Specialty Fabrics Review February 2020 - 54

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The seats on this luxury yacht are
damaged from mold and pink stain
bacteria, a typical problem for
marine and other outdoor fabrics.
Pink staining bacteria produces a
red liquid that diffuses into vinyl,
creating a stain that cannot be
cleaned. Antimicrobial topcoats
can help to prevent such damage.
Photo: APV Engineered Coatings.

Topcoat technology
When compounded performance additives in vinyl aren't enough,
antimicrobial lacquers and topcoats offer extra protection.
BY HUGH BARRETT

Inhibiting or reacting?
A truly effective antimicrobial topcoat
inhibits cell reproduction rather than
reacting with the organic cell, a process
that is difficult to control and may have
unforeseen consequences. For example,
a silver-based antimicrobial can break
down an organic coating because of its
catalytic nature. Silver can also affect
the cure rate of the coating process.

icrobes, such as bacteria and fungi, can live on a surface for months. Manufacturers of
flexible vinyl, films, fabrics and textiles use engineered antimicrobial (AM) lacquers
and barrier topcoats to offer an extra level of protection against harmful microbes,
even when they have incorporated AM additives or biocides into the vinyl formulation during
the compounding process. A liquid AM finish applied to a fabric or flexible vinyl provides
a bacteria-fighting layer directly on the surface and blocks the migration of the additives
in the vinyl, a food source for microbe growth, over time. Topcoats, finishes and lacquers
also protect against environmental stresses such as UV exposure, abrasion, oxidation and
biodeterioration of the substrate.
AM topcoats are especially effective for manufacturers of wallcoverings, upholstery,
thermoformable polyvinyl chloride (PVC) laminates, mass transit seating and a range of
other applications in health care, marine, hospitality and public and commercial facility
settings-anywhere high humidity and/or microbial contamination are significant problems.
PRODUCING FLEXIBLE VINYL
Flexible vinyl is made by mixing powdered PVC in a liquid plasticizer to produce a plastisol.
Additional ingredients such as fillers, pigments, flame retardants, smoke suppressants and heat
stabilizers are then mixed with the liquid plastisol to impart desired features. The plastisol is
cast on release paper, passes through an oven at about 320 degrees (F), and then is cooled to
form the flexible vinyl film. Next, cooled flexible vinyl film is either stripped of the release
paper and used as-is or coated to improve its properties and performance.
Flexible vinyl is subjected to a phenomenon called plasticizer migration, in which liquid
plasticizer is slowly squeezed out of the material over time due to pressure applied by intermolecular attractive forces between PVC molecules. Those attractive forces (cohesive energy
density) cause other ingredients with lower energy than PVC to be released as well. As the
plasticizer evaporates, creating the familiar "new car smell," the flexible vinyl loses flexibility
and eventually begins cracking.
Diffusion or migration of the plasticizer directly correlates to the performance and aesthetic
of the vinyl fabric. This migration also affects the performance of traditional lacquers, as the
plasticizer diffuses into the protective coating, opening a pathway for stains and microbial
growth to infiltrate the vinyl substrate.

54 REVIEW FEBRUARY 2020

Specialty Fabrics Review February 2020

Table of Contents for the Digital Edition of Specialty Fabrics Review February 2020