Question

The temperature of the air in melt blown process is set close to ________ of the polymer.

• A. Glass transition temperature
• B. Melting temperature
• C. Crystallisation temperature
• D. Cryogenic temperature

Hint:

In melt blowing, the hot air temperature is set close to (and often slightly above) the melting temperature (Tm) of the polymer to keep it molten and allow for fiber attenuation.

Answer 1

The Correct Option is B

Step 1: Understanding the Melt Blown Process: The melt blown process is a nonwoven manufacturing technique where a thermoplastic polymer is melted and extruded through a die with numerous small nozzles. High-velocity hot air is blown on either side of the extruded polymer streams, attenuating them into very fine fibers (microfibers). These fibers are then collected on a conveyor belt to form a nonwoven web. 

Step 2: Importance of Air Temperature: The temperature of the hot air is critical for several reasons: 
 Maintaining Polymer Melt State: It must keep the extruded polymer in a molten state long enough for it to be drawn into fine fibers. 
 Preventing Premature Solidification: It prevents the polymer from solidifying too quickly, which would result in coarse fibers or shot (small, solidified polymer droplets). 
 Facilitating Fiber Attenuation: The hot air provides the drag force to attenuate the fibers to their final diameter. 

Step 3: Temperature Setting: Because the polymer needs to be molten, but not degraded, the air is supplied at a temperature close to the melting temperature (Tm) of the polymer, it will typically be a little higher than the Tm. The other options are incorrect: 
 Glass Transition Temperature (Tg): Tg is too low; the polymer would be in a rubbery or semi-solid state, not molten. 
 Crystallization Temperature (Tc): Tc is lower than Tm. 
 Cryogenic Temperature: Cryogenic temperatures are extremely low temperatures and are completely irrelevant to melt blowing.