Polyvinyl chloride

Lore & Background

Polyvinyl chloride is a white, brittle solid at room temperature. It is soluble in ketones, chlorinated solvents, dimethylformamide, tetrahydrofuran, and dimethylacetamide. The polymer is linear and strong, with monomers arranged predominantly head-to-tail, placing chlorine atoms on alternating carbon centers. Its stereochemistry is mainly atactic, meaning the orientation of chloride groups along the chain is random, though some syndiotactic segments introduce a few percent crystallinity that influences material properties. Approximately 57% of PVC’s mass is chlorine, and its density is 1.4 g/cm³, notably higher than related plastics like polyethylene (0.88–0.96 g/cm³) and polymethylmethacrylate (1.18 g/cm³). PVC exists in rigid and flexible forms. Rigid PVC is used in construction for pipes, doors, windows, plastic bottles, packaging, and cards. Flexible PVC, achieved by adding plasticizers, is employed in plumbing, electrical cable insulation, flooring, signage, phonograph records, inflatable products, and rubber substitutes; combined with cotton or linen, it produces canvas. Unmodified PVC requires additives such as heat stabilizers, UV stabilizers, plasticizers, processing aids, impact modifiers, thermal modifiers, fillers, flame retardants, biocides, blowing agents, smoke suppressors, and pigments before fabrication. Among common plastics, PVC uniquely accepts large amounts of plasticizer, with properties ranging from rigid solid to soft gel; nearly 90% of all plasticizer production goes into flexible PVC, which can contain over 85% plasticizer by mass, while unplasticized PVC contains none. The most common plasticizers are phthalates, categorized by molecular weight. Low-molecular-weight phthalates like bis(2-ethylhexyl) phthalate and dibutyl phthalate pose health risks and are being phased out, whereas high-molecular-weight types such as diisononyl phthalate and diisodecyl phthalate are considered safer.

Reader's Guide

Polyvinyl chloride is a white, brittle solid that becomes soluble in several organic solvents including ketones and chlorinated solvents. Its molecular structure is primarily linear with monomers arranged head-to-tail, and the chloride groups are randomly oriented, giving an atactic stereochemistry with some syndiotactic segments that produce a few percent crystallinity. The polymer is denser than polyethylene and polymethylmethacrylate, with about 57% of its mass coming from chlorine, which imparts properties distinct from those of polyethylene. First synthesized in 1872 by Eugen Baumann, who observed a white solid form in a flask of vinyl chloride left for four weeks, early attempts at commercialization by Ivan Ostromislensky and Fritz Klatte were hindered by the material’s rigidity and brittleness. Waldo Semon and B.F. Goodrich overcame this in 1926 by blending PVC with additives, notably dibutyl phthalate by 1933, to plasticize it. Production relies on polymerizing vinyl chloride monomer, with suspension polymerization accounting for roughly 80% of output, yielding particles 100–180 micrometers in diameter, while emulsion polymerization produces much finer particles. The reaction is exothermic and requires cooling, with water added to maintain suspension as volume decreases. Unmodified PVC always requires additives such as heat stabilizers, UV stabilizers, plasticizers, impact modifiers, fillers, flame retardants, and pigments, with the specific blend tailored to end uses like underground pipe, window frames, intravenous tubing, or flooring. Phthalates are the most common plasticizers, with low-molecular-weight types like DEHP and DBP facing health concerns and phase-outs, while high-molecular-weight phthalates such as DINP and DIDP are considered safer. DEHP was used in medical devices for decades, notably stabilizing red blood cells in blood bags, but was permanently banned in U.S. children’s products in 2008. Flexible PVC can contain over 85% plasticizer by mass, while unplasticized PVC contains none. The material’s versatility—from rigid construction pipes and window frames to flexible cable insulation, flooring, and inflatable products—makes it essential in construction, medical, and electrical fields, though its production and additive use remain under regulatory scrutiny.

Did You Know?

• About 57% of PVC's mass is chlorine, giving it a density of 1.4 g/cm³, higher than polyethylene or polymethylmethacrylate.
• Flexible PVC can contain over 85% plasticizer by mass, while unplasticized PVC (UPVC) contains none.