Printing film inspection service

Printing Film Inspection Service – Quality Assurance for Flexible Packaging, Labels and Decorative Films

At zhongxi testing, we provide specialized printing film inspection services to flexible packaging manufacturers, label converters, printing houses, brand owners, and export‑oriented packaging suppliers in Bangladesh. Printing films – including BOPP, PET, PVC, PE, CPP, and metallised films – are widely used in food packaging, pharmaceutical blister packs, labels, shrink sleeves, decorative laminates, and industrial packaging. The quality of printing films affects printability, adhesion, barrier properties, mechanical strength, and appearance. Defects such as poor surface tension, inadequate adhesion, low tensile strength, high haze, colour variation, or insufficient heat seal strength can lead to print defects, delamination, reduced shelf life, and customer complaints. Our ISO/IEC 17025 accredited laboratory performs comprehensive testing – including thickness measurement, tensile strength and elongation, haze and clarity, surface tension (dyne level), ink adhesion (cross‑cut and tape test), heat seal strength, coefficient of friction, shrinkage, water vapour transmission rate, and UV resistance – to ensure compliance with international standards and the stringent quality requirements of Bangladesh’s packaging and printing sectors.

Types of Printing Film Samples We Test

Our laboratory handles a wide range of printing film products used across Bangladesh’s packaging, labelling, and printing industries:

• BOPP (biaxially oriented polypropylene) films – plain, white, pearlised, and metallised grades
• PET (polyethylene terephthalate) films – clear, metallised, and coated grades
• PVC (polyvinyl chloride) films – rigid and flexible grades for labels and shrink sleeves
• PE (polyethylene) films – LDPE, LLDPE, and HDPE for flexible packaging
• CPP (cast polypropylene) films – for laminates and food packaging
• Metallised films – with aluminium or other metallic coatings
• Coated films – with heat‑seal coatings, primer coatings, or barrier coatings
• Laminated films – multi‑layer structures combining different polymers
• Shrink films – for shrink sleeves and shrink labels
• New production batches (incoming quality assurance for converters and printers)
• Printed films from production runs (post‑print quality verification)
• Competitor benchmarking (optical and mechanical properties comparison)

Key Testing Parameters and Methods for Printing Films

1. Thickness Uniformity – ASTM D374 / ISO 4593

The primary parameter in printing film inspection is thickness consistency. Using a digital micrometer (accuracy ±0.001 mm) or a laser thickness gauge, we measure thickness at 10 points across the film width and along the length. For a 20 µm BOPP film, acceptable tolerance is ±2 µm (i.e., 18‑22 µm). For metallised films, we also measure the aluminium coating thickness using X‑ray fluorescence (XRF) – typical metallisation thickness is 20‑40 nm. Thickness variation > ±2 µm leads to print density variation and web handling issues.

2. Tensile Strength and Elongation – ASTM D882 / ISO 527‑3

We cut 15 mm wide specimens from the film in both machine direction (MD) and transverse direction (TD). Using a universal testing machine at 50 mm/min (or 250 mm/min for high‑speed films), we pull the specimen until break. For a 20 µm BOPP film, tensile strength in MD should be ≥ 120 MPa, TD ≥ 200 MPa; elongation at break in MD should be ≥ 120%, TD ≥ 50%. Low tensile strength (< 80 MPa) indicates poor polymer quality or degraded film.

3. Haze and Clarity (Optical Properties) – ASTM D1003 / ISO 14782

We measure haze (%) and clarity (%) using a haze meter with an integrating sphere. For clear BOPP films, haze should be < 2% and clarity > 98%. For matt or white films, haze can be up to 80%. High haze (> 5% for clear films) indicates poor dispersion of additives or surface contamination.

4. Surface Tension (Dyne Level) – ASTM D2578 / ISO 8296

We measure the surface energy (dyne/cm) of the film using dyne test pens of increasing surface tension (30‑50 mN/m). For good printability, the film surface must have a surface tension ≥ 38 mN/m for solvent‑based inks and ≥ 40 mN/m for water‑based inks. Low dyne level (< 34 mN/m) causes ink reticulation, poor adhesion, and print defects. For corona‑treated films, we check the treatment uniformity across the film width.

5. Ink Adhesion (Cross‑Cut and Tape Test) – ASTM D3359 / ISO 2409

We print a test pattern on the film (or use a sample of printed film) and perform a cross‑cut adhesion test. We cut a grid (6×6 lines, 1‑2 mm spacing) through the ink layer, apply pressure‑sensitive tape (25 mm wide, 10 N/25mm adhesion), and pull it off at a 60° angle. We rate adhesion from 0 (no removal) to 5 (complete removal). For flexible packaging films, rating 0 or 1 is required. Poor adhesion (rating > 2) indicates inadequate surface treatment or incompatible ink‑film combination.

6. Heat Seal Strength – ASTM F88 / ISO 20266

For films used in heat‑sealable packaging, we seal two film specimens together using a heat sealer at a specified temperature (e.g., 120‑160°C), pressure (e.g., 0.2 MPa), and dwell time (e.g., 1‑2 seconds). We cut 25 mm wide strips from the sealed area and test the peel strength using a universal testing machine at 300 mm/min. For a typical heat‑sealable BOPP film, the heat seal strength should be ≥ 5 N/25mm at the recommended sealing temperature. Low seal strength (< 3 N/25mm) causes package leaks and seal failure.

