Friability Test

Friability Test

The friability test is carried out in an instrument called a friabilator. A friability testing apparatus should stimulate the conditions that the product will be exposed to during the process of production. This test is a method to determine physical strength of uncoated tablets upon exposure to mechanical shock and attrition.

This instrument consists of a plastic chamber for placing the tablets which is attached to a horizontal axis. The drum has an inside diameter of 287mm and is about 38mm in depth, made of a transparent synthetic polymer with polished internal surface. A set of pre weighed tablets [if one tablet weigh 650mg or less then approx 6.5g of total weight should be taken and for more than 650mg/tablet weight, 10 tablets should be taken] are placed in the plastic chamber revolving at 24-25rpm for 4 min. The tablets are subjected to combined effects of abrasion and shock. The tablets are dropped at a distance of six inches on each revolution.

If the tablet size or shape becomes irregular adjust the drum so that base forms an angle of about 10 degrees with bench top and the tablets fall freely when drum is rotated.

The instrument is operated for 100 revolutions after which the tablets are dusted and reweighed.

Conventional compressed tablets that lose less than 0.5% to 1% of weight are considered acceptable.

Most effervescent tablets and some chewable tablets undergo high friability weight loss which is an indication for the special stack packing that is required for these types of tablets.

In case of hygroscopic tablets a humidity-controlled environment (relative humidity less than 40%) is required for testing.

Tablets prone to capping during the test are considered unfit for commercial use.

Friability is affected by various external and internal factors like:

1) Punches that are in poor condition or worn at their surface edges, resulting in ‘whiskering’ at the tablet edge and show higher than normal friability values.

2) Friability test is influenced by internal factors like the moisture content of tablet granules and finished tablets. Moisture at low and acceptable level acts as a binder