31.5 mm ROPP Aluminum Cap

The 31.5 mm ROPP (Roll-On Pilfer-Proof) aluminum cap is a precisely engineered closure solution widely used in industries such as beverages, pharmaceuticals, cosmetics, and edible oils. It is designed to be roll-sealed onto glass or PET bottles, providing both a tamper-evident seal and reliable re-closure.

The 31.5 mm ROPP (rolled and tamper-evident) aluminum cap is made from high-grade aluminum material (typically 8011-H14/H16 alloy) and features tamper-evident functionality. The cap undergoes precision stamping, knurling, coating, and printing processes to ensure excellent sealing, anti-counterfeiting, and leak-proof performance.

HC Aluminum is a leading manufacturer, exporter, trader, and supplier of premium 31.5 mm ROPP bottle caps. These caps are manufactured using top-quality raw materials and complex processes to meet common market standards. We offer bottle caps in various sizes and shapes to meet customer requirements. All caps are tested by our quality experts to ensure flawless performance.

31.5 mm ROPP Aluminum Cap Specifications

Material: High-quality aluminum alloy (typically 8011-H14 or 3105-H16)
Height: Typically 18 mm or 24 mm (depending on bottle neck type)
Thread Type: Pre-threaded or formed during the roll-on capping process
Liner Options: EPE (Expanded Polyethylene), PVC-free liner, or induction heat seal (IHS) for airtight sealing

31.5 mm ROPP Aluminum Cap Product Details

Parameter	Standard Value	Tolerance Range
Inner Diameter (ID)	31.5 mm	31.1–31.5 mm
Outer Diameter (OD)	31.9 mm	31.5–31.9 mm
Height	18 mm (standard)	17.5–18.3 mm

Custom heights: 24 mm (common), 44 mm (tall variants).

31.5 mm ROPP Aluminum Cap Material

Aluminum Grade: 8011-H14/H16 (food-grade/pharmaceutical-grade).

Weight: 1.85–4 grams, depending on height and liner type.

Liner Options

Standard: PE, EPE, or PP composite liners for moisture/oxygen barrier.

Specialized: Anti-corrosion liners, vertical seal, or integrated plastic pourers (e.g., for olive oil).

31.5 mm ROPP Aluminum Cap Features

Tamper-evident band: Breaks upon opening to ensure product integrity
Corrosion-resistant coating: Protective lacquer applied to both inner and outer surfaces
Excellent sealing performance: Prevents leakage and maintains product freshness

Customization:

Colors: Gold, silver, black, red, green, and custom shades.
Surface finishes: Brushed, electrophoretic coating, anodizing, or embossing.
Printing: Screen printing, offset printing, hot stamping, or UV printing for branding/patterns.

Compatibility:

Suitable for 31.5 mm neck glass/PET bottles (e.g., compliant with ISO 9006 standard).
Requires ROPP capping machine.

31.5 mm ROPP Aluminum Cap Common Applications

Food & Beverage: Olive oil, wine, beer, spirits, mineral water.
Pharmaceuticals: Oral liquids, syrups, and medicine bottles.
Cosmetics & Chemicals: Essential oils, agrochemicals, and industrial liquids.

Industry	Usage Example
Wine and Spirits	Closures for wine bottles, vodka, gin, whiskey
Edible Oils	Olive oil and specialty vinegar bottles
Pharmaceuticals	Syrups and liquid medications
Cosmetics	Essential oil bottles, serums, tonics

Advantages of 31.5 mm ROPP Aluminum Cap

Secure and tamper-evident
Lightweight and recyclable
Suitable for high-speed bottling lines
Resistant to transportation pressure and impact
Offers a premium appearance to enhance brand image

Packaging of 31.5 mm ROPP Aluminum Cap

Standard cartons: 8, 000 – 12, 000 caps per box
Bulk or pallet packaging: customized as per client requirements
Export pallet packaging: ensures damage-free transport

Manufacturing Process of 31.5 mm ROPP Aluminum Cap

Stamping → Knurling → Brushing → Inner Coating → Printing.
Visual inspection system for defect detection.
Quality certifications: ISO 9001, SGS.

31.5 mm ROPP Aluminum Cap Selection Guide

Liner and contents compatibility:

Use PE liner for food packaging; use anti-corrosion liner for chemical packaging.

For oil packaging, choose integrated pourer spout.

Height considerations:

18 mm: Standard height for liquids (e.g., beverages).

44 mm: Tall cap for ≥250 ml bottles (e.g., 500 ml Dorica bottles).

Machine compatibility:

Ensure the cap size matches the ROPP capping equipment.

Regulatory compliance:

Use food/pharmaceutical-grade aluminum and non-toxic coatings.

31.5 mm Aluminum Caps You May Be Interested In

Product	Description
31.5 mm Black Polypropylene Foam Lined Aluminum Cap	This cap features a robust aluminum shell with a black polypropylene foam liner, designed to create a secure seal against 31.5 mm ROPP bottle finishes. The foam lining ensures tamper evidence, a tight fit, and leak prevention, making it ideal for bottling oils, syrups, and sauces.
31.5 mm Aluminum Cap With Pourer	This ROPP-style aluminum closure incorporates an integrated LDPE/plastic anti-drip pourer insert. It provides controlled dispensing—perfect for olive oil, dressings, or syrups—while maintaining a tamper-evident roll-on seal that requires machine application .
31.5 mm Pourer Aluminum Cap Black	Fully black aluminum screw cap featuring a built-in plastic pourer and tamper-evident seal. It offers drip-free pouring, is compatible with standard 31.5 mm ROPP finishes, and is well-suited for oil, vinegar, or sauce bottles.

The 31.5 mm ROPP aluminum cap combines precision engineering, safety, and versatility, making it suitable for a wide range of industries. HC Aluminum offers a variety of customization options in color, liner, and surface treatment. However, proper application requires specialized ROPP equipment. For optimal performance, please select the liner and size that best match your product’s viscosity, volume, and regulatory requirements.

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