Tensile Testing of Plastic Films & Sheets: ASTM D 882 Method, Machine & Tips

Tensile strength and elongation are the two numbers every film buyer asks for. Whether the product is a mono-layer liner, a 5-layer barrier film, a raffia tape or a laminate, ASTM D 882 and ISO 527-3 define how those numbers must be measured — and small procedural details change results dramatically.

Here is how the test is run on a Single Screw Tensile Testing Machine, and how to get repeatable, buyer-defensible data.

The ASTM D 882 Test in Practice

Strip specimens (typically 15–25 mm wide) are cut in both machine direction (MD) and transverse direction (TD), conditioned, and clamped in line-contact or rubber-faced grips. The machine pulls at a constant rate — commonly 500 mm/min for elongation-dominant films — while recording force and extension until break.

MD and TD must always be reported separately: blown and cast films are oriented during production, and a film that is strong in MD can be weak in TD. A single averaged number hides exactly the defect a converter needs to see.

Common Errors That Ruin Film Tensile Data

• Jaw breaks — specimens failing at the grip line indicate wrong grip faces or over-clamping; those results must be discarded.
• Ragged specimen edges — nicks from blunt blades initiate early failure; use a fresh cutter or precision sample cutting press.
• Unconditioned samples — humidity changes elongation of polyamide and cellulosic films by double-digit percentages.
• Wrong gauge length or speed — results are only comparable when the standard's specimen geometry and rate are followed exactly.

Built-In Programs for Film Producers

International Equipments' single-screw tensile testers include pre-loaded programs for tensile and elongation per ASTM D 638, ASTM D 882 and ISO 527, plus routines for peel, seal and bond strength — letting one bench machine cover the daily QC of a film plant. For heavier laminates and woven sacks, step up to a twin-screw UTM.

Frequently Asked Questions