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Woven Polypropylene (WPP) Glossary

a guide to WPP

Woven Polypropylene Sacks Glossary


Polypropylene (PP) – A type of polymer used in producing mono-filament and multi-filament yarns and threads. It is recyclable and is used as our standard fabric for Woven Polypropylene bags.

Yarn / Tape – Extruded PP sheet, slit and stretched in annealing ovens to form part of the woven fabric for the bag.

Warp – Yarn or tape in a fabric, oriented perpendicular to the Weft yarn during weaving. This would go from top to bottom in the body fabric.

Weft – Yarn or tape in a fabric, orientated perpendicular to the Warp yarn during weaving. This would go from left to right in the body fabric.

Woven – Combined with many polypropylene yarns or tapes in two directions (warp and weft) to form fabric.

Denier – The weight of yarn in grams per 9,000 meters. 
Fabric Mesh – The measure of the density of the fabric weave, measured as the number of yarns per inch in both the Warp and Weft directions. Like 10x10 mesh.

Fabric Weight – The measure of the fabric weight in ounces per square yard or grams per 100 square centimetres.

Stitches per Inch – A sewing specification requiring “X” number of stitches per inch. Like 4 stitches per inch.

Seam – A sew line made by the attachment / assembly of two or more components.

Top Hemmed / Hemming – A fold and sew operation which prevents fraying of cut fabric. This also provides a clean finish to the woven polypropylene bag. It may be either towards the inside or outside of the bag.

Body Fabric – The tubular portion of a seamless or circular woven bag.

Breathable Fabric / Bags – Uncoated or non-laminated fabric / bags.

Circular Woven Bag – Also called a tubular bag, it is made from fabric woven on a circular loom, which is then cut to the proper length for a specified bag height, thereby eliminating the seams on each of the bag’s sides.

Coated Fabric / Bags – Fabric lining coated / laminated with Polypropylene (PP) to prevent moisture intrusion or sifting of the inside contents of sack. Also called Non-breathable Woven or Laminated Woven Sacks/ Liner fabric.

Bag Size – width and length. Length dimension of the woven polypropylene bag measured from the Top Seam to the Bottom Seam. Sizes can vary of typical tolerance of + / - 3%

UV Stabilized – A feature of an unit of woven polypropylene bag that provides protection from prolonged exposure to the sun’s degrading Ultra Violet rays. A pigment is added to the resin prior to extrusion process of the yarns to provides UV stabilization to sacks.


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