oxide butylene oxide and the like these are generally referred to as u201c polyether polyols u201d another example is the graft copolymer polyols which include but are not limited to conventional polyether polyols with vinyl polymer grafted to the polyether polyol chain yet another example is polyurea modified polyols which consist of conventional polyether polyols with polyurea particles dispersed in the polyol examples of polyols used in polyurethane modified polyisocyanurate foams include but are not limited to aromatic polyester polyols such as those based on complex mixtures of phthalate type or terephthalate type esters formed from polyols such as ethylene glycol diethylene glycol or propylene glycol these polyols are used in rigid laminated boardstock and may be blended with other types of polyols such as sucrose based polyols and used in polyurethane foam applications catalysts used in the manufacture of polyurethane foams are typically tertiary amines including but not limited to n alkylmorpholines n alkylalkanolamines n n dialkylcyclohexylamines and alkylamines where the alkyl groups are methyl ethyl propyl butyl and the like and isomeric forms thereof as well as heterocyclic amines typical but not limiting examples are triethylenediamine tetramnethylethylenediamine bis 2 dimethylaminoethyl ether triethylamine tripropylamine tributylamine triamylamine pyridine quinoline dimethylpiperazine piperazine n n dimethylcyclohexylamine n ethylmorpholine 2 methylpiperazine n n dimethylethanolamine tetramethylpropanediamine methyltriethylenediamine.