Sintering is one of the most practical methods for fabricating the porous polymeric microstructures through controlling the interfacial welding and mutual chain diffusion of polymeric particles. Porosity of sintered samples can be estimated using an offered simplified equation, considering sintering neck radius. Particles welding taking place through global or segmental relaxation and diffusion of polymeric chains at particles interface, exhibits a severe sensitivity to processing temperature, especially on the borderline between solid and melt states. Easier relaxation of chains was attributed to destruction of some crystalline regions and more freely motion of chains due to a transition to amorphous state as temperature increases. In this work, in order to simulate and control the microstructural porosity, the coalescence rate of two separated particles has been studied, using hot stage microscopy (HSM). Consequently, the necessary time for particles welding and coalescence with special neck radius to achieve determined final porosity, is estimated. The microporous structure has been confirmed by means of SEM images; and finally based on DSC and shear punch mechanical test results, interfacial microstructural changes and welding quality of particles in sintered porous samples have been discussed.