𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞 : 𝐖𝐡𝐲 𝐦𝐨𝐥𝐞𝐜𝐮𝐥𝐚𝐫 𝐰𝐞𝐢𝐠𝐡𝐭 𝐢𝐬 𝐚𝐯𝐞𝐫𝐚𝐠𝐞 𝐢𝐧 𝐩𝐨𝐥𝐲𝐦𝐞𝐫𝐬

𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞

𝐖𝐡𝐲 𝐦𝐨𝐥𝐞𝐜𝐮𝐥𝐚𝐫 𝐰𝐞𝐢𝐠𝐡𝐭 𝐢𝐬 𝐚𝐯𝐞𝐫𝐚𝐠𝐞 𝐢𝐧 𝐩𝐨𝐥𝐲𝐦𝐞𝐫𝐬

Polymers are long-chain molecules formed by linking repeating units called monomers.

Example: Polyethylene (PE)

Repeating unit: –CH₂–CH₂–

During polymerization, chain growth does not occur uniformly:

Some polymer chains remain short

Some grow to medium length

Some become very long

As a result, a single polymer sample contains a mixture of molecules with different chain lengths.

For instance, one chain may contain 500 repeat units, another 5,000, and another 50,000, all chemically identical, yet with different molecular weights.

Because polymers do not have identical molecules, their molecular weight cannot be represented by a single value. Instead, we use average molecular weights, such as:

Number average molecular weight (Mn)

Weight average molecular weight (Mw)

Polydispersity Index (PDI = Mw / Mn)

These averages help explain and predict:

Chain length distribution

Mechanical strength

Melt flow behavior

Processability in extrusion, blown film, and molding

The impact of molecular weight on the properties of polymers, with reference to the article below.

source : Uttam Singh

#PolymerScience #MolecularWeight #Polyethylene #Extrusion #BlownFilm