Packaging Basics | An Overview of Cosmetic Container “Neck Finish” Standard Systems and Measurement Methods

Packaging Basics | An Overview of Cosmetic Container “Neck Finish” Standard Systems and Measurement Methods

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Introduction:
For cosmetic packaging procurement professionals, a deep understanding of the matching logic between neck finish specifications and components (pumps, caps) is core to ensuring a fully functional packaging system. Below is a systematic analysis centered on key technical points of neck finishes, covering standard systems, critical parameters, material compatibility, and supplier collaborative management. This content is provided to support procurement decision-making for U-Package community members.

Author: Xiao Caizi
Collaboration: Deepseek


ONE: Neck Finish Standard System & Specification Coding

1. Main International Standards (Priority Knowledge)

Code SystemStructure AnalysisApplication ScenariosExample & Matching
28mm / 400Outer Diameter (OD) ≈28mm, Internal plug seal (seals inside the bottle neck)Lotion bottles, Serum bottlesMatches droppers with internal plugs, screw-on caps
28mm / 410Outer Diameter (OD) ≈28mm, Flat top seal (seals via compression on the top finish surface)Press pumps, Vacuum pumpsRequires flat gasket (silicone/foamed PE)
24/415OD 24mm + 415 sealing structure (small diameter flat top seal)Serums, Small dose productsMatches small diameter pumps
18/415Ultra-small diameter (18mm) flat top sealAmpoules, High-end serumsMatches micro pumps or droppers
  • 400: 18mm to 120mm (1 turn of thread)

  • 410: 18mm to 28mm (1.5 turns of thread)

  • 415: 13mm to 33mm (Tall – 2 turns thread)

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  • GB/T 17449-2019 “Packaging – Glass containers – Finish dimensions”: Specifies diameter, thread, and sealing surface tolerances for glass finishes.

  • GB/T 13508-2011 “Polyethylene blow molded containers”: Specifies dimensional tolerances for plastic finishes (e.g., ovality ≤ 0.5%).


TWO: Core Neck Finish Parameters & Measurement Methods

1. Dimensional Tolerances (Determine Component Compatibility)

ParameterAllowable ToleranceMeasurement ToolFailure Risk
Outer Diameter (OD)±0.3mmDigital Caliper (take avg. of 3 pts)Pump collar loose or unable to install
Inner Diameter (ID)±0.2mmPin Gauge / Inside MicrometerInternal plug falls out or is too tight to insert/remove
Pitch Diameter±0.1mmThread Gauge (Go/No-Go)Cap cross-threads or requires excessive torque
Lead Height±0.15mmDepth GaugePump collar cannot lock securely
Finish Flatness≤0.08mmSurface Plate + Feeler GaugeLeakage with flat top pumps (requires gasket compensation)

Procurement Action: Require suppliers to provide CPK reports for finish dimensions (Process Capability Index ≥ 1.33).

2. Sealing Structure Types (Determine Component Selection)

Finish StructureCompatible ComponentsSealing PrincipleTest Standard
Plug Seal (Linerless)Droppers/Caps with internal plugsElastomer (silicone/TPE) pressed inside bottle neckGB/T 15171 Negative Pressure Test
Flat Top SealPumps with flat gaskets/Foil sealsCompression of gasket forms seal on top surface0.05MPa/30min no leakage
Tapered SealCaps with tapered silicone plugsInterference fit on tapered surface45° tilt, 24h static, no leakage
Thread + GasketScrew caps with internal gasketsGasket deforms under compression when tightenedTorque Test (0.4-1.2N·m)

THREE: Impact of Material Properties on Neck Finish | Key Procurement Decision Points

1. Plastic Bottles (PET/PETG/PP/PE)

  • Shrinkage Variation: PET shrinkage rate 1.5-2.2% → Inner diameter may shrink 0.1-0.3mm after cooling.

    • Solution: Require suppliers to perform final inspection 24 hours after molding (avoid measuring “hot” finishes).

