A new polymeric binder for ­gypsum-based grout mortars

Wacker’s VINNAPAS® 4800 G is a specially-developed polymeric binder for gypsum-based joint fillers in drywall technology: It not only improves tensile adhesive strength, but also the mortar’s processability. Plus, it allows the formulation of low-emission products.

The advantages of drywall technology also increase gypsum plasterboard production. Today, over one third of global gypsum production flows into the manufacture of gypsum boards. According to Global Gypsum estimates, worldwide demand for gypsum board is set to grow by 8.6 % annually by 2016 and reach a surface area of 10.7 billion m². Global Gypsum attributes 70 % of this additional demand alone to China and its rapidly growing housing-construction market.*

As the demand for interior finishing rises, the necessary materials must offer ever-increasing quality and ease of processing. Polymeric binders are a key component of these materials, such as jointing compounds and joint fillers. They ensure the necessary stability, adhesion and flexibility in gypsum mortar. With VINNAPAS® 4800 G, Wacker has developed a new dispersible polymer powder that meets rising interior-finishing requirements (Fig. 1).

Stable joints and homogeneous surfaces

The product was specifically designed for gypsum drymix mortars used as jointing compounds and joint fillers in drywall applications. These are necessary to smooth out joints that form following the installation of gypsum blocks. Usually, a so-called reinforcing strip made of paper, glass fiber or specialty nonwovens is placed on the joint and plastered over. This increases the joint’s stability and reduces the risk of cracks forming (Fig. 2). At the same time, jointing compounds modified with ­VINNAPAS® 4800 G offer further advantages. They are easier to process – and require fewer coats to achieve a smooth surface. Moreover, the binder ensures that uneven surfaces and edges are leveled out, resulting in a particularly homogeneous surface. A smooth surface is of primary importance for subsequent wallpapering.

Better adhesion and bonding strength

VINNAPAS® 4800 G dispersible polymer powder is based on vinyl acetate and ethylene and was specially developed for the improvement of gypsum-based joint-filler compounds. It imparts outstanding adhesion, both to gypsum plaster-board and reinforcing strips. That ensures higher overall mechanical strength of the joint structure.

The binder serves as an adhesion promoter between the organic paper and the inorganic gypsum. The formation of polymer bridges between the two substrates creates a very resilient bond. VINNAPAS® 4800 G is impressive in adhesion tests – such as the paper-strip test (Fig. 3), which is primarily used on the French market. Gypsum drymix mortars modified with Wacker dispersible polymer powder withstand a tensile force of some 2000 grams. By comparison, mortars without a binder show a value of 200 grams in laboratory trials.

Environmentally compatible end products

A further key aspect of interior finishing is that, as far as possible, materials do not emit any pollutants. Wacker binders perform well here, too: VINNAPAS® 4800 G is free of plasticizing additives that could be emitted as volatile organic compounds (VOCs) into the air. Due to its flexible ethylene segments, there’s no need for adding any plasticizer, which enables the formulation of low-emission end products. This dispersible polymer powder is therefore ideal for improving environmentally compatible gypsum-based drymix mortars such as joint fillers and jointing compounds for interior finishing.

Thus, Wacker offers an ideal product for processing gypsum, which is also known to be a “green” material. The reason is that relatively low temperatures of just 200 °C are needed for its manufacture. With synthetic gypsum, also known as flue gas desulfurized gypsum (FGD gypsum), even harmful air-polluting compounds can be neutralized permanently. In addition, the gypsum plasterboard itself is easy to recycle.

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