Meaning
Chemical proportions dictate the efficiency of polymerization and the final properties of a synthetic resin. Stoichiometry governs the ratio of monomers and additives required to achieve a specific molecular weight or cross-link density. In polyurethanes or epoxies, an incorrect balance between resin and hardener leads to soft parts or brittle failures.
Precise control over these quantities is required to maintain the specified performance of the polymer.
Reaction Balance
Exact matching of reactive sites ensures that no unreacted monomers remain in the final part. These leftover chemicals can act as plasticizers or migrate to the surface as an oily film.
Endgroup Ratio
Monitoring the concentration of functional groups at the ends of polymer chains allows for the control of chain extension. In condensation polymers like PET, the balance between acid and glycol groups determines how long the chains can grow during the reaction. Deviating from the ideal ratio limits the potential viscosity and strength of the resin.
This chemical balance is often adjusted during the manufacturing process to produce different grades for extrusion or injection moulding. Lab analysis verifies that the feedstock meets the required chemical signature before it is shipped to the customer.
Molecular Weight
Proper balance of reactants leads to the long chains that give polymers their characteristic toughness. Shorter chains result in lower melt strength and poorer resistance to chemicals.
