Diallyl orthophthalate (DAOP) is investigated as a reactive plasticizer to aid the processing of PVC by reducing the melt's viscosity and thus minimizing the processing temperature so that decomposition of PVC can be effectively avoided during time-consuming processing operations such as rotational moulding. A range of PVC/DAOP blends have been prepared with dicymyl peroxide (DCP) or cumyl hydroperoxide (CHP) as radical initiators, and their chemorheology, properties and morphology have investigated by dynamic rheometry, DMTA, SEM and solvent resistance. DCP was found to be a better initiator than CHP for polymerization of DAOP in blends with PVC because the former's high decomposition temperature matches well with the processing temperature of the PVC/DAOP blends. DMTA indicates that the T-g of the cured PVC/DAOP blends are very close to that of PVC and have a higher storage modulus at the rubbery region. SEM images show that phase separation occurs during Cure of the blend and that solid poly(DAOP) nano-particles are embedded in the PVC continuous phase when the PVC content is more than 30 wt%. This cure and phase separation of DAOP from the PVC matrix can successfully recover the PVC's thermal-resistance properties. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.