Examination of the chemical changes in cured phenol-formaldehyde resins during storage

• Py-GCMS is useful to assess chemical changes occurring during storage of resins.
• Py-GCMS results supported by FT-NIR and IGC data.
• Py-GCMS showed that chemical changes occurred during resins storage are limited.
• Innovative application of IGC.
• Worse adhesion of resites to abrasive grains due to the decrease of their surface energy during storage.

Chemical changes occurring within cured phenol-formaldehyde resins (resite and novolak type) during their storage were investigated by FT-NIR, py-GCMS and inverse gas chromatography. It was shown that a mixture of resite with novolak was less stable than resite or novolak itself as regards bulk properties. This aging phenomenon is mainly due to reaction of ammonia (product of hexa decomposition) with CH2OH groups present in resite. FT-NIR technique seems to be the least sensitive method for assessment chemical changes occurring during cured resins storage. Applications of py-GCMS and IGC method made able to indicate that more significant changes were for bulk samples (py-GCMS results) than on their surface (IGC results).