surface-treated version can be discussed if compatibility needs improving.
Is a surface-treated version available?
Yes, surface treatment is available on request. A treated grade can improve wetting and dispersion in non-polar systems and slow reaction with humid air during handling. Please share your polymer system and process so that we can propose a suitable treatment and supply a sample for comparison.