Page 27 - Plastics News August 2021

FEATURE

our know-how, we will develop new collaboration and sustainability to of new process and material solutions
processes for sustainable packaging help our customers achieve their goals in this important market segment.
solutions together with SABIC,” and drive the industry forward. The Together, we will leverage our synergies
Application Center will accelerate the to stimulate value chain interaction,
In addition to Netstal’s state-of-the-art
injection molding, in-mold labeling and pace at which we bring new material identify new leads and help our customers
part handling capabilities, the Application and processing technologies to our joint succeed.” SABIC’s Waleed Al Shalfan
Center provides advanced tooling and customers while we engage with them V.P, Technology and Innovation for
testing equipment. First new systems more closely to embrace global trends, Polymers, “The joint Application Center
installed by SABIC include molding turn challenges into opportunities and brings new momentum in how we grow
equipment designed to investigate accelerate the development of both and implement our expertise in polymer
injection compression molding options profitable and sustainable thin-wall science and processing from a more
and test the mechanical properties of thin- packaging solutions.” Renzo Davatz CEO collaborative approach. The value chain
wall packaging applications. Said Abdullah KraussMaffei HighPerformance said, interactions and innovation sessions
Al-Otaibi, SABIC general manager “We have a long history of innovation with customers will further enhance
engineering thermoplastics business & in thin-wall injection molding and our understanding and will enable us to
market solutions, petrochemicals “This welcome the collaboration with SABIC, respond more efficiently and effectively
significant milestone underscores our who share our values of ideation and to our customers’ needs and create lasting
continuous investment in innovation, commitment to the further development value for all players, industry and society.

Understanding Roll Deflection In Sheet Processing

Jim Frankland

Nowadays, with the conversion of many sheet products to polypropylene, this has resulted in many
roll stacks having unacceptable roll deflection, resulting in sheet that is crowned. One needs to un-
derstand how the variables contribute to the separating force.

any of the older sheet stacks although to a lesser degree, the larger top
Mstill in use today were made for roll only reduces—but not eliminates—
polystyrene or other easily deformed the problem. So the issue with excessive
polymers. In these stacks, the top roll was deflection occurs predominantly with
usually smaller in diameter to facilitate an thinner PP sheet. With most thin sheet,
easier and safer “string-up” of the line the shear rates are typically low in the
(Fig.1). Since the polymer contact time roll nip, so there is little shear thinning to
with the top roll is only a few inches, the consider except at very high line speeds.
smaller roll causes almost no cooling. But Roll radius is squared in the calculation,
nowadays, with the conversion of many so its easy to see how roll diameter
sheet products to polypropylene, this resolves the deflection issues.
has resulted in many roll stacks having One needs to understand how the
unacceptable roll deflection, resulting In old-style stacks designed for PS, the variables contribute to the separating
in sheet that is crowned. Polypropylene top roll was usually smaller in diameter force. Taking the bank width times the
requires greater nip force to calender due to facilitate easier and safer “string-up” separating force per inch equals the
to its viscoelastic properties as well as its of the line. Adding a larger-diameter total separating force. That can then be
tendency to increase in viscosity under top roll to an existing roll stack requires factored into standard beam calculations
certain levels of strain. very extensive machine modifications; to determine the roll deflection. The best
and if the middle roll is also deflecting, way to determine the separating force is

26 PLASTICS NEWS AUGUST 2021 27 PLASTICS NEWS AUGUST 2021