Secondary bonding forces include van der Waal bonds and hydrogen bonding. Hydrogen bonding occurs in certain polymers that contain atoms with unpaired electrons. 1 Figure 4. Two adjacent polyethylene macromolecules showing the attractive forces of van der Waal bonding. Hydrogen bonding between two polymers.
Polymers exhibit anisotropic properties during mechanical loading.
Typical systems will produce a modulus of approximately 100 to 400 GPa when tested in the direction of the molecular alignment. Conversely, when tested in the transverse direction, the strength of the material will drop approximately 100 times. Shown below in Table 1 are the bond strengths of the three type of bonds found in polymers. Hydrogen 10 Van der Waal 1 Table 1. Increasing the amorphous character of the bulk material will increase the transverse strength through entanglement of the long polymer chains.