All about Ski and Snowboard Materials
A general overview of Snowboard materials
Snowboard base material
Snowboard and ski bases are generally produced from ultra-high molecular weight polyethylene, a dense, abrasion resistant plastic with low friction properites. Base material grades vary slightly in their density and additives, but all are capable of absorbing wax, and differ from regualar UHMW because they are specially treated for bonding with epoxy resin. P-tex, Isospeed, and Durasurf are the 3 main brand names in the industry, and all are high quality parts, used by most major manufacturers.
Base material is generally of two types - Extruded and Sintered. Extruded bases are made from polyethylene pellets melted down then forced under pressure through an extruder, which determines the thickness of the finished material. The finished material is usually sanded on one side of the material to increase its surface area (to aid in bonding), and is then also "flame treated" or Corona treated" to oxidize the plastic and give it better bonding properties. Natural UHMW has very poor bonding characteristics. Extruded base material is less expensive to produce, less abrasion resistant, and tends to hold less wax, and is thus generally slower than a properly structured and waxed sintered base. From a technical standpoint, most extruded bases have much lower molecular weight, higher shrinkage characteristics and more tensile creep than sintered bases. Extruded base (when not colored) also exhibits better clarity than sintered material.
Sintering involves crushing
polyethylene pellets together under high pressure. This causes them to melt
together and fuse, and the resulting sintered material is generally of higher
density, higher molecular mass, and exhibits better abrasion resistance than
extruded material. Sintered Base material as a rule has better wax absorbtion
characteristics, and ultimately better hydorphobic (water resistant) properties
as a result. Graphite and electra bases contain additional graphite additives
and cross linking agents added with the pellets during manufacturing. These
additives do several things - harden the plastic, decrease friction properties,
and conduct static electricity - all making the base slide better in the snow..
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wood cores
Most cores in modern snowboards are built from vertically laminated strips of wood. Using several pieces tends to make the core stronger and less likely to warp - a single piece of wood can contain knots and irregularities which can affect the strength and flex performance characteristics. By using several pieces these imperfections are reduced and the properties of the core tend to be more consistent. Often, a mixture of hardwood and softwood strips are combined to provide a balance of high strength to light weight. Choice of wood types varies, the most popular being spruce, fir, aspen, and poplar. The width of the wood laminates also has an effect on torsion - lots of narrow laminates are somewhat more resistant to twisting forces, but there is a higher proportion of glue to wood which can make the cores heavier. Most snowboard cores have approximately 20 vertical laminations, although cores that use veneer thickness lumber may have well over 100 vertical laminates.
alternative cores
A core can also be made of molded plastic or polyurethane foam, as well as a variety of other alternative materials. Polyurethane foam is the usual choice of material, and is available in sheet form to be cut and shaped, or may be injected into the mold during lamination (hence the term "injection molded"). Foam cores are light, strong enough for most requirements, and do not require as much labor to manufacture. Inexpensive polyurethane foam cores (called PU for short) sometimes do not retain their molded shape as well as wood cores, as the structure of the foam can break down over time as it is stressed, resulting in "dead" flex. Though this is not necessarily the case with high performance foam formulations, the manufacturers of wood core products have done an excellent job of discrediting all PU core boards as "cheap" and "low performance", when in reality there are some very high performance alternative materials used.
sidewalls
Sidewall or "sandwich construction" designs have plastic strips bonded to the outside of the core to prevent water from damaging the core. The material choices are usually ABS (acrylonitrile butadene styrene), HMWPE (P-Tex) or Phenolic plastics.
nose/tail inner core material (tip fill)
A tip spacer is a plastic or composite insert used when the core ends before the tip of the board, to fill in the space and close out the walls of the board. It also closes out honeycomb panels used in the tips to safeguard against crushing. Materials to consider are ABS, polyethylene, or fiberglass. Many tip spacers add weight when compared to a full length wood core, but can offer protection against direct impact with rocks and obstacles.
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edges
Snowboard edges are on a snowboard to give you grip while turning, and they also protect the board from damage on ice and rocks. Made from L-shaped steel extrusions, the edge consists of a 1.5mm (approx) square spine with T-shaped flanges or square "windows" stamped out of the extrusion it at close intervals to allow better bonding in the snowboard laminate. Edges are usually sand-blasted to prepare for bonding, For durability the steel is tempered (hardened).
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Binding inserts
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Composite Reinforcements
Composites re-inforcements are used to reinforce the snowboard and bond it together.
These reinforcements typically consist of fibers, either woven together, randomly scattered, or arranged unidirectonally. Copmposite laminates provide most of the strength in the finished component, and are the main "load bearing" layers. A reinforcement made of fibers arranged only at 0 degrees will be strong parallel to the fibre orientation, but will break quite easily along the 90 degree axis. For this reason, most laminates are oriented in at least two different axes. Snowboards usually use non-woven biaxial (0/90 fiber orientation) or triaxial (three axes, 0' +45' and -45') reinforcements.
Fiberglass is the typical
reinforcement used in snowboards, and comes in woven and non-woven fabrics
of different fiber orientation and density. The weight of the cloth is a weight
measurement, and is usually expressed in ounces per square yard. Structural
layers will typically use 20 - 24 oz fabrics, although many variations exist.
Carbon fiber is a higher performance reinforcement, and is typically about
five times more expensive than fiberglass. It is significantly stiffer at
a comparable weight, so often the overall weight of a laminate is less because
less materials is necessary for a given stiffnss.
Kevlar is another common material used in composite laminations, and while not as strong as carbon fiber in tensile strength, it is a higher performance laminate than fiberglass, and is fairly light when compared to fiberglass at a given stiffness.
Often, hybrid fabrics are woven from a mixture of these different materials, usually a high percentage of fiberglass with a smaller amount carbon, kevlar or other high performace "stringers". These hybrid laminates offer increased performance over basic laminates, but are often less expensive to produce than "pure" carbon fiber and other premium materials. They sometimes also feature different fiber orientations for each material.
Prepreg fabrics are already impregnated with epoxy when they are made. Prior to use they are stored in a freezer to keep the resin from setting.To properly cure, prepregs must be heated to approximately 120'C which tends to require high end materials and cores to be used to prevent melting and gassing during lamination.
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topsheets
The topsheet serves two functions - to protect the board laminates from abrasion and ultraviolet light, and to act as a surface for the board graphics. Material choices include polyethylene, polyester (PBT), ABS, various Polyamids and other materials.