ALPHARETTA - Working in partnership with the major chemicals company Covestro, Neenah – which has just merged with SWM to become Mativ – has developed a meltblown nonwoven with shape memory properties.

The new material has the ability to temporarily store a structural change and return to its original form when subjected to a temperature increase.

The key to this, explained Neenah’s director of filtration R&D, Simon Gravot, speaking at EDANA’s International Nonwovens Conference held in Lyon, France, on June 8-9, is a thermoplastic polyurethane (TPU) base material with a specially tailored molecular structure.

Unlike common TPUs, the plastic has a crystalline soft phase that changes to an amorphous state at around 40-50 °C, allowing deformation at low force. This state is stored by cooling until a renewed increase in temperature leads to a return to the permanent form.

Controlled strength

In practical terms, this effect means that the nonwoven can temporarily remain in a stretched shape and only shrinks to its original size at temperatures above 50°C. In addition, the nonwoven has all the properties that generally characterise a TPU nonwoven – it consists of fibres with diameter of about 10 µm making it highly permeable to air. The material can be produced in a wide range of mass per unit area, which makes it possible to control the strength and the force applied when the material shrinks. It also exhibits elasticity with good recovery, even when cold.

The combination of shape memory effect and fibrous structure allows the nonwoven to be used in countless applications. In addition to the properties of the nonwoven itself, it can be combined with a wide variety of other materials Neenah’s lamination technologies allow extensive possibilities to combine two or more layers without losing functions such as air permeability.  

One application is in support bandages, which in their temporary form – created by stretching at approximately 60°C and then cooling under tension – can be loosely pulled over the hand, significantly simplifying the dressing. When heated with a blow-dryer to temperatures above 50°C, the bandage shrinks At the same time, it retains its porosity and air permeability, which helps to prevent skin irritation caused by moisture. The elasticity allows for good mobility of the arm.

Neenah can produce meltblown materials with weights ranging from 25-600gsm or alternatively, to be applied directly to a carrier medium, creating combination media in a single step.

In addition, many other options are available to customise meltblown nonwovens such as fibre diameter, thickness, basis weight, food compliance, surface design, chemical resistance, heat resistance, compostability, dust loading, UV protection, antibacterial properties, colours and electret charge.