Non Fluorinated Durable Water Repellent Wet Processing Specifications
Non-fluorinated DWR wet processing requires bath pH 4.0-5.5, WPU control, and core cure temperatures of 150-170°C with crosslinkers to pass 10 ppm fluorine limits.
Chemical Add-on Rate
Quantitative Measure
Mass ratios measuring dry chemical solids deposited relative to untreated fabric weight determine the exact finish load delivered during continuous processing. Calculating the chemical add-on rate requires multiplying wet pickup percentage by the solids concentration of the padding liquor. Finishing facilities utilize this metric to regulate resin deposition, flame retardant levels, and hydrophobic agent consumption on running fabric webs.
The metric establishes dry mass deposition independent of water evaporation volume, isolating dry active solids from overall moisture uptake. Application ceases to follow this calculated metric when volatile bath components evaporate prematurely or padding liquor solids precipitate out of solution.
Calculated Loading
Mathematical determination relies on strict bath concentration and wet expression values. Establishing the chemical add-on rate begins by dividing the dry mass of applied auxiliary solids by the original bone-dry weight of the greige or prepared fabric substrate. When a finishing pad delivers seventy percent wet pickup from a bath containing ten percent dry solids, the resulting active deposition calculates to seven percent on weight of fabric.
Gravimetric checks verify this value by drying treated swatches to bone-dry state and comparing them against unpadded baseline swatches. Precision balances inside mill testing laboratories confirm that deposition matches the specified formulation recipe before bulk running proceeds.
Substrate Interaction
Surface energy and yarn absorbency directly influence bath uptake across varying fabric constructions. Denser woven twills require altered squeeze roll pressures to deposit an identical chemical add-on rate compared to open plain weave fabrics. Hydrophilic cotton fibres absorb pad liquor internally, whereas synthetic polyester filaments carry the chemical mass predominantly as an external surface film.
Uneven preparation or patchy scouring causes localized variation in active finish distribution across the continuous web.
Inspection Tolerance
Commercial tolerance windows define the allowable variance between specified and delivered active solids. Finishing specifications stipulate acceptable add-on boundaries to balance functional performance against physical property degradation. Substandard deposition fails functional testing protocols such as water repellency spray ratings, while excessive deposition stiffens fabric hand and reduces tear strength.
Chemical add-on rate consistency across long production runs prevents shade variations caused by resin-induced dye migration.