Novel low-profile additives for room-temperature processes

At JEC Europe 2013, Wacker Chemie highlighted two new low-profile additives (LPAs) for room-temperature processes.

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At JEC Europe 2013, Wacker Chemie (Munich, Germany) highlighted two new low-profile additives (LPAs) for room-temperature processes. As the latest additions to the Vinnapas range of polyvinyl acetate (PVAc) solid resins for optimized nonshrink surfaces, they have been shown to reduce the shrinkage of unsaturated polyester resins to less than 0.05 percent.

The first is Vinnapas LL8588. The photo shows that fiber print-through is evident when no additives are used (left), but Vinnapas LL8588 enables a smooth Class A surface (right). The additive boasts a novel polymer architecture composed of PVA and polystyrene (PS) segments. The resulting block polymer not only has a low viscosity in the liquid resin formulations and keeps shrinkage in check during cure, even at room temperature, but also ensures that the finished product has low water uptake. The product was developed for semiautomated, low-emissions infusion processes, where it is said to promote rapid resin infusion and boost production efficiency by eliminating the need for intermediate layers while safeguarding a consistently high level of quality. It is suitable for complex composite parts in automotive or boat and yacht applications.

The second is Vinnapas LL 8251, a copolymer of vinyl acetate and crotonic acid. Because its viscosity is similar to that of saturated polyesters, it is said to be easy to process, even at high fiber and filler contents. Formulations based on saturated polyesters have a tendency to yield end-products of reduced rigidity and strength. In contrast, Vinnapas LL8251 offers effective shrinkage control combined with very high rigidity. The very good mechanical properties are said to lead to stable molded composite parts with extremely smooth Class A surfaces, which, in addition to their flat structure, offer excellent gloss and consistently high product quality. Aside from typical applications in the automotive sector, it has potential for use in composites for construction applications, such as windows, doors, industrial profiles and railings.