New Water-Based Latex Dispersion For Abrasive Carrier Textiles

Abrasives such as abrasive belts, fibre discs, flap discs, abrasive sleeves and polishing tools are available in a wide variety of designs, sizes and formats. They are not only used for sharpening, but also for smoothing and polishing objects and for dimensional stability. Textile-based industrial abrasives are one of the key segments of abrasives.

For decades, aqueous polymer dispersions have increasingly been used to manufacture such products – to improve mechanical and thermal resistance as well as adhesion between layers as muchas extending the service life of the material.

Aqueous latex dispersions give industrial abrasives on textile substrates important properties such as flexibility, heat resistance and durability during the actual grinding process. Typically, the abrasive consists of an impregnated fabric made of cotton, polyester or a blend as carrier. The backing is lacquered on the back and the abrasive particles sit on the backing, fixed with phenolic resin.

The use of aqueous polymer dispersions to impregnate and coat the backing allows modifications to the stiffness of the fabric. It improves the mechanical properties and adhesion between the abrasive particle layer and the backing. It also improves heat resistance and durability to coolants. And it also acts as a barrier to prevent the phenolic resin from damaging the backing through the top layer, write Michael Karnop and Sören Butz of Synthomer Deutschland GmbH in the trade journal Melliand International.

Optimisation And Quality

Newer products have better peel strength and higher thermal resistance and are clearly more environmentally friendly.
 The parameters of the polymerization process are optimized to ensure a clean, low VOC product with low CO2 emissions.

One of the key functions of such a polymer dispersion in textile-based abrasives is to improve the mechanical bond between the abrasive particles and the backing, regardless of the fibre type. This contributes directly to the durability and life of the abrasive.

Grinding and polishing is usually carried out at a very high speed. Thermal resistance is therefore a decisive property that must be taken into account when developing a high-performance dispersion for industrial abrasives. The composition of this polymer dispersion, in particular the monomers and crosslinker components, has a significant influence on the thermal resistance.

New products also have good compatibility with phenolic resin, which is often used to grind the sand fixation on the surface. By mixing a small amount of these products with the resin, a change in flexibility is achieved so that the final product can withstand the bending process towards the end of production. This involves stretching and bending abrasives at different angles to better match the abrasives and substrates.

By optimizing process parameters and modern quality control, current products can be developed that contain ten percent more solids with a constant particle size distribution than their predecessors.

Photo: Kadmy

Fibre-Plastic Composites As High-Performance Products And Smart Materials

Technical textiles are assigned more and more properties. Fibre-plastic composites (FKV) are already being used as promising smart materials. These belong to a special type of functional materials that perceive environmental stimuli, react to them and can return to their original state once the stimulus has subsided.

For 20 years now, FKV have enjoyed increasing popularity in the field of resource-efficient mobility. Due to their high stiffness and low weight compared to traditional materials such as aluminium, steel or magnesium, FKVs are used as load-bearing structures in aircraft, automotive, rail and marine traffic.

By integrating functional materials into layered structures, they are provided with structure-integrated functions, such as lighting, de-lcing or continuous structure monitoring, as well as guidance and activation functions. They thus become said smart materials.

Particularly promising smart materials are shape memory alloys (FGL), which are characterized by a high energy density, a high force generation potential and enormous formability and stability in the high-temperature phase. The integration of the FGL during the manufacturing process of reinforcing fabrics guarantees long-term stability, reproducibility and cost reduction with regard to adaptive FKV (AFKV for short), according to the report by Moniruddoza Ashir, Jan Hindahl, Andreas Nocke and Chokri Cherif (Technical University of Dresden) in the technical journal Technische Textilien.

The research of the Dresden scientists shows promising approaches in lightweight structures with morphing capabilities - thanks to the development of AFKV based on FGL actuators. A structural integration of FGL wires in reinforcing fabrics was implemented fully automatically in a single process step and with the aid of weaving (textile) technology.

Further research activities of the Dresden researchers from the "Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik" (Institute for Textile Machinery and High-Performance Textile Technology) will in future aim to promote the development of adaptive, tapered FKV with locally adjustable bending stiffness in order to ultimately achieve an even greater degree of deformation. Exemplary applications for the developed AFKV include aerodynamic flaps or rudders, for example, but also medical applications for humanoid kinematics and various technical applications for clamping and gripping devices.

Digital printing with pigment inks allows high colour fastness

Printing results in digital textile printing with qualities such as excellent edge sharpness, good colour fastness and a soft touch require a good prepress as well as corresponding pigment inks. However, it is not trivial to meet and reconcile these requirements. The German Institutes for Textile and Fiber Research (DITF) in Denkendorf have set themselves this task and are developing a chemical product preparation system for inkjet printing. Textilchemie Dr. Petry GmbH, together with the DITF, is researching the pre-treatment with "Pericoat" and "Perijet" for inkjet textile printing with these pigment inks and their properties.

