Evaluating resins for yellowing resistance and outdoor weathering
Distinguishing between initial colours, yellow transformations, loss of light, powdering and coating ageing, illustrates the common effects of resin, hardener, paint and stabilization systems on outdoor performance.
Let's start with a few concepts.
The initial colour description material begins to look, yellow changes focus on colour changes over time, and tolerance also includes loss of light, powdering, cracking, attached decline and mechanical decay. Transparency paints, white topcoat and dark-colour systems vary in the degree to which changes are visible, and evaluation indicators should correspond to actual uses.
The so-called "0 class Yellowing response" must indicate the test method, time, light source, film thickness and method of determination. The slogan of graduation cannot replace technical data.
Resin and Hardener
Polyaspartic resin provides an important foundation for the system, but the structure is equally critical. If the aromatic community isocyanate or uses inappropriate components, the outdoor colour may change rapidly even if resin is of low colour.
Material purity, residues, storage oxidation and high temperature processing may also affect colour. A combination of colour differential control of raw materials to finished products should be established in light products.
Painting and stabilization aids
Inorganic pigments, some high-performance organic pigments and reasonable UV absorbents, retardant stabilizers can increase color protection, but there may be problems of competition, migration or compatibility between the aids. The addition is not as high as possible.
Research and development should focus on the storage position, dissolved state and long-term stability of the stabilizers in the resin and hardener groups and be confirmed through a full formulation ageing test.
How to design a weathering test
The accelerated aging of irradiated lamps or QUVs is suitable for the selection of formulations and relative comparisons, and the tests record irradiation, spray, condensation, blackboard temperature and circulation systems. The result cannot simply be a direct conversion of the outdoor years in hours.
Key projects should combine natural exposure, physical contamination clean-up and repainting tests, with continuous observation of colour differentials, glitter maintenance, powdering, cracking and attachment.
Construction also affects appearance life.
Inadequate membranes, uneven mixing, needle holes, substrate pollution and premature water intake reduce the duration of outdoors. Colour batches, scrolling directions and construction successions also affect initial perceptions.
The waiting scheme should specify the material, hierarchy, film thickness, construction window and maintenance cycle at the same time, rather than specifying only one resin.