A neutral PE-coated paper type test program provides a systematic framework for verifying that extrusion-laminated paper products consistently meet physical, chemical, and food-contact safety requirements before mass production and certification. This technical guide explains the scope, sampling rules, test items, reference standards, test methods, acceptance criteria, and reporting requirements for neutral laminated paper. It is written for quality engineers, laboratory personnel, certification specialists, and procurement teams in the paper and packaging industry.
Technical Overview
Neutral PE-coated paper (neutral laminated paper) is a packaging substrate consisting of a base sheet manufactured under neutral sizing conditions—typically using AKD or ASA sizing agents with calcium carbonate filler, giving a near-neutral extract pH of approximately 6.5 to 8.0—and a polyethylene layer that is extrusion-coated onto one or both sides. The PE layer, typically applied at 12 to 30 g/m² per side, provides heat-sealability, liquid barrier performance, and lamination compatibility, while the neutral papermaking system offers long-term aging stability, high bulk, and reduced corrosivity.
A type test (type examination) is a full-scope conformity test performed on a representative sample of a defined product type to verify that the design, materials, and process can consistently meet the requirements of the applicable product standard, specification, or certification scheme. A neutral PE-coated paper type test program therefore consolidates the test basis, sampling rules, test items, methods and conditions, acceptance criteria, judgment rules, and reporting requirements into a single controlled document, normally operated under an ISO/IEC 17025-compliant laboratory management system.
A type test is typically required in the following situations:
- Initial design finalization or new product release before mass production;
- Application for product certification or production licensing;
- Changes in base paper furnish, sizing system, PE resin grade or supplier, coating weight class, or coating structure;
- Major changes in process equipment or parameters affecting product characteristics;
- Resumption of production after a prolonged shutdown, commonly more than six months;
- Periodic verification, typically every 12 months or as stipulated by the certification body or customer contract.
Testing Samples
Defining the Product Type and Batch
A type test sample must be fully representative of the declared product type, which is defined by a consistent combination of fiber furnish and neutral sizing system, base paper grammage class, coating structure (single-sided or double-sided PE), PE coating weight class, and production route. Samples are normally drawn from three consecutive production lots, or from one continuously produced and statistically stable lot, in accordance with GB/T 10342 for paper and board sampling; where lot acceptance procedures apply, GB/T 2828.1 / ISO 2859-1 may be referenced. A typical submission consists of 50 to 100 full-width sheets or two rolls at least 500 mm wide, sufficient for all test groups plus a 30 percent reserve for retests.
Conditioning and Pre-Treatment
All physical test specimens shall be conditioned at (23 ± 2) °C and (50 ± 5) % relative humidity for at least 24 hours in accordance with GB/T 10739 / ISO 187 before testing. Specimens for migration testing are cut into pieces of known area, typically 1 dm² test faces, while avoiding contamination of the food-contact surface. Specimens for microbiological testing are handled under aseptic conditions and transported in sterile containers.
Sample Allocation
- Group A – Physical and mechanical properties: grammage, thickness, tensile strength, bursting strength, tearing resistance, and moisture content;
- Group B – Coating performance: PE coating weight, heat seal strength, coating adhesion and delamination resistance, Cobb water absorptiveness, grease resistance, and coating continuity;
- Group C – Chemical properties: extract pH, ash content, fluorescent whitening agents, and heavy metal content;
- Group D – Food contact safety: total (overall) migration and specific migration, required for food-grade declarations;
- Group E – Microbiological cleanliness, required for food and medical applications;
- Retained samples: sealed and stored for the period defined in the contract, typically not less than three months.
Testing Items
The item set below represents the core scope for neutral PE-coated paper; the final list shall be confirmed against the applicable product specification and end-use requirements.
Physical and Mechanical Properties
- Grammage (g/m²) and grammage deviation;
- Thickness (µm) and thickness deviation;
- Tensile strength and elongation at break, machine direction (MD) and cross direction (CD);
- Bursting strength (kPa);
- Internal tearing resistance (mN), MD and CD;
- Moisture content (%);
- PE coating weight per side (g/m²).
