How to Tell Polyethylene From Fiberglass

Canoes often are made of either fiberglass or polyethylene.

Polyethylene is a type of plastic that is inexpensive, flexible and durable. It comes in a variety of densities that affect the thickness and pliability of the plastic. Fiberglass is made from glass fiber mixed with carbon and epoxy composites, resulting in a material that is lightweight, rigid and strong. High-density polyethylene and fiberglass are both used in the construction of a number of products, such as canoes and kayaks, as well as storage sheds and septic tanks. Which substance is preferable is widely debated. Both have their pros and cons. There are several ways to determine if a product is polyethylene or fiberglass.

Things You'll Need

• Scale
• Safety pin
• Heat lamp

Instructions

1. Test the weight. Take equal-sized pieces of each product and weigh them on a scale. High-density polyethylene weighs 5.04 lbs. per cubic foot. Fiberglass weighs 2 lbs. per cubic foot.

2. Perform a scratch test. Use something small such as a safety pin and scrape the point of the pin along the underside each surface where a scratch will not show. Polyethylene scratches more easily than fiberglass.

3. Test the flexibility of the product. Lay both pieces under a heat lamp for about 10 minutes, or outside in the sun in temperatures of 80 degrees or higher. Fiberglass will not become any more flexible in the heat and will remain brittle. Polyethylene becomes flexible in heat and can become misshapen, although it usually reverts to its proper shape when it cools down. On an extremely hot day, some polyethylene canoes will change shapes as you paddle.

4. Use the price test. Compare two similar products with the same quality of add-ons, if any. Because plastics can be mass-produced more easily than fiberglass, a fiberglass product typically costs more than a similar polyethylene one.

5. Check on the repairability of the product by questioning salespeople or experts in repairing the product you are considering. Fiberglass can be easily repaired. While plastic is not impossible to repair, it is much more of a challenge. In canoes and kayaks, a fiberglass hull can be easily repaired and a fiberglass patch is barely noticeable. A hole in plastic is much harder to repair, if it can be repaired at all.

References

• Paddlers Kayak Shop: Plastic vs. Fibreglass – Myth Busting
• Packaging Today: An Introduction to the History of Plastics