Be it a food container or a soft drink bottle, plastic is an essential part of our lives. Most of the things we use incorporate plastic in one way or the other. LDPE is a thermoplastic built from monomer ethylene. ScienceStruck gives an in-depth information about LDPE.
Did You Know?
LDPE is the first grade of polyethylene manufactured in 1933 by a British company named Imperial Chemical Industries.
LDPE is the abbreviation used for ‘low-density polyethylene’. Polyethylene can be generated by ‘low pressure’ or ‘high pressure’ method. The low pressure method generates HDPE (high-density polyethylene) while the high pressure method generates LDPE.
During the high pressure process, ethylene gas is heated at very high pressure in the presence of oxygen to convert it into a solid substance. Oxygen acts as an initiator in this reaction. The temperature and pressure maintained are about 100°-300°C and 1500-3000 psi respectively.
The LDPE structure consists of bundled polymer chains which are placed in irregular fashion and hence, it is not very strong. This optimally robust and flexible plastic is a very good option for prosthetic machines. The symbol in the accompanying image depicts the plastic grading. The ‘chasing arrows’ contain a number 4 for LDPE, which indicates the type of plastic used to make a particular product.
The physical and chemical properties of LDPE are as follows:
♦ Its density is 0.915 – 1.13 g/cc.
♦ It is flexible and has a specific gravity of 0.92.
♦ Its tensile strength is between 8-12 Mpa.
♦ It has low crystallization capacity which is about 50-60%.
♦ The melting point for LDPE is 239 °F-275 °F (115 °C-135 °C).
♦ It is semi-transparent or translucent and flammable.
♦ LDPE is not autoclavable.
♦ It is not resistant to dry heat sterilization.
♦ It is resistant to moisture and chemicals, as well as continuous changes in temperature.
♦ It can be used to store food as it meets all the food storage guidelines.
Presented below is a chart that depicts LDPE resistance to various chemicals.
*(Very Good-5, Good-4, Fair-3, Moderate-2, Poor-1)
|Greases and oil||2-3|
Advantages of LDPE
♦ Due to its low costs, it contributes to reduction in the price of the final product.
♦ It can be recycled (mostly) and hence, reused.
♦ It is splinterproof. Therefore very ideal for slippery bathrooms.
♦ It can be processed easily by most of the thermoplastic processing methods (injection molding, extrusion, pressing and forming to list a few).
Disadvantages of LDPE
♦ It cannot be transparent.
♦ LDPE is not resistant to stress and tends to crack.
♦ Products made from LDPE can be reused. However, they cannot be recycled always.
♦ Although it can be seldom recycled, the products made by using the recycled LDPE are not very strong.
♦ LDPE offers less resistance to weather conditions.
Products and Applications
♦ Packaging films or plastic wraps are made from LDPE. This is one of the largest markets for LDPE.
♦ It is used to make containers, trays, shampoo bottles, squeezable bottles, and aerated drink bottles.
♦ It is used to make carrier bags for carrying purchases, dry cleaner bags, and tote bags.
♦ It is used to make garden slides and toys.
♦ The outer protective cover or insulation for electrical wires is made of LDPE.
♦ It is used in home-decor such as carpets, furniture, and computer components such as hard disks, optical disks, etc
Does LDPE contain BPA?
♦ BPA also known as bisphenol A is a chemical which is found in most of the plastics. The presence of this chemical makes any plastic unsafe for use. If a food container contains BPA, it will be ingested with the food and can cause harmful effects. It is counted as a chemical which can cause reproductive system problems, birth defects, autism syndrome etc. LDPE plastic is said to be free from BPA content and therefore comparatively safer to use as compared to other plastic.
Recycling of LDPE
♦ When it comes to recycling plastics, it is important to check the plastic grade beforehand. Depositing plastic with plastics of different grade can lead to contamination of the recycling of entire set of plastics. Check with your waste authority if they accept grade 4 LDPE for recycling. Another way is depositing the unused plastic with local curbside recycling programs. Some of the stores also have the collection facilities through which they collect shopping bags or plastic bags. Check if the plastic is grade 4 and deposit it with the respective store for recycling.
For a long time, LDPE was not accepted by most recyclers. Nonetheless, its acceptance for recycling at the recycling programs is widely increasing. Although a large number of polymers have been introduced in the market, LDPE still holds its position as an important grade of plastic. This is because recycled LDPE can be used in making shipping envelopes, bins, liners, floor tiles, paneling, furniture etc.