Breathability describes a fabric‘s ability to allow air and water-vapour to permeate, preventing the accumulation of moisture. Breathable materials thus increase comfort in use and avert skin irritation, particularly in applications involving direct skin contact. 

• Hygiene products & wound dressings: Breathable nonwovens allow the skin to breathe, increasing wear comfort whilst preventing an accumulation of fluids and skin irritation, particularly during extended use.
• Automotive: Breathable textiles in the car seat increase driving comfort, especially on long journeys. 
• Construction industry: Permeable nonwovens contribute to the health of the occupants. They allow the walls of buildings to breathe when required. Simultaneously, they avert the accumulation of moisture, thus preventing structural damage and potential health issues caused by mould formation.
• Mattresses & bedding: Breathable materials allow for a restful and comfortable sleep.
• Fashion: Breathability is a vital function for product performance. 

Breathability, also referred to as resistance to water vapour permeability, can be measured according to DIN EN 31092, respectively ISO 11092 using the thermo-regulatory model of human skin. Breathability indicates the rate at which perspiration is transported through the material. 

Mechanical stability is a vital property in nonwovens. It describes their resistance to tearing or breaking caused by mechanical influences. In many applications, nonwovens are subject to strains such as vibrations during processing and use or to compression. Mechanically stable nonwovens withstand these forces, being tear-resistant and having low elongation values in machine and cross machine directions. 

• Wipes: Variants featuring reduced elongation for household and industrial cleaning support even heavy-duty applications.
• Filtration: Mechanically stable nonwovens resist the volume flow in use as well as vibration in the filtration plant. 
• Technical applications: Mechanically stable nonwovens are used for sheathing and other reinforcements. 

To determine a material’s mechanical stability, maximum tensile force and maximum elongation in machine and cross-machine directions are measured at varying parameters according to WSP 110.4. Mechanical stability also embraces several properties specific to the respective application:

Abrasion resistance

In car seats, in furniture, in technical applications and even in cleaning wipes nonwovens are subject to abrasion, which may weaken the nonwoven’s structure. Since the nonwoven is made up of single fibres, these fibres have to be well anchored in the fibre matrix to provide appropriate cross-directional stability. In this way, abrasion resistance is achieved. In the production of nonwovens, Sandler relies on fibres with a high resistance to breakage, thereby fulfilling these requirements.

The abrasion resistance of a nonwoven can be determined using the so-called Martindale test method or according to the DIN EN 530 standard. The materials are classified in requirement categories, depending on the number of scrub cycles as determined by testing. The more cycles endured by the nonwoven, the higher its abrasion resistance. This test can be carried out by our external partners if required. 

No fibre shedding and minimised fibre breaking

Sandler nonwovens are made of synthetic fibres that do not shed and due to their elasticity and resistance to breakage, result in the minimum of fibre debris. These media do not cause skin irritation and present no health risks—for example in the automotive industry or in construction. Sandler nonwovens thus meet the requirements of product class 1 of the Oeko-Tex^® standard 100, bearing the “Confidence in Textiles” label.

In filtration, this characteristic is of paramount importance: If the fibres are brittle, fibre fragments may become detached and contaminate the source of the clean air stream. 

Bending stiffness

Materials featuring high resistance to bending demonstrate high stability even under strain. This property is particularly relevant for use in self-supporting structures intended to be installed overhead using only few fastening points. Vibrations may develop in use, transposing the component’s weight into a strain. Stiff materials do not deform under load and do not sag. They retain their residual stiffness over the long term. 

• Automotive: Nonwovens featuring high bending stiffness are in demand for moulded parts such as headliners. 
• Construction industry: Stiff nonwovens are applied for acoustic ceiling panels and other ceiling structures. 

At Sandler, bending stiffness is determined using the three-point-method according to DIN EN ISO 14125: A sample is deformed at a constant rate; the applied force and the deflection are measured. This test is performed in our own laboratory. 

Tread-proof

In roof construction, the raw materials are literally being walked on. Sandler nonwovens for insulation laid on the rafters or bituminous strips feature a pressure- and tread-proof upper side for safety in roof work. Even under pressure they remain firm, due to their high bending stiffness.

Especially in technical applications, nonwovens come into contact with various fluids, chemicals including organic solvents and may also be exposed to sunlight or humidity. Sandler nonwovens are predominantly made of synthetic raw materials such as polyester or polypropylene and are resistant to most inorganic and organic substances. This resistance makes them durable and their specific properties are maintained throughout their operating life. By choosing a suitable Sandler nonwoven, discolouration, softening, bulging, detachment of coatings or blistering become things of the past.

In the automotive industry, this durability is tested according to VDA 621 by dripping selected test fluids on the material or moistening it with them. The temperature at which the test is performed may vary. Sandler nonwovens are tested according to VDA 621 by external institutes.

