Final answer:
Polyvinyl chloride (PVC) has plasticizer added to it to provide flexibility, making it suitable for various applications where softness and pliability are needed.
Step-by-step explanation:
Polyvinyl chloride commonly has plasticizer added to it to provide flexibility. Plasticizers work by taking up space between the polymer chains and acting as lubricants, allowing the chains to slip over each other more easily. This reduction of viscosity or increase in plasticity makes the material softer and more flexible, which is essential for many of its applications, such as in electrical cable insulation, shower curtains, and upholstery. Without plasticizers, PVC would maintain its native rigidity, as exhibited in applications like rigid piping and vinyl records.