40.4 .Technical Questions

Q. 1. What is the Spherilene process ? Explain how spherilines are developed ?

Ans: The Spherilene process is a new, gas – phase Polyethylene ‘swing' technology. It is based on a well – established technology, known as the Reactor Granule Technology (RGT), which is basically a refinement of gas – phase and bulk – polymerization reactors.

In the Spherilene process, Zeigler spherical – form – supported catalyst particles act as microreactors. In the first and second gas – phase reactors, the polymerizing particles grows on itself in a gradual manner. However, during the whole growing process , the particles retain their original spherical form, and allows for perfect control of the final morphology of the polymer.

 

Q.2. What are General – purpose Polystyrene (GPPS) and High – impact Polystyrene (HIPS) ? How are they different ?

Ans: GPPS is also known as crystal polystyrene. It has good clarity and fairly good mechanical properties. Although GPPS can be processed into most types of objects, it is relatively brittle. It is used in applications where light transmission properties are important.

On the other hand, HIPS contains an elastomer like polybutadiene rubber, which improves its mechanical properties. It has appreciable impact strength and hence, is milky or opaque in appearance. HIPS is tougher than GPPS, and also has good processing properties.

 

Q.3. In high pressure technology, which one is more advantageous – Centrifugal Compressors or Reciprocating Compressors? Why?

Ans: In high pressure technologies, centrifugal compressors are more advantageous than reciprocating compressors. This is because centrifugal compressors have low investment and maintenance costs, and ensures more reliability than the formerly used reciprocating compressors. Moreover, they require less space and provide high efficiencies even at high flow rates.

 

Q. 4. What are the problems that may be encountered when the reactor walls are contaminated with polymer materials? How can this problem be mitigated ?

Ans: If the polymer material builds up on the reactor walls, then it can lower the rate of heat transfer considerably. Moreover, it can also have detrimental effects on the quality of the product. This problem is very much encountered in the Poly vinyl chloride manufacture process.

The reactor walls can be kept free of the polymer material by using certain build – up suppressing agents or anti – fouling agents. In addition, cleaning of the reactors with high pressure water after a certain number of batches ensures the reactor walls free from polymer materials.

Q. 5. In conventional drying processes, why is the method of selective drying so important ?

Ans: Selective drying is important in most drying processes, because , it ensures the prevention of thermal degradation of the material being processed. Moreover, the overdrying of the drying goods is avoided using this method.