Hot Melt Adhesive Film Transparent

Solamni's transparent hot melt adhesive film QC protocol emphasizes optical clarity, thickness uniformity, and bond consistency - the three quality dimensions that determine whether the adhesive line remains invisible after lamination.

Extrusion process control. TPU resin is dried at 90–105°C for 3–4 hours to moisture below 0.02%, preventing hydrolytic degradation and optical haze from micro-voids during film formation. The cast-film extrusion line uses a polished chrome chill roll (Ra ≤ 0.02 μm) held at 25–35°C ±1°C to produce a crystal-clear surface. In-line laser thickness gauges scan the full web at 500 Hz, and automatic die-lip adjustment maintains thickness within ±0.005 mm. For release-lined film, the lamination station applies silicone-coated PET or paper at controlled tension to prevent wrinkling.

Optical and physical testing (per batch).

• Light transmission and haze - spectrophotometer / hazemeter, ASTM D1003, 5 specimens per roll.
• Thickness - micrometer, 10 points across web width, ±0.005 mm tolerance.
• Activation temperature - DSC (differential scanning calorimetry) at 10°C/min, peak endotherm recorded.
• Melt viscosity - Brookfield viscometer at activation temperature ±1°C.
• Peel strength - 180° peel, 25 mm strip, 300 mm/min, on specified substrate pairs after 24 h cure at 23°C / 50% RH.
• Lap shear - 25.4 mm × 12.7 mm overlap, 1.5 kN/min, ASTM D1002.
• Open time - automated heat-press test, timed from removal to loss of tack.
• Optical defect inspection - 100% in-line camera inspection for gels, fish eyes, specks, and streaks > 0.3 mm; defects are flagged and mapped to roll position.
• Thermal stability - film held at activation temperature + 15°C for 30 min, no yellowing (ΔE ≤ 1.0) or viscosity shift > 10%.
• Moisture content - Karl Fischer titration, ≤ 0.05%.

Chemical and regulatory testing. Each TPU resin lot is verified by melt flow index (190°C / 2.16 kg) and FTIR spectral matching. Finished film is screened by GC-MS for REACH SVHC and ICP-OES for RoHS restricted elements. Food-contact and skin-contact grades are additionally tested for extractables per EU 10/2011. OEKO-TEX Standard 100 compliant grades are available for textile and apparel applications. Third-party SGS or Intertek reports are issued on request.

Equipment backing production stability. The plant operates 3 cast-film extrusion lines (width up to 1,800 mm) with polished chill rolls, 2 release-liner lamination stations, 4 precision slitting and rewinding machines, in-line laser thickness gauges, an in-line optical inspection system, and a hazemeter / spectrophotometer lab. This setup supports thickness variation below 3% CV and zero visible adhesive line after lamination on light-colored and transparent substrates.