Thermoplastic polyester resin VYLOPET™│TOYOBO Engineering Plastics│ENPLA Department │TOYOBO


Discover VYLOPET™

VYLOPET™ is a thermoplastic polyester that showcases TOYOBO MC's advanced polymerization and compounding tecnologies.
VYLOPET™ is used in a wide range of applications, especially automotive, home appliance, and mechanical component applications.

  *Values and properties listed here are typical values, not guaranteed values.

Topics List


Thermoplastic polyester resin VYLOPET™

  • Mechanical properties are not compromised by water absorption
  • Minimal dimentional changes with ambient temperature
  • Can be used in high heat applications
  • Easy to achieve an excellent surface appearance
  • High flow properties enable thin-wall molding
  • Excellent electrical properties
  • Recyclable


Chemical Structure

  • Structural formula of PET

  • Structural formula of PBT

Main Grades

Type Property Grade Feature
PET GF Reinforced EMC-330K GF30%, High Cycle
Flame Retardant EMC-133T GF30%, Flame Retardant (V-0 Equivalent Rating/1.6mm), Hydrolysis Resistant
PBT/PET GF Reinforced EMC-430X-8 GF30%, Good Appearance
GF Reinforced EMC-445 GF40%, Good Appearance
High Stiffness EMC-450 GF55%, High Stiffness, Good appearance
High Stiffness EMC-060A GF60%, High Stiffness, Good appearance
Low Warpage EMC-405AX-14A MD20%, Low Warpage、High Flow
Flame Retardant EMC-617Y (GF+MD)35%, Flame Retardant (V-0 Equivalent Rating/3.2mm)
PBT Unreinforced EMC-701EXT Unreinforced, High Cycle, Low to No Outgassing
GF Reinforced EMC-HF715 GF15%, Easy Welding
GF Reinforced EMC-736P GF30%, Easy Welding
GF Reinforced EMC-730L GF30%, Hydrolysis Resistant

Comparison to Other Resins

Item Polyester Polyamide PC PP
Heat resistance Excellent Average Average Excellent Fair Poor
Flammability Average Average Excellent Excellent Average Average
Rigidity Excellent Average Average Average Average Poor
Impact resistance Poor Poor Average Average Excellent Average
Fatigue endurance Good Good Average Average Poor Average
Organic solvent resistance Excellent Excellent Excellent Excellent Poor Excellent
Mild acid resistance Excellent Excellent Average Average Excellent Excellent
Weak alkali resistance Average Average Average Average Average Excellent
Electrical properties Excellent Excellent Poor Poor Excellent Excellent
Dimensional Accuracy Average Average Poor Poor Excellent Average
    • Dry/Conditioned Flexural Modulus for Various Materials

    • Heat Deflection Temperature of Various Materials


Main Applications

  • Applications:Headlamp Bezels

    Advantages:low warpage, heat resistance, high flow
    and low outgassing

  • Applications:Electric Rice Cooker Parts

    Advantages:heat resistance
    and flame retardance

  • Applications:Automotive Air Vent Fins

    Advantages:high rigidity
    and excellent surface appearance

  • Applications:Accelerator Pedal

    and two-shot molding compatibility

VYLOPET™ Processing Conditions

Setting Molding Conditions

  • Pre-Drying
  • A small amount of moisture could be the cause for not only bubble release, leak from the cylinder nozzle, and bad surface appearance but also deterioration of properties due to hydrolysis of the thermoplastic polyester material. The pre-drying process is important for molding stability and to ensure good quality. Additionally, material exposed to the air for more than 30minutes must be dried.

Pre-drying Conditions

Resin Temperature Drying Time
130℃ 4〜6hrs
140℃ 3〜5hrs

VYLOPET™ must be dried before molding.
VYLOPET™ should be processed with a moisture content of less than 0.025% (Ideally less than 0.020%).

VYLOPET™ can be dried with either a shelf-type dryer or a hopper type dryer, but a dehumidification dryer is strongly recommended. Recommended drying conditions vary slightly depending on the dryer type and amount of resin to be dried, so please check the pellet temperature. For parts that are particularly susceptible to gassing isses, we recommend reducing the moisture content as much as possible with a longer drying time.

  • Molding Conditions
  • Typical Temprature

    Typical cylinder temperature settings (except under the hopper) are shown in the table. For flame resistant grades, it is important to set the cylinder temperature as low as possible.

Example Grade EMC-330 EMC-430X-8 EMC-730
C1 245~265℃ 240~260℃ 220~250℃
C2 265~285℃ 260~280℃ 240~270℃
C3 265~285℃ 260~280℃ 240~270℃
NZ 265~285℃ 260~280℃ 240~270℃
Mold Temperature 120~140℃ 50~100℃* 50~90℃

*Ideal range for appearance parts : 80-120℃

Residence Time

Long residence time in the cylinder leads to material degradation, deterioration of mechanical properties, changes in flow properties, and discoloration. Residue left in the cylinder should be removed by several shots of purge when the machine is stopped for longer than for 10 minutes.

Mold Temperature

The mold temperature should be set based on consideration of the dimensions of the part, warpage, surface appearance, and cycle time. For PET types, it is generally recommended to set the temperature to 120℃(-135℃) higher.
Molding at 40-70°C is also possible for PET materials, but the second-order shrinkage becomes large.
The general molding temperature of PBT/PET materials is 50-70°C for a typical molded part, though a mold temperature of 80-100°C is recommended for molded parts requiring a good surface appearance.

Injection speed

An easy way to get a good surface appearance with VYLOPET™ is to set a high injection speed. However, a high injection speed may lead to warpage or burn marks on the surface of the part. Appropriate judgment will be necessary when balancing these concerns to achieve a good surface appearance.

