materials feature | Additives for PET
CrystalClear UV absorber from Ampacet prevents yellow tints in transparent bottles
commercial for a while but only recently promoted to the industry at large. The process aid, which Ampacet identifies by the
product code 704552, is in the rollout stage. Introduced late last year, it eliminates die lines in extruded parts such as pipes and tubes, film and sheet, and in extrusion blow moulded bottles and containers. The die lines are caused by contaminant build-up on die surfaces. “Over time, PET can have a problem with formation of machine-direction die lines. The material prevents die lines from forming,” says Morgan Gibbs, director of technical service development at Ampacet. “We find that there is a big need for this type of additive.” The grade is an innovative formulation, perhaps even unique, adds Gibbs. He declines to discuss the propri- etary chemistry, but says the additive has an affinity for metal, and deposits on all internal metal surfaces. This deposition displaces contaminants in dies, both by purging them and by preventing subsequent build-up. The material also has aesthetic benefits in that it
Ampacet’s light-diffuser additive provides
consistent light scattering
generates an extremely smooth flow of extrudate through dies. Gibbs says this yields flat, shiny surfaces on both sides of film, sheet and profiles, as well as blow moulded containers. Supplied as a masterbatch, the recommended dosing is 2%, although higher or lower loadings can be used based on compounding and application needs. Ampacet’s PET light diffuser additive, product code 7000013-NP (a version for PETG is coded 704458), uses an undisclosed technology to achieve 80 to 96%-plus light transmission in internally lit applications, depend- ing upon loading levels. These applications can include industrial lighting, as well as keypads and automotive dashboards. “Both grades [for PET and PETG] are cost-effective,” says Doug Brownfield, Ampacet’s strategic business manager. “A user doesn’t need much of this additive to achieve a good light-scattering capability. We have found quite a few homes for this technology.” The light transmission is multidirectional and
56 COMPOUNDING WORLD | March 2014
achieved with no bright spots or hot spots. Masterbatch loadings typically average 0.6 to 1.0% (6,000 to 10,000 ppm), which Gibbs says is 2 to 3 times less than in competitive technologies. The additive is formulated with an undisclosed synthetic material rather than a mineral such as calcium, which can hinder light transmission or create a hazy appearance in parts. The UV absorber that Ampacet is promoting is called
CrystalClear (product code 603192-PT). Brownfield says it has primarily been marketed to major OEMs for two years or so (PepsiCo has approved its use in beverage bottles), and is now targeted at a wider array of end users. Key features of the material include elimination of
the yellowish tint that occurs with many UV absorbers, and an ultraviolet blocking capability that Ampacet reports is 75% more effective than in most competitive materials. Brownfield adds that CrystalClear is economical.
With a recommended letdown ratio of 0.5 to 1.0%, depending on bottle thickness, the product can be as much as 40% less expensive for a given weight than conventional UV absorbers. Brownfield believes the additive will find growing use
in large-volume household applications such as dishwashing soap and shampoo bottles, for the benefits it provides in clarity.
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