Melt spinning

The melt spinning process can be applied to the production of filaments when the polymer on melting will give a viscous liquid without decomposition. So an important requirement of the polymer to be melt spun is that it must have a melting point and should not degrade when softened by heat. Hence a polymer that is degradable at the spinning or extrusion temperature is certainly not suitable for melt spinning.

The process of melt spinning is simple involves feeding and melting of the polymer forming the melt. The melt is extruded through a spinnerette at a constant rate, and pressure of 70-150 Kg/cm2 with application, of lubricant and antistatic agents, to a spinning line of 4-6 mts long. The filaments are solidified by a cooling medium, usually air. After solidification, the filaments are collected on bobbins. In view of the high temperature used, the standard of engineering precision of the extrusion apparatus must be of high order, and must be capable of producing filaments and fibres with high tolerance

Melt spinning process is the preferred one because of the following advantage

(a) The process is simple and economical

(b) Any production rate i.e. lowest to highest can be obtained with minor charge

(c) There is no requirement of solvent or chemical and its recovery.

(d) The properties of the finished product can be controlled by suitable manipulation.

(e) The process is more versatile.

However, melt spinning process, at present, suffers with following disadvantages.

(a) Only limited polymers, not all the polymers can be converted into fibres by melt spinning process. For example cellulose and PVC do not give a stable melt and so these polymers have to form into filaments by solution spinning method.

(b) Structural development is poor because of higher solidification rate.

(c) Because of inadequate structural development, maximum strength cannot be achieved

(d) Higher production at also leads to higher waste Optimum properties.

(e) Accurate temperature control is very critical for uniform and optimum properties.