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IMPREGNATION OF CARRIER TEXTILES FOR ABRASIVESIntroducing the next generation of dispersions
Acralen SNX as new market benchmark in coating carrier textilesAbrasives used not only to sharpen but also to smooth and polish objects e.g. turbine blades Abrasive consists of an impregnated fabric and the abrasive particles on top of it, fixed with phenolic resinPolymer impregnation of the carrier improves adhesion between abrasive particle layer and carrier Acralen SNX enables manufacture of textile based industrial abrasives with higher performance and durabilityStand-out features like remarkably high peel adhesion, enduring thermal resistance and 10% more solids
Figure 1: Various types of abrasives
Flap disc Fibre disc Abrasive sleeve Polishing tool
What‘s new? Higher peel, higher solids, higher thermal resistance. Aqueous latex dispersions impart important properties such as flexibility, heat-resistance and durability to industrial abrasives on textile substrates in the grinding process. Terpolymers such as the new Acralen SNX offer improved properties for use in machine grinding of materials made of metal, wood and stone, thanks to their composition with increased solids content and optimized particle size distribution. distribution.
Today, abrasives are produced in different versions and are used not only to sharpen but also to smooth and polish objects, and make them dimensionally stable. Some of the most common forms are abrasive belts, fiber discs, flap discs, abrasive sleeves and polishing tools, available in different sizes and formats to cater for the application needs (Fig. 1 ). Textile based industrial abrasives are one of thethe key segments in abrasives. For over 30 years water-borne polymer dispersions have been increasingly used in the manufacturing of such products to enhance mechanical resistance, thermal resistance and adhesion between layers, to prolong the life span of the material.
Typically, the abrasive consists of an impregnated woven fabric made of cotton, polyester or a blend as the carrier. The carrier is back and top coated, and the abrasive particles sit on top of the carrier, fixed with phenolic resin (Fig. 2).
The use of water-borne polymer dispersions to impregnate and coat the carrier allows modification of hand and rigidity of the fabric. It improves mechanical properties and peel strength adhesion between abrasive particle layer and carrier, improves heat-resistance and durability against cooling fluids and also acts as a barrier to prevent the phenolic resin from the topcoat damaging the carrier.
WithWith the ever increasing technical and regulatory demands, Synthomer Deutschland GmbH, Marl/Germany, developed a new generation product Acralen SNX with improved mechanical properties over a long proven market benchmark Acralen BS. The new product shows better peel strength adhesion and higher thermal resistance, and is more environmentally friendly.
InIn this development, different key raw materials such as base monomers, functional monomers, cross-linkers and surfactants were improved. Our R&D also optimized the polymerization process parameters to attain a clean, low VOC product.
Polymer dispersion propertiesAcralenAcralen SNX is characterized by 10 % higher solid content (50 % TSC compared to 40 % TSC in Acralen BS). A further aim of the development was an improvement in mechanical resistance and maintaining the other performance parameters of the predecessor product such as chemical resistance and thermal resistance. Polymerization process optimization was implemented to ensure the polymer dispedispersion produced has less coagulum despite 10 % more in solids, and the particle size consistency to improve the product quality (Fig. 3 and Table).
Peel strength and adhesionOne of the key functions of a polymer dispersion in textile based industrial abrasives is to enhance the mechanical bond between abrasive particles and carrier. This is linked to the durability and life span of the abrasive. The mechanical bond of an abrasive is determined through measuring the peel adhesion at 90° of a fully refined grinding fabric glued to a defined base using the tensile machine. The degree of teartear assessed through visual observation provides information on the quality of the finishing.
In this study, the newly developed Acralen SNX was evaluated against the market benchmark Acralen BS, a competitor benchmark and 3 other internal references. Acralen SNX showed the highest peel strength among all products and it is 10% better than its predecessor Acralen BS as well as the competitor benchmark. (Figure 4).
Figure 2: Schematic abrasive construction
Basic bond (red) and coating bond (blue) (resin)
Impregnated textile carrier (CO, PET)1st top coating
2nd top coating
Back coating
Figure 4: Peel strength test at 90° comparing dispersions
Volume share [%]
Peel strength at 90°
peel angle in N/20mm
Acralen SNX
Acralen BS
Volume share [%]
Figure 3: Particle size distribution
Product Solid Content [%] pH value Viscosity [mPa*s] Tg [°C] Mean Particle Size [nm]
Acralen BS
Acralen SNX
*Data describe typical properties - not product specifications
40.0
50.0
7.5
7.5
< 50
< 500
35
35
80 ± 10
135 ± 5
Comparison of the polymer dispersion properties*
Figure 5: TMA test method
1. Heating internal reference 32. Heating internal reference 3
1. Heating Acralen SNX2. Heating Acralen SNX
Thermal resistance Grinding and polishing happen at very high speed. Thermal resistance is therefore another crucial property to look at when developing a high-performance dispersion for industrial abrasives.
TheThe formulation of polymer dispersion, in particular the monomers and cross-linker components, has a significant influence on thermal resistance. For this reason, Acralen SNX was evaluated against other synthomer products with different monomer compositions and cross-linkers.
TheThe Thermal Mechanical Analysis (TMA) test was used to determine the thermal resistance of polymers by measuring the needle penetration on a test specimen at gradually elevated temperature, from -150°C to up to 150°C constant load 500 mN.
EachEach specimen was tested for 2 cycles, in order to draw conclusions on the degree of cross-linking. Fig. 5 shows the Acralen SNX softens slightly at around 40°C then remains relatively stable up to 150°C. The other tested specimens showed a higher degree of softening that continues throughout the testing duration.
The product showed improved thermal resistance during the 2 cycle test, indicating that the cross-linker was activated at high temperature during first cycle. Compared to the internal reference, the effect of Acralen SNC is obvious, and the thermostability is clearly improved.
Blending with phenolic resinAcralenAcralen SNX has good compatibility with phenolic resin, which is commonly used for grinding sand fixation on the surface. By blending a small amount of Acralen SNX to the resin, it provides flexibility to the resin allowing the finished product to withstand the flexing process towards the end of manufacturing where the abrasives are stretched and bent at various angles to better adapt to the grinding tools and substrasubstrates.
Conclusion The newly developed Acralen SNX exhibits very good peel strength adhesion and thermal resistance to enable the manufacturing of textile based industrial abrasives with higher performance and boosted durability. Through the optimization of process parameters and modern quality control, a new product was developed which is 10 % higher in solids (compared to its predecessor) with consistent paparticle size distribution.
America, Europe and South East Asia. In March 2017, we acquired the coalescing agents and Butyl Ethyl Propanediol (BEPD) business from Perstorp Oxo Belgium AB. The newly acquired businesses significantly improve our footprint to a number of speciality markets which we will continue to serve through a strong network of local technical service and sales branches, supported by regional application dedevelopment and production in our key markets. We deliver the right formula, globally, individually.
Synthomer is one of the world’s leading suppliers of emulsion and speciality polymers supporting leadership positions in many market segments including coatings, construction, technical textiles, adhesives, paper and synthetic latex gloves. The company has its Head Office in London (UK) and provides customer focused services from operational centres in Harlow (UK), Marl (Germany), Kuala LumpurLumpur (Malaysia), Shanghai (China) and Dubai (UAE). In June 2016 we have acquired the Monomers, Dispersions and Powders business (MDP) from Hexion with dedicated production sales and customer service facilities in North
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