Oh boy - you asked for it....
Resin is a fluid so it has fluidics characteristics that come into play.
Resin directly in contact with the PVC will have zero velocity relative to the pipe wall due to friction and intermolecular forces creating a no-slip condition (which means the fluid "sticks" to the pipe wall).
Because of the viscosity there is an internal friction between layers of fluid in the pouring resin. The layers nearest the pipe wall move slowest while the center of the resin mass moves fastest.
The adhesive forces between the resin molecules and the PVC pipe molecules cause the resin to cling to the surface. There are also cohesive forces that cause an attraction between the resin molecules themselves that hold the fluid resin together as a cohesive mass with the surface molecules pulled inward, reducing the surface area -- aka Surface Tension.
Then there is the Coanda effect which is the tendency of a moving fluid to follow a nearby surface. And if the surface is curved the fluid will follow the curve because of pressure differences generated by the fluid's motion and the curved surface.
So, the physics of fluids, fluidics, is likely the cause more so than any static charge. Fluidics is also why the thin rod (skewer) suggested by Steve (SteveG) would help as it (the rod) becomes the curved surface the resin interacts with rather than the wall of the PVC pipe.
Dave
PS I learned this fluidics stuff back in the late 1970's when studying electronics as some machine controls are more suited to low pressure (like 3 PSI) fluidics as fluidic controls are immune to electromagnetic interference and vibration which makes the ideal for applications like nuclear reactors and some aerospace applications. Also they eliminate electrical hazards which are more suitable for use in ultra clean or highly volatile (exposive) environments -- no sparks - no Boom! Fluidic systems are put together much like electronic circuits and there are functional equivalent components for switches, indicators, and even logic gates.
