On the Structure and Strength of Solvent-Welded Joints: The Intrinsic Joint Strength and the Effect of Dissolved Polymer in the Solvent Cement

It is proposed that the intrinsic strength of a solvent-welded joint can be represented by the magnitude of its critical principal strain. A large critical principal strain implied a high intrinsic weld strength. With poly(vinylchloride) adherends, solvent welds formed using pure tetrahydrofuran (THF) and cyclohexanone bonding solvents had high intrinsic joint strengths while solvent welds from pure methyl ethyl ketone (MEK) bonding solvent had lower intrinsic joint strength. In the THF bonding system, the introduction of dissolved polymer in the bonding agent led to significant decreases in the strength of the solvent-welded joint. Additions of up to 2% by weight of dissolved polymer in the MEK bonding agent increased the strength of the solvent weld. However, further increases in the dissolved polymer content in MEK bonding agent also led to decreases in strength.