MATERIALS | FILM ADDITIVES
Figure 2: Hydrolysis stability in PE zip bags using LXR 568 and other phosphorus-containing stabilisers. Level of free DTBP (di-ter-butyl peroxide) is a measure of level of hydrolysis Source: Clariant
Business Development Manager for Polyolefin Additives, went into a detail about the advantages of using AddWorks LXR 568 in polyethylene and polypropylene films. He said that the additive has a much lower melting point than single phosphite stabilisers (around 90°C against 180°C or so), which contributes to superior melt homogeneity and an efficient reduction of gels in films. Sibert went on to discuss the advantages of the new additive in production of BOPP and LLDPE films. In BOPP film production, he said AddWorks LXR 568 gives 44% better MFR protection than PS 168, as well as 68% better colour protection and a two thirds reduction in the number of gels. When processing LLDPE, stabilisation solutions based on AddWorks LXR 568 provide superior retention of melt flow during multiple passes, as well as better resistance to yellowing (Figures 3 and 4).
Figure 3: Effect of multiple extrusion passes at 240°C on MFI of LLDPE (0.918 density) containing different stabilisation packages Source: Clariant
Better barrier Milliken has adopted a more hands-on approach in recent months in advancing the use of an additive system based on its established nucleating technology that can significantly improve not only the optics of polyethylene films but barrier proper- ties too. Optics are improved because the additives provide more nucleation sites and so smaller crystals, while barrier is improved by changes the additives induce in crystal orientation. The company has offered its Hyperform HPN
Figure 4: Effect of multiple extrusion passes at 240°C on yellowness index of LLDPE (0.918 density) containing different stabilisation packages Source: Clariant
nucleating agents for several years. Last year, it launched a family of masterbatches containing the additives under the UltraGuard banner. “By producing masterbatches, we can tailor our solutions per industry and class,” says Cliff Bynum, Leader UltraGuard Technical Team. The new masterbatches, which area available in pellet form and can also contain additives such as process aids and pigments, are being targeted predominantly at film converters, but also at compounders. The additives modify the crystalline structure of polyolefins, creating networks that considerably increase barrier to oxygen and water vapour as
Above: AddWorks LXR 568 is available as free-flowing dust-free micro-pellets 24 FILM & SHEET EXTRUSION | March 2018
www.filmandsheet.com
PHOTO: CLARIANT
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