A relatively small subdivision of matter ranging in diameter from a few angstroms (as with gas molecules) to a few millimeters (as with large raindrops). A particle can have various shapes and dimensions.


Ability of a membrane or other material to permit substances to pass through it.

pH value

Used to describe the hydrogen ion concentration of a solution. A pH of 7 is neutral.
Below 7, acidity increases – above 7 alkalinity increases.
The pH value is a non-dimensional figure. It is the negative logarithm of the hydrogen ion activity.

Plain Reverse Dutch weave (PRD)

It has a high thread count in the warp direction and a low thread count in the weft direction.

Plain weave (PLN)

Most basic weave – over and under pattern.

Pneumatic stretching system

Pneumatic stretching systems are consisting of individual clamps and a central control unit. Depending on the system, they are operated with air pressure and one or two air control circuits. The number of clamps is depending on the frame size.

Pore size

Filters are rated according to the size of particles they can remove. Particles that are bigger than the indicated pore size are removed. Smaller particles pass through the fabric. The size of particles is measured in micro-meters or 'microns', one micron being equal to one-millionth of a meter, the typical size of coal dust or flour. The smallest bacteria are about 0.5 µm.


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