Essays. FSF Columns

by Bruce Sterling

  market in which every major national economy has a stake. The

  adhesives industry has its own specialty magazines, such as

  Adhesives Age andSAMPE Journal; its own trade groups, like the

  Adhesives Manufacturers Association, The Adhesion Society, and the

  Adhesives and Sealant Council; and its own seminars, workshops and

  technical conferences. Adhesives corporations like 3M, National

  Starch, Eastman Kodak, Sumitomo, and Henkel are among the world’s

  most potent technical industries.

  Given all this, it’s amazing how little is definitively known

  about how glue actually works — the actual science of adhesion.

  There are quite good industrial rules-of-thumb for creating glues;

  industrial technicians can now combine all kinds of arcane

  ingredients to design glues with well-defined specifications:

  qualities such as shear strength, green strength, tack, electrical

  conductivity, transparency, and impact resistance. But when it

  comes to actually describing why glue is sticky, it’s a different

  matter, and a far from simple one.

  A good glue has low surface tension; it spreads rapidly and

  thoroughly, so that it will wet the entire surface of the substrate.

  Good wetting is a key to strong adhesive bonds; bad wetting leads

  to problems like “starved joints,” and crannies full of trapped air,

  moisture, or other atmospheric contaminants, which can weaken the

  bond.

  But it is not enough just to wet a surface thoroughly; if that

  were the case, then water would be a glue. Liquid glue changes

  form; it cures, creating a solid interface between surfaces that

  becomes a permanent bond.

  The exact nature of that bond is pretty much anybody’s guess.

  There are no less than four major physico-chemical theories about

  what makes things stick: mechanical theory, adsorption theory,

  electrostatic theory and diffusion theory. Perhaps molecular strands

  of glue become physically tangled and hooked around irregularities

  in the surface, seeping into microscopic pores and cracks. Or, glue

  molecules may be attracted by covalent bonds, or acid-base

  interactions, or exotic van der Waals forces and London dispersion

  forces, which have to do with arcane dipolar resonances between

  magnetically imbalanced molecules. Diffusion theorists favor the

  idea that glue actually blends into the top few hundred molecules of

  the contact surface.

  Different glues and different substrates have very different

  chemical constituents. It’s likely that all of these processes may have

  something to do with the nature of what we call “stickiness” — that

  everybody’s right, only in different ways and under different

  circumstances.

  In 1989 the National Science Foundation formally established

  the Center for Polymeric Adhesives and Composites. This Center’s

  charter is to establish “a coherent philosophy and systematic

  methodology for the creation of new and advanced polymeric

  adhesives” — in other words, to bring genuine detailed scientific

  understanding to a process hitherto dominated by industrial rules of

  thumb. The Center has been inventing new adhesion test methods

  involving vacuum ovens, interferometers, and infrared microscopes,

  and is establishing computer models of the adhesion process. The

  Center’s corporate sponsors — Amoco, Boeing, DuPont, Exxon,

  Hoechst Celanese, IBM, Monsanto, Philips, and Shell, to name a few of

  them — are wishing them all the best.

  We can study the basics of glue through examining one typical

  candidate. Let’s examine one well-known superstar of modern

  adhesion: that wondrous and well-nigh legendary substance known

  as “superglue.” Superglue, which also travels under the aliases of

  SuperBonder, Permabond, Pronto, Black Max, Alpha Ace, Krazy Glue

  and (in Mexico) Kola Loka, is known to chemists as cyanoacrylate

  (C5H5NO2).

  Cyanoacrylate was first discovered in 1942 in a search for

  materials to make clear plastic gunsights for the second world war.

  The American researchers quickly rejected cyanoacrylate because

  the wretched stuff stuck to everything and made a horrible mess. In

  1951, cyanoacrylate was rediscovered by Eastman Kodak researchers

  Harry Coover and Fred Joyner, who ruined a perfectly useful

  refractometer with it — and then recognized its true potential.

  Cyanoacrylate became known as Eastman compound #910. Eastman

  910 first captured the popular imagination in 1958, when Dr Coover

  appeared on the “I’ve Got a Secret” TV game show and lifted host

  Gary Moore off the floor with a single drop of the stuff.

  This stunt still makes very good television and cyanoacrylate

  now has a yearly commercial market of $325 million.

  Cyanoacrylate is an especially lovely and appealing glue,

  because it is (relatively) nontoxic, very fast-acting, extremely strong,

  needs no other mixer or catalyst, sticks with a gentle touch, and does

  not require any fancy industrial gizmos such as ovens, presses, vices,

  clamps, or autoclaves. Actually, cyanoacrylate does require a

  chemical trigger to cause it to set, but with amazing convenience, that

  trigger is the hydroxyl ions in common water. And under natural

  atmospheric conditions, a thin layer of water is naturally present on

  almost any surface one might want to glue.

