HDPE, or high-density polyethylene, is under ordinary circumstances a material of milky colour that differs from other polyethylene types by higher strength and ductility. Since the material is more consistent, the foils and packages produced from it are stronger. Therefore, an HDPE bag has a higher load capacity than a LDPE bag of identical thickness. This is beneficial in the production of very thin bags; HDPE bags can be made from thicknesses of 7 micrometers and more.
In addition to flexible packages, HDPE is also a very suitable material for making strong packaging. The best-known applications are cosmetics bottles (cleaining agents, shampoos), and containers.
HDPE is used also in technical applications, e.g. as septic tanks, in the production of pipes, and the sheathing of cables and harnesses. Septic tanks can posses highly complicated shapes and large capacities. The advantage of HDPE in these applications is its natural strength and consistency.
LDPE is a polyethylene of limited density. It is the most frequently used material in the production of foils, in particular for packaging purposes. All simple types of disposable bags, refuse bags and shopping bags are made solely from LDPE. The reasons for this include low cost and ease of processing.
Foils are manufactured by extrusion, either as 2D foils or hoses (tubular extrusion). Such foils can be very thin (bags for baked goods) or have thick-walls (large bags). The exact thickness of the packaging may be adapted to meet the given requirements - from 30 micrometers (0.030 mm) up to 200 micrometers.
Should the need exist for the eventual packaging to be resistant to perforation, PE foils can be laminated with another type of foil, improving the properties of the final package. For example, lamination with PET foil (polyethylene-terephthalate) occurs in the production of foodstuff bags for pets. Lamination with paper-based boarding is applied to produce fruit juice packaging (of Tetrapack type).
The benefit of LDPE is that it can be printed onto to a high standard. Shopping bags and large bags can be decorated with multi-coloured printing. This material can also be welded to achieve various shapes of pouches and bags. Recycled PE is applicable in the production of pouches and bags, contributing to protection of the environment.
PET (polyethylene-terephthalate) is a hard and clear polymer with extremely good mechanical properties. It shows excellent resistance to tearing and can resist to high pressure volumes without breakage, making it ideal for the production of packaging for beverages – e.g. PET bottles.
PET material is also suitable for making extruded foils. Subsequent biaxial stretching of the foil (in both directions) improves the strength in both directions significantly. It is notable for use as a packaging material for gift packs and baking foil. In foil form, PET is highly resistant to steam and permeability by gas, thereby providing protection to the products inside; it also resists the effects of oils and fats in the given food-stuff.
PET may be combined with other materials and create multi-layered packages, the features of which are modified for the specific application – the packaging of aromatic spices, cheese, smoked-meat products, etc. Up on a customer’s request, the foils an be produced in different colours, feature printing, possess metal-coatings (cosmetic industry, toothpastes), or be laminated (packages for pet foot).
Typical examples of PET applications include:
Fibres in the textile industry – dressmaking, winter jacket wadding (padding).
Bottles for beverages, in particular sparkling and alcohol-free beverages.
High-speed boiling pouches, precooked food bags and packages for non-perishable foods.
PET is one of the most common recyclable materials. PE bottles sorted from the municipal waste are most frequently reprocessed into fibres.
EVAC (a copolymer of ethylene with vinyl acetate) is a material distinguished by strength and transparency, it is soft, flexible and similar to rubber. It is manufactured with a vinyl acetate content of 2 to 40 %. Increasing the proportion of vinyl acetate results in a rise in its transparency, adhesiveness, softness and resistance to cracking. A natural non-slip characteristic is an interesting feature of this material, which is beneficial in applications such as non-slip pads for floors, cabinets, shelves, and drawers.
EVAC is resistant to mechanical stress and UV radiation. For example, it is used in the production of various sports equipment – ski boots, bicycle seats, boxing gloves and helmets, in items for use outdoors and in boots (Wellington boots), etc. This material can also be expanded as in the production of sleeping pads (Carry mats).