Calculating Chemical Cross-Link Density Effects on Trapped Shear Modulus
Trapped shear modulus rises linearly with chemical cross-link density while interstitial woven constraint scales effective shear stiffness by factor 1.4 to 2.2.
Average Molecular Weight between Cross Links
Network Density
Structural parameter defining the mean distance between adjacent chemical bonds in a thermosetting resin system. Calculating the average molecular weight between cross links allows a finishing mill to predict the stiffness of treated flax fabric. High values indicate a flexible network with few bridge points.
Mechanical Influence
Elasticity and tensile strength of the finished cloth vary with the density of the network. When the average molecular weight between cross links decreases, the fabric becomes more resistant to wrinkling but loses some of its original tear strength. Chain segments between junctions restrict fiber movement during deformation, which leads to the observed loss in strength.
Analytical Calculation
Determining this value usually involves measuring the swelling ratio of the resin in a specific solvent or using dynamic mechanical analysis. The measurement provides a number that dictates the chemical dosage needed in the pad bath. It stops being useful once the resin reaches its saturation point within the linen fiber.
Because raw flax contains natural waxes, the penetration of the resin must be verified to ensure the calculated average molecular weight between cross links accurately reflects the internal structure rather than just a surface coating. An accurate reading requires a pure sample.