Polyethylene properties vary based on the grade of virgin material and synthesis method. Low-density polyethylene is less dense and cheaper, while high-density polyethylene is more durable. Catalysts can produce ultra-high and high molecular weight polyethylene with high durability. Other factors affecting performance include impact strength, shear rate, and sag strength. Recycled polymer resins can also cause variations in properties.
The properties of polyethylene vary according to the grade of virgin material used to synthesize this thermoplastic and its structural crystallization. In general, the integrity of the end product polyethylene-based material in the plastics industry is based on its density and melting point. However, since this substance can be produced by a number of methods for polymerizing ethane, each will produce differences in the specific properties of the polyethylene. The variations that can lead to these differences concern the molecular weight, the density and the degree of branching of the molecular attachment of the carbon.
Most people are familiar with the two most common forms of this polymer: low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Because the polyethylene properties of the former contain a greater degree of long-chain branching, the matrix is less dense and does not offer the same tensile strength as the latter. Since this is the case, LDPE is less expensive to produce and process than similar polymers.
HDPE, on the other hand, is a more durable polyethylene grade due to higher density and linear crystallization. The polyethylene properties of this material make it suitable for use in the manufacture of many types of stress-resistant plastics for commercial and consumer use. For example, HDPE is used to make gallon-sized milk containers, as well as plumbing fixtures.
As mentioned above, the properties of polyethylene differ depending on the curing method employed. The process can be induced by stimulating free radical polymerization, by the introduction of an alkali amide or secondary monomer (anion addition polymerization and ion coordination polymerization, respectively), or by the use of a catalyst. Also, the application of high voltage is used to obtain extended chain crystalline polyethylene (ECC), which results in dense crystallization but renders transparency.
Catalysts are often the method of choice for obtaining material exhibiting desirable polyethylene properties. For example, ultra-high molecular weight polyethylene (UHMWPE) and high molecular weight polyethylene (HMWPE) are both catalyst-induced and have unusually high molecular weight and density. Due to the high degree of durability, UHMWPE is used to produce various machine parts, artificial joints and implants, and body armor. HMWPE is used to make chemical resistant items, such as fuel and storage tanks.
In addition to density, molecular weight, and stress resistance, other properties of polyethylene are thought to factor into function and application. These include impact or impact strength, shear rate — the melting and flow rate of the polymer — and sag strength, which refers to how well the material resists melting and remodeling. All of these factors affect the performance of the material during processing. Also, since much of the raw material used in the plastics industry today can come from recycled polymer resins, the properties of polyethylene can vary greatly, even between different batches presented as the same material.
Protect your devices with Threat Protection by NordVPN
