4.1 Defects in film are not acceptable to the end-user as there is a reduction in the fitness-for-use in many applications. This document is intended to be a practice to assist users in the inspection, quantification and observation of defects.

4.2 This practice is applicable in a laboratory environment, continuous inspection as a quality control or as a research tool. It is also appropriate for use in any commercial process used to produce film including extrusion, calendaring, etc.

4.3 This practice is also suitable for use as an evaluation or screening tool for materials intended to be used in other processes where defects of this nature are critical, such as fiber spinning non-woven, etc.

4.4 Results achieved by different equipment, even from the same vendor in the same laboratory, are often not directly comparable as a bias exists that cannot be fully addressed through consistent operating conditions. Results frequently shift when analyzer components are upgraded. Additionally, results are often not directly comparable between different product types. All results are to be considered as relative values rather than absolute.

4.4.1 Therefore, it is not recommended to provide absolute results as part of a sales contract between the buyer and seller. For sales contracts, it is recommended to establish product grade designations based on the historical relationship of the absolute results reported, and fitness-for-use or based on a reference material agreed by both parties. This is attained by the collection of data over a time-period to establish acceptable control limits.

4.4.2 The defect size range of interest is usually different between resin supplier and converters. Total defect counts are not one to one comparable between small laboratory extrusion lines and commercial extrusion lines. Therefore, an individual correlation is the aim to get accepted results for fitness-for-use.

Note 2: This was tested on Brabender, Collin, Goettfert, and OCS systems.

4.5 For support in a basic interpretation of the different results the following points may be helpful for comparison.

4.5.1 Size classes (number and definition)

4.5.2 Reported defect types

4.5.3 Comparable units (gels/kg, gels/m², class system, index...)

4.5.4 Vendor (type of equipment, for example, cast or blown film...)

4.5.5 Camera settings (sensitivity, grey level, resolution...)

4.5.6 Extrusion parameters

Note 3: For attribute data such as defect counts, C-type control charts are most appropriate per recommendations within Practice E2587, Section 9.