Knowledge about PE VS PVC


How to identify PE film and PVC film in a casual or daily method?


What you are looking for is the Beilstein test. It determines the presence of PVC by detecting the presence of chlorine. You need a propane torch (or Bunsen burner) and a copper wire. Copper wire by itself burns cleanly but when combined with a material containing chlorine (PVC) it burns green. Heat up a copper wire over a flame (use pliers to protect yourself and use a long wire) to remove unwanted residue. Press the hot wire against your plastic sample so that some of it melts onto the wire then replace the plastic covered wire onto the flame and look out for bright green. If it burns bright green, you have PVC.

Finally, PE burns with smell like burning wax while PVC has a very pungent chemical smell and extinguishes itself immediately once taken off a flame.


“Is polyethylene the same as PVC?” No.


Polyethylene has no chlorine in the molecule, PVC does. PVC has a chlorine-substituted polyvinyl, polyethylene does not. PVC is inherently more rigid than is polyethylene. CPVC even more so. PVC leaches compounds into water over time that are toxic, polyethylene does not. PVC ruptures under overpressure (so is not suitable for compressed air applications), polyethylene does not.


Both are thermoformed plastics.


Is PVC a polyethylene?

PVC, or polyvinyl chloride, is a substituted polyethylene. This means that every other carbon of the chain has one chlorine attached plus a hydrogen, rather than the two hydrogens normally found on polyethylene.



What is polyethylene plastic made out of?



Polyethylene (PE), light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins.


What is cross linked polyethylene?

Polyethylene is a long-chain hydrocarbon that is formed by sequential linking of ethylene molecules in a reaction known as polymerization. There are various ways to conduct this polymerization reaction.


If a Ti-based inorganic catalyst (Ziegler polymerization) is used, the reaction conditions are mild and the resulting polymer is in the form of very long saturated hydrocarbon chains with very little unsaturation (un-saturated -CH=CH2 groups) either as part of the chain or as a dangling group. This product is referred to as High Density Polyethylene (HDPE). Even when co-monomers such as 1-butene are included, the level of unsaturation in the resulting polymer (LLDPE) is minimal.

If a Chromium Oxide based inorganic catalyst is used, once again long linear hydrocarbon chains are formed, but some level of unsaturation is seen. Once again this is HDPE, but with long-chain branching.

If radical initiated polymerization is conducted, there is a chance for both long side-chains in the polymer, as well as several points of unsaturated -CH=CH2 groups as part of the chain. This resin is known as LDPE. Several co-monomers such as vinyl acetate, 1-butene and dienes can be incorporated to modify and functionalize the hydrocarbon chain, and also include additional unsaturation in the dangling groups.

LDPE, because of its high level of unsaturation content, is prime for cross-linking. This is a process that takes place after the initial linear polymer has been prepared. When LDPE is mixed with specific free radical initiators at elevated temperatures, it bridges the various chains through “cross-linking” via. the unsaturated side chains. This results in a tertiary structure (3-dimensional structure) that is more “solid”.

Crosslinking reactions are used to “set” a specific shape, either as a solid or as a foam, starting with a pliable, easily handled polymer. Similar process of crosslinking is used in the “vulcanization” of rubber, where a linear polymer made from isoprene polymerization is made into a solid 3-dimensional structure using sulfur (S8) as the agent to tie together various chains. The degree of cross-linking can be controlled to lend specific targets to the properties of the resulting polymer.

Post time: Oct-11-2022