Page 57 - Plastics News October 2016
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Technology
Nanoparticle coating for plasticating screws offers greater wear
resistance
Atechnology that uses exceedingly tiny tungsten carbide content above 35%, Nordson supplies the high-hardness
has yielded a coating for single and twin plasticating coating Xaloy® X-8000™.
screws that resists abrasive and corrosive wear better
than standard coatings applied by high-velocity oxygen New Xaloy MPX technology can be employed across the
fuel (HVOF) thermal spray. Nordson Corporation will full range of screw diameters and may be applied to
introduce the technology at K 2016. the entire screw or to specific areas. Standard layer
thickness is 300 microns, with variations depending on
The new Xaloy® MPX™ the area of the screw. The MPX screw coating should be
thermal spray coating used with a barrel lined with Nordson’s Xaloy® X-800®
from Nordson is made nickel / tungsten carbide alloy or a comparable inlay.
up of particles only 5 Xaloy MPX technology expands Nordson’s offering of
microns in diameter. screw encapsulations for high-wear applications. The
Consisting primarily Xaloy® X-8000™ coating is a nickel-based alloy with high
of tungsten carbide, tungsten carbide content that is first applied in an HVOF
the particles are process, then fused to the parent metal of the screw to
six to seven times form a metallurgical bond.
smaller than those in standard HVOF coatings and more
densely packed owing to a uniform spherical shape Dynamically-evolving
produced in a controlled plasma process. The combination polymers discovered
of ultra-fine particle size, higher coating density, and a
2.5 times greater application velocity results in a stronger Research led by Rein Ulijn,
bond with the parent metal of the screw and improved Director of the CUNY
resistance to wear. Advanced Science Research
Center (ASRC)'s Nanoscience
Compared with standard HVOF tungsten carbide coatings, Initiative and Professor
the Xaloy MPX technology exhibits 61% less mass loss in of Chemistry at Hunter
ASTM G65 abrasion testing, 18% less mass loss in ASTM College, has paved the way for the development of
G77 sliding wear testing, and 8.5% greater bond strength dynamically-evolving polymers that form spontaneously
in ASTM C633 bond testing. As an example of corrosion by adapting to their environment, which may lead to a
resistance, the Xaloy MPX coating survived more than number of product possibilities including drug delivery,
1,000 hours of salt fog testing, in part because of its food science and cosmetics, the results of which were
near-zero porosity. “Nordson’s Xaloy MPX screw coating published today in Nature Nanotechnology. By allowing
provides best-in-class wear protection compared with these peptides; strings of polymers composed of amino
standard HVOF coatings, and its higher bond strength acids; to continuously reorganize their sequences, they
eliminates potential for chipping,” said Mark Colella, will eventually form those polymers that are most
global product manager for the Xaloy brand. “This new suited to the environment at the expense of less favored
technology extends the working life of screws in extrusion structures. This method, which is inspired by the
and injection molding, enabling processors to work with principles of evolution, allowed Ulijn's team to identify
some of today’s most challenging materials.” Nordson a range of heretofore unseen peptide-based materials.
recommends the Xaloy MPX technology for resisting The new approach allows for unbiased discovery by
abrasion from compounds with medium (15 to 35%) filler self-selection of optimized structures.
loadings and for resisting corrosion from halogenated
materials, including flame retardants and PVC. For filler
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