The effect of low levels of plasticizer on the rheological and mechanical properties of polyvinyl chloride newsprint-fiber composites

Plasticizers play a key role in the formulation of semirigid and flexible PVC and in determining their physical properties and processability. This study examines the effects of the low phr levels of plasticizer (DOP) on the rheological and mechanical properties of rigid and semi-rigid PVC/newsprint-fiber composites. Mechanical and rheological properties of unfilled PVC compounds and PVC/newsprint-fiber composites at 45 phr were compared over the range of 0 to 15 phr of DOP plasticizer. Analyses of data using SAS procedures of ANOVA were also conducted to discern the effects of concentration of plasticizer on these properties. The following conclusions were reached: 1) DOP was relatively ineffective in improving melt flow index of the composites compared to unfilled PVC. 2) The composites were significantly inferior in tensile strength at yield and stiffer than unfilled PVC. The differences observed were roughly the same over the DOP range studied. 3) Elongation at break and toughness (break energy) were lower for the composites and were essentially independent of DOP level, whereas there was a significant improvement for unfilled PVC over the DOP range studied. 4) Impact strengths of the composites and unfilled PVC were essentially comparable up to about 11.25 phr of DOP. However, at 15 phr DOP, impact strength of the composite was far inferior to that of unfilled PVC. 5) The well-known antiplasticization effect was noted for the unfilled PVC, as well as to some extent for the filled PVC.