In the manufacturing process of PVC products, certain resins are added to impart special properties (either physical or chemical) to the final products or to improve its processing capabilities. These additives are of many kinds & include stabilizers, fillers, radiopacifying agents, colorants, lubricants, antioxidants, and others. Fillers – Fillers are kind of additives included in the extrusion process to impart special properties to the PVC pipes. For example, Calcined Clay is a filler that is added to the PVC pipes in order to improve their electrical properties. Some common types of fillers used for manufacturing flexible and semi-rigid PVC pipes are wet ground, dry-ground or precipitated calcium carbonate. Charcoal black is also a commonly used filler.
Plasticizers – Such kinds of additives are used to make PVC Pipes more flexible and to increase their elasticity without losing their shape. Such flexible PVC pipes find applications in myriad fields like medical & health care, architecture, cables, etc. Some examples of the common plasticizers are esters from Phthalic Acid, DOP, DIOP, DBP, DOA, DEP, Reoplast, Paraplex, DINP, DIDP.8, DEHP, BBP and DBP.
Stabilizers – Stabilizers are added to PVC pipe manufacturing process to impart heat stability and make the final product resistant to heat, UV and oxygen. Some examples of such stabilizers are lead, barium, cadmium, stearate, etc. Inorganic or organic salts of metals like tin, zinc, etc are also used as stabilizing agents.
Colorants - Colorants are available in the form of dyes or pigments are usually added to the PVC pipes in order to enhance their visual appearance.
Flame Retardants – These are also a common type of additive used in the PVC pipe manufacturing process. As suggested by the name itself, these kinds of additives impart fire retardant properties to the plastic pipes. Though rigid PVC pipes are inherently resistant to fire, other kinds of PVC pipes are not. In such cases, the use of flame retardants is common.
Lubricants – Internal lubricants like calcium stearate promote smooth flow and prevent the polymer chains from slippage within the compound melt. It also enhances the melt strength of the compound while reducing the melt viscosity at the same time. At specific temperatures and usage levels, it also acts as an external lubricant. Another example is a Paraffin wax, which is an external lubricant. It prevents the compound melt from sticking to metal surfaces within the extruder and the extruder die.
These are some of the commonly used additives which are utilized in the PVC pipe manufacturing process.
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