Optimization of manufacturing process for nanofibrillated spunbond composite products

A custom-designed, manufacturing process consisting of twin screw blending and spunbond spinning was optimized to achieve 100 nm nanofiber size in nanofibrillated spunbond composite products. Polypropylene (PP) as the matrix and polyethylene terephthalate (PET) were used as model common thermoplastics to investigate the formation of a nanofibril PET network throughout the PP matrix. The blends were twin-screw compounded, extruded through a spunbonding spinneret, and drawn through a drafter by intensive air flow. The resulting spun microfibers, with sea-island internal morphology were collected on a conveyor belt located underneath the drafter. A variety of samples were collected by changing the blending, spinning and drawing protocols. The inner fibers showed good levels of drawing at high drawing airspeeds of 15.9 m·s−1. Increasing the melt spinning temperature to 270 °C decreased the resistance of PET inner fibers to drawing, resulting in their improved attenuation. Accordingly, nanofibrillated spunbond composite containing PET inner fibers with an average diameter of as low as 84 nm were produced. Significantly improved crystallization kinetics in PP microfibers was obtained due to the nucleating effect of PET nanofibrils with a large interfacial area. Rheological investigations proved a dramatic enhancement in the storage modulus above those of the neat PP and its spherical blends with PET. Moreover, both tensile modulus and tensile strength were also enhanced by 65 % and 27 %, respectively.