The injection molding process is a process involving mold design, mold manufacturing, raw material characteristics, and raw material pretreatment method, molding process, injection molding machine operation, and other factors.
Today, we are talking about the tensile properties of injection molding materials.
The definition of tensile strength:
Tensile strength is the critical value of material transition from uniform plastic deformation. The deformation of the tensile specimen is uniform before it is subjected to the maximum tensile stress. Still, after it is exceeded, the material begins to shrink, that is, to produce concentrated deformation. For brittle materials with no (or very small) uniform plastic deformation, it reflects the fracture resistance of the material.
When testing the tensile strength, the specified sample is placed on the testing machine table, the two ends of the sample are clamped with a fixture, and the “distance sensor” is placed, and then the sample is stretched up and down until it breaks. The test speed is fixed, usually 0.2″/min (5mm/min) or 2″/min (50mm/min).
What is the tensile rate？
Stretch ratio, also known as the stretch ratio, is the ratio of the length of the polymer’s primary fiber after spinning and forming after the stretching process to the original size.
It is the ratio of fiber output speed to feed during stretching. The complete concept is that the stretching behavior occurs in two parts: one is spinneret stretching, that is, the ratio of the linear velocity of the spinning melt or liquid flowing out of the spinneret hole to the winding speed, and the other is the primary fiber stretching described above. These two kinds of stretching should be properly controlled in the process.
What is the elastic modulus？
Elastic modulus can measure the macroscopic mechanical properties of materials under normal temperature, and static load and is the main basis for determining various engineering design parameters. In the process of geological drilling, it is also used to measure the degree of rock plasticity.
The following table shows the tensile strength, elongation, and modulus of elasticity of typical injection molding plastic.
| Materials Type | Ultimate Tensile Strength | Tensile Elongation | Elastic Modulus |
| ABS | 40 MPa | 30% | 2.3 GPa |
| ABS + 30% Glass Fiber | 60 MPa | 2% | 9 GPa | Acetal Copolymer | 60 MPa | 45% | 2.7 GPa |
| Acetal Copolymer + 30% Glass Fiber | 110 MPa | 3% | 9.5 GPa |
| Acyrlic | 70 MPa | 5% | 3.2 GPa |
| Nylon 6 | 70 MPa | 90% | 1.8 GPa |
| Polyamide-imide | 110 MPa | 6% | 4.5 GPa |
| Polycarbonate | 70 MPa | 100% | 2.6 GPa |
| PE, HDPE | 15 MPa | 500% | 0.8 GPa |
| PET | 55 MPa | 125% | 2.7 GPa |
| Polyimide | 85 MPa | 7% | 2.5 GPa |
| Polyimide + Glass Fiber | 150 MPa | 2% | 12 GPa |
| Polypropylene | 40 MPa | 100% | 12.9 GPa |
| Polystyrene | 40 MPa | 7% | 3 GPa |
| Materials Type | Ultimate Tensile Strength | Tensile Elongation | Elastic Modulus |
| ABS | 40 MPa | 30% | 2.3 GPa | Acetal Copolymer | 60 MPa | 45% | 2.7 GPa |
| Acyrlic | 70 MPa | 5% | 3.2 GPa |
| Nylon 6 | 70 MPa | 90% | 1.8 GPa |
| PC | 70 MPa | 100% | 2.6 GPa |
| PE, HDPE | 15 MPa | 500% | 0.8 GPa |
| PET | 55 MPa | 125% | 2.7 GPa |
| Polyimide | 85 MPa | 7% | 2.5 GPa |
| PP | 40 MPa | 100% | 12.9 GPa |
| PS | 40 MPa | 7% | 3 GPa |
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