  Cyanoacrylate is a “thermosetting adhesive,” which means that

  (unlike sealing wax, pitch, and other “hot melt” adhesives) it cannot

  be heated and softened repeatedly. As it cures and sets,

  cyanoacrylate becomes permanently crosslinked, forming a tough

  and permanent polymer plastic.

  In its natural state in its native Superglue tube from the

  convenience store, a molecule of cyanoacrylate looks something like

  this:

  CN

  /

  CH2=C

 

  COOR

  The R is a variable (an “alkyl group”) which slightly changes

  the character of the molecule; cyanoacrylate is commercially

  available in ethyl, methyl, isopropyl, allyl, butyl, isobutyl,

  methoxyethyl, and ethoxyethyl cyanoacrylate esters. These

  chemical variants have slightly different setting properties and

  degrees of gooiness.

  After setting or “ionic polymerization,” however, Superglue

  looks something like this:

  CN CN CN

  | | |

  - CH2C -(CH2C)-(CH2C)- (etc. etc. etc)

  | | |

  COOR COOR COOR

  The single cyanoacrylate “monomer” joins up like a series of

  plastic popper-beads, becoming a long chain. Within the thickening

  liquid glue, these growing chains whip about through Brownian

  motion, a process technically known as “reptation,” named after the

  crawling of snakes. As the reptating molecules thrash, then wriggle,

  then finally merely twitch, the once-thin and viscous liquid becomes

  a tough mass of fossilized, interpenetrating plastic molecular

  spaghetti.

  And it is strong. Even pure cyanoacrylate can lift a ton with a

  single square-inch bond, and
one advanced elastomer-modified ’80s

  mix, “Black Max” from Loctite Corporation, can go up to 3,100 pounds.

  This is enough strength to rip the surface right off most substrates.

  Unless it’s made of chrome steel, the object you’re gluing will likely

  give up the ghost well before a properly anchored layer of Superglue

  will.

  Superglue quickly found industrial uses in automotive trim,

  phonograph needle cartridges, video cassettes, transformer

  laminations, circuit boards, and sporting goods. But early superglues

  had definite drawbacks. The stuff dispersed so easily that it

  sometimes precipitated as vapor, forming a white film on surfaces

  where it wasn’t needed; this is known as “blooming.” Though

  extremely strong under tension, superglue was not very good at

  sudden lateral shocks or “shear forces,” which could cause the glue—

  bond to snap. Moisture weakened it, especially on metal-to-metal

  bonds, and prolonged exposure to heat would cook all the strength

  out of it.

  The stuff also coagulated inside the tube with annoying speed,

  turning into a useless and frustrating plastic lump that no amount of

  squeezing of pinpoking could budge — until the tube burst and and

  the thin slippery gush cemented one’s fingers, hair, and desk in a

  mummified membrane that only acetone could cut.

  Today, however, through a quiet process of incremental

  improvement, superglue has become more potent and more useful

  than ever. Modern superglues are packaged with stabilizers and

  thickeners and catalysts and gels, improving heat capacity, reducing

  brittleness, improving resistance to damp and acids and alkalis.

  Today the wicked stuff is basically getting into everything.

  Including people. In Europe, superglue is routinely used in

  surgery, actually gluing human flesh and viscera to replace sutures

  and hemostats. And Superglue is quite an old hand at attaching fake

  fingernails — a practice that has sometimes had grisly consequences

  when the tiny clear superglue bottle is mistaken for a bottle of

  eyedrops. (I haven’t the heart to detail the consequences of this

  mishap, but if you’re not squeamish you might try consulting The

  Journal of the American Medical Association, May 2, 1990 v263 n17

  p2301).

  Superglue is potent and almost magical stuff, the champion of

  popular glues and, in its own quiet way, something of an historical

  advent. There is something pleasantly marvelous, almost Arabian

  Nights-like, about a drop of liquid that can lift a ton; and yet one can

  buy the stuff anywhere today, and it’s cheap. There are many urban

  legends about terrible things done with superglue; car-doors locked

  forever, parking meters welded into useless lumps, and various tales

  of sexual vengeance that are little better than elaborate dirty jokes.

  There are also persistent rumors of real-life superglue muggings, in

  which victims are attached spreadeagled to cars or plate-glass

  windows, while their glue-wielding assailants rifle their pockets at

  leisure and then stroll off, leaving the victim helplessly immobilized.

  While superglue crime is hard to document, there is no

  question about its real-life use for law enforcement. The detection

  of fingerprints has been revolutionized with special kits of fuming

  ethyl-gel cyanoacrylate. The fumes from a ripped-open foil packet of

  chemically smoking superglue will settle and cure on the skin oils

  left in human fingerprints, turning the smear into a visible solid

  object. Thanks to superglue, the lightest touch on a weapon can

  become a lump of plastic guilt, cementing the perpetrator to his

  crime in a permanent bond.

