Why does HDPE have a higher density than LDPE GCSE?
LDPE (low density polyethene) is made of branched chains, which are also held by intermolecular forces. Due to its branched nature, there are more gaps between the individual chains and overall there are less intermolecular forces. This means that LDPE is both less dense and less strong than HDPE.
What is the main difference between HDPE and LDPE?
As its name suggests, low-density polyethylene (LDPE) has a lower density, strength, and temperature resistance. Meanwhile, high-density polyethylene (HDPE) is characterized by higher specific strength and heat resistance.
When was LDPE discovered?
Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization.
What are LDPE and HDPE how are they formed?
LDPE is produced by compressing monomer ethylene gas in an autoclave or tubular reactor to facilitate polymerization—i.e., the linking of monomers into polymer chains. HDPE is created by heating petroleum to very high temperatures.
Which is stronger LDPE or HDPE?
HDPE has higher abrasion and tear resistance than LDPE, along with higher tensile and shear strength.
Why is the density of HDPE and LDPE difference?
In a nutshell: the chemistry of LDPE and HDPE
From that chain another chain branches off. These side branches stop the polymer molecules from lining up in an orderly fashion. LDPE’s structure is not crystalline. This irregularity is what gives LDPE its lower density.
What are the advantages and disadvantages of LDPE and HDPE?
LDPE is more flexible and softer than HDPE. It is also translucent and has a lower melting point of 115° C. However, compared to HDPE, it is more likely to rupture under stress. On the other hand, HDPE is more rigid and durable and offers better chemical resistance.
Why is LDPE weaker than HDPE?
HDPE has less branching in its polymer chains and has HDPE has stronger intermolecular forces. LDPE has more branching in its polymer chains; thus, it’s intermolecular forces are weaker.
When was HDPE invented?
Phillips introduced HDPE in 1954, under the brand name Marlex® polyethylene.
When was HDPE pipe invented?
In 1953 Karl Ziegler of the Kaiser Wilhelm Institute and Erhard Holzkamp invented HDPE (High Density Polyethylene). From there, two years later, in 1955, HDPE was produced as pipe. Ziegler was awarded the 1963 Nobel Prize for Chemistry.
Why is HDPE not biodegradable?
]. PE is a low degradability polymer because it is mainly composed of C–C and C–H bonds ( bonds) whose bond energy is in the order of 300–600 kJ/mol.
Why do LDPE and HDPE differ in density?
Does LDPE melt?
LDPE has a melting point of 105°C. It is water-resistant, not reactive in contact with alkali, salt solutions, organic and inorganic acids. It is insoluble at room temperature and does not swell in any known solvents.
Why HDPE has higher tensile strength than LDPE?
This results in a plastic that is softer and more flexible, but which also has lower tensile strength. The polymer chains in HDPE, on the other hand, are more linear. They pack closer together, resulting in greater intermolecular forces and a more “crystalline” structure. HDPE has greater tensile strength than LDPE.
Which is better LDPE or HDPE?
HDPE has higher abrasion and tear resistance than LDPE, along with higher tensile and shear strength. If you’re going to bury your cables underground, then opt for HDPE. Otherwise, LDPE is an excellent choice. LDPE cable conduits give you outstanding flexibility, a high fatigue life and high-impact strength.
What are the uses of LDPE and HDPE?
HDPE is easy to fabricate and weld using thermoplastic welding equipment. It is an excellent choice for fabricated water tanks and chemical tanks. LDPE (low density polyethylene) is a soft, flexible, lightweight plastic material. It is often used for orthotics and prosthetics.
What are the disadvantages of HDPE?
The Disadvantages of HDPE Include
- Poor Weathering.
- Highly Flammable.
- Sensitive to Stress Cracking.
- Not Biodegradable.
- Can’t Be Composted.
- Not Resistant to Oxidizing Acids.
- Not Resistant to Chlorinated Hydrocarbons.
- High Thermal Expansion.
Who invented HDPE plastic?
Karl Ziegler
Who Discovered HDPE? Technically, Karl Ziegler of the Kaiser Wilhelm Institute (now known as the Max Planck Institute) invented HDPE in 1953. As a result, he received a Nobel Prize for chemistry in 1963. But the road to HDPE started much earlier, somewhere near the end of the 19th century.
How old is HDPE pipe?
1948: First high-density polyethylene pipe systems made available. 1978: American Water Works Association (AWWA) approves HDPE pipe for water tubes up to 75 mm (3 in.) in diameter.
Why HDPE pipes are used?
HDPE pipe has very high flow capacity, because of its smooth bore and end-to-end jointing methods. HDPE pipe does not corrode in the environment, and will maintain its flow capabilities over time, unlike ferrous piping systems, which will rust and build up internal resistance to fluid flowing through it.
Does HDPE break down?
HDPE is non-biodegradable and can take centuries to decompose, so it is imperative that these bags and containers are recycled and used again. Recycling HDPE has many benefits. For example, it is more cost-efficient to produce a product from recycled HDPE than it is to manufacture ‘virgin’ plastic.
Does LDPE break down?
LDPE: This is what plastic grocery bags are made of.
If exposed to ultra violet light, these bags have been estimated to break down in as little as 500 years with a conservative average time of 1000 years.
Which is stronger HDPE or LDPE?
Is burning HDPE toxic?
Hazardous Combustion Products: At temperatures above 300 C, polyethylene may emit various oligomers, waxes and oxygenated hydrocarbons as well as carbon dioxide, carbon monoxide and small amounts of other organic vapors (e.g. aldehydes, acrolein). Inhalation of these decomposition products may be hazardous.
How hot can HDPE get?
The high operating temperature for most HDPE is 160°F (71°C). iPoly has developed Sani-Armor HDPE sheet to withstand 170°F (77°C). As with any material, when you come near to maximum operating temperatures, the physical characteristics will weaken.