Specific applications require resistance against specific media or exposures:

Resistance to alkali

In construction, nonwovens come into contact with materials such as concrete or cement mortar. If the level of humidity increases, these building materials are prone to emit large quantities of alkaline salts. Sandler nonwovens are resistant to these alkalis: The nonwoven is unaffected, no disintegration occurs and fabric remains stable. These nonwovens are therefore highly suited to applications in construction. Their resistance to alkali is determined by subjecting them to different test media, usually over a period of several months. A subjective examination of the nonwoven’s structure is subsequently carried out and any decrease in weight and tear-resistance are measured. Sandler nonwovens are tested for resistance to alkali in our in-house laboratory.

Hydrophobicity & hydrophilicity

Hydrophobic nonwovens are water-repellent resulting in reduced fluid absorption. This characteristic is achieved without any additional finishes, using only specific polymers and the appropriate manufacturing technology. 

• Automotive: Hydrophobic nonwovens in exterior applications such as wheel house liners withstand any wind and weather. 
• Construction: Hydrophobic nonwovens dry quickly and thereby prevent an accumulation of moisture.  

In contrast, hydrophilic nonwovens easily attract water and transport it. Special product variants can also be applied for storing fluids. These nonwovens are highly suited to hygiene products or wipes.

Oleophobicity & oleophilicity

The term oleophobicity describes the characteristic of repelling oils and fats. These substances do not penetrate the material but simply run off its surface. Sandler nonwovens for the automotive industry are permanently resistant to engine fluids such as transmission fluid, engine oil or diesel and are  in-house tested for oleophobicity according to the drop test method. Likewise, Sandler nonwovens for filtration are resistant oils and fats.

Oleophilic nonwovens, on the other hand, easily absorb oils and fats and amongst others are especially in high demand for environmental applications.

Resistance to fungi, bacteria and moisture

Sandler nonwovens made of thermoplastic polymers are bacteriostatic, i.e. they prevent the proliferation of colony-forming units by denying any breeding grounds for fungi or bacteria. In humid conditions, this characteristic is particularly enhanced by their resistance to moisture: The fibres do not absorb moisture, therefore the nonwoven dries quickly.

• Filtration: Sandler nonwovens are tested for their resistance by external institutes. Corresponding certificates attest to the nonwovens’ suitability for application in ventilation and air-conditioning systems according to VDI 6022.
• Construction: This characteristic helps to prevent the growth of mould in buildings, protecting the health of the occupants.

Bacteriostatic properties are determined according to the DIN EN ISO 846 standard by evaluating the impact of micro organisms on synthetic materials. The nonwoven is placed on a culture medium to which different fungal spores and bacteria are applied. After a period of 4 weeks under defined temperature and lighting conditions, the growth of both fungi and bacteria is visually observed.

UV-resistance

In construction, for roofing and façades as well as in technical applications the utilised materials are frequently subjected to sunlight. Use of specifically chosen polymers result in Sandler nonwovens being UV-resistant: The material’s structure remains intact, neither discolouration nor disintegration being an issue.

UV-resistance is determined by means of an exposure test. Samples of the nonwoven may for example be placed behind window glass and subjected to real climate variations. Prior to and after the test, the nonwoven’s mechanical properties are determined, by checking for any detrimental effect from exposure to the UV-rays, in relation to the duration of exposure. 

At every stage of the manufacturing process, Sandler relies on sensible raw material usage in order to conserve natural resources. A major focus is thus placed on both preventing and reutilising production waste. Whenever the requirements of the production process will allow, accruing by-products are reprocessed by feeding into production as raw materials. If this internal utilisation is not possible, these surplus raw materials are recycled externally. In this way, both raw materials and nonwovens are part of a closed raw material cycle, conserving valuable resources. 

Manufactured without any additives, our single-polymer nonwovens support this recycling philosophy. Sandler polyester nonwovens e.g. in construction applications or in the automotive industry can be recycled after use and reprocessed into new raw materials without having to employ elaborate separation processes. With product specification compliance, recycled polyester fibres are increasingly used—familiar to most every consumer from the recycling of PET bottles.  

In selecting raw materials for wipes substrates sustainability is also of major importance. Rayon fibres of European origin derived from controlled forestry and certified according to PEFC™ oder FSC^®  standards are utilised. The product range also offers biodegradable product variants, made from 100 % rayon fibres.

An energy management system installed directly on our production lines optimises energy consumption and reduces CO₂ emissions: energy monitors show the actual consumption during production. Our experienced staff can adjust the settings to minimise energy usage without influencing the properties of the finished product. Use of heat recovery systems further reduces energy consumption. For several years, an energy task force has been monitoring energy consumption throughout the company, identifying potential reductions and proposing measures for implementation.

