High voltage insulators are disclosed, along with related methods of manufacture and use. The disclosed high voltage insulators include a core strength member joined to one or more end fittings and secured with one or more elastomeric members. A plastic body surrounds the core strength member, the elastomeric member, and at least a portion of the end fitting. In particular, the plastic body is molded over the elastomeric member(s) and, upon cooling, the plastic body exerts a radial compressive force on the underlying elastomeric member(s) to seal the joint of the high voltage insulator and protect it from moisture, even throughout temperature fluctuations in the field.