Polarity
Polypedia > Properties of polymers > Physical properties
| Polarity | ||
The presence of atoms of different nature causes that, in the covalent bonds, the electrons move towards the more electronegative atom, thus creating a dipole that changes the polarity. Polymers or elastomers that contain these highly electronegative atoms, such as fluorine (F), chlorine (Cl), oxygen (O), nitrogen (N), sulfur (S) etc. they will be polar compounds, which influences the properties of the material. If the polarity increases, mechanical strength, rigidity, heat resistance, water and moisture absorption, hardness, chemical resistance, as well as permeability to polar compounds such as water vapor and adhesiveness and adhesion to metals. While the polarity decreases, on the other hand, it decreases the thermal expansion, the electric isolation power, the tendency to accumulate electrostatic charges and the permeability to polar molecules (CO2, O2, N2). |  | |
| Polars | ||
In general, monomers containing only C and H atoms, similar as electronegativity, are non-polar. In general, the greater the cohesion forces (hydrogen bridges) between the chains, the more rigid the polymer will be and the higher the melting temperature in the case of crystalline polymers or the softening temperature in the case of non-polymer polymers. crystalline (amorphous). |  | |
| No polars | ||
The monomers contain highly electronegative atoms, such as Cl, F, O, N, S that give rise to polymers that contain permanent electric dipoles called polar polymers. |  | |