Coating and Surface Performance
- Heat seal strength (N/15 mm) at specified temperature, pressure, and dwell time;
- Coating adhesion and resistance to delamination between the PE layer and the base paper;
- Cobb 60 water absorptiveness of the uncoated surface (g/m²);
- Grease and oil resistance (Kit rating) for direct food contact grades;
- Brightness, whiteness, and opacity of the printable surface;
- Coating continuity, verified as freedom from pinholes by dye or colored-liquid penetration;
- Surface smoothness or roughness where print quality is specified.
Chemical Properties
- pH of aqueous extract (cold extraction), confirming the neutral papermaking system at approximately 6.5 to 8.0;
- Ash content (%), reflecting filler level;
- Fluorescent whitening agents, which shall be absent for food-contact grades;
- Heavy metal content: lead, cadmium, mercury, and hexavalent chromium;
- Residual formaldehyde where chemically relevant.
Food Contact Safety
Where the product is declared food grade, testing shall demonstrate conformity with GB 4806.8 for paper and board intended for food contact, supported by the GB 31604 series of test methods, covering:
- Total (overall) migration, with a limit of 10 mg/dm²;
- Heavy metals (as lead) migration;
- Formaldehyde migration;
- Specific migration of other restricted substances associated with the PE resin and additives;
- Sensory assessment: no abnormal odor and no taste transfer.
Application-Specific Items
- Microbiological cleanliness (total aerobic count, coliforms, and pathogen screening) for food and medical packaging;
- Seam and side-seal integrity for cup and container stock;
- Heat-aging resistance for long-life industrial interleaving applications;
- Print adhesion and rub resistance for pre-printed grades.
Testing Methods
Physical Testing
- Grammage: GB/T 451.2 / ISO 536 / ASTM D646, minimum ten specimens of at least 100 cm² each;
- Thickness: GB/T 451.3 / ISO 534 / ASTM D645, minimum twenty measuring points;
- Tensile properties: GB/T 12914 (constant rate of elongation) / ISO 1924-2 / ASTM D828, ten strips per direction;
- Bursting strength: GB/T 454 / ISO 2758 / ASTM D774, at least ten specimens;
- Tearing resistance: GB/T 455 / ISO 1974 / ASTM D689, at least ten specimens per direction;
- Moisture content: GB/T 462 / ISO 287, oven drying at (105 ± 2) °C to constant mass;
- PE coating weight: gravimetric differential method—weigh a defined conditioned area, separate the PE layer by hot delamination or selective dissolution, reweigh the base sheet, and calculate the coating mass per unit area.
Coating Performance Testing
- Heat seal strength: QB/T 2358 or ASTM F88 with sealing windows validated by ASTM F2029; typical evaluation ranges are 130 to 170 °C, 0.3 to 0.5 MPa, and 0.5 to 1.0 s, followed by peel testing at 300 mm/min;
- Coating adhesion: GB/T 8808 peel testing or a controlled delamination check at a defined angle and speed, reporting the failure mode (cohesive, adhesive, or fiber tear);
- Cobb 60: GB/T 1540 / ISO 535, performed on the uncoated side;
- Grease resistance: TAPPI T559 Kit number method;
- Coating continuity: application of a dye or colored surfactant solution for a defined contact time with visual inspection of penetration points.
Chemical Testing
- Extract pH: GB/T 1545 / ISO 6588 cold extraction method;
- Ash content: GB/T 742 / ISO 2144, ignition at (900 ± 25) °C;
- Heavy metals: microwave digestion followed by ICP-MS or AAS determination;
- Fluorescent whitening agents: ultraviolet inspection at 254 nm and 365 nm, with extraction-fluorimetric confirmation where required;
- Formaldehyde: acetylacetone spectrophotometry after water extraction.
