The gradient-oven saves time and money in R & D as well as QC testing of raw materials (e.g. additives, pigments, resins, and coatings). It allows to simulate the conditions of a production oven in the laboratory by downloading temperature profiles recorded with our temp-gard oven recorder (see pages 257-260). Thus, material properties, baking conditions and production ovens can be optimized for best quality and economical operation. Temperature stability of iron oxide pigments: Depending on the chemical composition the various iron oxide pigment types show different temperature stabilities:

Chemical etch resistance of automotive topcoat systems:
Acid rain, bird droppings, fuel, antifreeze and many other environmental factors can damage automotive finishes. Especially, in summertime some substances can be very aggressive and cause severe damage. Therefore, automotive paint manufacturers as well as auto makers need to find out how different environmental phenomena will interact with a coating system. Throughout the world panels are tested on weathering sites for years to evaluate the influence on color, gloss as well as physical properties. The gradient-oven has been approved by the automotive industry as an accelerated test method. It allows to predict how a particular coating system is reacting to a specific material at increasing temperature levels. This test method is specified by several automotive companies.

Test procedure:
In a standard test 5 different chemicals can be tested on one panel - e.g. H2SO4 which simulates atmosphere and acid rain, NaOH for car wash detergents, pancreatine (bird dropping), brake fluid, and tree resin. The panels are coated and baked under the specified processing conditions. Using a pipette droplets (approx. 0.05 ml) of these various materials are placed about 6 mm apart vertically on the test panel. Repeat this length down the panel with spacing about every 2-3 cm. The gradient-oven is then programmed to have a linear gradient in the range of 35 ° C - 80 ° C. The panels are now baked at either 20, 30 and / or 60 minutes to allow for evaluation of the coating. After the baking process the panel is washed under running water, dried and visually evaluated. The evaluation should be done after approx. one hour and again after 24 hours to see if any additional etching has occurred.
The temperature is documented at which the first visual changes and damages occurred.

Utility:
The gradient-oven helps to speed up R & D projects saving time and money. In QC testing of baked coating systems the gradient-oven produces repeatable results many times faster than using traditional convection ovens.