Best Protective Face Mask Materials

The best protective face mask materials for virus protection are nonwoven polypropylene fabrics — above all meltblown polypropylene as the filter layer, usually supported by spunbond polypropylene for strength, often combined as a three-layer SMS laminate. Medical masks typically use several layers of these nonwovens because fine meltblown fibres give filtration while spunbond layers give the mask durability and structure.

The right material depends on the protection you are seeking, because not all face masks are created equal: some are designed to protect against viruses, some against cold weather, and others against flying hockey pucks. This guide focuses on personal protective equipment — PPE — masks intended to reduce the spread of virus particles, including the aerosol-sized particles that drove mask use during the Covid-19 epidemic in 2020. A note of care: this is textile information, not medical advice, and mask guidance from health authorities such as the CDC should always be checked for current recommendations.

Meltblown: The Filter Layer

Melt-blown nonwoven fabric is a common material for making quality face masks. A nonwoven is produced directly from the fibre stage, or from polymers in granular form, to fabric without an intermediate process such as spinning or yarn formation. In melt blowing, a polymer melt is extruded through small nozzles surrounded by high-speed blowing gas, transforming polymer chips or granules in a single step into a randomly laid web of micro- and nanofibres on a rotating drum.

Meltblown fibres are very fine — generally ranging from 1 micrometre to 10 micrometres in diameter — which gives the web a smaller pore size and greater filtration efficiency than a spunbond web. The material is typically white, light in weight and soft to the touch, which is why it suits surgical masks that must be supple, light and relatively comfortable to wear. Its weakness is strength: the meltblown web is softer, bulkier and a bit weaker, with relatively weak tensile properties, so in most filter applications it is used with support from another web or as part of a composite structure.

Spunbond and SMS: Strength Meets Barrier

Spunbond fabrics are produced by depositing extruded, spun filaments onto a collecting belt in a uniform random manner and bonding the fibres, which are separated during web laying by air jets or electrostatic charges. Spunbond polypropylene resists tears and punctures and has high tensile strength in all directions. It is an extremely versatile material precisely because it is both strong and light, making it the natural support layer in a mask.

Combining the two materials lets each make up for the weakness of the other. Meltblowns have limited strength, so they are combined with spunbond to become a strong material, and spunbonds gain barrier performance from the addition of meltblown. The best-known combination is SMS — Spunbond Meltblown Spunbond — a tri-laminate nonwoven made of a top layer of spunbond polypropylene, a middle layer of meltblown polypropylene and a bottom layer of spunbond polypropylene. Together they create a strong product that also offers a barrier to fluids and particles.

Polypropylene and What N95 Actually Means

Polypropylene is the polymer behind most of these fabrics and is a commonly used material for N95 masks. It is a nonwoven textile material made directly without spinning or weaving, and most polypropylene fabrics are copolymers. To get through a filter of interlaced layers of polypropylene fibres, small particles have to wind through a rather tortuous path and as a result tend to get stuck — the filtration picture described in a National Academies of Sciences, Engineering, and Medicine report. Polypropylene also has chemical and bacterial resistance, which is why it appears across medical applications from vials and syringes to specimen bottles.

N95 means that the mask can filter out at least 95 percent of particles of all sizes from the air. Two cautions follow. First, just because a mask is made of polypropylene does not mean it is an N95 mask — there are various qualities of polypropylene and different techniques and requirements to qualify as N95. Second, polypropylene melts at relatively low temperatures, so molten fabric can cause serious burns and the fabric cannot be washed at high temperature. Like other synthetic textiles it is derived from hydrocarbon fuels and persists in the environment for a very long time.

How Many Layers, and of What?

Medical face masks typically use nonwoven fabrics in multiple layers — many masks are made with three layers, though more are possible. One three-layer example seen in the market combines a composite fibre layer, a filter layer and a nonwoven fabric layer. A five-layer example uses spunbond polypropylene for the first and fifth plies, meltblown polypropylene as the filter in the second and third plies, and an ES material as the fourth ply.

ES nonwoven fabric is mainly PP+PE or PET+PE — polyethylene and polyethylene terephthalate — and the ES material used for surgical face masks needs to be non-shedding, lint-free and non-toxic, so PP+PE materials are mostly used for medical face masks. The pattern across all of these constructions is the same: spunbond outside for strength and wearer comfort, meltblown inside for filtration. Finally, fit and correct use matter as much as material: cloth face coverings should not be placed on young children under age 2, anyone who has trouble breathing, or anyone unable to remove the mask without assistance.