Spunbond Meltblown Spunbond, commonly known as SMS is a tri laminate non woven fabric. It is made up of a top layer of spunbond polypropylene, a middle layer of meltblown polypropylene and a bottom layer of spunbond polypropylene.
How is SMS manufactured?
This fabric involves two components, spunbond polypropylene and melt blown polypropylene. In a previous article, we have briefly looked at the manufacturing process of spunbond polypropylene where we compared it to spunlace click here for more information
So, let's turn our attention to the melt blown process. This process was actually started over 75 years ago by the US Naval Research Laboratories. The research was brought about by the desire to collect radio active particles from the layers of Earth's upper atmosphere. To do this, it was necessary to produce fibres to be used in micro denier filters.
In the early 1970s the first unit was completed to produce micro denier webs leading to the manufacture of fabric from polymer using a single integrated process.
The process today starts with thermoplastic chips being melted and then extruded. To date, Polypropylene has been the most widely used polymer for melt blown technology. The extrusion is then constantly filtered and metered to produce the filament. The use of high velocity air stretches the filaments to finer diameters and ensures thickening occurs as well as better random laying of the filament.
Whilst SMS can be produced off line by laminating layers of spunbond and meltblown webs, multi denier spinning allows for the combination of spunbonded and melt blown materials into one nonwoven web. This web is then pre bonded and passes through calendar rollers for thermal bonding.
Why combine spunbond polypropylene with melt blown polypropylene to create SMS?
As we know spunbond polypropylene has many excellent properties, strength and durability being just two of those. On the otherhand, meltblown has relatively weak tensile properties but due to the smaller fibres and larger surface area taken up by the fibres, it has excellent wicking and barrier properties. So together, they can create a strong product which can also offer a barrier to fluids and particles.
