Passing the smell test

Struktol has two additives aimed at reducing odor and improving processing of plastics with high recycled content.The additives originally were developed for another application but have become increasingly popular for use with recycled resin, according to Mike Mikolay, senior fellow at Struktol.

The two products are labeled RP 17, primarily an odor mask to improve the final product’s scent, and RP 53, an odor neutralizer. The additives work with polypropylene and polyethylene resins.

RP 17 can be added during compounding, extrusion or molding to eliminate or mask undesirable odors caused by postindustrial or postconsumer material or other ingredients added during compounding. It especially is useful in automotive applications where higher process temperatures often make odors more noticeable.

At low dosages, Struktol says RP 17 tends to neutralize odor, while higher dosages will impart a fresh, “clean” odor. The company recommends a starting dose of 0.5 percent and typical doses are 1 percent to 3 percent.

RP 17 is white pastille with a dropping point of 221 F to 248 F and specific gravity of 0.94. A pastille is like a resin pellet but more spherical. The company says it offers consistent melt behavior and seamless integration into processing lines.

It is available in 55-pound bags and can be stored for at least two years.

RP 53 also can be added during compounding, extrusion or injection molding to mask odors and is suitable for automotive applications where high temperatures increase odors.

It targets mercaptans, amines and phosphites and has volatile organic compound absorption properties.

Recommended starting dosage is 0.5 percent, but more or less may be used for desired results, according to Struktol.

It is an off-white pastille with a dropping point of 212 F to 266 F and specific gravity of 1.07. It is also sold in 55-pound bags and can be stored for at least two years.

“Critically, these additives support sustainability initiatives by enabling the use of 100 percent recycled-content compounds without compromising the end product’s sensory or physical quality,” Struktol says in a news release.

RP 17 also functions as a process lubricant and mold release agent, Struktol says, improving processability, reducing plate-out, easing part release and minimizing cleaning requirements.

The odor masking and odor neutralizing elements of the additives use a Struktol lubricant as a carrier, making each of them a dual-function additive, according to Mikolay.

Struktol also says both additives improve dispersion of fillers and recycled content, reduce processing time and improve the surface finish of end products.

Because small amounts of RP 17 or RP 53 typically are used, they do not change the final product’s recyclability. They typically do not wear off very quickly because plastic has low permeability.

“Whatever is inside tends to stay inside longer,” Mikolay says.

Both products can be added anywhere along the processing chain, but compounders tend to be the biggest users of odor-elimination additives.