7. Coefficient of Friction (COF) – ASTM D1894 / ISO 8295

We measure the static and kinetic coefficient of friction (μ) of the film surface against itself and against a standard metal surface (steel). We place the film on a horizontal platform, place a 200 g sled (covered with film), and pull at 150 mm/min. For automatic packaging lines, the COF should be 0.2‑0.4 for both static and kinetic friction. High COF (> 0.6) causes film sticking and feeding problems; low COF (< 0.15) causes film slippage and register errors.

8. Shrinkage (for shrink films) – ASTM D1204 / ISO 11501

We cut a 100×100 mm specimen from the shrink film, mark its dimensions, and place it in an oven at 100‑150°C (depending on film type) for 30‑60 seconds. We measure the length and width shrinkage (%). For PVC shrink films, typical shrinkage is 30‑50% in MD and 10‑30% in TD. For PET‑G shrink films, shrinkage is 40‑70% in MD and 5‑15% in TD. Low shrinkage (< 20%) indicates poor film orientation; high shrinkage (> 70%) may cause film tearing during shrinking.

9. Water Vapour Transmission Rate (WVTR) – ASTM F1249 / ISO 15106

For barrier films used in food and pharmaceutical packaging, we measure the water vapour transmission rate (g/m²·24h). We mount the film in a permeation cell and measure the amount of moisture passing through the film at 38°C, 90% RH. For a high‑barrier film (e.g., metallised PET), WVTR should be < 5 g/m²·24h. For standard OPP films, WVTR is typically 5‑10 g/m²·24h. High WVTR (> 20 g/m²·24h) indicates poor barrier performance, reducing product shelf life.

10. UV Resistance and Yellowing – ASTM G154 / ISO 4892‑2

We expose film samples to xenon arc radiation (0.35 W/m² at 340 nm, 60°C black panel, water spray cycles) for 500‑1000 hours. After exposure, we measure the colour change (ΔE) using a spectrophotometer. For clear films, acceptable ΔE is < 3 after 500 hours. For white films, ΔE < 4. For metallised films, we also check for tarnishing or delamination. High ΔE (> 5) indicates poor UV stability, leading to yellowing during shelf storage.

11. Blocking Resistance – ASTM D3354 / ISO 11502

We stack two film specimens face‑to‑face and apply a 2 kg weight at 50°C for 24 hours. We then separate the films and measure the force required to peel them apart (or rate the degree of blocking). For a high‑quality printing film, there should be no blocking (0 N peel force). Blocking (peel force > 1 N) causes film sticking during unwinding and printing.

Quality Grading and Acceptance Criteria

Based on our printing film inspection, we classify films into three grades (clients provide specific acceptance criteria for their printing and packaging process):

• Grade A (Premium – High‑Speed Printing and Lamination) – Thickness tolerance ±1 µm, tensile strength ≥ 95% of spec, haze < 1.5%, surface tension ≥ 40 mN/m, ink adhesion rating 0, seal strength ≥ 6 N/25mm, COF 0.2‑0.35, shrinkage within spec, WVTR < 5 g/m²·24h, UV ΔE < 2.
• Grade B (Standard – General Printing and Packaging) – Thickness tolerance ±2 µm, tensile strength ≥ 85% of spec, haze < 3%, surface tension ≥ 38 mN/m, ink adhesion rating 1, seal strength ≥ 4 N/25mm, COF 0.2‑0.4, shrinkage within spec, WVTR < 10 g/m²·24h, UV ΔE < 4.
• Grade C (Reject – Not Suitable) – Thickness tolerance > ±3 µm, tensile strength < 70% of spec, haze > 5%, surface tension < 34 mN/m, ink adhesion rating > 2, seal strength < 2 N/25mm, blocking, high WVTR, visible yellowing – immediate batch rejection.

Reporting and Deliverables

Our printing film inspection report includes: sample identification (film type, thickness, manufacturer, batch number, surface treatment), thickness map (min, max, average, CV%), tensile strength and elongation (MD and TD), haze and clarity, surface tension (dyne/cm), ink adhesion rating, heat seal strength (N/25mm), COF (static and kinetic), shrinkage (%), WVTR (g/m²·24h), UV resistance (ΔE), blocking resistance, and a clear pass/fail conclusion based on client‑supplied criteria. Raw data (stress‑strain curves, spectrophotometer logs, seal curves) are archived for 10 years.

In summary, a comprehensive printing film inspection service from zhongxi testing ensures that your films deliver consistent print quality, adhesion, barrier performance, and mechanical durability for Bangladesh’s expanding packaging and printing sectors. Contact our laboratory to schedule batch testing for your next film procurement.

Applications in the Bangladesh Packaging and Printing Industry

• Flexible packaging for food, snacks, and confectionery (printed films for pouches and sachets)
• Pharmaceutical packaging (blister packs, strip packs, and sachet films)
• Labels and shrink sleeves (beverage, personal care, and household products)
• Decorative laminates and surface films (furniture and interior decoration)
• Industrial packaging (shrink wrap, stretch wrap, and protective films)