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.
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.