Thermal bonding: Thermally bonded webs are made up of synthetic fibres. The TWE Group specialises in the field of carded webs. Once the fibres have passed from the bale-opener through the mixing chambers and to the card, the pile is placed in the card. To create a web from pile that is held together only by fibre-fibre friction, there are various ways of bonding the pile to a web. One of these is thermal bonding whereby the pile is transported to the oven where, through the effects of temperature, a fibre component is melted into the pile and then acts like an adhesive to bond the individual fibres. After cooling, the web is wound up and can then be conveyed to the next step: assembly. Thermal bonding enables light to medium weights to be produced at high production speeds. Chemical bonding: The chemical bonding of nonwovens refers primarily to applying liquid -based bonding agents to the web bed. The most commonly used polymers are acrylate, styrene butadiene and vinyl acetate. The most frequently used water-based bonding agents are adhesives, foams, in in certain cases organic solvents. A chemical bond can be applied using the following technologies: spraying, foam foulard and immersion.Temperature is then added to evaporate the water from the solutions and bond the nonwoven by bringing about consolidation of the bonding agent. Mechanical bonding: There are two main types of mechanical bonding – needle-punching and water jet bonding. The TWE Group has both these technologies.Needle-punching creates a bond between the fibres through friction and positive locking. The fibre pile is first created in the car and doubled up by means of the compensation stacker, and then reinforced using needles. The needles, which have notches on them, are punched multiple times into the fibre pile, so that the fibres become interlaced.This method of bonding enables the manufacture of fully synthetic, natural fibre, glass fibre and mixed fibre webs.TWE Group needle-punched web can subsequently undergo thermal and/or chemical processing. Further, a powder coating or film or foam lamination can be appliedWhere nonwovens are mechanically bonded using water jets, the fibre pile that comes from the card is compressed between two perforated compacting rollers and then bonded using water jets with a pressure of 50 – 200 bar. Because of the high pressure, the fibres are swirled, together which gives the web its strength. This creates high-strength nonwovens with a low surface weight as well as good drapeability and elongation. These webs also have a highly homogeneous distribution of fibres and a smooth surface.
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