Screen Pack Filtration Test

An alternative approach is to determine the extent of the presence of agglomerates by extrusion filtration. There are two techniques based on extrusion of a fixed quantity of compound or masterbatch through a screen pack. This eliminates the very small scale of examination and human judgement involved in the microscopy tests, which may also view unrepresentative areas. Measurement is by one of two techniques  

1) A microscope count of the number of agglomerates retained on the wire mesh screen pack. 

This can be illustrated by describing comparisons made for four compositions containing low-density polyethylene (LDPE) and carbon black as used at the time for pipes meeting standards for cold water services [8]. These were as follows  

2) A compound of commercial origin rejected by the supplier as unsatisfactory but supplied as a sample for comparison. 

3) A pellet blend of natural LDPE and 5 wt% of a carbon black masterbatch. 

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