Statistical modeling of the dip-spin coating process to describe colloidal PTFE dispersion coating on the external surface of a small diameter hollow tube was developed by using 2 4 factorial design with a center point to predict the coating thickness in a range of 4-10 m. The coating parameters included viscosity, withdrawal rate, spin speed, and immersion time. The adequacy of the predicted model was verified by coefficients of determination and lack-of-fit test. Model accuracy was verified by comparing predicted values with experimental results. The significant interaction effects on the coating thickness were three-way interaction among withdrawal rate, spin speed, and immersion time and two-way interactions between viscosity and withdrawal rate, viscosity and spin speed, and viscosity and immersion time. Cube plot for coating thickness reveals a trend of increasing coating thickness towards high levels of viscosity, withdrawal rate, and immersion time and lower level of spin speed.

Abstract. To develop new polymer blends having reduced friction force of fluorinated ethylene propylene (FEP) dispersion and improved adhesion of polydimethylsiloxane (PDMS) fluid, FEP dispersion was blended with PDMS fluids at different viscosities of 20 cSt and 100 cSt by using solution mixing method. The FEP/PDMS blends were coated on short hollow tubes and examined by penetrating the tubes into the rubber stoppers. It was found that the tubes coated with the blends showed reduced penetration and friction forces and improved adhesion. The tubes coated with the 100 cSt-PDMS blend in the ratio of 5:1.5 demonstrated the penetration and average friction forces as low as 3828 mN and 1524 mN, respectively. The formation of physical blends was characterized and confirmed by FTIR and DSC analyses. IntroductionFluorinated ethylene propylene (FEP) dispersion are commonly used as non-stick coating in many applications that require friction-reducing property, electrical insulation, biosafety, chemical resistance, and wear resistance [1]. An appropriate choice of the second polymer with specific properties can be blended for a variety of physical and chemical properties. Properties of the blend will depend largely on the degree of compatibility, miscibility of the polymers at the molecular level, and the characteristics of components and compositions [2]. Polydimethylsiloxane (PDMS) fluid is a hydrophobic material used for self-cleaning and lubricant coating in many applications [3]. PDMS fluid readily dissolves in solvent-born paints and, as a result, reduces the surface tension of the coating materials. PDMS fluid is, however, non-curable and able to be removed from the substrate [4]. Commonly, PDMS fluid is blended with organic coating materials such as alkyd, epoxy, and phenolic resins for reduced coefficient of friction of coating materials and improved adhesion and hardness, drying properties and durability of some exterior maintenance coating [5].To combine the advantages of FEP dispersion and PDMS fluid, the aim of this study was to develop a polymer blend that could reduce friction force of FEP dispersion and improve adhesion of PDMS fluid. Blending of FEP dispersion and two different viscosities of PDMS fluids using a solution mixing technique was investigated. Miscibility of the FEP/PDMS blends was characterized and analyzed using Fourier transform infrared spectroscopy and differential scanning calorimetry.