Plastic sandwich panels for formwork and scaffold systems

Glass-reinforced plastics have not only revolutionised car production, but are also boosting efficiency on the construction site

Processed into light but extremely hard-wearing thermoplastic sandwich panels, the "MultiQ" solid plastic panel is replacing conventional plywood from steel and aluminum frames. The innovative plastic composite has now also made it onto the scaffold – as a durable and extremely load-bearing and heavy-duty plank.


Conventional formwork panels made of plywood swell, discolor, rot and have to be cleaned very carefully so that they achieve the desired concrete surface quality during their service life of 50 to 80 uses. The inherent problem is that any moisture penetrating the wood impairs the panel's technical and mechanical properties. While a plastic coating does improve the properties of wooden panels, it has its drawbacks as well. For instance, nail holes or cuts in the surface allow moisture to penetrate the core, causing local swelling and rot. And the difference in the thermal expansion behavior of the wooden core and the plastic coating may – in extreme cases – cause detachment of the latter.


Quadrant Plastic Composites, the world's leading manufacturer of high performance thermoplastic composite materials, has taken a different approach and, by using two proven polypropylene-based materials (proprietary materials that are mainly used in the automotive industry), has developed solid thermoplastic composite panels. These have a lightweight, glass-reinforced PP (poly-propylene) core reinforced on both sides by a polypropylene-fiberglass fabric in such a manner that there is no need for a reinforcing metal layer.

 

Higher-grade concrete surfaces with fewer efforts


The patented MultiQ sandwich panel meets all the mechanical properties expected of formwork while being far superior to conventional plywood. It is lighter and resistant to moisture, aggressive media and temperature fluctuations. The composite panel does not swell, rot or shrink and is UV, impact and scratch resistant. Moreover, it can be worked the same way as plywood, i.e. it can be nailed, sawed and drilled without splintering while allowing for a much easier and faster handling. The immaculately smooth plastic surface permits that the panels can be stripped effortlessly from the concrete and are very easy to clean. Damaged areas can be repaired easily and almost invisibly with identical material. The result: less wear and an almost unchanged high-quality concrete surface throughout the plastic formwork panel's entire service life. This may amount to as many as 250 uses, as extensive practical experience of the last few years has shown. Thereafter, the panel can be recycled environmentally friendly (into injection moldings, for instance), given that it consists exclusively of glass and polypropylene. This is another advantage over phenol-impregnated, resin-containing plywood panels and metal-reinforced plastic panels.

 

Materials technology


In the development of the solid plastic sandwich panel, Quadrant Plastic Composites has successfully managed to join two materials. The core consists of SymaLITE, a laminated nonwoven fabric of glass and polypropylene fibers, which is mainly used in automotive interiors and underfloors. The material of the cover layers is high-strength, thin and UV-resistant GMTex, a glass-mat polypropylene with an additional glass fabric inlay. In the production of MultiQ, the two sheet-like materials are fused into 9 to 22 mm thick sandwich panels through the application of heat. The surface of the new composite is homogeneous and smooth. The special combination of multi-directional glass fibers in the core and cover layer fibers oriented in the direction of pull offers the desired high material stiffness with a low weight per unit area. For instance, the 11 mm thick MultiQ used in ceiling formwork panels weighs 7.8 kg/m² and has a flexural strength of 70 N/mm2.

 

Now also available as a scaffold plank


The MultiQ product line is a modular system. The composition and thickness of the GRP sandwich panels offers plenty of scope for variation and permits design to customer specification. Quadrant makes it possible to have panels manufactured in different colors and sizes up to a maximum of 2.4 x 3.5 m. Under the name of MultiQ Concrete, panels are being marketed as a plywood substitute for formwork construction. MultiQ Impact, on the other hand, is another variant designed as a plank for construction scaffolds and other walkways with high demands on impact resistance (e.g. floors in trucks). The scaffold planks factory-finished with an integrated non-slip surface are already included as standard in the scaffold systems of a well-known manufacturer. Like the panel used as formwork, the plastic scaffold plank scores well in terms of its durability, moisture resistance, UV-resistance, low weight and ease of cleaning.

 

Incredibly impact-resistant


When used as walkway and work surfaces in particular, another technical feature of the composite material comes into play – its incredible impact resistance. The test described in ISO 6603-2 in which the puncturing behavior of solid plastics is checked with controlled and measured impacts showed that a 10 mm thick MultiQ panel with an area weight of just under 7 kg/m² has greater energy absorption than a 14 mm thick plywood panel (area weight 10-13 kg/m²). This is a characteristic that remains unchanged even after multiple uses, whereas wooden planks lose their initial load-bearing capacity as a result of damage and the inherent moisture absorption and may fail. The successfully completed impact tests that are required for the approval of reliable scaffold planks confirm the technical characteristics of this innovative scaffold plank made of glass mat reinforced plastic. It is even suitable for use in safety and protective scaffolds. Given the weight reduction of up to 22 % which results in faster scaffold erection and dismantling as well as increased efficiency in transportation, the slightly higher purchase price should pay for itself quickly.

IMAGE: Quadrant, MultiQ/1271075537.jpg
CAPTION: The patented MultiQ sandwich panel meets all the mechanical properties expected of formwork while being far superior to conventional plywood

IMAGE: Quadrant, MultiQ/1271075606.jpg
CAPTION: The immaculately smooth plastic surface of MultiQ Concrete permits that the panels can be stripped effortlessly from the concrete and are very easy to clean

IMAGE: Quadrant, MultiQ/1271075656.jpg
CAPTION: MultiQ Impact with its integrated non-slip surface is designed as a plank for construction scaffolds and other walkways with high demands on impact resistance

IMAGE: Quadrant, MultiQ/1271075715.jpg
CAPTION: Like the panel used as formwork, the plastic scaffold plank scores well in terms of its durability, moisture resistance, UV-resistance, low weight and ease of cleaning

IMAGE: Quadrant, MultiQ/1271076384.jpg
CAPTION: Plywood loses up to 55 per cent of its flexural properties, while MultiQ values remain unchanged by humidity

IMAGE: Quadrant, MultiQ/1271076422.jpg
CAPTION: Comparision plywood to MultiQ

Alain Charles Publishing, University House, 11-13 Lower Grosvenor Place, London, SW1W 0EX, UK
T: +44 20 7834 7676, F: +44 20 7973 0076, W: www.alaincharles.com

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