What is Heat Setting? | Working Process of Heat Setting | Stenter Machine

Heat Setting
Heat-setting is a heat treatment by which shape retention, crease resistance, resilience and elasticity are imparted to the fibres. It also brings changes in strength, stretchability, softness, dyeability and sometimes on the colour of the material. All these changes are connected with the structural and chemical modifications occurring in the fibre.

This operation is crucial for fabrics made of synthetic fibres (PE, PA, elastomers), for triacetate, and partly for PAC fibres (setting), since it grants excellent dimensional stabilisation and creaseproof properties, maintained till the fabric is exposed (by air blowing) to temperatures exceeding the heat setting one (after being treated with water at a temperature above the second order glass transition temperature, i.e. 80-85°C for acrylics).

Heat setting is carried out on gray fabrics (scarcely applied), on scoured fabrics (frequently applied) and on dyed fabrics (scarcely applied). The process grants excellent dimensional stability and good crease-proof properties. As far as operating conditions are concerned, the fabric must be treated in accurately controlled moisture and temperature conditions.
 
Heat setting of Some Fibers

Fibre
Min T. °C
Max. T. °C
Time in sec
Polyester (PE)
170
210
15-50
Polyamide PA 6.6
170
210
15-40
Polyamide PA 6
160
180
15-40
Triacetate
160
180
15-40
Acrylic (PAC)
160
180-200
15-40
Elastomers
170
180-200
15-40
 
Stages of Heat Setting
Heat-setting can be carried out at three different stages in a processing sequence i.e. in grey condition; after scouring; and after dyeing. The stage of heat-setting depends on extent of contaminations and types of fibres or yams present in the fabric. Heat setting after dyeing could lead to the sublimation of disperse dyes (if not accurately selected).

Stenter Machine
Stenters are widely used for stretching, drying, heat-setting and finishing of Fabrics. The stenter frame is usually 80-100 feet long and 70-100 inches wide. The speed ranges from 10-45 m/min with a maximum setting time in the setting zone 30 sec at temperature ranging from 175 to 250~ depending upon the thickness and type of the material. 
 
Stenter machine in heat setting

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