Difference between LDPE and HDPE

LDPEandHDPEare also used as polymers of ethylene. Of course, they have many similarities: for example, they have the same weight and light weight, good tensile strength, acid and alkali corrosion resistance, high recyclability, low production cost, fast injection molding, and no need to use products after molding. Drying, etc., but when selecting models, understanding their differences will help choose the right product.

The difference between molecular structure

LDPEandHDPEmust first start with the molecular structure: As shown in the figure below,the molecular structure of LDPE has many branches, and the lengths of the branches are different, and the molecules are not tightly arranged, so the density of theLDPEmaterial is low and cannot be crystallized; whileHDPEhas only a small number of short branches in the molecular chain, and the molecules can be arranged in an orderly manner. The attraction between polymer molecules can also make the molecules arranged tightly, so theHDPEmaterial has a high density.

Mechanical properties

Due to their different molecular structures, physical and mechanical properties are also different:LDPEis soft, has good extensibility, is more elastic, has higher relative transparency, and iseasier to crack than HDPE. It can usually be used as plastic wrap, transparent plastic bags and other film-type products;HDPEis harder, has a higher relative melting point, better wear resistance, high strength and hardness, and high compressive strength. It is generally used in higher-strength environments or as a hard shell material.

Recycling classification

Although they are all recyclable thermoplastics, due to the difficulty of recycling and the different post-recycling treatment, they need to be distinguished during recycling, as shown in the following figure:LDPEis classified asrecycling No. 4, andHDPEis classified asrecycling No. 2. Among them, therecycling of LDPE may cause the recycled machine to be involved in the recycling due to the soft and thin material, so pay attention during transportation.

(Tuyuan Network)

Technical support: Guo Honghua

Editor: Liu Kangli