| Film Construction and Material Control |
| Film polymer | Flexible medical-grade polyvinyl chloride (PVC) suitable for fluid-contact applications. | Review material specification, formulation declaration, and incoming inspection records. | Supports consistent flexibility, weldability, and compatibility with the intended medical application. |
| Nominal film thickness | 0.25–0.35 mm, with a controlled tolerance defined in the purchasing specification. | Measure at multiple locations using a calibrated thickness gauge; avoid sealed edges and printed areas. | Thicker film generally improves puncture and handling resistance, but excessive thickness can reduce flexibility and increase sealing energy. |
| Thickness uniformity | Target variation: no more than ±10% from the nominal thickness within a roll or lot. | Take measurements across the web width and along the roll length using a documented sampling plan. | Uniform thickness helps maintain consistent heat transfer, seal formation, and mechanical performance. |
| Plasticizer and additive disclosure | Full formulation disclosure to the applicable regulatory assessor, including plasticizer type, stabilizers, pigments, and processing aids. | Supplier declaration supported by chemical documentation and, where required, extractables or biocompatibility evaluation. | Plasticizer migration, odor, discoloration, or incompatibility can affect safety and product durability. |
| Visual appearance | No pinholes, gels, cracks, foreign particles, delamination, or visible streaks in the functional area. | 100% visual inspection under controlled illumination, supplemented by leak testing. | Surface defects can become leakage paths or stress-concentration points during use. |
| Seal Strength and Leak-Resistance Verification |
| Seal strength acceptance criterion | Minimum ≥1.0 N/mm of seal width. This equals ≥25 N per 25 mm of seal width. | ASTM F88/F88M seal-strength testing. Report the force, specimen width, seal mode, failure mode, and test conditions. | Provides a measurable minimum strength for welded seams and reduces the risk of seal opening during filling, transport, or handling. |
| Recommended ASTM F88/F88M specimen | Specimen width: 25 ± 1 mm; test at least five specimens per production lot or according to the validated sampling plan. | Cut specimens perpendicular to the seal and avoid corners, tubing junctions, and visibly defective areas unless those locations are being evaluated separately. | A consistent specimen geometry makes results comparable between lots and process settings. |
| Test conditioning | Condition specimens for at least 24 hours at 23 ± 2°C and 50 ± 5% relative humidity, unless the validated procedure specifies otherwise. | Record conditioning time, temperature, humidity, seal age, and equipment identification. | Temperature and humidity can change PVC flexibility and produce misleading seal-strength results. |
| Test speed and jaw separation | Use a validated constant crosshead speed, such as 200 mm/min, and apply the same speed to comparative testing. | ASTM F88/F88M-compatible tensile tester with calibrated load cell; document the selected test method and speed. | Test speed affects measured peak force and must remain consistent for meaningful trend analysis. |
| Seal failure mode | Prefer cohesive film failure, controlled yielding, or peel failure above the minimum strength; reject channel leaks, unsealed areas, and brittle tearing. | Record the failure mode for every specimen, not only the numerical peak force. | A high force value alone may not identify a continuous leakage path or a localized weak point. |
| Seal width | Use a continuous seal width appropriate to the bag design; a nominal 3–6 mm welded area is common for many flexible medical-bag constructions, subject to design validation. | Measure the actual welded width at several locations and verify the complete perimeter or seam design. | Adequate seal width distributes load and helps compensate for normal variation in film thickness and process temperature. |
| Seal process window | Establish validated ranges for temperature, pressure, dwell time, and cooling time rather than relying on a single setting. | Run process-window studies and confirm that all tested settings maintain at least 1.0 N/mm with acceptable failure modes. | A process window improves robustness against changes in equipment, line speed, ambient conditions, and film lots. |
| Leak test after sealing | No visible leakage or pressure decay exceeding the validated product limit. | Use a validated air-pressure decay, immersion, vacuum, or dye-penetration method appropriate to the finished bag. | Seal-strength testing measures mechanical resistance, while leak testing confirms functional fluid containment. |
| Mechanical and Functional Performance |
| Tensile strength | Set a project-specific minimum in both machine and transverse directions; a practical development target for flexible PVC film is approximately 15–25 MPa, subject to formulation and thickness. | Test according to ISO 527-3 or another validated thin-film tensile method, reporting direction, specimen type, speed, and conditioning. | Helps prevent tearing during bag filling, suspension, transport, and connection to drainage tubing. |
| Elongation at break | Define a minimum based on the bag geometry; flexible PVC constructions commonly require high elongation to tolerate bending and handling. | Measure with the same tensile method used for tensile strength and report machine and transverse directions separately. | Insufficient elongation can cause cracking or tearing when the filled bag is flexed or dropped. |
| Puncture and tear resistance | Use internally established minimum values based on bag volume, wall design, packaging, and transport hazards. | Evaluate with validated puncture and tear procedures, such as ISO 6383-2 for tear propagation where applicable. | Urine bags may contact bed rails, clamps, packaging edges, and other objects that can initiate a tear. |
| Flex-crack resistance | No functional cracks or leakage after the validated repeated-flexing cycle. | Perform a product-specific flexing test on film and finished bags, followed by visual inspection and leak testing. | Repeated folding around tubing connections or during storage can weaken the film even when initial strength is acceptable. |
| Tube and port attachment | Attachment seals must meet the same or a separately validated mechanical and leak-resistance requirement as the main bag seam. | Conduct tensile pull, torque or bend evaluation, and leak testing on representative finished assemblies. | Ports and tubing junctions are common stress concentrations and should not be qualified only by flat-film seam testing. |
| Transparency and readability | Film should permit visual monitoring of liquid level, color, and particulate matter, with haze controlled to the product requirement. | Use a validated haze or optical inspection method and inspect filled finished bags under intended-use lighting. | Clear visual observation supports monitoring of volume and unusual contents during clinical use. |
| Lot Release and Documentation |
| Lot traceability | Each film lot should have traceable resin/additive records, manufacturing date, roll identification, thickness, and test results. | Review the certificate of analysis and match roll labels to production and inspection records. | Traceability enables containment and investigation if a seal or leakage trend is detected. |
| Routine seal-strength testing | Test start-up samples, periodic production samples, and samples after material, tooling, or process changes. | Use a documented sampling plan with a minimum acceptance value of ≥1.0 N/mm and defined retest rules. | Routine testing verifies that the validated sealing process remains in control throughout production. |
| Finished-bag visual and leak inspection | No open seams, pinholes, wrinkles crossing seals, incomplete welds, or visible contamination. | Inspect 100% of finished bags where feasible, followed by the validated leak test required by the product specification. | Detects defects that a small number of flat-seal tensile specimens may not represent. |
| Change control | Requalify film and seals after changes to PVC formulation, plasticizer, thickness, supplier, sealing equipment, tooling, or process parameters. | Repeat applicable seal-strength, leak, mechanical, and compatibility evaluations using documented change-control procedures. | Small material or process changes can alter sealing behavior, flexibility, extractables, and long-term durability. |
| Overall purchasing decision | Accept only when the film meets the approved medical-material requirements, the seal strength is ≥1.0 N/mm, failure modes are acceptable, and finished bags pass leak testing. | Review the complete qualification package rather than relying on thickness or seal-strength data alone. | Durability is a combination of material consistency, seam performance, attachment integrity, and finished-product leak resistance. |
