Substrate priming is first step of any industrial flooring system. Below are some important points regarding purpose, technologies and techniques of substrate priming.
I. Purpose of substrate priming for industrial flooring
1. Sealing of the substrate
- Prevention of air from the substrate appearing as pores on body-coat
- Dust binding
- Pore sealing – when different degrees present
- Reduction of consumption of body coat
- Cost reduction of overall system
- Improvement of bond strength of successive layers
2. Consolidation of the substrate
3. Provide better cohesion – poor or inadequate
II. Available technologies
1.Water (for water tolerant top-coats)
2.Single component acrylic resins
3.Epoxy resins 100% solids or water based (with or without broadcast)
- Mortar slurries (+ latex or acrylic polymers)
- Epoxy resins + fine aggregates or thickeners
- PU modified screeds
III. Important time concepts
- Shelf life – Time to store the material
- Pot life or Application time: Time to place the mixed material
- Walk-on time: Time to step without (much) damage
- Open time:Time to place the next layer
- Service time: Time when material has sufficient performance properties to start service.
IV. Effect of primer age on performance
Open time is the optimum “time window” for next layer placing. It will affect type of break when tested, and if surpassed, the opposite effect can achieved. Results will vary with type of product, ambient and substrate conditions, etc.
V. Why broadcasting?
Depending on the body coat technology, broadcasting may be inadequate, convenient, necessary or imperative. For some systems it is a must! Broadcast aggregate provides a “key effect” to increase bond and shear strength resistance, reducing the chances of debonding and shrinkage cracks.Amount of aggregate also has influence: light broadcast (< 1 kg/m2), full broadcast (1 – 2 kg/m2), broadcast in excess (> 2 kg/m2). Warning: Aggregates tend to entrap air, so care must be taken to select adequate aggregate size.
As a rule of thumb:
- The finer the aggregate, the better the grip / bond strength à greater specific surface
- The coarser the aggregate the more air is entrapped.
- Insufficient primer consumption is detrimental for good results.
- (Whether due to excessively absorbent substrates or lack of coverage)
VI. Primer dilution
- Not applicable to every flooring technology.
- Can be used on some acrylic dispersions or some water based epoxy primers
- Helps improve penetration on dense substrates
- Reduces cost of first primer coat on excessively porous primers
In conclusion, substrate priming is a integral part of a flooring system. “Savings” in the priming process will be reflected in the body coat and top coat of the floor. Proper priming can make the difference between a successful or a failed flooring application.