Structure And Properties Of Cross-linked Polyvinyl Chloride Foam Modified By Phthalic Anhydride

Rigid PVC foam cross-linked by isocyanate offers good thermal stability, low water absorption and water vapor permeability, extremely high strength-to-weight ratio, good resistance to solvents and compatibility with the polyester resins. Now Rigid PVC foam is widely used in load-carrying structure as core material for sandwich structure composites, i.e., wind turbine turbines, marine, aircraft and vehicle application. Although isocyanate/anhydride crosslinking PVC foam was developed very early, but there is few references about studying of the chemical structure of cross-linked rigid PVC foam. The relationships between the structure and the properties of PVC foam is also a lack of systematic reporting.Here rigid cross-linked PVC foams with different contents of phthalic anhydride were prepared in this study. The FTIR results showed that the content of imide structure in the foams increased with the increase of PA content. The formation reason of imide structure was proposed. Then the chemical structure of cross-linked PVC foam modified by phthalic anhydride was studied. We also investigated the influence of phthalic anhydride loading on the chemical structure of cross-linked PVC foam.Based on the results of prefoam and the fractions from the extraction of PA100 sample, the chemical reactions during the preparation of cross-linked PVC foam were put forwarded. The formation of imide structure was proved in the cross-linked network.Next, the mechanical performances of cross-linked PVC foams were investigated.The influence of PA loading and PVC loading on the cell size and density of PVC foams were proved. The influence of foam density and PA loading on mechanical performances of PVC foams were discussed. The relationship between the mechanical performances and the chemical and negotiation structure were offered. The results showed that the mechanical performance of PVC foams became weaker with more PA loading. The formation of imide structure cut cross-linked networks, which influenced the aggregation state structure and caused the decrease of mechanical properties.