Needlepunch process

Needlepunch technology uses fine-barbed steel needles to entangle dry-laid short staple fibres into a coherent felt-like fabric with relatively high bulk and conformable structure. The facility to intimately blend dissimilar fibres in a single web enhances the functionality of the nonwoven fabrics. In addition, the needlepunch process uses crosslapping technology to give fully isotropic fibre orientation and in-plane properties. The schematic below demonstrates the basics of the needlepunch process.

Characteristics

Characterised by binder free processing, even fibre dispersion, through thickness fibre architecture and relatively low bulk, needlepunched nonwovens have relatively low tensile strength and high elongation combined with good dimensional stability.

On-line heat setting further increases the potential material properties available from this flexible process.

With potential base weights of 60 – 900g/m2 the needlepunch process gives a non woven with the following material characteristics:-

• intermediate weight, high elongation yet durable
• homogeneous, flexible, conformable
• binder free and high elongation – easily conformable around complex curvatures and deep surface patterning
• 3 dimensional fibre orientation
• crosslapped for isotropic MD:CD properties
• rapid wet-out, easy-to-impregnate

Composite processes

Needlepunched nonwovens are suitable for the following composite manufacturing processes:-

• hand and spray lay-up
• vacuum infusion
• resin transfer moulding (RTM) and vacuum assisted resin transfer moulding (VARTM)
  • continuous lamination

Applications

Needlepunched non –woven products for applications in composites include:-

• polyester for high quality surface, enhanced resistance to corrosion and UV exposure
• para-aramid for improved impact, wear and environmental erosion resistance
• basalt, pre-ox and phenolic fibres for surface fire protection
• conductive blends for surface static dissipation, EMI shielding and heating applications, etc.
• flax for biodegradable eco-friendly credentials, good vibration and UV absorption properties and a pleasing, natural aesthetic finish.