MATERIALS | FILM ADDITIVES
Right: UltraGuard nucleated HDPE bag-in- box film for packaging dry foods provides improved barrier, gloss and clarity
well as the larger molecules that are found, for example, in aromas. The improvements can range from 30% up to around 60%, depending on the host polymer.
“Some polymers are less favourable to the solution than others and working out where it works best has been a hard nut to crack,” says Bynum. “But we’ve come a long way. We have developed lots of very effective screening techniques so we can now predict outcomes quite well.” He says the expertise required in using the additives has seen Milliken change the way it interfaces with the market for this type of product.
Bynum points out that UltraGuard may
produce greater improvements in polymers that have lower inherent barrier than higher-barrier polymers. Factors that need to be taken into consideration include density, melt flow index and molecular weight distribution. UltraGuard also changes the role that film thickness plays (Figure 5) and results in improved optics.
Processing aids Polyfil Corp has developed a high-performance line of polymer processing aid (PPA) concentrates based on what it says are superior chemistries together with optimised particle size dispersion. “This combination brings previously unattainable performance and efficiency to the extrusion industry allowing processors to improve yields and productivity,” it says. “A unique interfacial agent and the most advanced fluoroelastomer technol- ogy combine to make these PPAs the most
versatile in the industry today.” The company says that to make these concen-
trates even more potent, it employs specialised compounding methods that ensure the fluoroelas- tomer particles are dispersed for optimised performance at the film extrusion stage. “Polyfil’s PPAs more than pay for themselves by allowing extruders to reduce start-up waste, increase production rates, and improve extrusion line utility,” the company claims. “On blown film lines, excellent flatness is achieved while melt fracture and port lines are easily eliminated twice as fast using only half as much additive compared to conventional processing aids. “Perhaps the greatest advantage of this new technology, however, is its ability to be used in higher temperature applications. Cast film extruders and extrusion coaters are able to utilise these new PPA grades at temperatures as high as 300°C, unlike most other PPAs on the market which cannot be used effectively above 240°C,” the company claims. Time between die-lip cleanings due to build-up
are said to be greatly extended due to combination of additive performance and thermal stability. Polyfil says a recent study showed it was able to extend the time between die cleanings by 400% for a multilayer extrusion customer using a 1% loading of its PAC-0001-21LL concentrate.
Figure 5: Effect of UltraGuard and film thickness on water vapour transmission rate of two different grades of PE. Grades differ in density, melt index, and ratio of indices at high (21.6 kg) and standard (2.16 kg) loads – a measure of molecular weight distribution. Source: Milliken
56 COMPOUNDING WORLD | January 2018
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.dowcorning.com �
www.croda.com �
www.ampacet.com �
www.tosaf.com �
www.clariant.com �
www.milliken.com �
www.polyfilcorp.com
www.compoundingworld.com
PHOTO: MILLIKEN
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