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Chemistry Reading Articles
Article 1: Bowling Balls
By Lauren K. Wolf
A chemist recently asked me to join his bowling team.
During the intense negotiation of my team contract, I
inquired about custom-made balls for our squadron.
Maybe a transparent ball with an intimidating skull in the center? Or perhaps a test tube or
beaker?
The joke was on me. My friend matter-of-factly replied: "Of course not. That kind of bowling
ball isn't used by the pros—it has terrible dynamics." Properly rebuked for my naïveté, I began
reading up on bowling science.
The game was invented by the ancient Egyptians, who made their bowling balls by carving
stone. Eons later, during the early 1900s, balls were made of wood and then rubber. Around
1960, bowling ball manufacturers used polyester resin for the first time, enabling the production
of plastic balls with bright, swirled colors.
Once polymers were introduced, the science of bowling took off. In fact, the materials chemistry
of bowling balls has advanced so much that a national governing body, the U.S. Bowling
Congress (USBC), now sets regulations on ball manufacturing. "We're always looking at ways to
better control the environment of bowling," says Paul Ridenour, a research engineer for the
USBC Specifications & Certifications team.
Ten-pin bowling balls are no longer made just of hard solid rubber or plastic. "Modern-day
bowling balls are made from a three-piece construction," Ridenour says. The pieces include an
inner core, an outer "filler" core, and a shell (or coverstock, in bowling lingo) that work in
concert to achieve the ultimate in success on the bowling lanes—the strike.
"The specific, desired weight of a ball is achieved by changing the density of the inner parts,"
says Victor Marion, a technical service representative at Brigham City, Utah-based manufacturer
Storm Products. Heavy 16-lb bowling balls are quite dense, but balls weighing 10 lb or less have
such a low density that they can float in water. The exact materials that go into making each part
of the ball, Marion says, are considered "proprietary
technologies that are closely guarded."
But "it's all straight polymer chemistry," Ridenour notes.
The inner core, the shape of which influences rotational
properties of the ball, often is made of urethane, and the
outer core can be some combination of calcium carbonate,
barium sulfate, and emulsifying agents, he adds. Shell
materials vary depending on whether a bowler is using the
ball to go for a strike or "pick up" a spare.
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With a little help from a 7-foot-tall robot named Harry, USBC investigators determined at their
climate-controlled bowling research facility in Wisconsin that a ball's surface roughness is the
parameter that most affects its overall performance.
Most professional bowlers, for whom anything less than a strike amounts to failure, use balls
with reactive resin shells that can create a lot of traction-generating friction with the lane,
Ridenour notes. Like tire treads in snow, the surface pores in a reactive resin ball can absorb the
mineral oil used to lubricate the bowling lane and allow the ball to gain traction as it rolls. Rather
than skidding straight down the lane as hard-surfaced, lower friction polyester coverstock balls
do, reactive resin balls can "hook" or curve across the lane, given a little applied "spin" from the
bowler. Pro bowlers use this hooking technique to gracefully arc the ball into the pins, aiming
slightly behind the head pin for a sweet spot called the pocket.
First marketed in the early 1990s, reactive resin shells—used to help improve ball friction—are a
mixture of urethane and a proprietary ingredient that generates surface porosity while the
polymer base cures. Ball makers mix isocyanates and polyols to form the base urethane resin, but
companies are loath to reveal the exact identity of the various reactive plasticizer ingredients
they use, Ridenour says.
Some manufacturers have gone even further than reactive resins. In the late 1990s, a particlebased bowling ball coverstock was developed with a single purpose: more aggressive friction
with the lane. These shells still have a urethane base but are also mixed with particulates, which
can be sharp or hollow and made of "anything from calcium carbonate to potter's glass,"
Ridenour says.
The USBC tests led to a new specification on bowling ball surface roughness that will take effect
next year. Peak-to-valley average roughness can no longer be more than 50 microinches, as
measured by a profilometer, the use of which "is akin to dragging a record needle across the
surface of the bowling ball," Ridenour says. USBC is also planning future studies on how a
bowling ball's performance relates to its materials and surface details: They will use a differential
scanning calorimeter to measure the glass transition temperatures of shell materials.
Regretably, the science of bowling indicates that the plastic Elvis-themed bowling ball I've had
my eye on may not be the best choice for my new bowling career. But there are other ways of
personalizing your bowling ball, my chemist friend told me. "I bought a ball that smells like
blueberries," he said.
