Design Guide - Solvay Plastics

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In general, glass and mineral/glass reinforced grades creep less than the unreinforced grades. The time required to observe measurable creep will also be shorter for the unreinforced grades. Apparent or creep modulus will decrease at elevated temperatures with a corresponding increase in creep. At temperatures above the glass transition temperature (T g ), the apparent modulus of the unreinforced grades is so low that even relatively low loads can result in significant creep, and therefore these unreinforced grades are usually not recommended for use in structural applications above these temperatures. Structural applications that will be exposed to elevated temperatures should be specified in the glass or mineral/glass reinforced grades. Creep can occur in tension, compression, or flexural modes. Therefore, to evaluate creep properties, strain is measured as a function of time while a specimen is subjected to a constant tensile, compressive or flexural load at specified environmental conditions. The procedure followed is described in ASTM D2990, Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics. ISO Method 899, Plastics - Determination of Creep Behaviour is similar, but because of differences in the test specimen may not yield exactly the same results. The general trends shown by either method should be comparable, but material comparisons should only be done using data generated by the same method. The normal progression of creep occurs in these three stages: • A rapid initial deformation • Continued deformation at a slow and constant rate • Yield followed by rupture for ductile materials, or rupture for non-ductile materials The significance of data from creep tests is that they can be used to calculate the time dependent creep strain and creep modulus for use in stress calculations and to determine the safe stress levels for specific time and temperature conditions. If the creep tests are conducted until failure occurs at various stress levels, a creep rupture curve can be produced. Another aspect of creep may further complicate the analysis: under a given stress, creep will occur at the expected rate based on the apparent modulus. However, depending on how the stress is applied, the initial creep can result in stress relaxation. For example, if a plastic part is clamped with a bolt torqued to achieve a compressive stress on the plastic. As creep strain occurs, the compressive stress will drop, resulting in less creep. The compressive stress will drop until an equilibrium is established at a lower stress level. A "single point" analysis would indicate that torque retention would drop to a failure level, while, in reality, an acceptable equilibrium is reached before failure levels occur. Further discussion of the influence of creep on part design, including examples, can be found on page 70. Tensile Creep Tensile creep was measured at three temperatures: 23°C (73°F); 125°C (257°F); and 175°C (347°F) and two stress levels: 13.8 MPa (2000 psi) and 34.5 MPa (5000 psi). Test specimens were 3.2 mm (0.125 in.) thick injection molded ASTM D638 Type I tensile bars. Samples were placed under test in the "dry, as molded" condition. The samples tested at the two elevated temperatures were placed in air circulating ovens. Although the strain is measured, the results are typically presented as the apparent modulus, which is calculated by dividing the strain by the applied stress. The apparent modulus is the value design engineers use in their mechanical design calculations when designing components that must perform when subjected to sustained load. The materials tested were A-1133 HS (33% glass fiber) and A-1145 HS (45% glass fiber). The results of the room temperature testing are shown in Figures 38 and 39. The results of the tensile creep testing at 125°C (257°F) are shown in Figures 40 and 41, and at 175°C (347°F) in Figures 42 and 43. 32 Amodel ® PPA Design Guide www.SolvaySpecialtyPolymers.com
Figure 38: Apparent Modulus at 23°C (73°F) and 13.8 MPa (2 kpsi) Figure 41: Apparent Modulus at 125°C (257°F) and 34.5 MPa (5 kpsi) Apparent Modulus, GPa 20 15 10 5 0 Tensile Creep at 13.8 MPa (2,000 psi) and 23°C (73°F) A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Apparent Modulus, Mpsi Apparent Modulus, GPa 12 10 8 6 4 2 0 Tensile Creep at 34.5 MPa (5,000 psi) and 125°C (257°F) A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 1.5 1.0 0.5 0.0 Apparent Modulus, Mpsi Figure 39: Apparent Modulus at 23°C (73°F) and 34.5 MPa (5 kpsi) Figure 42: Apparent Modulus at 175°C (347°F) and 13.8 MPa (2 kpsi) Apparent Modulus, GPa 20 15 10 5 0 Tensile Creep at 34.5 MPa (5,000 psi) and 23°C (73°F) A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Apparent Modulus, Mpsi Apparent Modulus, GPa 10 8 6 4 2 0 Tensile Creep at 13.8 MPa (2,000 psi) and 175°C (347°F) A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Apparent Modulus, Mpsi Figure 40: Apparent Modulus at 125°C (257°F) and 13.8 MPa (2 kpsi) Figure 43: Apparent Modulus at 175°C (347°F) and 34.5 MPa (5 kpsi) 14 Tensile Creep at 13.8 MPa (2,000 psi) and 125°C (257°F) 2.0 8 Tensile Creep at 34.5 MPa (5,000 psi) and 175°C (347°F) Apparent Modulus, GPa 12 10 8 6 4 2 0 A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 1.5 1.0 0.5 0.0 Apparent Modulus, Mpsi Apparent Modulus, GPa 7 6 5 4 3 2 1 0 A-1133 HS A-1145 HS 1 10 100 1,000 Time, Hours 1.0 0.8 0.6 0.4 0.2 0.0 Apparent Modulus, Mpsi Property Data Amodel ® PPA Design Guide 33
Page 1: Amodel® Amodel ® PPA Design Guide
Page 4 and 5: Electrical Properties. ............
