PVC and HDPE are two types of polymeric synthetic plastic materials which are used in many industrial applications. The key difference between HDPE and PVC is the difference in density; HDPE is denser than PVC, and this leads to differences in their physical properties and industrial applications. In addition, the difference in chemical structure and manufacturing process also give them some unique material properties.
PVC is the abbreviation for Polyvinyl Chloride. PVC is the third-most extensively produced synthetic plastic polymer, next to polyethylene and polypropylene. It is a synthetic polymeric material which is available in two forms: rigid and flexible. The pure form of polyvinyl chloride is a white colored brittle solid which is insoluble in alcohol, but fairly soluble in tetrahydrofuran. The composition of PVC is about 57% of chlorine which is derived from industrial grade salt and about 43% of carbon, mostly taken from oil and gas from ethylene. Therefore, PVC is less dependent on crude oil or natural gas than the other polymers. Chlorine gives PVC an excellent fire resistance.
HDPE stands for High Density Polyethylene, and it is the high density version of polyethylene plastic. Compared to the other types (LDPE), it is hard, strong and a little heavy, but is less ductile and lighter than water. HDPE can be moulded, machined, and welded together. The weather resistance of HDPE can be improved by using UV-stabilizators (carbon black); however they are black in colour.
HDPE is produced from petroleum, and its physical appearance of HDPE is wax-like, lustreless and opaque. Although HDPE is a denser material, it can be recycled and has the number “2” for its resin identification code.
PVC: PVC is produced by the polymerization of vinyl chloride molecules.
HDPE: The polymerization of ethylene molecules gives polyethylene polymer having the molecular formula of -(C2H4)n–
PVC comes in two forms (rigid PVC – RPVC and flexible PVC – FPVC), and some of their properties slightly vary.
PVC: RPVC (1.3–1.45 g cm-3) is denser than FPVC (1.1–1.35 g cm-3).
HDPE: HDPE has a large value for strength-to-density ratio, and its density ranges from 0.93 g cm-3 to 0.97 g cm-3.
PVC: RPVC (0.14–0.28 Wm-1K-1) has a wide range of the thermal conductivity and FPVC (0.14–0.17 Wm-1K-1) has a narrow range.
HDPE: Thermal conductivity of HDPE is around 0.45 – 0.52 Wm-1K-1.
PVC: Hardness and mechanical properties of PVC are relatively high, and mechanical properties increase as the molecular weight increases, and it decreases with the temperature. When comparing RPVC and FPVC, RPVC has good mechanical properties.
HDPE: HDPE is a non-linear viscoelastic material and it has time-dependent properties. It can withstand relatively high temperatures (120 0C) for short time intervals, but it can’t withstand normal autoclaving conditions.
PVC: As PVC has two forms; rigid PVC and flexible PVC, they are used in distinct applications according to their properties.
RPVC: The rigid PVC is used in manufacturing pipes, bottles, non-food packaging materials, cards (bank cards), doors and windows.
FPVC: The flexible PVC is used in many areas including plumbing, electrical cable insulation, imitation leather production, signage and in inflatable products. Moreover, it is an alternative material for rubber.
HDPE: HDPE is used to produce many plastic products; some examples are chemical drums, jerricans, carboys, toys, picnic ware, plastic bottles, corrosion resistant pipes, geomembranes, plastic lumber, household and kitchenware, cable insulation, carrier bags, a food wrapping material.