Let’s first look at their origins and backbone (molecular structure). LDPE (low-density polyethylene): Like a lush tree! Its molecular chain has many long branches, resulting in a loose, irregular structure. This results in the lowest density (0.91-0.93 g/cm³), the softest, and most flexible. HDPE (high-density polyethylene): Like soldiers in a row! Its molecular chain has very few branches, resulting in a linear structure that is tightly packed and orderly. This gives it the highest density (0.94-0.97 g/cm³), the hardest, and the strongest. LLDPE (linear low-density polyethylene): An “evolved” version of LDPE! Its backbone is linear (like HDPE), but with evenly distributed short branches. Its density lies between the two (0.915-0.925 g/cm³), combining some flexibility with higher strength.
Key Performance Summary: LDPE: Soft, transparent, easy to process, and generally low in cost. However, it suffers from poor strength, rigidity, and heat resistance, making it easily punctured. LLDPE: The toughest! It offers exceptional impact, tear, and puncture resistance, excellent low-temperature performance, and good flexibility, but is stiffer than LDPE. Its transparency and barrier properties are superior to LDPE, but processing requires some caution. HDPE: The toughest! It offers high strength, high rigidity, excellent chemical resistance, good heat resistance, and the best barrier properties. However, it suffers from poor flexibility and low transparency.
Where is it used? It depends on the application!
LDPE’s applications include: various flexible packaging bags (food bags, bread bags, clothing bags), plastic wrap (for household and some commercial use), flexible containers (such as squeeze bottles of honey and ketchup), wire and cable insulation, lightweight injection molded parts (such as bottle cap liners and toys), and coatings (milk carton linings).
LLDPE’s strengths include: high-performance films such as stretch wrap (a must-have for industrial packaging), heavy-duty packaging bags (for feed and fertilizer), agricultural mulch films (thinner, tougher, and more durable), large garbage bags (unbreakable), and intermediate layers for composite films. Injection molded parts requiring high toughness include barrels, lids, and thin-walled containers. Pipe linings and cable jacketing are also used.
HDPE’s strengths include: rigid containers such as milk bottles, detergent bottles, medicine bottles, and large chemical barrels. Pipes and fittings include water pipes (cold water), gas pipes, and industrial pipes. Hollow products include oil drums, toys (such as building blocks), and automobile fuel tanks. Injection molded products include turnover boxes, pallets, bottle caps, and daily necessities (washbasins and chairs). Film: Shopping bags (sturdier), product bags, and T-shirt bags.
One-sentence selection guide: Looking for soft, transparent, and inexpensive bags/film? —————LDPE. Looking for ultra-tough, tear-resistant, and puncture-resistant film, or requiring low-temperature toughness? —LLDPE (especially for heavy packaging and stretch film). Looking for hard, strong, chemical-resistant bottles/barrels/pipes for liquids? —HDPE
Post time: Oct-17-2025