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. 

Hydrophilic nonwovens easily absorb water and transport it on. Use of special product variants enables storage of the fluid. Oleophobic nonwovens are capable of absorbing high levels of oils and fats.

• Hygiene products: In these applications, nonwovens are required to quickly transport the maximum amount of fluid to the absorbent core for storage and prevent rewet.
• Wipes: The lotion applied to the nonwoven is absorbed but allows a sufficient amount to be released again during application.
• Automotive: Nonwovens used in the seat are required to quickly and reliably absorb water vapour, creating a continually pleasant micro-climate in the seat.  
• Environmental applications: In this area of use, highly absorbent nonwovens are applied to assimilate oils, water or other fluids. 

Hydrophilic properties are tested according to WSP 10.1. For example, capillary rise is determined by the speed of fluid absorption and its distribution. The wider the distribution throughout the material, the better the storage capacity. this property for instance, is exploited in the absorbent core of a hygiene product. Another test focuses on maximum fluid intake, determining the level of fluid the medium can store.    

See also: Resistance

The fibrous structure of nonwovens combined with diverse bonding technologies creates a multitude of different structures and surfaces, optimising and complementing function and efficiency of these materials depending on their respective application:

Plain surface

No plain surface is like the other. Depending on the requirements of the application, numerous “plain“ surfaces variants are available. A smooth / plain surface also characterises optimised surface integrity.

• Wipes: Smoothing the surface reduces linting. Furthermore, the nonwoven gains a more compact feel and becomes more stable due to a reduction in elongation.
• Automotive industry: Surface smoothing lends stability to the material and improves processability.
• Fashion: A well-bonded surface prevents fibres from penetrating the outer fabric.

Perforation

Perforating or aperturing offers a specific method of surface structuring. It changes the material’s surface, giving the nonwoven a special design as well as additional functional properties. In wipes substrates perforation improves the cleaning effect: It enlarges the material’s surface area, enhancing its dust hold capacity.

Embossing

Embossed nonwovens combine design and function. The material can be embossed with various motifs as a visual eyecatcher. In many cases, however, these designs also enlarge the nonwoven’s surface—a definite “plus” when it comes to dirt collection in wipes or absorbency in hygiene products. Multi-layer structures may be bonded via an embossing process, attaining adhesion between the layers without binders. Depending on the material and the utilised polymers these structures can be created thermally or by using hydro embossing. Visit our Design section for more details.

In offices or public spaces embossed acoustic components made of nonwovens may also offer a design feature.

Printing

Many Sandler qualities are available with end use oriented print motifs. Various designs for the hygiene and wipes industry emphasise the respective application. Visit our Design section and see for yourself or contact Sandler for your customised print design.

In technical applications such as filtration or construction, performance parameters such as the filter grade, relevant testing standards or the classification pertaining to thermal conductivity can be printed onto the material using inkjet printing upon special request of the customer.

Multi-layered structure

Nonwovens can also be used in the form of composites consisting of several layers. Different nonwovens are combined with one another or with other materials. These multi-layered structures combine the diverse properties and functionalities into one product, fulfilling the highest quality standards. Multi-layer composites may also facilitate processing. The possible combinations are virtually unlimited:

• Hygiene industry: Multi-layer nonwovens combine several functions in one product, such as the transport and storage of fluids. 
• Medical applications: Together with other materials nonwovens also function as padding for improved in use comfort, particularly in extended use.
• Wipes: In cosmetics and other applications the combination of fine and coarse layers improves the cleaning effect. 
• Automotive & upholstered furniture: Multi-layer nonwovens facilitate processing and lend stability, for example to leather seats: when laminated onto the leather, they prevent overextension in use, thereby reducing unsightly creases in the seat.
• Filtration: Multi-layer composites lend stability to the products: Ceiling filters, for example, are rendered more stable by a polyester fabric laminated to the medium.
• Technical applications: Composites of nonwovens or with a multitude of other materials can increase the stability or even the resistance to heat, acids or other influences.
• Fashion: Lamination to nonwovens imparts optimum surface integrity and prevents pilling and fibre penetration.

Soft Sandler nonwovens are gentle on the skin, thus increasing comfort in use, particularly in direct contact, and preventing skin irritation. They may be adapted to the requirements of the specific application by ways of different product structures and surfaces.

• Hygiene products: In diapers, femcare products and medical applications soft Sandler nonwovens protect the skin, particularly during extended use. Nevertheless, they feature high stability. In temporary braces, nonwovens add to the comfort of the user.
• Home textiles: In upholstered furniture and other home textiles voluminous, soft Sandler nonwovens increase our living comfort. They adapt to the furniture contours, allowing for loose as well as attached processing, for example for soft upholstery of the backrest.
• Fashion: Soft nonwovens render outdoor clothing into “feel-good” clothes.

One way of testing softness is the cup-crush-method according to WSP 402. During this test, the nonwoven sample is placed over the top of a cylinder in a testing apparatus and pushed in using a hemispherically shaped piston. The force necessary to push in the nonwoven is measured.

Finishes

Sandler nonwovens can be offered with different finishes to supplement functionality: for example with lotions, cleaning agents, an antibacterial finish or a flame-retardant finish to increase flame-resistance.

Printing

Nonwovens can be printed all-over or with detailed motifs using thermal transfer printing, digital printing, flexo printing or other established printing technologies. 

• Hygiene & wipes industry: Print motifs emphasise the application and offer visual differentiation. 
• Office design: Acoustic components for interior decoration can be printed to offer a design facet. Thermal transfer printing increases surface bonding and smoothes the nonwoven’s surface.

With the intention of improving the print result, the surface of Sandler nonwovens may also be pre-treated by roughening the fibres.

Adhesive coating

Adhesive coating can be applied on one or both sides of the nonwoven. In filtration for example, ceiling filter media are coated with an adhesive finish to facilitate processing in the end application. The coated parts are protected by a release film. Once this film is removed, the nonwoven can be used as intended. Pleatable filter media can be equipped with spacers made of hotmelt adhesive.

The nonwoven can also be pre-treated to enlarge the fibres’ surface to improve bonding with the adhesive.

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.