Migration Testing
Migration tests follow the general rules of GB 31604.1. Food simulants are selected according to the intended food type: 10% ethanol for aqueous foods, 4% acetic acid for acidic foods, 20% to 50% ethanol for alcoholic foods, and 95% ethanol or isooctane for fatty foods. Time-temperature conditions represent the worst foreseeable use—for example, 100 °C for 30 min for boiling-water contact, 70 °C for 2 h for hot filling, or 40 °C for 24 h for room-temperature storage. Total migration is determined by GB 31604.8 and reported in mg/dm², while heavy metals and formaldehyde are determined by the corresponding methods in the GB 31604 series.
Data Processing and Judgment Rules
- Report each item as the mean with maximum and minimum values, and the standard deviation where the method requires it;
- A product type passes only when every tested item meets its acceptance criterion;
- If a non-safety item fails due to an identified anomaly, a retest on double the specimen count from retained samples is permitted;
- Migration and safety items are judged on every individual specimen, and failures are not averaged away;
- Where judgments are borderline, results shall be evaluated together with measurement uncertainty.
Acceptance Criteria and Reporting
The governing acceptance criteria are those of the applicable product standard, certification scheme, and customer specification. Representative reference values for neutral PE-coated paper are:
- Grammage deviation: within ±5% of nominal, or as agreed;
- Extract pH: 6.5 to 8.0, confirming neutral sizing;
- Moisture content: 6.0 to 9.0%, or as agreed;
- Total migration: no more than 10 mg/dm²;
- Heavy metals (as lead) migration: no more than 4 mg/kg;
- Formaldehyde migration: no more than 1 mg/kg;
- Fluorescent whitening agents: not detectable on food-contact surfaces;
- Heat seal strength and Cobb values: conforming to the declared specification and application requirement.
All limits shall be verified against the current effective versions of the cited standards before use. The test report shall include product identification (name, model, base grammage, coating structure and weight class, manufacturer, lot, and production date), the complete list of applied standards, sampling and conditioning records, all results with units and individual judgments, equipment calibration status, laboratory accreditation status such as CNAS or CMA, an overall conclusion with authorized signatures, and statements on report validity. Physical and chemical testing generally completes within 7 to 10 working days, while migration and microbiological testing may extend the timeline to approximately 15 to 25 working days.
Applications
Neutral PE-coated paper that has passed a full type test is widely used across packaging and industrial sectors:
- Disposable paper cups, bowl stock, and lids requiring heat-sealable, liquid-tight barriers;
- Fast-food packaging, sandwich wrap, and food containers with direct fat and moisture contact;
- Baking papers, trays, and microwaveable packaging;
- Pharmaceutical and medical device packaging demanding neutral, aging-stable substrates;
- Labels, tags, and release liner base papers;
- Industrial interleaving and moisture-barrier wrapping for metals and electronics.
FAQ
What is the difference between a type test and routine factory inspection?
A type test is a full-scope design verification performed once per product type or per certification cycle, covering all physical, chemical, and safety items. Routine factory inspection is a reduced, high-frequency check of key process parameters and a few critical properties used to maintain ongoing consistency between type tests.
How often must a type test be repeated?
Commonly every 12 months for certified products, or immediately whenever the base paper recipe, PE resin, coating weight class, or production process changes materially, and after resuming production following a prolonged shutdown. Certification bodies may define different cycles.
How many samples should be submitted?
A typical submission is 50 to 100 full-width sheets or two rolls of at least 500 mm width, allocated across all test groups with roughly 30% reserve for retests. Exact quantities are stated in the test plan for each individual item.
What happens if an item fails?
Non-safety failures with an identified anomaly may be retested on double the specimens from retained samples. Safety-related failures require root-cause analysis, corrective action, and a completely new type test submission, and the product may not be released until conformity is demonstrated.
Does passing a type test prove food safety?
Only if the test scope included GB 4806.8 and the GB 31604 series under accredited conditions. Physical and mechanical conformity alone does not demonstrate food contact safety; food-grade claims additionally require migration, heavy metals, formaldehyde, fluorescence, and sensory testing.