WHY DID MY SPARE TIRE GO BAD?

A tire is made up of polymers which are
very susceptible to damage from ultraviolet light and ozone.

To protect against UV, the manufactures mix a sacrificial element
with the polymers called carbon black. There are other sacrificial
substances (also called UV stabilizers) that can be used but
carbon black is by far the cheapest. This is why tires are black.

The carbon black will absorb the UV rays and convert it into heat
which dissipates harmlessly saving the polymer from damage.

(25 years ago, manufacturers came out with a tire using another
sacrificial ingredient. The tires were translucent and had lights
inside that would light up at night making the tire glow. The tires
had different colors. It was impractical as the stabilizers were too
expensive and it would not sell.)

As the carbon black is sacrificed over time the tire will turn gray.

Ozone is the second agent that will deteriorate a tire.
Manufacturers mix a special wax with the polymer that is slowly
squeezed to the surface as the tire is flexed in use. The wax puts
a barrier between the oxone and the rubber. It is also sacrificial
as it is slowly eaten away by the ozone. When the ozone reaches
the polymer it causes it to dry, check and finally crack. The side
wall will eventually fail.

That is why a spare tire on a trailer will deteriorate while the ones
on ground remain in good shape. It is also why a trailer that is not
used will have its’ tires go bad far sooner than one on the ground.
Agents from the car parts store that make tires look black and
shiny remove this wax and hasten the demise of the tire. These are
petrochemicals and silicones. They can cancel the tire warranty.

Vinyls like on your boat cushions are made of polyvinyl chlorides
with a plasticizer. The plasticizer keeps the vinyl soft and supple.
Vinyl has a surface layer called the "topcoat" which keeps the
plasticizers from evaporating away. When this happens, the vinyl
become brittle and will crack.

The surface layer is slowly destroyed by UV light, the plasticizer
evaporates and the cushion is ruined. To keep the topcoat intact,
never use house hold cleaners or abrasives. Petroleum and
silicone products attack the top coat. Use Ivory Soap, warm water
and a soft cloth.

To kill mildew, use four parts water to one part ammonia. For bad
mildew add a little hydrogen peroxide. Then rise with water.

Fiberglass also has a protective surface called the gelcoat. It made
of made of polyester resin and also is damaged by UV light. Colored
gelcoat degrades faster.

So how do we protect our boats, tires and cushion? Keeping them
out of the direct sun helps cut down the UV exposure. Spare tires
can have acrylic covers put over them. Acrylic cloth is very
resistant to UV. Cushions and kayaks can be stored inside. An
acrylic awning is great. Never clean them with harsh chemicals, use
soap and water. Use your boat trailer once in awhile to keep the waxes
coming to the surface and rotate with the spare tire. There are 2
products that I know of that can be placed on rubber, vinyl and
fiberglass as a sacrificial layer to the UV and ozone. They each
last about a month so you have to keep putting them on.

They are "303 Protectant" and "Turtle Wax Formula 2001." 303 is
available from West Marine and is very expensive, so use with
care. 2001 is available from car parts stores and is much
cheaper. To save money, you can buy a large container of either
one and keep refilling spray bottles. Don’t use the 2001 on mats,
running boards or fiberglass where you may walk as it makes
things very slippery. 303 is much safer here and will restore faded
color. Waxes on fiberglass which do not inhibit the UV prevent the
303 or 2001 from forming a barrier, it beads. Just wait a month and
the wax will be degraded away by the UV.

David Brinker AP

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