Tag Archives: Injection Molding

Common Plastic Terminology for Trench Drains

It’s time to discuss some plastic terminology!

Disclaimer: I am not an organic chemist or a plastics engineer. I’m gathering this information from other sources and I may not be explaining it as accurately as I need to.

Polyolefin — is a polymer produced from a simple olefin, or alkene as a monomer. For example, polyethylene is a polyolefin produced by “polymerizing” the olefin “ethylene”. Another common polyolefin is polypropylene. I consider polyolefin a general term for a family of plastics. (http://en.wikipedia.org/wiki/polyolefin)

Polyethylene — is a semi-crystalline plastic with excellent chemical resistance, good fatigue, and wear resistance. They can have a wide range of properties which are determined by the length and degree of branching of their polymer chain. In general, polyethylenes have good resistance to organic solvents, high impact strength, are light weight, resistant to staining, and have a low moisture absorption rate. They are easy to distinguish from other plastics because they float in water. (http://en.wikipedia.org/wiki/polyethylene)

HDPE (High Density Polyethylene) — HDPE is the most common polyethylene used in industry. It offers excellent impact resistance and high tensile strength. Technically speaking, it has a low degree of branching and thus a stronger intermolecular forces. HDPE is non-toxic and meets FDA and USDA certifications for food processing. It is commonly used for the manufacturing of milk jugs, margarine tubs, detergent containers and trash cans. It is also an excellent material for use in trench drain and storm sewer pipe.

Polypropylene is an economical material that offers a combination of outstanding physical, chemical, mechanical, thermal and electrical properties not found in any other thermoplastic. It has a lower impact strength that does HDPE, but it also has better tensile strength and superior heat resistance.

Structural Foam — is a structure imparted to an olefin during processing that gives the plastic addition strength and resilience. More on this later.

PVC (Polyvinyl Chloride) — Is a widely used thermoplastic polymer. Over 50% of the PVC products manufactured are used in construction as a building material. PVC offers excellent corrosion and weather resistance and has a high strength-to-weight ratio. PVC is inexpensive, easy to clean, and a popular replacement for wood and concrete building materials. It is used in house sidings, drainage pipe, window profiles and plumbing fixtures (such as some trench drain). Despite appearing to be an ideal building material, concerns have been raised about the costs of PVC to the natural environment and human health. (http://en.wikipedia.org/wiki/polyvinyl_chloride)

Fiberglass Reinforced Polyester — Polyester is a category of condensation polymers which contain the ester functional group in their main chain. This group also includes polycarbonates. Polyesters are popular for being used as a woven fabric. When fiberglass is added to polyester, the resultant material is more durable and resistant to impact.

UV Inhibitors — These are chemical additives that are added to plastic which help to retard the damaging effects of ultraviolet light to the plastic.

Injection Molding — This is a forming method by which intricate trench drain products (or other plastic shapes) can be shaped. In this process, a heated and liquid thermoplastic is injected into a mold that contains a cavity that has the shape which is desired. Once injected with plastic, the mold and part is cooled. The resulting plastic shape is removed from the mold and trimmed of flashing (excess plastic). This method is needed to form pre-sloped trench channels. Though mold costs are expensive, one mold is required for each size of pre-sloped channel.

Extrusion — Another method of making trench channel is extrusion. In this process, a heated batch of thermoplastic is continuously injected through a water-cooled die. The shape of the die will determine the cross-section of the extruded part. This method can be used to make simple, non-complex parts such as pipe, tubes and u-shaped channels. The most inexpensive channel drain products are made using this forming method.