Polyethylene (Poly) is a polymer, or compound of high molecular weight, formed from ethylene, a petroleum derivative. It is a lightweight thermoplastic that is resistant to chemicals and moisture and is used where low cost, light weight and flexibility are desired.

Poly is generally categorized according to its density and is available in high, medium and low densities. The density is determined by the branching of the polymer chains. The more branches that exist, the more difficult it becomes for the material to arrange itself in a compact order, resulting in less density.

• High density polyethylene (HDPE) is characterized by very few polymer branches; therefore, it is the strongest and most resilient of the three. This dense material does not suit landscape edging well as it tends to be rigid and not very pliable.
• Low density polyethylene (LDPE) has many polymer branches and as a result is extremely pliable and susceptible to breaking and tearing. Without significant additives, LDPE weathers poorly; within a few months of outdoor exposure it becomes brittle and discolored.

Polyvinyl Chloride (PVC) is one of the most widely used plastics in the world. It is a dense thermoplastic polymer which is very hard in its resin form, but can be made softer and more flexible by the addition of plasticizers. It is impossible to manufacture flexible PVC without the addition of plasticizers. Plasticizers are a form of internal lubricant added to plastics to improve flexibility, resiliency, and melt flow. Plasticizers are only one of many types of additives that can be used to change the properties of PVC.

Additives are used in plastic material to enhance environmental properties and increase the shelf life of plastic products. They are also used to improve the strength, stability, chemical resistance and weathering properties of plastic products. Processed plastics would be useless without additives. Unfortunately, not all additives enhance or improve the quality of plastic, some are used solely to reduce manufacturing costs. For better or worse, these are a few of the additives commonly found in plastic landscape edging:

Beneficial Additives

• Many plastics, such as PVC, are brittle and must be modified to improve their ability to absorb shock. To impart better flexibility and impact strength without affecting rigidity, a group of polymeric additives called Impact Modifiers, or processing agents, are used. They are used at the level of 2-10% depending upon the requirement of impact strength.
• Fillers, or extenders, are widely used in plastic extruding and they are categorized as active or inert. Active Fillers produce improvements in physical or mechanical properties, such as: strength, hardness, thermal stability, chemical resistance, and appearance. Carbon black concentrate is one example of an active filler.

Quality Reducing Additives

• Inert Fillers, on the other hand, are low cost additives which are used to replace the higher cost plastic. In other words, they reduce cost by decreasing the amount of actual plastic used. Most fillers come in powder form and can be minerals, rock, calcium carbonates (chalk), talc, silica (sand), walnut shells, sawdust, wood pulp and rubber.
• Chemical Foaming Agents (CFAs), or chemical blowing agents, are used to foam plastics to impart a cellular or hollow structure to the material. CFAs decompose to release gas when heated to their activation temperature. The CFAs reduce the amount of plastic required to produce a part, thus reducing weight and also reducing cost. The amount of foaming agent added will determine the porosity of the plastic. The most common CFAs are hydrochlorofluorocarbons, methylene chloride, methyl chloroform, n-pentane, isopetane, acetone, carbon dioxide, nitrogen, and water.

Oly-Ola’s entire paver restraint line is made up of high quality PVC due to its strength and rigidity, while our landscape edgings are made up of MDPE because of its more pliable nature. The only exception is Super-EdgTM which is composed of PVC to increase the rigidity of their 6” high landscape edging.

To be Specific:

• Oly-Ola’s PVC line is made up of 100% recycled high quality PVC with only impact modifier added to strengthen the material and increase UV protection.
• Oly-Ola’s Poly line is made up of 100% recycled high quality MDPE with only carbon black concentrate added as a colorant and UV inhibitor.

It is that simple! There are no hidden additives or ingredients used to reduce cost and/or create the illusion of thickness or size. Oly-Ola challenges any other Poly or PVC edging manufacturer to state exactly what their edgings are made of!