Proper selection of packings will be driven by three factors. First is the chemical nature of the coating/ fluid your spraying, second is the abrasive property of the chemical your spraying, and third is whether the coating will be hot while spraying.
Abrasive Materials Packing Considerations
In general, UHMWPE combined with leather wears slower due to abrasion and is the standard packing set that is in the majority of airless paint sprayers from the factory. If your set comes with UHMWPE and not with leather also it can be worth changing to leather/ UHMWPE as this will improve the life of your packings. The leather cushions and flexes which helps reduce the wear on the UHMWPE packing increasing the overall life of the packing set.
Chemical Coating Considerations
The second factor to consider is the chemical composition of the coating or fluid you will be spraying. Coatings that tend to be more chemically aggressive will often require a PTFE packing as it better resists chemical effects than UHMWPE. Sometimes UHMPWE and PTFE will be combined which will provide resistance against chemical composition as well as abrasive issues. One surefire way to ensure your packing set is well suited for your spray application is to see the chemical compatibility guide that Graco offers here. You can enter the chemical that your coating is composed of and then determine the best type of packing for it from a chemical resistance standpoint.
In addition to the abrasive and chemical composition of the coating, you have to consider whether the material will be sprayed with heat. Material that is heated can include things like finishes that are heated to help keep the need for solvents down along with a variety of other situations. PTFE packings typically are better at resisting heat (heat being defined as 140F or higher). However, they do not do tolerate abrasion well.
By choosing the proper packings for your airless paint sprayer you will achieve longer lasting performance from your packings which will help you keep equipment repair costs down. For additional equipment tips we recommend downloading our complete guide to paint equipment or you can contact us with any questions.