The printing result in inkjet printing does not only depend on the resolution of the inkjet printer and the print heads used. Rather, the print quality depends primarily on the quality of the print pre-treatment. With a good pre-treatment and ideally matched textile auxiliaries, however, low-viscosity inks can be used to produce the desired properties such as sharp edges, clear contours and good colour fastness. At the same time, the thickener and binder systems used in pretreatment should not impair the fabric handle.

For good fastness results, a relatively high concentration of binder must be applied in pigment printing. It is not possible to formulate pigments plus binder completely in the ink at will. With higher binder quantities, the viscosity of the ink would increase so much that it can no longer be printed. The binders must therefore be applied in a separate process before printing with the pigment inks.

The market already offers a wide range of binders and pretreatment chemicals that are suitable for modifying the surface of the textile printing substrate and improving it for inkjet printing. However, due to the wide range of available chemical additives, each with its own mode of action, it may be difficult to achieve targeted improvements in digital printing results.

Setting process parameters

A screening of the chemicals in question makes it possible to identify particularly suitable active substances. In the subsequent development phase, these chemicals were therefore optimally adjusted with regard to their use as pretreatment chemicals in the injection pressure. Both the concentrations and the mixing ratios of the individual components were adjusted. Particularly important here was the adjustment of the flowability so that the chemical active ingredients were neither too thin nor too thick for application to the textiles.

The next step in development was to set the process parameters for applying the pretreatment chemicals. The number of chemicals applied, the type of application and the adaptation of intermediate drying phases – all these process steps ultimately have an effect on the printing result. According to the authors Reinhold Schneider and Ulrich Hageroth, the pigment inks used in the research project were developed in-house by DITF.

Finely divided pigment dispersions are produced from organic colour pigments. The addition of binding agents enables the pigments to adhere well to the textile substrate. The addition of additives can also influence other properties of the pigment inks, such as their hygroscopic or rheological characteristics.

Photo: amixstudio

The Trend Towards Sustainability: Nonwovens Industry Reacts With A Broad Product Range

For the provision of sustainable nonwovens, it is necessary already today to design more materials for the use of tomorrow in the whole range of materials technology. The goal is to achieve optimal recycling and disposal »after tomorrow« in terms of ecology and economy. This is an important task for process and product developers in research and industry, who already offer first products to the market.

The nonwovens industry certainly creates innovative impulses with economic and functional products, for example for filtration, for channeling and storing water, for obtaining usable surface water, for preventing evaporation of water and for protecting glaciers and ice against melting. Peter Böttcherin the journal »Nonwovens & Technical Textiles« (avr).

Plastic products such as films or nonwovens are referred to as bioplastics if they are biodegradable or compostable regardless of the raw material base according to the European standard EN 13432. Among the bio-polymers of plant raw materials, the polylactide (PLA) is given great opportunities because it combines good functional properties with excellent degradation properties. In addition, to save food resources, PLA should in future be obtained from biomass instead of corn starch.

For example, Trevira offers a range of PLA fibre types for the production of nonwoven fibre fabrics – for example, fibres for mechanical nonwoven-bonding by needle punching or water jet blending, or the use of Biko fibres for thermal consolidation in wet nonwoven production.

Of course, the decisive factor is the actual production process, which above all aims to provide energy sustainability by reducing energy consumption. Examples are: Solutions for increasing surface mass uniformity and thus reducing nonwoven fabric mass plus developing plant technology for processing renewable raw materials such as Lyocell and PLA. The use of combined heat and power plants for the supply of electricity and heat, heating with gas instead of electricity as well as energy efficiency packages for calanders with housing, use of efficient motors and frequency-controlled pumps are most energy efficient – as much as recovery of braking energy and heat recovery from exhaust air.

Example Applications For Current Sustainable Nonwovens

Nonwoven fabrics in the hygiene sector are mostly used as so-called »disposable products«. Here the not so sustainable use of raw materials create significant positive effects for the economic and ecological disposal of solid or liquid problematic waste. In his article in avr issue 3/18, Peter Böttcherlists further concrete examples:

The nonwoven fabrics company Freudenberg, for example, offers an eco version of wadding made of fibreballs. This sustainable high-performance padding for use in sports is made of 80 percent recycled fibres. The remaining 20 percent is a binder material that serves as a padding for the production of a coherent surface.

Geosynthetics such as needle nonwoven fabrics or geogrid are produced with relatively low energy consumption and emission-free. Their use in civil engineering and road construction not only has economic but also ecological effects. In a project involving the construction of a two-lane overpass, for example, the Huesker company demonstrated that, instead of classical construction and the replacement of clay ,the use of geosynthetics show that transport-related C02emissions could be reduced by 35 per cent and construction costs by 55 per cent.

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