Polyvinyl chloride, or PVC, is the technical name for vinyl, a polymer developed in the 1920s. Unplasticized-polyvinyl chloride, or uPVC, is the same product as PVC except, as the name implies, it is made without the use of any plasticizers during the manufacturing process.
PVC resin must first be combined with additives and modifiers in order to the create the vinyl compound used in the manufacturing of various vinyl products. Due to its rigidity, this compound can be difficult to move through the presses which cut and shape it. Additives known as plasticizers are mixed in with the compound to improve the flexibility of the PVC and help it move through the presses. Concerns have still risen over the safety of plasticizers due to the presence of phthalates and BPA found in the additive, despite no confirmed reports of adverse health effects from exposure and the manufacturing process being regulated by a number of agencies including the EPA and FDA. In response to these concerns, the makers of vinyl now offer uPVC as an alternative. Because it does not use plasticizers, uPVC is not as flexible as regular PVC, which makes it not uncommon to hear uPVC referred to as rigid PVC.