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 System | Structure Analysis | Application Scenarios | Example & Matching |
|---|---|---|---|
| 28mm / 400 | Outer Diameter (OD) ≈28mm, Internal plug seal (seals inside the bottle neck) | Lotion bottles, Serum bottles | Matches droppers with internal plugs, screw-on caps |
| 28mm / 410 | Outer Diameter (OD) ≈28mm, Flat top seal (seals via compression on the top finish surface) | Press pumps, Vacuum pumps | Requires flat gasket (silicone/foamed PE) |
| 24/415 | OD 24mm + 415 sealing structure (small diameter flat top seal) | Serums, Small dose products | Matches small diameter pumps |
| 18/415 | Ultra-small diameter (18mm) flat top seal | Ampoules, High-end serums | Matches 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)
| Parameter | Allowable Tolerance | Measurement Tool | Failure Risk |
|---|---|---|---|
| Outer Diameter (OD) | ±0.3mm | Digital Caliper (take avg. of 3 pts) | Pump collar loose or unable to install |
| Inner Diameter (ID) | ±0.2mm | Pin Gauge / Inside Micrometer | Internal plug falls out or is too tight to insert/remove |
| Pitch Diameter | ±0.1mm | Thread Gauge (Go/No-Go) | Cap cross-threads or requires excessive torque |
| Lead Height | ±0.15mm | Depth Gauge | Pump collar cannot lock securely |
| Finish Flatness | ≤0.08mm | Surface Plate + Feeler Gauge | Leakage 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 Structure | Compatible Components | Sealing Principle | Test Standard |
|---|---|---|---|
| Plug Seal (Linerless) | Droppers/Caps with internal plugs | Elastomer (silicone/TPE) pressed inside bottle neck | GB/T 15171 Negative Pressure Test |
| Flat Top Seal | Pumps with flat gaskets/Foil seals | Compression of gasket forms seal on top surface | 0.05MPa/30min no leakage |
| Tapered Seal | Caps with tapered silicone plugs | Interference fit on tapered surface | 45° tilt, 24h static, no leakage |
| Thread + Gasket | Screw caps with internal gaskets | Gasket deforms under compression when tightened | Torque 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 Item | Standard Method | Pass Criteria | Tool |
|---|---|---|---|
| Sealing Performance | GB/T 15171 Negative Pressure | No bubbles at -0.08MPa | Vacuum Seal Tester |
| Opening Torque | ASTM D2063 Torque Test | 0.4-1.2N·m (≤0.6N·m for elderly) | Digital Torque Gauge |
| Pump Actuation Life | QB/T 4634 Continuous Actuation | ≥5000 cycles without failure | Automatic Actuation Tester |
| Low-Temperature Seal | Seal test after 24h at -18°C | No leakage | Thermal 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 Phenomenon | Potential Finish Responsibility | Potential Component Responsibility |
|---|---|---|
| Pump tilts after installation | Lead height tolerance exceeded > 0.2mm | Pump collar dimensions incorrect |
| Screw cap cross-threads | Pitch diameter too small (below lower limit) | Cap thread profile angle incorrect |
| Leakage in low temperatures | Finish 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 Spec | Compatible Pump Model | Suitable Content Viscosity | Gasket Material |
|---|---|---|---|
| 28/410 | P-28A-0.3ml | 1-3000cP | Foamed PE |
| 24/415 | P-24B-0.15ml | 1-500cP | Silicone |
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.
