A textile calendar is a machine, not something you hang on the wall that tells you the date for Thanksgiving. A calendar consists of one or more sets of heavy rolls that can be pressed together with tremendous pressure. Usually one or both of the rolls can be heated and one of the rolls may be engraved with a pattern. Sometimes both rolls are steel but often one of the rolls is covered with nylon or compressed cotton. Calenders can be use for:
- Melting fibers under pressure—often called thermal bonding
- Embossing fabric—putting a special pattern on the fabric
- Reducing the thickness of fabric
Calenders are used in nonwovens to thermally bond carded thermoplastic fibers like polypropylene and polyester. They are also used to thermally bond continuous fibers produced by hot melt spinning of polyester and polypropylene. This is call spunbond or spunlaid. In the needlepunch industry they give additional strength to the needlepunched fabric and/or impart special surface characteristics such as making the material slick on one side.