ADDITIVES | SURFACE MODIFICATION
Figure 1: P171 scratch test results for PP samples comparing performance with two different Clariant anti-scratch additives. From left: no additive, 2% silicone-based Cesa-scratch PPA0025889 and 2% non-silicone Cesa-scratch PPA0025913 Source: Clariant
ides. Tegomer AntiScratch L is another liquid (an alkyl-modified siloxane) intended mainly for thermoplastic elastomers. Clariant produces several anti-scratch solutions under the trade name Cesa-scratch for use in injection-moulded and extruded polypropylene components for interior and exterior automotive applications. “Polyolefin components tend to reflect visible surface damage in the form of scratches or mars,” the company points out. “Anti-scratch additives generally work not by preventing these types of damage, but by affecting the material surface in ways that make damage harder to spot, essentially by concealing it.” Clariant offers two silicone-based anti-scratch masterbatches (Cesa-scratch PEABNR12020 and PPA0025889) and one non-silicone formulation (PPA0025913) that are all intended to be used at let-down ratios of up to 3%, as well as colour “combibatches” for automotive and consumer goods applications. It says the selection of these packages depends on different parameters, including process, application, resin grade, colour, presence of fillers, as well as the standards to be fulfilled. “None of these solutions negatively
influence surface migration or VOC emissions,” the company adds.
Effective additions The effectiveness of the masterbatches and combibatches have been demonstrated in labora- tory tests using textured plaques (Figure 1). First, plaques were prepared with P100 and P171 textures using both filled (17%) and non-filled polypropylene and a variety of different master- batch additives and concentrations. Then, the finished plaques were scratch-tested according to PSA Test (Standard D45-5525). Selected data is shown in Figure 2 (CESA-scratch grey is a coloured combibatch based on PPA0025913). The Clariant data shows all three anti-scratch masterbatches have significantly lower Delta L scores than the additive-free plaque (delta scores signify a lower contrast in colour between the scratched and non-scratched surfaces and indicate that the scratches are more difficult to identify). Another additives company supplying a mix of
Figure 2: Delta L values for filled PP compounds containing different anti-scratch additives after Erichsen scratch testing to D45-5525 Source: Clariant
58 COMPOUNDING WORLD | November 2017
anti-scratch additives is BYK. It currently offers two mixed-mineral types, BYK-TS 3200 and 3201 (TS stands for Tough Surface), for use in talc-filled PP compounds. They reduce the visibility of scratches and, the company says, considerably reduce scratch depth compared to conventional solutions. BYK-TS 3200 is described as a proprietary block copolymer, while BYK-TS 3201 is an organically modified siloxane, adsorbed onto a polypropylene carrier. The products also provide a similar reinforc- ing effect to talc, but at much lower doses (typically 5% versus 15%), enabling density reductions in compounds of around 8%. Croda Europe also offers several anti-scratch additives for polypropylene. It says the products – which are not silicone-based – not only reduce scratch width, depth and visibility but, due to their high stability, also offer no negative impact on parts including low visible bloom (see Figure 3), low
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