Medium Density Polyethylene (MDPE)
Medium Density Polyethylene (MDPE) is part of the polyethylene family of thermoplastics which include HDPE and LDPE. MDPE, is usually black or blue and may also be referred to as black alkathene. It has a relatively dense molecular structure, which is lower than HDPE and higher than LDPE.
When ethylene is polymerised it has straight polymer chains, with branches from a main chain. LDPE has the most branching and so is least dense, whilst HDPE has the least branching so is the more dense, whilst MDPE is in between. LDPE, HDPE, LLDPE, PP (polypropylene) are polyolefins, which are high molecular weight hydrocarbons. They are some of the few plastics that have a low specific gravity, weighing less than water. They are susceptible to oxidation and UV damage.
MDPE is, as with other polyethylenes, lightweight and flexible, so it is often used in the manufacture of gas pipes and fittings, sacks, carrier bags, and screw closures. On construction sites and factories it is often used as a shrink wrap, slightly heavier duty than LDPE shrink wrap.
[edit] Related articles on Designing Buildings
- Glass reinforced plastic GRP
- Glass fibre reinforced plastic
- High Density Polyethylene (HDPE)
- High Density Polypropylene (HDPP)
- Low Density Polyethylene (LDPE)
- Polycarbonate plastic.
- Polypropylene in the construction industry.
- Plastic cladding.
- Plastic coating market.
- Plastic in construction.
- Plastic in concrete.
- Recycled plastic bridges.
- Wood plastic composites market for construction
Featured articles and news
A case study and a warning to would-be developers
Creating four dwellings... after half a century of doing this job, why, oh why, is it so difficult?
Reform of the fire engineering profession
Fire Engineers Advisory Panel: Authoritative Statement, reactions and next steps.
Restoration and renewal of the Palace of Westminster
A complex project of cultural significance from full decant to EMI, opportunities and a potential a way forward.
Apprenticeships and the responsibility we share
Perspectives from the CIOB President as National Apprentice Week comes to a close.
The first line of defence against rain, wind and snow.
Building Safety recap January, 2026
What we missed at the end of last year, and at the start of this...
National Apprenticeship Week 2026, 9-15 Feb
Shining a light on the positive impacts for businesses, their apprentices and the wider economy alike.
Applications and benefits of acoustic flooring
From commercial to retail.
From solid to sprung and ribbed to raised.
Strengthening industry collaboration in Hong Kong
Hong Kong Institute of Construction and The Chartered Institute of Building sign Memorandum of Understanding.
A detailed description from the experts at Cornish Lime.
IHBC planning for growth with corporate plan development
Grow with the Institute by volunteering and CP25 consultation.
Connecting ambition and action for designers and specifiers.
Electrical skills gap deepens as apprenticeship starts fall despite surging demand says ECA.
Built environment bodies deepen joint action on EDI
B.E.Inclusive initiative agree next phase of joint equity, diversity and inclusion (EDI) action plan.
Recognising culture as key to sustainable economic growth
Creative UK Provocation paper: Culture as Growth Infrastructure.
Comments
[edit] To make a comment about this article, or to suggest changes, click 'Add a comment' above. Separate your comments from any existing comments by inserting a horizontal line.