China Adhesive 2019: WACKER Presents Dispersible Polymer Powder for EPI Wood Glue and Highly Hydrophobic Pyrogenic Silica

EPI wood glues are mainly used for producing window frames, furniture parts, finger joints load-bearing constructions. An important wood origin and wood processing area in China is the northeast, a region which is exposed to low temperatures in winter. As the dispersion in EPI wood glues is easily demulsified in cold weather, manufacturers have to undertake costly insulation and packaging measures when transporting and storing dispersions.

WACKER looked into this problem and came up with a solution NEXIVA^® PA 210. The powder consists of vinyl acetate and ethylene copolymer (VAE). When formulating the final glue product, wood glue compounders only need to mix NEXIVA^® PA 210 with water and filler powder. The same applies to users if they want to mix the glue formulation with water, filler powder and curing agent directly on site.

With NEXIVA^® PA 210, transportation and storage issues of EPI wood glues in China’s northerly regions are resolved. Formulations based on the new product do not require special insulation which makes packaging and packaging disposal significantly less costly. Compared to conventional water-based binders, NEXIVA^® PA 210 also provides better adhesion. D4 tests (EN-204) show that formulations based on NEXIVA^® PA 210 have a shear strength of over 5Mpa, about 40% more than commodity dispersion grades can offer.

HDK^® H21: Additive for High-Strength Industrial Adhesives

Another product highlight at the show is WACKER’s new HDK^® H21, a hyperpure pyrogenic silica which has a large specific particle surface area. Although it is highly hydrophobic and non-polar, it can be readily incorporated into polar liquids compared to other hydrophobic products. Its rheological activity is extraordinarily high in epoxy, vinyl ester and polyurethane based adhesives. This makes it suitable for manufacturing high-performance adhesives efficiently and in less time.

As a consequence of its large specific surface area and its hydrophobicity, HDK^® H21 gives pronounced shear-thinning properties to polar liquids. A suitable amount of pyrogenic silica will make the compound viscous when at rest and prevent sagging. When shear forces are applied, however, the viscosity drops. As a result, a polar industrial adhesive containing the new additive can be readily pumped and precisely applied. When modified with the appropriate concentration of HDK^® H21, adhesive compounds will not run until fully cured – not even when applied in very thick layers and when the bonding surface is sloping or curved.

In this way, HDK^® H21 creates the conditions for efficient adhesive application and a reproducible, flawless bond. The product also enhances the shelf life of reactive adhesive components. It prevents fillers from settling and, due to its hydrophobic character, barely interacts with the adhesive matrix. Moreover, as a white powder, HDK^® H21 will not influence the colour of the formulation and can be used in transparent system.

HDK^® H21 is perfect for use as a rheological additive in high-strength industrial adhesives, such as those in automotive industry bonding applications, in chemical dowels for the construction industry, and in bonds between the half shells of wind turbine rotor blades.