Bodyboard Materials, as seen by LMVogue
WHAT ARE THE MATERIALS USED?
Generally speaking, bodyboards have always been manufactured using closely related members of the polyolefin
polymer family. The original bodyboard was basically a slab of polyethylene foam, and the majority of
bodyboards still use materials that are very closely related to this.
"Plastics are polymers. What is a polymer? The simplest definition of a polymer is something made of many units. Think
of a polymer as a chain. Each link of the chain is the "mer" or basic unit that is made of carbon, hydrogen, oxygen,
and/or silicon. To make the chain, many links or "mers" are hooked or polymerized together. Polymerization can be
demonstrated by (hooking together hundreds of paper clips to form chains)".
An olefin is a hydrocarbon with a carbon-carbon double bond. Polyolefins are polymers created
by breaking this double bond, with the polymerisation process then joining mers together at the available carbons.
Polyethylene (PE, polythene): Polyethylene, in it's various densities and guises, is still the
most popular material used in bodyboard manufacturing. Ethylene is the simplest of the olefins, being only two
carbons with four hydrogens attached. When it is polymerised, it basically forms a long repeating chain of carbons
with hydrogens hanging off both sides.
|Ethylene with C=C bond
||PE Polymer segment, broken C=C bond
now available to bond with other mers
The PE foams used in bodyboard manufacturing are usually around 8lb/cubic foot density for decks/rails, and about 2lb density for cores. The standard densities have been gradually increasing as performance increases, as PE is fairly flexible and susceptible to creasing - higher densities make the foam more rigid - however this is also a matter of cell-size, ie. the same density could be achieved with either larger bubbles with thicker walls, or smaller bubbles with thinner walls, each of which has it's own pros and cons.
Cross-linked PE is a modification of the basic PE polymer, in that the long polymer chains, which are usually separate in
PE, are periodically linked together. This linking reduces the degree of freedom of the chains, which generally results in a
more rigid polymer which is also less susceptible to permanent deformation (ie., creasing).
Surlyn is essentially a modified low-density polyethylene. It is the random copolymer poly(ethylene-co-methacrylic acid) (EMAA), but the methacrylic acid content is typically low. The introduction of methacrylic acid forms a kind of crystalline ionic compound, with a controlled amount of short-chain branching, which greatly alters the viscoelastic properties of the PE.
What does this mean? Basically, surlyn is a springier, more resilient form of low-density PE.
Polypropylene (PP, Polypro): Polypro is kind of like PE's mutant big brother. Propylene is similar in structure to Ethylene, but it has a Carbon-Hydrogen side-chain
in place of one of the Hydrogens found in Ethylene. The polymerisation process occurs in the same way as with PE, but the properties of the resultant polymer are different due to the side-branching, which
restricts chain movement, resulting in a more rigid, more resilient polymer.
|Propylene with C=C bond, single C side chain
||PP Polymer segment, broken C=C bond
now available to bond with other mers, single C
side chain inhibits movement
Polypropylene also has higher melting temperatures, and as such makes it difficult to heat-laminate PE and PP together (ie. PP core with PE deck/rails and surlyn slick). This problem has recently been reduced by introducing a substrate between the two, a copolymer, poly(ethylene-co-propylene). Essentially this means PE can be heat-laminated to the PE component of the copolymer, while PP can be heat-laminated to the PP component. It's not quite that simple, but that's the basic idea behind it.
This P(E-co-P) substrate also plays a major role in board characteristics, depending on it's exact composition and density. As such, you may notice companies calling their cores different things, even though they may be using the same polypro core, as the substrate is in essence a co-core, and changes the
overall way the core reacts.