Design Guide - Solvay Plastics

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Design Information The rules for designing articles to be produced using polysulfone are similar to those which apply to other thermoplastics. Good design will not only result in a better product but also a product which is easier to manufacture and will quite often be lower in cost. The goal of a plastic part design is to meet the physical strength and deformation requirements with minimum volume of material, considering the effects of stresses caused by assembly, temperature changes, processing. and environmental factors. Mechanical Design The use of classical stress and deflection equations provide starting points for part design. Mechanical design calculations for Udel resins are similar to those used with any engineering material, except that the physical constants used must reflect the viscoelastic nature of the polymers. The material properties vary with strain rate, temperature, and chemical environment. Therefore the physical constants, like elastic modulus, must be appropriate for the anticipated service conditions. For example, if the service condition involves enduring load for a long period of time, then the apparent or creep modulus should be used instead of the short-term elastic modulus. When the loading is cyclical and longterm, then the fatigue strength at the design life is the limiting factor. Stress Levels The initial steps in the design analysis are to determine the loads that the part will be subjected to and to calculate the resultant stress and deformation or strain. The loads may be externally applied loads or loads that result from the part being subjected to deformation due to temperature changes or assembly. An example of an externally applied load is the weight of medical instruments on a sterilizer tray. Deformation loads might arise when a switch housing is bolted to a base plate, or when the temperature of the assembly increases and the dimensions of the plastic part change more than the metal part to which it is bolted. Stress-Strain Calculations To use the classical equations, the following simplifying assumptions are necessary: 1. The part can be analyzed as one or more simple structures. 2. The material can be considered linearly elastic and isotropic. 3. The load is a single concentrated or distributed static load gradually applied for a short time. 4. The part has no residual or molded-in stresses. Bending Stress A variety of parts can be analyzed using a beam bending model. Table 38 lists the equations for maximum stress and deflection for some selected beams. The maximum stress occurs at the surface of the beam furthest from the neutral surface, and is given by: σ = Mc I where = M Z M = bending moment, inch pounds c = distance from neutral axis, inches I = moment of inertia, inches 4 Z = I = section modulus, inches C 3 Table 39 lists the cross sectional area (A), the moment of inertia (I), the distance from the neutral axis (c), and the section modulus (Z) for some common cross sections. Tensile Stress In the elastic region of the stress-strain curve, the strain can be related to the applied stress by Hooke’s Law. Hooke’s Law can be expressed as σ = Eε where σ = tensile stress E = modulus of elasticity ε = elongation or strain The tensile stress is defined as: σ = F A where F = total force A = cross-sectional area 42 Udel ® Polysulfone Design Guide www.SolvayPlastics.com
Table 38: Maximum Stress and Deflection Equations Simply Supported Beam Concentrated Load at Center Cantilevered Beam (One End Fixed) Concentrated Load at Free End F FL σ = 4Z (at load) F FL σ = Z (at support) L Y 3 FL Y= 48EI (at load) L Y 3 FL Y= 3EI (at load) Simply Supported Beam Uniformly Distributed Load Cantilevered Beam (One End Fixed) Uniformly Distributed Load F (total load) FL σ = 8Z (at center) F (total load) FL σ = 2Z (at support) L Y 3 5FL Y= 384EI (at center) L Y 3 FL Y= 8EI (at support) Both Ends Fixed Concentrated Load at Center Both Ends Fixed Uniformly Distributed Load F FL ½ L σ = 8Z (at supports) F (total load) Y FL σ = 12Z (at supports) L Y FL 3 Y= 192EI (at load) L FL 3 Y= 384EI (at center) Table of Contents Udel ® Polysulfone Design Guide 43
Page 1: Udel® Udel ® PSU Design Guide SPE
Page 4 and 5: Environmental Resistance. .........
Page 6 and 7: List of Tables Table 1: Temperature
Page 8 and 9: vi Udel ® Polysulfone Design Guide
Page 10 and 11: Therefore, large amounts of inciden
Page 12 and 13: Approvals A number of organizations
Page 14 and 15: Table 2: Typical Properties (1) of
Page 16 and 17: Tensile Properties Tensile properti
Page 18 and 19: Figure 7: Glass Fiber Increases Fle
Page 20 and 21: After the impact the pendulum conti
Page 22 and 23: Long-Term Creep Properties The resp
Page 24 and 25: Thermal Properties The ways a mater
Page 26 and 27: Deflection Temperature Under Load O
Page 28 and 29: Thermal Conductivity Polymers in ge
Page 30 and 31: Combustion Properties UL 94 Flammab
Page 32 and 33: Thermal Stability Thermogravimetric
Page 34 and 35: Electrical Properties Many applicat
Page 36 and 37: Table 22: Short-Term Electrical Pro
Page 38 and 39: Figure 40: Tensile Elongation After
Page 40 and 41: Radiation Resistance Test specimens
Page 42 and 43: Stress Cracking Resistance To evalu
Page 44 and 45: Table 32: Environmental Stress Crac
Page 46 and 47: Table 34: Environmental Stress Crac
Page 48 and 49: Rockwell Hardness Rockwell hardness
Page 52 and 53: Table 39: Area and Moment Equations
Page 54 and 55: A typical rib design is shown in Fi
Page 56 and 57: Stress Concentrations Classical mec
Page 58 and 59: Designing for Injection Molding Bec
Page 60 and 61: Bosses Bosses are protrusions off t
Page 62 and 63: Fabrication Drying Polysulfone must
Page 64 and 65: Injection Molding Figure 65: Screw
Page 66 and 67: Injection Rate and Venting The inje
Page 68 and 69: Regrind Sprues, runners, and discre
Page 70 and 71: Extrusion Udel ® polysulfone can b
Page 72 and 73: Purging Polysulfone can be easily p
Page 74 and 75: Secondary Operations Cleaning and D
Page 76 and 77: Finishing and Decorating Udel resin
Page 78 and 79: Solvent Bonding Solvent bonding is
Page 80 and 81: Figure 69: Boss Design for Self-Tap
Page 82 and 83: G Gates . . . . . . . . . . . . . .
Page 86: Specialty Polymers Worldwide Headqu

Design Guide - Solvay Plastics

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