Polyethylene
Manufacturing
Polyethylene is plastic materials obtained from polymerization of ethylene, i.e. linking of large number of ethylene molecules (monomers) in one macromolecular chain or polymer.
Conditions in which the reaction takes place, most of all pressure, determine the features – type of polyethylene and its further processing and use.
Low density polyethylene (LDPE) is produced by polymerization of ethylene at high pressure (1,500-3,000 bars) in presence of free radicals.
High density polyethylene (HDPE) is produced by polymerization of ethylene at low pressure (cca. 42 bar) with catalyst.
Processing
Several techniques of plastic mass processing can be applied on polyethylene. Basically, melted polymer is thrusted through extruder, forming a foil, pipe, profile or a fiber. Polyethylene melt can also be injected into mold, and cooled into desired form. Film extrusion can be used for laminating cardboard for food packaging or for making insulation lining on electric conductors.
Use
Polyethylene is the most used of all polymers due to their mechanical properties, processability and wide usage possibilities. Use of polyethylene is especially dominant in packaging, since modern production and product handling are no longer possible without water-proof and healthy safe packaging, which is also light and attractively designed. Polyethylene packaging protects the products and extends its shelf life, with the possibility of diverse shapes and prints, together with the lower costs of transport and storage.
Low density polyethylene (LDPE) is mostly used for production of shopping and household bags, milk and water packaging foils, industrial bags, shrink and agricultural foils, insulation of electric conductors and cardboard lining.
High density polyethylene (HDPE) is used for production of bottles for food, pharmaceutical and chemical products, for pipes, barrels, tanks, boxes, carriers, packaging films and foils, shopping and household bags, toys and consumer goods.
Emulsion styrene-butadiene rubber (E-SBR)
Manufacturing
E-SBR is produced by copolymerization of 1,3-butadiene and styrene, where 1,3-butadiene participates with approximately three quarters. Process is continual, in presence of catalysts and other additives, and with mild reaction conditions – cold reaction, which enables achieving good physical properties of the product.
Processing
After compounding (adding vulcanizing agents, additives, fillers), E-SBR is processed by same techniques as other polymer materials – extrusion, calendering, injection, pressing or coating.
Use
E-SBR is one of the most utilized polymers due to its versatile applications, from making of car tires to toys. This synthetic rubber is compatible with natural rubber and can fully replace it, and in comparison, it has better processability and resistance to abrasion and aging.
E-SBR is also compatible with other types of synthetic rubber, which together with good processability and additive absorption, enables the use of various formulas for different types of products.
The largest quantities of E-SBR (around 70%) are used for production of automotive tires, but there is also a wide range of products in which E-SBR is irreplaceable. These are rubber-technical products – conveyer and transmission belts, tubes and hoses, seals, technical parts and products for various industries (machine, pharmaceutical), flooring and door mats, rubber footware and soles, cable insulation, adhesives, toys.