Polymers and Viscosity Demystified

What is a Polymer?

A polymer is basically the consequence of organic foundations called monomers linked together in the form of a solvent.Depending on the mix and proportions of crude materials and diverse response conditions, numerous kinds of polymers can be created, as an example, polystyrene, polycarbonate, polyethylene and PMMA. Composition of principle crude materials and added substances also bring about polymers of different grades. SMM (Polymer) is presently producing 6 distinctive PMMA grades: MH, EX, EXN, MG, LG and LG2.

What is Viscosity?

Viscosity is home of a fluid that offers resistance to its flow. Viscosity is because of the internal friction of molecules and mainly is dependent upon the character & temperature of the liquid. 
The polymerisation reaction is conducted within specific conditions and boundaries. The grade of the PMMA polymer thus developed can be evaluated by viscosity, which is asignificant characteristic for many materials, especially polymers. For liquids, viscosity determines flow characteristics, heat transfer and mass transfer. For polymers, viscosity is often a measuring stick. Viscosity data is essential as it helps in predictingbehavioural properties of the polymer. Also, measurement of viscosity is very important in monitoring the SMM (Polymer) process.

Determining Viscosity

How do you determine the viscosity of a great cube of polymer? 
Polymer viscosities can vary from 103 to 107 Poise so one testing method cannot cover them all. So, two common testing methods are used: melt and solution.

Melt Viscosity

The melt index is a common testing technique that studies parameters like compression weight and testing temperature, predominantlyin higher viscosity polymers. Needless to say, the outcome depend on the kind of polymer. For instance, for the melt viscosity test of polyethylene, the study parameters incorporate a temperature of 190˚ C and weight of 10 kg. After having a certain time (say 10 minutes), the extruded polymer is weighed. The melt index is then expressed as grams of polymer/10 minutes and this value corresponds to the average molecular weight of the polymer. Polyethylene comes with an average molecular weight of 150,000 g/mole and a melt index near to 0.3 / 10 minutes. 
For processes or final products where easy processing is necessary, melt indices above 15 g/ 10 minutes are desirable.Where mechanical properties are needed, melt indices below 1 g/10 minutes are preferred.

Solution Viscosity

Solution viscosity testing involves dissolving the polymer in a solvent, usually followed by gentle heat. The clear answer is then allowed to travel through an apparatus like a pipette and the travel is timed. The time for the pure solvent to flow through exactly the same apparatus can be calculated. These two values are then compared, producing a relative viscosity – which is essentially the ratio of the polymer viscosity to the solvent viscosity.

While melt viscositytechnique is carried out by SMM(P) in regular frequency to ensure the polymer formed is well in check, solution viscosity is executed by SCASS during product certification stage as a final confirmation.

Sumitomo Chemical Singapore is one of leading producers of the polymer - PMMA (Polymethyl Methacrylate), a polymer of MMA (Methyl Metacrylate Monomer).Visit us to find out about polymers, PMMA and MMA. 

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