By Mandy Searle, Head of Technical Services at Norcros Adhesives
Reinforced Polymer Technology (RPT) is undoubtedly the next stage in the evolution of tiling adhesives. RPT enables the most advanced, superior bond yet achieved in a tiling adhesive. The main benefit gained from the incorporation of RPT is that the increased polymer level, combined with the incorporation of polymer strands, gives reinforced flexural and bond strength. It also provides enhanced crack bridging, anti-shrinkage and thermal ageing properties. From a technical point of view, the key to product development is to optimise the polymer chain lengths for each of the products in the range. A mineral component is added, in addition to the polymer, which improves the adhesive qualities and delivers much more.
RPT is at the most advanced end of fibre strand technology. Generally the fibres provide reinforcement and the main source of strength, while the matrix ‘glues’ all the fibres together in shape and transfers stresses between them. Fibre reinforcement adds rigidity and greatly impedes crack propagation in the composite material.
These composite materials have gained popularity in high-performance products in many different industries. For example in construction, fibre-reinforced concrete contains fibrous material which increases its structural integrity. Fibres are usually used in concrete to control cracking caused by shrinkage. They also reduce the permeability of concrete and thus reduce water ingress.
In fibre-reinforced screeds, polypropylene fibres are combined with the sand and cement and thoroughly dispersed during the mixing process. The use of fibres inhibits shrinkage, settlement cracking and increases strength, permeability and makes the screeds more resistant to impact stresses.
Synthetic polymer fibres are now being brought into the development of ceramic tile adhesives and floor preparation products.
The key development with Reinforced Polymer Technology (RPT) is the optimisation of the polymer chain length during product formulation. Synthetic polymer strands made from propylene monomers are used. This is in addition to a higher re-dispersible polymer content. It is the length of these strands which helps push product performance even further than other types of fibre.
RPT gets right down to the molecular level of a polymer, which has a structure built up chiefly from a large number of similar units bonded together, to get the correct interactions from the polymer chains within tile adhesive formulations.
In this way RPT enables a huge step forward in the development of tile adhesives and associated floor preparation products such as levelling compounds. The RPT product range created by Norcros Adhesives delivers the best solutions available for the most challenging tiling environments. They are especially suited to locations subject to thermal variation, especially heated floors, and installations where substrate movement is an issue, such as strengthened timber floors.
The RPT range of adhesives from Norcros Adhesives has been classified as S1 in accordance with British Standard BS EN 12004. It includes Norcros Rapid Porcelain & Stone S1 Tile Adhesive: a highly polymer modified, fast-setting, white cement-based powder adhesive designed with increased flexural strength and extended open time for fixing all types of tiles, including light-coloured and translucent natural stone to a variety of building surfaces in internal, external and total immersion locations.
The increased polymer level gives reinforced flexural and bond strength in addition to crack bridging properties up to 3mm. The adhesive has excellent ageing properties and is particularly suitable for heated floors and strengthened timber floors. A further benefit of the adhesive is its anti-shrinkage properties, making it suitable for a bed thickness of up to 10mm.
Norcros Rapid Porcelain S1 Tile Adhesive has similar properties to the above, but is available in grey, making it suitable for porcelain and dark coloured stone tiles.
Norcros Standard Set Flexible S1 Tile Adhesive is suitable for fixing all types of tiles, including light-coloured and translucent natural stone to a variety of building surfaces in internal, external and total immersion locations. It is ideal for use in heavy duty areas such as swimming pools, commercial showers and locations where thermal variation may occur such as heated floors. It is suitable for bed thicknesses up to 10mm, and has an extended pot life and a setting time of 16 to 24 hours at 20C.
The final product in the S1 range from Norcros Adhesives, featuring RPT, is Tile to Gypsum Adhesive. This is a fibre-reinforced, anhydrite-based thin bed adhesive designed for the internal fixing of fully-vitrified porcelain, ceramic and natural stone tiles directly to gyvlon/gypsum/anhydrite/calcium sulphate-based screeds. It can also be used on gypsum plaster walls, where the relative humidity is less than 85 per cent. Unlike when cement-based adhesives are used, surfaces do not require sealing. However, highly absorbent surfaces should be primed using Norcros Prime Bond in a mix of 1 to 4 with water and allowed to dry before fixing commences. The adhesive has a setting time of two hours at 20C, permitting early trafficking of the tiled installation. Once cured, the adhesive achieves comparative strengths to a conventional C2 cement-based adhesive.
Another product in the Norcros Adhesives range to feature RPT is Norcros Pro 50 Levelling Compound: one of an expanding range of levelling compounds from the company. Norcros Pro 50 Levelling Compound is a single part, fibre-reinforced self-smoothing floor underlayment, suitable for use from 3mm to 50mm in one application without the need for additional granite chippings.
It is ideal for levelling a variety of substrates including concrete, screed, flooring grade asphalt, terrazzo and quarry and vinyl tiles. It can be used with undertile heating mats and on timber floors.
“The qualities that this range delivers are remarkable,” says Mohammed Nawaz, Quality and Business Improvement Manager. “The products feature much greater flexibility, the polymer bridges gaps and helps to interlock the cement matrix, giving incredible strength. It has impressive non-slip properties and takes impact really well, too. We have sought to respond to our customers’ requests for specific products for specific uses, including a levelling compound.”
More information on RPT is available in a CPD seminar created by Norcros Adhesives. Reinforced Polymer Technology for Tiling is developed for architects, specifiers and large contractors, providing important information for professionals who need to keep their CPD qualifications up to date. The presentation is available on the Norcros Adhesives website at www.norcros-adhesives.com.