Polyethylene is a polymer of ethylene, and it has two categories. One is HPDE, and the other is MPDE. Polyethylene is also called polythene.
This thermoplastic polymer is mainly used in industries to manufacture packaging materials, plastic bags, and so on. Polythene, when formed by combining monomers of ethylene, forms a long chain that has different densities.
Key Takeaways
- HDPE stands for High-Density Polyethylene, while MDPE stands for Medium-Density Polyethylene.
- HDPE has a higher density and is stronger, more rigid, and more resistant to heat and chemicals than MDPE.
- MDPE, on the other hand, is more flexible and has better impact resistance than HDPE.
HDPE vs MDPE
The difference between HPDE and MPDE is their densities. Their major difference is due to the density of these polymer chains. Branching and density are the two significant factors that differentiate from one another. Their mechanical properties are also different based on the branching, extent of branching, and also Their molecular weight. HPDE and MPDE also vary in their crystal structures.
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HPDE is high-density polyethylene. It has a higher density and thus its name. It has a density of about 0.941 g/cm3 or even higher than this value.
HPDE has a strong and powerful intermolecular force and also a very high tensility. Its tensile strength is because of the lower degree of ranching. The branching can be further lowered using catalysts.
MDPE stands for medium density polyethylene. It has a medium-density due to the name 0.926 to 0.940 gm/am3 for the manufacture of this polymer chromium catalysts, silica catalysts, and others like Ziegler – Natta and metallocene catalysts.
It has good chemical resistance and has high stability at room temperature.
Comparison Table
| Parameters of Comparison | HDPE | MDPE |
|---|---|---|
| Full-Form | HDPE stands for high-density polyethylene. | MDPE stands for medium density polyethylene. |
| Density | HDPE has a high density of about 0.914g/cm3. | MDPE has a low density of about 0.926 to 0.940 gm/am3. |
| Sensitivity | HDPE is highly sensitive. | MDPE is comparatively less sensitive. |
| Stress Cracking Resistance | HDPE has low resistance to stress cracking. | MDPE has a higher resistance to stress cracking. |
| Branching | HDPE has the most minimal branching. | MDPE has minimum branching, too, but a little higher than HDPE. |
What is HDPE?
HDPE is known for its high strength density ratio, which is about 930 to 970 kg/m3. The density of HDPE is only marginally greater than LDPE. It also has strong intermolecular forces. It has high tensile strength.
It is harder and opaque in nature. The physical properties depend more on the type of catalysts used. It cannot be glued as it is not soluble in solvents.
It is used in many areas like in banners, boats, bottle caps, and also fireworks. It is used in a lot of places. It is also of graded quality to perform plastic surgeries. This hydrocarbon polymer is prepared from ethylene or also from petroleum.
It is thermoplastic and can withstand high temperatures. It is easy to mold and weld; hence it is found in many applications. It can be used in several places, and thus it is such a boon.
It has lightweight, and it is strong. It is impact resistant and does not get damaged easily. It is also extremely resistant to bad and extreme weather conditions.
It is also capable of withstanding mold, mildew, rotting, and insects, and hence it can be used in underground pipes. It is an extremely good alternative for heavy materials.
What is MDPE?
MDPE is also a thermoplastic that is prepared by applying low pressure with the help of using transition metal catalysts like metallocene catalysts. It is comparatively less opaque when compared with HDPE.
It is extremely crack resistant but less rigid and hard. It is less expensive and easily affordable. It is flexible and thus used in manufacturing bags. This is stronger but not tough enough.
This is produced on a smaller scale when compared with other density polyethylene. It is both stiff as well as flexible at the same time. It has less chemical resistance and rigid.
It is used in the manufacture of pipes due to its favorable mechanical qualities like high ductility, impact strength, and also low friction. It has favorable properties that make it suitable for a lot of commercial applications.
It is resistant to both acid and base and also resistant to oxidants and reducing agents. There is a high demand in the market for this thermoplastic due to its good quality, affordable price, and also sue to its favorable mechanical properties.
Gas pipes, water, waste, and sewage are carried through the pipes of MDPE polymers. It is also used in agriculture due to its flexibility and easiness.
It takes less time and less effort to manufacture, and hence it is easy to manufacture. The biggest advantage is that it is nontoxic and nonhazardous, and extremely safe.
It has high impact resistant properties and resistance to moisture and chemicals. It is recyclable in this is one of the best quality that makes this so popular. These are also used in automobile applications.
Main Differences Between HDPE and MDPE
- HDPE is high-density polyethylene, whereas MDPE is medium-density polyethylene.
- As the name suggests, HDPE has a higher density when compared with MDPE.
- HDPE is more sensitive than MDPE.
- HDPE is less resistant to stress cracking, whereas MDPE is more resistant.
- HDPE has minimum branching, and MDPE, though it has a minimum branching, is slightly higher than that of HDPE.
- https://www.sciencedirect.com/science/article/pii/S221478531933295X
- https://www.sciencedirect.com/science/article/pii/S0261306912008321
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
