BENEFITS OF
ACRYLIC PAINT
TECHNOLOGY


THE ADHESION OF ACRYLIC GLOSS PAINTS


Number
in a series of technical bulletins issued by the Paint Quality Institute, the leading source of quality paint information worldwide.


© 2000 Paint Quality Institute,
All rights reserved.
The technology that is incorporated into acrylic gloss paints is based on over 40 years history of research and development by the world's major polymer manufacturers. Landmarks in this development include the introduction in 1953 of the first 100% acrylic emulsion developed specifically for house paints, and in 1961, of the first acrylic emulsion with exceptional adhesion, wet and dry, to wood. In 1964 the Rohm and Haas introduced the first emulsion with good flow and rheology, making possible in the 1970's a range of semi-gloss emulsions, leading to the final objective of emulsions with full gloss potential in the 1980's.

Acrylic gloss paints based on quality acrylic polymers have excellent adhesion to all commonly encountered surfaces. This is made possible by the chemical inertness of the acrylic backbone, combined with unique adhesion technology incorporated into the polymer. Specifically, this adhesion technology was designed to give improved adhesion in wet and dry conditions to wood and to repainted old solvent based finishes.

The adhesion of acrylic gloss paints to the most commonly encountered surfaces is discussed and illustrated in more detail below. In addition to these surfaces, acrylic gloss paints will also adhere well to all masonry surfaces, PVC, and aluminium, which makes them suitable for most types of exterior construction surfaces.
fig. 1

RE-PAINT SURFACES
.
Adhesion is measured by applying acrylic gloss paint to the previously painted surface. In an area of 25mm x 25mm square, a grid of 100 squares is cut into the test film using a sharp blade. To test wet adhesion, the grids are soaked under a pad of wet cheese-cloth for 3O minutes. The surface is blotted dry before pressing a piece of transparent tape onto the grid. The tape is peeled slowly from the substrate, and the degree of failure is recorded in percent. Visual examples appear in figure 1.
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The procedure for dry adhesion is similar, except that the test paints are not wetted before the tape test.

In fig. 1, the paint on the right is showing very good adhesion, with no removal of test paint; the test paint on the left is showing failure both in wet and dry conditions. This demonstrates the need for acrylic gloss paints to be formulated with emulsions containing this specific adhesion technology.

ALKALINE SURFACES
.
fig. 2
(Fresh Masonry, Fibre Cement, Plaster)

Acrylic gloss paints are alkali resistant, and may be applied directly to all alkaline surfaces such as fresh masonry, stucco, fibrous cement and plaster. The photograph (fig. 2) shows a fibrous cement panel, with acrylic gloss paint on the left showing excellent performance, while the solvent based alkyd gloss paint on the right is attacked by the alkali, leading to blistering and loss of adhesion.



GALVANISED STEEL
.
fig. 3
In this test (fig. 3), galvanised steel down-spouts were coated with alkyd paint (left) and 3 acrylic paints (right). The acrylic paints have maintained their integrity after 11 years exposure whilst the conventional alkyd point has peeled and flaked badly. The alkyd paints typically fail, because the acid component of alkyd oils reacts with the zinc from the galvanised surface.

WOOD
.
fig. 4
The photograph (fig. 4) shows wood panels which have been exposed for 2 years. The paint on the right hand side was based on a polymer without adhesion technology, whilst that on the left hand side contained the adhesion technology. The flexible nature of the acrylic paint also contributes to its excellent performance over wood. This again highlights the need to specify quality acrylic paints.
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"Sandcastles" Residential Units - Noosa, Queensland. The exterior masonry was refurbished with acrylic paint to give long lasting protection from sun and sea salt whilst retaining bright colours.
North Sydney Fire Station



 Hawthorn Town Hall
Historic Restoration with Acrylic Paint. Two fine examples of restoration of historic buildings over 100 years old. The Hawthorn Town Hall celebrated its Centenary year in 1989.
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For further details about the contents of this bulletin, and other bulletins in this series,
please contact the Paint Quality Institute, care of Rohm and Haas Company in Australia or New Zealand.
Paint Quality Institute, PO Box 115, Camberwell, Vic. 3124. Australia. Phone 1800 338 015.
Paint Quality Institute, PO Box 22-220, Otahuhu, Auckland 6, New Zealand. Phone (09)276 4866.
By email at Ask PQI