When purchasing packaging with cap, you need to understand these basic knowledge points

Introduction: Caps are the main accessories of cosmetic containers. They are the main content dispenser tool besides lotion pumps and spray pumps. They are widely used in cream bottles, shampoos, shower gels, tubes and other packaging. In this article, we briefly describe the basic knowledge of caps as a packaging material for your reference:

ONE

Product definition

Caps are one of the primary dispensing mechanisms for cosmetic containers. Their primary functions include protecting the contents from external contamination, facilitating opening for consumers, and conveying corporate branding and product information. A standard bottle cap must demonstrate compatibility, sealing performance, strength, ease of opening, resealability, versatility, and decorative qualities.

TWO

Manufacturing process

1. Molding process

The main materials of caps for cosmetic packaging are plastics, such as PP, PE, PS, ABS, etc., and their molding methods are relatively simple, mainly injection molding.

2. Surface treatment

There are many ways to treat the surface of the caps, such as oxidation process, vacuum plating process, spraying process, etc.

3. Printing and text processing

The surface printing methods of caps are various, including hot stamping, silk screen printing, pad printing, heat transfer printing, water transfer printing, etc.

THREE

Product structure

1. Sealing principle

Sealing is the fundamental function of a bottle cap. It aims to create a perfect physical barrier to seal the bottle opening, where leakage (gas or liquid contents) or intrusion (air, moisture, or impurities from the outside environment) is possible. To achieve this, the liner must be elastic enough to fill any irregularities on the sealing surface, while also maintaining sufficient rigidity to prevent it from squeezing into surface gaps under sealing pressure. Both elasticity and rigidity must be maintained consistently.

To achieve a good seal, the liner pressing against the bottle neck must maintain sufficient pressure throughout the package's shelf life. Within a reasonable range, the higher the pressure, the better the seal. However, it's obvious that when the pressure reaches a certain level, it can cause the bottle cap to crack or deform, the glass neck to shatter, the plastic container to deform, and the liner to break, rendering the seal ineffective.

Sealing pressure ensures good contact between the liner and the bottle neck sealing surface. The larger the bottle neck sealing area, the more distributed the load applied by the bottle cap is, and the poorer the sealing effect at a given torque. Therefore, achieving a good seal doesn't necessarily require excessively high tightening torque. The width of the sealing surface should be minimized without damaging the liner or its surface. In other words, if maximum effective sealing pressure is to be achieved with a low tightening torque, a narrow sealing ring should be used.

2. Cap classification

In the cosmetics field, caps come in various shapes: according to product material: plastic caps, aluminum-plastic combination caps, electrochemical aluminum caps, etc.; according to opening method: swing caps, flip caps (butterfly caps), screw caps, snap caps, plug hole caps, diverter caps, etc.; according to supporting applications: hose caps, lotion bottle caps, laundry detergent caps, etc.; bottle cap auxiliary accessories: inner plugs, gaskets and other accessories.

3. Classification structure description

(1) Disc top cap

(2) Flip cap

The flip cap is usually composed of several important parts, such as the lower cover, liquid guide hole, hinge, upper cover, plunger, inner plug, etc. According to the shape, it can be divided into round cover, oval cover, special-shaped cover, two-color cover, etc. According to the matching structure, it can be divided into screw-on cover and snap-on cover. According to the hinge structure, it can be divided into integrated type, bow-tie type, strap-on type (three-axis type), etc.

(3) Rotating cap

(4) Plug hole cap

(5) Liquid diversion cap

(6) Solid dispensing cap

(7) Ordinary cap

(8) Other caps (mainly used with cosmetic tubes)

（9）Other accessories

A. Bottle stopper

B. Gasket

FOUR

Cosmetic applications

Caps are one of the content dispenser tools in cosmetic packaging, in addition to pump heads and sprayers. They are widely used in cream bottles, shampoos, shower gels, hoses and other products.

FIVE

Procurement Critical Control Points

1. Opening Torque

The opening torque of the bottle cap must meet the standard. Too much torque may cause the cap to not open, while too little torque may cause leakage.

2. Bottle Finish Size

Bottle finishes vary in structure, and the cap must be designed to effectively coordinate with them, meeting all tolerance requirements. Otherwise, leakage is likely to occur.

3. Positioning Notch

To enhance product aesthetics and create a unified image, many brands require the cap and bottle body to have separate designs. Therefore, positioning notches are often included. The positioning notches must be used as a guide during printing and assembly.