An overview of the basic knowledge of PET bottle blowing

Introduction: When we pick up a common shampoo bottle, there will be a PET logo on the bottom of the bottle, which means that this product is a PET bottle. PET bottles are mainly used in the washing and care industry and are mainly large-capacity. In this article, we mainly introduce the PET bottle as a plastic container.

ONE

Product Definition

PET bottles are plastic containers made from PET plastic material through one-step or two-step processing. PET plastic has the characteristics of light weight, high transparency, impact resistance and not easy to break.

TWO

Manufacturing Process

1. Understand the preform

Preforms are injection molded items. As the intermediate semi-finished product for subsequent biaxial stretch blow molding, the bottleneck of the preform has been finalized during the injection molding stage, and its size will not change during heating and stretching/blowing. The size, weight, and wall thickness of the preform are factors that we need to pay close attention to when blowing bottles.

A. Preform structure

B. Preform molding

2. PET bottle molding

One-step method is a process that completes the injection, stretching and blowing processes in one machine. The one-step method is to do the stretching and blowing after the preform is cooled after injection molding. Its main advantages are power saving, high productivity, no manual work and reduced pollution.

Two-step method: The two-step method separates injection and stretch blowing, and performs them on two machines at different times, also known as injection stretch blow molding. The first step is to use an injection molding machine to inject the preform. The second step is to reheat the room temperature preform and stretch blow it into a bottle. The advantages of the two-step method are that the preform is purchased for blow molding. It can reduce investment (talent and equipment). The volume of the preform is much smaller than that of the bottle, which is convenient for transportation and storage. The preform produced in the off-season can be blown into a bottle in the peak season.

3. PET bottle molding process

THREE

Product Structure

1. PET material:

PET, polyethylene terephthalate, also known as polyester. The English name is Polyethylene Terephthalate, which is produced by the polymerization reaction (condensation) of two chemical raw materials: terephthalic acid (PTA) and ethylene glycol (EG).

2. Common knowledge about bottle mouth

The diameters of bottle mouths are Ф18, Ф20, Ф22, Ф24, Ф28, Ф33 (corresponding to the T size of the bottle mouth), and the thread specifications are usually divided into: 400, 410, 415 (corresponding to the number of thread turns). Generally speaking, 400 is 1 thread turn, 410 is 1.5 thread turns, and 415 is 2 high thread turns.

3. Bottle body

PP and PE bottles are mostly solid colors, PETG, PET, and PVC are mostly transparent, or colored and transparent, with a sense of translucency, and solid colors are rarely used. PET bottles can also be sprayed. There is a convex point at the bottom of the blow-molded bottle. It is brighter under light. There is a bonding line at the bottom of the blow-injected bottle.

4. Supporting equipment

The main supporting equipment for bottle blowing includes inner plug (commonly used for PP and PE materials), outer cap (commonly used for PP, ABS and acrylic, also electroplated, and electroplated aluminum, mostly used for oil spray toner), pump head cover (commonly used for essence and lotion), swing cap, flip cap (flip cap and swing cap are mostly used for large circulation daily chemical lines), etc.

FOUR

Cosmetic Applications

PET bottles are widely used in the cosmetics industry, mainly in the cleaning industry, where shampoo, shower gel bottles, toner, makeup remover bottles, etcare all blown.

FIVE

Procurement Notes

1. Blowing bottles can be made of materials. PET is only one of them. There are also PE blowing bottles (softer, more solid colors, one-time forming), PP blowing bottles (harder, more solid colors, one-time forming), PETG blowing bottles (better transparency than PET, but not commonly used in China, high cost, high waste, one-time forming, non-recyclable materials), PVC blowing bottles (harder, not environmentally friendly, less transparent than PET, but better brightness than PP and PE).

2. One-step method equipment is expensive, while two-step method is relatively cheap

3. PET bottle molds are cheaper.