  • Chemical Resistance: Essential oil products require solvent-resistant materials (e.g., PP) → Prevents stress cracking at the finish.

2. Glass Bottles (Soda-Lime Glass / Borosilicate Glass)

  • Annealing Stress: Residual stress > 50 nm/cm at the finish → Risk of chipping/cracking (detect with polariscope).

  • Micro-cracks on Sealing Surface: 100% finish inspection required for glass (cracks >0.1mm deep cause leakage).


FOUR: Pump/Cap and Neck Finish Matching Verification Process

1. Dimensional Compatibility Check (Supplier Collaboration)
[Image – likely showing measurement/check process]

2. Functional Test Items (Must be specified in procurement contracts)

Test ItemStandard MethodPass CriteriaTool
Sealing PerformanceGB/T 15171 Negative PressureNo bubbles at -0.08MPaVacuum Seal Tester
Opening TorqueASTM D2063 Torque Test0.4-1.2N·m (≤0.6N·m for elderly)Digital Torque Gauge
Pump Actuation LifeQB/T 4634 Continuous Actuation≥5000 cycles without failureAutomatic Actuation Tester
Low-Temperature SealSeal test after 24h at -18°CNo leakageThermal Chamber

FIVE: Supplier Collaboration Requirements

1. Precise Requirement Communication Template

“We require a PETG 28/410 finish, matched with a white PP pump:

  • Finish Requirements: OD 28.2±0.2mm, Flatness ≤0.05mm, Lead Height 3.0±0.1mm

  • Pump Requirements: Delivery 0.2ml/actuation, Gasket material food-grade silicone (Hardness 50±5 Shore A)

  • Validation Standard: Must pass -0.08MPa seal test and 5000 actuation life test.”

2. Common Issue Accountability Logic

Fault PhenomenonPotential Finish ResponsibilityPotential Component Responsibility
Pump tilts after installationLead height tolerance exceeded > 0.2mmPump collar dimensions incorrect
Screw cap cross-threadsPitch diameter too small (below lower limit)Cap thread profile angle incorrect
Leakage in low temperaturesFinish ovality > 0.3mm (plastic shrinkage)Gasket hardens and fails at low temperatures

SIX: Technical Database Building (Procurement Core Competitiveness)

1. Build a Neck Finish – Component Compatibility Table

Finish SpecCompatible Pump ModelSuitable Content ViscosityGasket Material
28/410P-28A-0.3ml1-3000cPFoamed PE
24/415P-24B-0.15ml1-500cPSilicone

2. Collect Material Certification Reports

  • Plastic Finishes: FDA 21 CFR / EU 10/2011 Migration Test Reports

  • Silicone Gaskets: LFGB Anti-Sulfur Reversion Test Reports

Procurement Action Guide:

  • Must-Check Dimensions: Finish OD, Flatness, Lead Height (determines pump collar lock)

  • Must-Test Items: Negative Pressure Seal (-0.08MPa), Low-Temp Seal (-18°C), Opening Torque

  • Risk Control: Account for plastic shrinkage allowance; enforce 100% stress inspection for glass

  • Technical Collaboration: Require suppliers to provide 3D matching analysis reports; reject “drawing compliant but functionally failing” parts.


Summary

As a professional procurement specialist, develop a systems-thinking approach encompassing “Finish – Component – Contents“. The contents’ viscosity (e.g., serums needing small finishes to prevent oxidation) and filling process (e.g., negative pressure filling requiring higher sealing) jointly determine finish design. Remember, a physical sample library is more critical than drawings – collect 100+ physical finish samples labeled with specs for on-site matching demonstrations. Strive to become a packaging procurement expert. For instance, when a product manager says “I want the same bottle type as XX major brand,” immediately respond: “That brand uses a 28/410 standard finish; we could consider pairing it with a 0.2ml定量泵头 (metering pump).” Mastering these technical points will shift your role from passive purchasing to technologically-driven procurement, accurately preventing quality incidents like leakage or difficult opening caused by finish mismatch, ultimately making you a value creator within the supply chain.

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