In their respective applications nonwovens contribute to conserving valuable resources: Durable materials prolong replacement intervals of filters and other products, reducing raw material requirements for replacement products. In the automobile nonwovens also function as heat insulators in the engine compartment, preventing loss of temperature. Thereby, cold starts are reduced; fuel consumption and emissions are lowered and resources are conserved. For this market Sandler developed simulation software in cooperation with partners from the industry. It allows the required product properties to be computer-simulated, foregoing resource-intensive trial productions. 

Sound absorption describes the conversion of sound energy into heat. Materials featuring high sound absorption are excellently suited to sound insulation in construction or the automotive industry. Fibrous components such as nonwovens commend themselves to these applications owing to their porous structure. Fine fibres create a more or less flexible “fibre skeleton“, featuring a large inner surface. Sound is diffracted in numerous places, whereby sound waves are absorbed and dampened by the nonwoven. Their structure also makes nonwovens an ideal heat insulator.

Properties such as the material’s thickness, density, porousness and flow resistance determine the level of absorption. The measurement of sound absorption under random incidence is carried out in a reverberation room according to DIN EN ISO 354, or in a smaller alpha cabin. Sound absorption under vertical sound incidence can be determined according to DIN EN ISO 10534 in a Kundt's tube, or impedance tube. Sandler nonwovens are tested for their sound absorption properties in cooperation with external institutes.

Together with renowned partners from research and the automotive industry, Sandler developed a simulation tool, enabling the calculation of the required absorption level. New variants and products can be computer-simulated based on the required absorption profiles before the first trial production is undertaken. In this way, time and costs are saved and valuable resources conserved.

See also: Air-permeability

Flame-resistant products meet particular demands in the event of fire. Subjected to blaze, sparks or open fire, they do not catch fire immediately. When ignited, these structures do not continue to burn, but extinguish after a specific time.

Depending on the specific application and national regulations, various test standards apply:

• Automotive applications: DIN 75200, MV SS 302, PV 3357 and UL 94
• Filtration: The provisions regarding flame-resistance are laid down in DIN 53438 standard.
• Construction: Nonwovens for office fittings and mattresses used on ships and trains are evaluated according to DIN 4102 or DIN EN 13501 standards.
• Upholstered furniture: BS 5852 standard is decisive in this sector.

Our nonwovens are tested for flame-resistance in cooperation with external testing institutes.

Retaining heat, preventing heat loss. Allmost everyone is familiar with these requirements when it comes to buildings, since we want to feel comfortable inside a building and be protected from wind and weather. However, whilst our cloths equally fulfil this function, efficient thermal insulation saves energy and costs. 

Nonwovens are characterised by a special open-pored structure, featuring a porosity of up to 95 percent. The structure comprises very fine fibres and a large inner surface which also contains air—a very efficient heat insulator—setting the stage for excellent thermal insulation. The density and fibre structure of a nonwoven influence its thermal conductivity. By tailoring basis weight, thickness and fibre blend, the required level of thermal insulation can be achieved, thus having the ability to create a specific nonwoven for every application.

• Automotive: In the automobile, nonwovens also function as heat insulators. For instance they contribute to reducing fuel consumptionwhen used to retain heat in the engine compartment.
• Construction: Used as insulation materials for interior and exterior applications in roof and walls nonwovens add to a feel-good atmosphere, lowering the energy input by efficiently retaining heat, thus reducing costs.
• Outdoor clothing: Nonwovens retain body heat to maintain warmth.

In determining thermal insulation properties, the nonwoven’s thermal conductivity is vital. It is stated in the lambda coefficient of thermal conductivity: The lower the value of lambda, the higher the thermal insulation. Thermal conductivity is measured according to ISO 8301 or DIN EN 12667 using the heat flow method with plates. The test is carried out at an average sample temperature of 10°C. 

Pleating 

Sandler's pleatable nonwovens for the filtration industry are suitable for processing on knife as well as rotation pleating lines. A homogenous, longitudinally oriented fibre structure provides for particularly accurate pleating and high pleat depths. The polymers utilised are temperature-stable, elastic and resistant to breakage, thus offering high stability: The pleats are dimensionally stable, yet are also flexible. They withstand mechanical influences during processing and temperature and humidity during use.

Cutting & die-cutting

Sandler nonwovens are easy-to-process using established cutting technologies such as band knives, CNC cutters, straight knives, water-jet cutting or laser cutting. Perforation cuts for tearoff wipes, for example, are also possible.

For hygiene products, automotive industry products, and for mat filters die-cutting is used, to which Sandler nonwovens are highly suited. Particularly in automobiles precision contouring facilitates accurate assembly onto the particular component. The material is also not distorted during die-cutting, resulting in accurate cuts with clean edges.

Sewing

By selecting appropriate fibres, Sandler nonwovens are easily processable and can be sewn without difficulty—in the manufacture of fashion, mattress covers, car seats, and for pipe insulation or the production of pocket filters.