Page 6 and 7: List of Figures Figure 1: Modulus C
Page 9 and 10: Introduction Amodel ® Polyphthalam
Page 11 and 12: Moisture Effects Like other polymer
Page 13 and 14: Nomenclature Amodel ® PPA grade no
Page 15 and 16: Table 4: Glass-Reinforced Grades -
Page 17 and 18: Table 6: Glass-Reinforced Grades -
Page 19 and 20: Table 8: Toughened Grades - Mechani
Page 21 and 22: Table 10: Toughened Glass-Reinforce
Page 23 and 24: Table 12: Toughened Glass-Reinforce
Page 25 and 26: Table 14: Mineral and Mineral/Glass
Page 27 and 28: Mechanical Properties The mechanica
Page 29 and 30: Figure 10: Tensile Elongation of 30
Page 31 and 32: Tensile Modulus, GPa Figure 18: Ten
Page 33 and 34: Figure 23: Flex Strength of GR A-10
Page 35 and 36: Compressive Strength and Modulus Co
Page 37 and 38: Figure 33: Izod Impact of Amodel ET
Page 39: Table 18: Poisson’s Ratio for Amo
Page 43 and 44: Stress, MPa Apparent Modulus, GPa F
Page 45 and 46: Figure 50: Flex Fatigue of GR Resin
Page 47 and 48: This phenomenon becomes of signific
Page 49 and 50: Figure 56: Dimensional Change of 40
Page 51 and 52: Figure 59: HDT of 30% - 33% GR Resi
Page 53 and 54: Table 20: Thermal Conductivity of A
Page 55 and 56: Thermal Stability The general term,
Page 57 and 58: Table 21: Relative Thermal Indices
Page 59 and 60: Table 24: Smoke Density Grade D s @
Page 61 and 62: Electrical Properties Many applicat
Page 63 and 64: Table 31: Dissipation Factor of Amo
Page 65 and 66: UL 746A Properties of Amodel Resins
Page 67 and 68: Table 40: Screening Chemical Resist
Page 69 and 70: Table 42: Screening Chemical Resist
Page 71 and 72: Design Information In this section,
Page 73 and 74: Table 46: Maximum Stress and Deflec
Page 75 and 76: Using Classical Stress/ Strain Equa
Page 77 and 78: Figure 68: Adding Ribs to Increase
Page 79 and 80: Considering Stress Concentrations C
Page 81 and 82: Designing for Assembly Interference
Page 83 and 84: Figure 76: Torque Developed During
Page 85 and 86: Table 48: Strain Recommendations fo
Page 87 and 88: Figure 84: Draft - Recommended Rib
Page 89 and 90: Secondary Operations Welding Compon
Page 91 and 92:
Figure 91: Typical Energy-Directing
Page 93:
Table 51: Suppliers of InkJet Print
Page 96:
M Mechanical Design . . . . . . . .
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Design Guide - Solvay Plastics

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