Manufacturing

Mainbar

MAnufacturing

Synthesis of PET bottles in industry

Yanting Li¹,*

Backgroud

Manufacturing part gives detail information of how to produce PET bottles. To be concrete, this section will conclude the main stages of process, method and appearance processes in industry.

QMES Academic, this issue

Abstract

The PET bottles are most commonly produced from PET. The advantages of using PET for bottling are its recyclability, light weight anf strength. There will introduce the injection stretch blow moulding method involving two steps which is widely used in the industrial manufacturing process of PET bottles. Besides, the surface treatment and transparency are also introduced in this page.

PET Bottle Manufacturing Process

From the raw materials to the final products, every stages of production strictly adheres to the benchmark of inductry and shown as the following figure.

Figure 1: Manufacturing Process of PET Bottle

These stages mentioned above are the general manufacturing process in the industry. And they can be concluded into three common steps:

STEP 1 PET is first heated up and placed in a tube shaped mold called a parison, which is cut into the suitable length after it is cooled. STEP 2 The parison is also heated up and placed into a bottle shaped mold, with a screwtop included. A mandrel (steel rod) is inserted into to allow highly pressurized air to enter and stretch the plastic. The molecules then polarize, because of the combination of stretching and high temperature to produce a product. STEP 3 The bootle is cooled quickly to aviod creep and then removed.

Injection Stretch Blow Moulding(ISBM) [2]

A wide variety of bottles, jars, and other containers can be moulded by using the versatile injection stretch blow moulding referred to as ISBM. Performs can be molded into the final containers via 1-step method or saved as stock for later use in the 2-step method. Here we will summarize all the stages above into two stages which product on an integrated 2 stage injection stretch blow moulding machine.

Step 1 [2]

In industry, plastic pellets are the raw materials. And in step 1, it is necessary to melt the pellets and inject the melten plastic into a fixed mould to form a initial shape of bottles.

图片1.png.2

Figure 2: melting and injection process

A: Plastic is extruded firstly, which means the plastic pellets are fed into an extruder with a rotating screw creating enough friction to melt the pellets. B: The molten plastic is injected into a perform mould which is around a core rod. C: This preform mold shown above determines the final neck finish of the bottle.

Step 2 [2]

In step 2, the initial shape need to be processed into the shape of the final bottle by the stretching and blowing method . And it is significant to check the sealed quality.

图片2.png.1

Figure 3: stretching and blowing process

A: Tranfer the performs to the second station and capture them with the cavity mould. Then a stretch rod is introduced through the neck and stretches the malleable plastic performs to the full length of the cavity mould. B: Blow pressurized air introduced by the stretch rod into the performs to form the shape of the final bottles.

Then the final formed bottles are all cooled. Finally, these bottles are ejected from the rotation and transported to a final quality check which needs to blow a pressurized air into the sealed bottles to check for leaks.

Surface Treatment [3]

The importance of making the final packaging for a product to look more professional is an increasing trend in many bottle industries. In simple case, surface treatment activates surface to create the bonding sites, which is a preparation of a plastic surface to make maximum adhesion between plastic and other materiaks, such as ink, glue, and coatings.

In real industry, corona treatment of plastic bottles is considered a good way due to the low operation cost and environment protection. With this surface treatment, it will save on adhesive materials, coatings and inks.

Surface Transparency [4]

Glass-like transparency is a desired quality for drinking water bottles. In industry, co-polymerisation with diethyleneglycol (DEG) and isophthalic acid (IPA) is always implemented to minimize polymer thermal crystallisation during the manufacture performs and the blow-moulding process. And both the co-momomers decrease the size of spherulites. As a consequence, the final bottle is transparent.

References

[1] Dynaplast.com.my. 2020. Our Services – Dynaplast. [online] Available at: <http://dynaplast.com.my/our-services/>.

[2] Oberk.com. 2020. [online] Available at: <https://www.oberk.com/packaging-crash-course/ISBM>.

[3] Tantec.com. 2020. Bottletec. [online] Available at: <https://tantec.com/surface-treatment-of-plastic-bottles-bottletec.html>

[4] Coniglio, et al. (2020). Polyehylene Terephthalate. Non-Intentionally Added Substances in PET-Bottled Mineral Water. Cham, Springer International Publishing: 29-41.