About HDPE. HDPE (a.k.a. High Density Polyethylene) is one of the three main types of polyethylene, figuring among the most used polymers worldwide. It is the most widely used polyethylene resin. HDPE may be either ethylene homopolymer or a copolymer of ethylene and alpha-olefins (1-hexene, 1-butene). Polyethylene is considered to be high density when having density greater than 0.94 g/cm³. Despite having density only marginally higher than that of low-density polyethylene (LDPE), HDPE presents larger strength-to-density ratio, due to its little branching and consequent stronger intermolecular forces. The high demand for polyethylene is in large part due to a combination of the availability of ethylene raw material, its relatively low cost and a wide variety of applications.

HDPE may be either ethylene homopolymer or a copolymer of ethylene and alpha-olefins, and is manufactured on commercial scale via low-pressure polymerization processes using mainly Ziegler-Natta or chromium-based catalysts. The main technologies suitable for its production include slurry, solution, and gas phase processes. The most common comonomers used commercially are 1-hexene and 1-butene. The physical and mechanical properties of final HDPE depend on its density, type, molecular weight (MW), and molecular weight distribution (MWD), characteristics controlled by the catalyst employed and reaction conditions.

HDPE Handling. HDPE may react with strong oxidizing agents and should not be stored near such materials. The bags must be stored at room temperature (preferably below 50 °C), in a well ventilated position and under dry conditions. HDPE can also be stored and/or transported in car silos, containers, or large cartons to avoid contamination, heat, and direct sunlight.

HDPE Production. HDPE Homopolymer production consists in the polymerization of ethylene without any other alpha-olefins, in such a way that different HDPE manufacturing routes are related to different sources of ethylene. In this context, typical HDPE production routes are based on ethylene manufacturing (via steam cracking of paraffinic hydrocarbons). Raw materials and the respective production processes employed in the manufacturing of HDPE are listed below.

HDPE Uses. The primary commercial forms of HDPE are injection molding, blow molding, and film. Blow molding grade demands low viscosity at high shear and high zero-shear viscosity to prevent sagging in the mold. Resins with broader molecular weight distributions, particularly with higher molecular weight, are preferred, and chromium catalysts are well-suited. The injection molding grade has a narrow molecular weight distribution to prevent frozen orientations, minimizing warping and fragility. Ziegler catalysts are often used to achieve this distribution. The blown-film grade often uses chromium-based or bimodal resins from Ziegler catalysts. Metallocene resins are also employed for high-clarity HDPE films. Typically, high-molecular-weight HDPE is employed in such applications (HMW film), although there are polymers with higher MW (e.g., UHMWPE ultrahigh MW Polyethylene).

Blow molding is the predominant application of HDPE, utilized for mass-producing items. It is widely applied in producing bottles for various industries, including food packaging, detergents, oil, household materials, industrial drums, fuel tanks, and toys. Injection-molding resins have lower average molecular weights, falling within the 3–80 melt index range. Various products, including cups, toys, and containers, are made with injection-molded HDPE. HDPE films, ranging from 0.007 to 0.125 mm thick, are versatile and used for various purposes, including food packaging, grocery bags, merchant bags, and drum liners.