  And surely it would be simple justice if the world’s first

  convicted superglue mugger were apprehended in just this way.

  “Creation Science”

  In the beginning, all geologists and biologists were creationists.

  This was only natural. In the early days of the Western scientific

  tradition, the Bible was by far the most impressive and potent source

  of historical and scientific knowledge.

  The very first Book of the Bible, Genesis, directly treated

  matters of deep geological import. Genesis presented a detailed

  account of God’s creation of the natural world, including the sea, the

  sky, land, plants, animals and mankind, from utter nothingness.

  Genesis also supplied a detailed account of a second event of

  enormous import to geologists: a universal Deluge.

  Theology was queen of sciences, and geology was one humble

  aspect of “natural theology.” The investigation of rocks and the

  structure of the landscape was a pious act, meant to reveal the full

  glory and intricacy of God’s design. Many of the foremost geologists

  of the 18th and 19th century were theologians: William Buckland,

  John Pye Smith, John Fleming, Adam Sedgewick. Charles Darwin

  himself was a onetime divinity student.

  Eventually the study of rocks and fossils, meant to complement

  the Biblical record, began to contradict it. There were published

  rumblings of discontent with the Genesis account as early as the

  1730s, but real trouble began with the formidable and direct

  challenges of Lyell’s uniformitarian theory of geology and his disciple

  Darwin’s evolution theory in biology. The painstaking evidence

  heaped in Lyell’s Principles of Geology and Darwin’s *Origin of

  Species* caused enormous controversy, but eventually carried the

  day in the scientific community.

  But convincing the scientific community was far from the end

  of the matter. For “creation science,” this was only the beginning.

  Most Americans today are “creationists” in the strict sense of

  that term. Polls indicate that over 90 percent of Americans believe

  that the universe exists because God created it. A Gallup poll in

  1991 established that a full 47 percent of the American populace

  further believes that God directly created humankind, in the present

  human form, less than ten thousand years ago.

  So “creationism” is not the view of an extremist minority in our

  society — quite the contrary. The real minority are the fewer than

  five percent of Americans who are strictly non-creationist. Rejecting

  divine intervention entirely leaves one with few solid or comforting

  answers, which perhaps accounts for this view’s unpopularity.

  Science offers no explanation whatever as to why the universe exists.

  It would appear that something went bang in a major fashion about

  fifteen billion years ago, but the scientific evidence for that — the

  three-degree background radiation, the Hubble constant and so forth

  — does not at all suggest why such an event should have happened

  in the first place.

  One doesn’t necessarily have to invoke divine will to explain

  the origin of the universe. One might speculate, for instance, that

  the reason there is Something instead of Nothing is because “Nothing

  is inherently unstable” and Nothingness simply exploded. There’s

  little scientific evidence to support such a speculation, however
, and

  few people in our society are that radically anti-theistic. The

  commonest view of the origin of the cosmos is “theistic creationism,”

  the belief that the Cosmos is the product of a divine supernatural

  action at the beginning of time.

  The creationist debate, therefore, has not generally been

  between strictly natural processes and strictly supernatural ones, but

  over how much supernaturalism or naturalism one is willing to

  admit into one’s worldview.

  How does one deal successfully with the dissonance between

  the word of God and the evidence in the physical world? Or the

  struggle, as Stephen Jay Gould puts it, between the Rock of Ages and

  the age of rocks?

  Let us assume, as a given, that the Bible as we know it today is

  divinely inspired and that there are no mistranslations, errors,

  ellipses, or deceptions within the text. Let us further assume that

  the account in Genesis is entirely factual and not metaphorical, poetic

  or mythical.

  Genesis says that the universe was created in six days. This

  divine process followed a well-defined schedule.

  Day 1. God created a dark, formless void of deep waters, then

  created light and separated light from darkness.

  Day 2. God established the vault of Heaven over the formless watery

  void.

  Day 3. God created dry land amidst the waters and established

  vegetation on the land.

  Day 4. God created the sun, the moon, and the stars, and set them

  into the vault of heaven.

  Day 5. God created the fish of the sea and the fowl of the air.

  Day 6. God created the beasts of the earth and created one male and

  one female human being.

  On Day 7, God rested.

  Humanity thus began on the sixth day of creation. Mankind is

  one day younger than birds, two days younger than plants, and

  slightly younger than mammals. How are we to reconcile this with

  scientific evidence suggesting that the earth is over 4 billion years

  old and that life started as a single-celled ooze some three billion

  years ago?

  The first method of reconciliation is known as “gap theory.”

  The very first verse of Genesis declares that God created the heaven

  and the earth, but God did not establish “Day” and “Night” until the