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Manufacturing Process

Crude oil and natural gas are the sources of raw ingredients used to make PET.  A typical misconception is that crude oil is mostly consumed by plastics and chemicals. However, when combined, they only represent less than 10% of yearly global usage. (PETRA, n.d.)

PET material has a relatively high density and manufactured by Ensinger in standard stock shapes for machining. They are available either as an amorphous or semi crystalline thermoplastic (Ensinger, n.d).

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Blow Molding

This process allows hollow plastic parts to be formed. The air pressure inflates the soft plastic into a mold cavity. It has two part plastic manufacturing process. (Thell, 2016)

  1. Crete starting tubes of molten plastic, called Parisons. They serve as base for the extrusion blow molding process. After the fabricated of parisons and ready to be molded, the second part begins.

  2. Air inflating of the tube or preform to the desired shape. It can be done by either 3 processes:

    • Extrusion blow molding

    • Injection blow molding

    • Injection stretch blow molding


Injection Molding

It is mainly used to enhance the modling of PET. Screw type injection machines was used and usually needs to be hardened to avoid wear after long term use. (Ningbo Leadway Machinary Tech Co., 2021)

  • Barrel temperature (unreinforces grades: 240-280℃)

  • Barrel temperature of glass fiber reinforces PET: 250-290℃

  • Temperature of nozzles: Should not exceed 300 C

  • Melt temperature: 280-310 ℃

  • Mold temperature: 140-160℃ to obtain a crystalline PET (for technical applications)

  • Screw with an L/D ratio of 18-22 is recommended

  • For transparent applications, mold temperatures should lie betweel 10 and 50℃

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Extrusion 3D Printing

PET is extruded to produce films and sheets (which can be thermoformed after) for food packaging applications. (Omnexus, n.d.)In the extrusion process, a hopper machine collects plastic beads or pellets melded together into one product.(Helmke, 2015)

PET is a thermoplastic resin therefore it can be melted and shaped repeatedly. With the plastic extrusion process, PET bottle flakes, and then an air compressor will turn the molten plastic into a synthetic fiber. (Milad & Simon, 2019)

PET is known to produce 3D Printed objects having high flexibility and toughness. PETG is PET copolyster with glycol modification. It is more heat-resistant and tough than PLA, but easier to print than ABS. The material also benefits from great thermal characteristics, allowing the plastic to cool efficiently with almost negligible warpage.(Omnexus, n.d.

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