For those who want a bit of aromatherapy while they bowl, reactive resin and particle bowling
balls are available in a variety of fragrances. Incorporated into the coverstock, "the fragrances are
engineered to last for at least 10 years," Storm's Marion says. "With the addition of a scented ball
to the bag" where "many bowlers store their shoes," he adds, the benefit of a fragrant ball is
undeniable. Move over Elvis, here comes chocolate-covered cherry.
Chemical & Engineering News
ISSN 0009-2347
Copyright © 2014 American Chemical Society
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Article 2: Contact Lens Solutions
By: Jyllian Kemsley
SLIPPING CLEANING FLUID into one's eye is not likely to be high on anyone's list of
hobbies, but contact lens wearers do it daily. After spending the night in cleaning solution, a
dripping contact lens is inserted into the eye—ideally, without causing any discomfort.
Historically, putting lens cleaning solution in the eye wasn't an option. Twenty years ago,
cleaning contact lenses was generally a multistep process requiring a cleaner, a disinfecting
agent, saline for rinsing off the cleaner or disinfecting agent, and an occasional enzyme tablet to
remove protein buildup from tear fluid.
But the more steps there are, the more likely wearers won't
follow them correctly, or at all—increasing the likelihood
of sight-threatening infections. Teenagers just starting to
use contact lenses are particularly likely not to comply with
complicated systems, says Srini Venkatesh, senior director
for lens care product development at Bausch & Lomb.
In response, manufacturers developed one-step systems for the soft lenses that dominate the
market today. These systems come in two types, peroxide and multipurpose solutions. Both
contain cleaners, such as bisphosphonate compounds, to break down proteins adhering to lenses
or surfactants, such as block copolymers, to interfere with the protein-lens interactions. The
solutions also typically contain moisturizing or conditioning agents such as cellulose, propylene
glycol, or polyvinyl pyrrolidone, ingredients that Ciba Vision's global head of research, Lynn
Winterton, hopes will make users say, "Wow, this feels great!" There are also buffers to maintain
an eye-friendly pH and preservatives to maintain shelf life.
The difference between the peroxide and multipurpose solutions lies in how they disinfect.
Peroxide systems, as their name would indicate, use peroxide as the disinfection agent. They
typically involve two components: a 3% peroxide solution and a neutralization catalyst. While
the peroxide does a fine job of killing whatever microbes might have latched onto lenses, it's not
very eye-friendly, so a platinum, palladium, or silver catalyst is used in the contact lens case to
completely neutralize the solution by reducing the peroxide to form oxygen and water.
The peroxide neutralization reaction itself, as well as the O2 product bubbling through the
solution, may further help to kill microbes, Venkatesh says. Typically, a lens wearer puts their
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lenses in the case with the peroxide solution and
catalyst, and returns four to six hours later to find their
lenses ready to wear.
Peroxide, of course, will oxidize many things other
than microbes, so one tricky aspect to solution
formulation is to find cleaners or conditioning agents
that can survive storage in a peroxide solution without
degradation.
Using polymers
instead of monomers
provides effective
antimicrobial activity
while still being gentle
to the eye.
In contrast to peroxide solutions, multipurpose
solutions typically use a polymeric disinfection agent
such as polyhexamethylene biguanide or polyquaternium, which incorporates quaternary
ammonium centers. As with peroxide solutions, the disinfectant presents the biggest challenge to
solution developers, although for a different reason: The solution, including the disinfectant,
must be gentle enough that lens wearers can put their lenses directly into their eyes without
rinsing.
The polymers, therefore, are a compromise. They're made from monomeric building blocks that
are effective at killing microbes but are too harsh to go in the eye in that form. Using polymers
instead of monomers provides effective antimicrobial activity while still being gentle to the eye.
One active area of contact lens solution research, Winterton says, involves finding ways to
eliminate preservatives from solutions so there's one less thing going into the eye. Another is to
develop dual-purpose conditioning agents that not only will keep lenses comfortable but will also
repel microbes.
Venkatesh notes that contact lens solutions offer chemists unique challenges. The solutions have
six or seven ingredients whose compatibilities must be balanced, but overall more than 95% of
the content is water. In addition to being mindful of chemical interactions, solution chemists
must also be cognizant of ingredients adsorbing to bottles and pipes. "When you start at a really
low concentration, if it drops even by 10% you can have huge differences in performance,"
Venkatesh says. "There's an art to developing solutions and a lot of skill."
Chemical & Engineering News
ISSN 0009-2347
Copyright © 2014 American Chemical Society
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