Mold Design

  • Mold Material

The typical mold materials for PET are wear-resistant steel alloys.
SKD11 (D2) is the most popular alloy for GF-reinforced material, but SKD-61 and stainless steels like SUS420 or SUS440 are used as well. The hardness of all should optimally be higher than R55 or R60 with HRC after hardening and tempering. SUS310 or SUS440 that have good corrosion resistance are effective for improving mold durability.

  • Mold Temperature Control

It is normal to use cartridge heaters, hot water, or hot oil to control the mold temperature.
The mold temperature is strongly affects cycle time, surface appearance and quality, therefore it is very important to check the mold temperature distribution, and cooling of the cavity's core.
To maintain a uniform temperature distribution, it is effective to use a heat insulating plate between the mold and the platen.

  • Runners and Sprues

Fully round or trapezoidal runners are preferred, semi-circular or rectangular runners should be avoided.
Cold slug catchers should be placed at the end of each runner and sprue.

  • Draft Angle

Though it depends on the mold surface, polish level and mold shrinkage of the material, normally the draft angle should be 0.4-1 degrees.

  • Venting

VYLOPET™ molds must be vented in order to allow for the air present in the mold to escape when the molten material fills runners and cavities. Inadequate venting can lead to incomplete parts, burn marks, flash, poor surface appearance, or weak welding lines. In addition, well-vented tools will allow for a faster cycle time.
The depth should be at least 0.02-0.05mm, width should be secured as wide as possible. The depth should be 3mm around 0.75mm far from cavities, and lead the vent to the edge of the mold.

Injection Molding Troubleshooting

Trouble Cause Countermeasure
Sink marks Condition 1. High resin temperature
2. High/low mold temperature
3. Low holding pressure
4. Insufficient holding pressure time
5. Insufficient cooling time
6. No cushion
1. Reduce the cylinder temperature
2. Set the mold temperature accordingly
3. Increase the holding pressure
4. Increase the holding pressure time
5. Increase the cooling time
6. Make cushion 5-10mm
Design 1. Small runner/ gate
2. Unsuitable gate location
1. Enlarge the runner/gate size
2. Relocate the gate to a thicker area
Machine 1. Back-flow during injection

1. Inspect or exchange the backflow valve

Warpage, Deformation Condition

1. Unsuitable injection conditions
2. Insufficient holding pressure time
3. Insufficient Cooling time

4. Temperature difference between cavity and core

1. Increase the injection pressure/speed
2. Increase the holding pressure
3. Increase the cooling time

4. Control the temperature of cavity and core separately

Mold 1. Unsuitable ejector pin placement
2. Insufficient ejector pin size

1. Balance ejector pin placement
2. Enlarge ejector pin size
3. Increase the draft angle


1. Unsuitable gate location
2. Extreme change in part thickness
3. Not enough gates for the part size

1. Change gate location
2. Even out the part thickness
3. Increase the number of gates
Flash Condition 1. High resin temperature
2. High injection speed
3. High holding pressure
4. Low mold clamping force
5. Filling resin Volume is too high
1. Reduce the resin temperature
2. Reduce the injection speed
3. Reduce the holding pressure
4. Increase the mold clamping force
5. Set the cushion about 5mm
Mold 1. Mold surface doesn't mate properly 1. Modify the mold
Burn marks Condition

1. High resin temperature
2. Air entrapment
3. High injection speed
4. Filling resin volume is too high

1. Reduce the resin temperature
2. Reduce the screw rotation
3. Reduce the injection speed
4. Decrease the residence time
Mold 1. Inadequate venting 1. Increase gas ventilation

1. Unsuitable gate location
2. Small gate size

1. Change the gate location to make the welding line on the PL

2. Enlarge the gate size

Welding line Condition 1. Low resin temperature
2. Low mold temperature
3. Low injection speed
1. Increase the cylinder temperature
2. Increase the mold temperature
3. Increase the injection speed
Mold 1. Inadequate holding pressure

1. Increase gas venting and/or change gate location to move the weld line onto the parting line.

Poor surface appearance Condition 1. Low resin temperature
2. Low mold temperature
3. Low injection speed
4. Inadequate holding pressure
5. Insufficient amount of resin for fill
1. Increase the cylinder temperature
2. Increase the mold temperature
3. Increase the injection speed
4. Increase the holding pressure/time
5. Make cushion 5-10mm
Mold 1. Inadequate holding pressure
2. Unclean mold
1. Increase the holding pressure/time
2. Clean the mold


  • Molding operation
  • When purged resin contains a large quantity of gas or steam, the resin may have been insufficiently dried. We recommend re-drying the resin.
  • Resin held in the cylinder for an extended period of time may lose viscosity or experience other impacts on quality. Please resume molding only after thoroughly replacing the resin that has been held too long in the cyliner with new resin.
  • When switching from VYLOPET™ to another polymer, replace the VYLOPET™ with polyethylene or polypropylene to purge. Local and general ventilation are recommended.
  • Keep hands and face away from the nozzle during molding to prevent burn injury.
  • Please ensure proper ventilation, as a small amount of gas and fine dust may be produced during molding.
  • Protective equipment
  • Wear appropriate protective equipment such as protective clothing, safety glasses, and gloves to protect eyes and skin from the molten resin.
  • Emergency response
  • Should molten resin adhere to the skin, cool the area immediately with cold water or an ice pack and then seek medical attention. Do not attempt to peel the resin off of the skin.
  • Other
  • Do not let molten resin touch electric wires or hoses.
  • Molten resin reaches high temperatures and can catch fire if it forms large clumps when purging. Break up large clumps and allow to cool before disposal.
  • Spilled pellets can be a slipping hazard, so be sure to clean them off the floor immediately.