Formulation and characterization of new ternary stable composites: Polyvinyl chloride-wood flour- calcium carbonate of promising physicochemical properties

Low cost massive wastes, wood flour (WF) and precipitated calcium carbonate (PCC-sugar origin(were used as fillers completely incorporated in polyvinyl chloride (PVC) matrix producing PVC/WF/PCC composites of lower density and cost with higher thermal stability and stiffness compared with PVC. Some hydrogen bonds formed between OH of lignin and cellulose in WF and α-H of PVC by incorporating of WF into PVC matrix. Tensile modulus of composites increased by adding both PCC and/or WF into PVC matrix which is probably due to restraining effect of filler on polymer molecules. Hardness Shore-D increased with increasing both WF and PCC of higher hardness than PVC matrix. Tensile and flexural strength of PVC/WF composite improved by adding low content of PCC that having good dispersion of PCC particles in PVC matrix (up to 10 wt.%) compared with the composite contains 62 wt.% WF. At higher wt.%, tensile and flexural strength are reduced due to the absence of uniform distribution of PCC in PVC/WF matrix which improves the mechanical properties. SEM images showed the morphology and possible interfacial adhesion within the composite. SEM micrograph for neat PVC compound showed homogeneous, smooth and uniform fractured surface while SEM micrograph for PVC/62 wt.% WF showed many voids indicating poor PVC-WF interaction. Some particles pulled out or remained loosely within the matrix resulting in poor stress transferring from matrix to the filler. SEM micrograph of PVC/52 wt.% WF/10wt.% PCC composite showed the best dispersion of PCC in PVC/WF matrix. Dispersion became non- homogeneous at the percentages higher than 10 wt.% due to the agglomeration of PCC particles leading to cavities in the matrix. The lower filler content leads to more uniform dispersion of PCC particles inside the matrix. H2O absorption and thickness swelling of PVC/WF/PCC composites were higher than PVC due to WF polarity. PCC enhanced thermal stability of composites and act as an acid acceptor for secondary stabilization of PVC neutralizing chloride ions.