Vinyl Chloride Polymers

Abstract

PVC has a large sales volume, second only to polyethylene. Its high chlorine content provides it with a high level of combustion resistance for building products, electrical enclosures, and wire and cable insulation. PVC has a unique ability to be compounded with a wide variety of additives, making it possible to produce materials in a range from flexible elastomers (the first thermoplastic elastomers) to rigid compounds, materials that are weatherable such as for siding and windows, compounds that have stiff melts and little elastic recovery for outstanding dimensional control useful in profile extrusion, or low viscosity melts which compete effectively with ABS and PC/ABS in thin‐walled injection molding parts such as computer monitor housings. Some PVC properties are attributed to unique morphology. The polymer precipitates from its monomer and grows into primary particles, which are later the melt flow units. Fusion into larger structures and product strength are controlled by breakdown of the grains into primary particles, by choice of additives, by amount of melting (temperature), and by number of tie molecules (molecular weight). The main type of polymerization is the suspension process, with significant polymerization made by the mass, solution, microsuspension, and emulsion processes. In the suspension process, the polymerization takes place in droplets of monomer suspended in water. From an environmental viewpoint, PVC is over 50% chlorine and as a result, is one of the most energy‐efficient polymers. PVC is an inherent flame retardant, and acts as a marker, enabling automated equipment to sort PVC containers from other plastics in the waste stream. All types of vinyl products can be recycled and processed into second generation products. The analysis from 155 large‐scale, commercial incinerator facilities found no relationship between the chlorine content of waste nor the addition of PVC, and dioxin emissions from combustion processes. New requirements from the U.S. EPA make scrubbers mandatory on all incinerators and are necessary whether or not PVC is present in the waste feed.

Vinyl Chloride Recovery in a Multitubular Adsorber on Maxsorb Carbon

“…Afterward, any residual VCM can be stripped under a nitrogen purge stream in a dedicated resin stripping unit. All vented monomer-rich streams are sent to a monomer recovery unit to be recycled to the polymerization cycle. , …”