Laminates
Last updated: February 12, 2009.
Have you ever fastened sticky-backed plastic onto a book to
protect the cover? Or glued cardboard to paper to make it stronger?
Perhaps you've coated a poster you've printed on your computer with
plastic to make it weatherproof? If you've
done any of these things, you've made yourself a laminate: a material
formed by bonding together layers of two or more other materials. Let's take a closer
look at laminates and how they work!
Photo: Laminating a paper poster in a heat-treating machine.
Photo by Michael Winter courtesy of US Navy.
What are laminates?
You'll find your dictionary defines a lamina as a thin sheet
or plate of material: a layer, in other words. Fix two or more sheets
of material together and you get a laminate, which is essentially
just a material made up of layers. Since the layers are usually
different materials, laminates are examples of composites (made of two or more different materials). A laminate isn't
simply several layers of materials: the materials have to be permanently bonded
together with something like adhesive, so they behave as one
material—not several.
Why would you want to make a laminate? Generally, because a
material you'd normally use by itself (say paper, wood, or glass)
isn't strong or durable enough to survive by itself. Paper isn't
waterproof, for example, while plastic is relatively hard to print
on. But what if you print on the paper then coat it with plastic? The
laminated composite material you've made gives you the best of both
worlds.
Photo: These inexpensive, laminated "wooden" bookshelves are much cheaper and lighter than solid wooden ones. The main body of each shelf is made of inexpensive chipboard coated with a plastic finish that has a wood grain. You notice they're laminates only when the glue fails, as it has here, and the coating starts to peel off—something that never happens with real wood!
What are laminates used for?
Laminates tend to be based on four main materials: wood, glass, fabric, and paper.
Wood
Laminated floors are very popular because they're really hard
wearing. Unlike a traditional hard wood floor, a laminate floor is
typically made of four layers. The top might be something like a thin
layer of transparent plastic designed to resist stains and scratches.
Underneath that, there's a thin layer of patterned wood (or even paper
printed with a wood pattern) that gives the floor its attractive appearance. The next layer is the core:
the bulk of the material, made from low-grade fiberboard. Finally, on
the base, there's a thin layer of hard, moisture-proof board. Many
low-cost furniture products that resemble solid wood are actually
laminates made of lower-grade wood products (known as chipboard or
particle board) with a thin coating of veneer, plastic, or even
paper. The main drawback of laminated floors is that they can split apart and warp
if they get wet.
Photo: A typical laminated wooden floor.
Glass
Car windshields and bulletproof glass are
actually very heavy laminates made from several layers of glass and plastic. The outer
layers of glass are weatherproof and scratchproof, while the inner
plastic layers provide strength and a small amount of flexibility to
stop the glass from shattering. You can read more in our main
article about bulletproof glass.
Photo: Bulletproof glass is an energy-absorbing sandwich of glass and plastic.
Picture courtesy of US Air Force.
Fabric
Most shoes and many outdoor clothes are made from laminated
materials. A typical raincoat usually has a waterproof membrane
between a hard-wearing outer layer and a soft, comfortable inner layer. Sometimes
the membrane is directly bonded to the inner and outer layers to make
a very tough and durable piece of clothing; this is known as a
3-layer laminate. If the membrane is bonded to the outer fabric with
no inner lining, that's called a 2.5 layer laminate. Waterproof
clothes made this way tend to be more "breathable" than 3-layer
laminates since moisture can escape more easily.
Photo: A laminated 2.5-layer waterproof nylon jacket by eco-friendly Welsh firm Howies. It looks like a single layer of nylon, but it's actually two layers laminated together. You can tell that because the inner and outer surfaces look totally different. The ultra-waterproof black outer layer is made of rip-stop nylon. The inner white surface is an extra coating that improves air circulation and breathability.
Paper
Many people own small laminating machines that coat pieces of
paper, card, or photographs in a thin but tough layer of durable
plastic. You simply buy a packet of plastic "pouches", insert
your paper item inside, and run this "sandwich" through the
machine. It heats or glues the plastic and presses it firmly together
to make a weatherproof and durable coating. Identification (ID) cards
and credit cards are also laminated with clear plastic so they can survive
several years of use.
