V Y D Y N E ® M O L D I N G G U I D E 2 What is Nylon? . . . . . . . . . . . .

V Y D Y N E ® M O L D I N G G U I D E 2 What is Nylon? . . . . . . . . . . . . . . . 3 Comparing Nylon to Other Engineering Thermoplastics . . . . . . 5 Amorphous Polymers . . . . . . . . . 5 Semi-crystalline Polymers . . . . . 5 Using the Polymers in Parts Fabrication . . . . . . . . . . . . . . . . . 5 Typical Characteristics of Nylon Polymers . . . . . . . . . . . . . 7 Tool Design. . . . . . . . . . . . . . . . . . 9 Tool Design for VYDYNE Nylon Resins . . . . . . . . 10 Tool Design Considerations . . . 10 Multi-cavity Tool Layout and Tool Balancing . . . . . . . . . . . . . 11 Runner Design . . . . . . . . . . . . 13 Sprue Bushing Considerations . . . . . . . . . . . . 14 Gate Design . . . . . . . . . . . . . . 15 Gate Location . . . . . . . . . . . . . 18 Vent Location . . . . . . . . . . . . . 20 Cooling and Mold Steels . . . . . 20 Draft Angles . . . . . . . . . . . . . . 22 Ejector Systems for Molding VYDYNE Nylon Resins . . . . . . 22 Mold Cooling . . . . . . . . . . . . . . 22 Injection-molding Process . . . . 25 Drying of Plastics Materials . . . . . 26 Hopper Dryer Design for Drying Hygroscopic Materials . . . . . . . . . . . . . . . . . 27 Dew Point Temperature and its Importance in Drying of Hygroscopic Materials . . . . . . . . . . . . . . . . . 27 Troubleshooting Drying of Plastics . . . . . . . . . . . . . . . . 28 How to Dry Nylon . . . . . . . . . . . 30 Processing Conditions for VYDYNE Nylon Resins . . . . . . . . 34 General Purpose VYDYNE Resins . . . . . . . . . . . 35 Heat-stabilized VYDYNE Resins . . . . . . . . . . . 36 Nucleated VYDYNE Resins . . . 38 Weather-resistant VYDYNE Resins . . . . . . . . . . . 40 Ignition-resistant VYDYNE Resins . . . . . . . . . . . 42 Mineral/Glass-filled VYDYNE Resins . . . . . . . . . . . 44 Glass-filled VYDYNE Resins . . . . . . . . . . . 46 Hydrolysis-resistant, Glass-filled VYDYNE Resins . . . . . . . . . . . 54 Nylon 66/6 Copolymer, Glass-Filled VYDYNE Resins . 56 Industrial-grade VYDYNE Nylon Resins . . . . . . 58 Screw and Molding Equipment Guidelines . . . . . . . . 60 Screw and Check Ring Design . . 61 Injection-molding Machine Type and Size . . . . . . . . . . . . . . . 64 Mold Shrinkage and Dimensional Stability . . . . . . . . . 65 Mold Shrinkage Prediction . . . . . . 66 Post-mold Shrinkage and Estimating Total Shrinkage . . . . . . 69 Post-mold Shrinkage . . . . . . . . 69 Estimating Total Shrinkage . . . . 70 Packing and Part Density. . . . . . . 71 Part Weight . . . . . . . . . . . . . . . 71 Flow Tabs. . . . . . . . . . . . . . . . . 71 Cavity Pressure Control . . . . . . 71 Coefficient of Linear Thermal Expansion (CLTE) . . . . . . . . . . . . 72 Troubleshooting Guide for Injection Molding Nylon . . . . . . . . 73 Coloring VYDYNE Nylon 66 Resins . . . . . . . . . . . . . 79 Safety and Handling Considerations . . . . . . . . . . . . . . 81 Contents 3 What is Nylon? Polyamides, otherwise known as nylon, can be produced in a num- ber of ways depending on the combination of monomers used to create the long chain. The amide group, shown in Figure 1, is the basic building block for most nylons or polyamides. Polyamides can be produced by combining and poly- merizing two monomers, one or two amine (or diamine) groups with one or two carboxylic acids (or diacid) groups, or by polymerizing a single monomer containing both amine and acid. The polymer structure will determine the physical properties of a particular polyamide. Figure 2 illustrates how nylon 6 and 66 are produced. The basic A monomer is the basic building block of a polymer. The monomer is reacted under the effect of heat and/or pressure and a catalyst monomer and links with more of the same monomer, or with differ- ent monomers, to form one long chain of monomers called a poly- mer, from the Greek “poly” meaning many and “mer” meaning units. O C H N Figure 1 – Basic Amide Group Found in Nylon Figure 2 – Manufacture of Nylon 6 and 66 monomer used to produce nylon 6 is caprolactam, a monomer with a ring-shaped structure containing an amide group. These polymerize by ring opening to form nylons which are designated based on the num- ber of carbon atoms in the lactam monomer. For nylon 6, -caprolac- tam (C6) is the main feedstock used. For nylon 12, laurolactam (C12) is used. Nylons designated with dual numbers, such as nylon 66 or nylon 612, are formed by combining diamines and diacids to form the polyamide polymer. These poly- mers are formed using condensa- tion polymerization. In the 4 Molding Guide designation of these types of nylons, the first number gives the number of carbon atoms in the diamine, and the second number notes the carbon atoms in the diacid. Therefore, as shown in Figure 3, various dual number nylons can be made with different combinations of diamines and diacids. These com- binations of diamines and diacids produce nylons which display differ- ent mechanical and physical prop- erties. This introduction will emphasize the properties of the most commonly used polyamides, nylon 6 and nylon 66. Figure 3 – Dual Number Nylons and How They Are Formed ®Registered trademark of Solutia Inc. used by The Dow Chemical Company under license. Table 1 – Property Comparison of Nylon 6 and Nylon 66 Property Nylon 6 Nylon 66 Nylon 6 Nylon 66 Nylon 6 Nylon 66 (Minimum Values) Unreinforced Unreinforced 35% Glass-filled 35% Glass-filled 40% Mineral-filled 40% Mineral-filled Specific Gravity, gms/cm3 1.12-1.14 1.13-1.15 1.38-1.43 1.35-1.45 1.44-1.54 1.45-1.55 Tensile Strength, psi (MPa) 10,150 (70) 10,150 (70) 22,475 (155) 24,650 (170) 10,875 (75) 11,600 (80) Flexural Modulus, psi (MPa) 319,000 333,500 1,087,500 1,160,000 652,500 725,000 (2,200) (2,300) (7,500) (8,000) (4,500) (7,500) Izod Impact, ft-lbs/in (kJ/m2) @ 70°F (21°C) .55 (3.0) .55 (3.0) 1.50 (8.0) 1.31 (7.0) .84 (4.5) .38 (2.0) @ -40°F (-40°C) .38 (2.0) .28 (1.5) .94 (5.0) 1.14 (6.1) .66 (3.5) .24 (1.3) DTUL @ 264 psi (1.80 MPa) °F (°C) 122 (50) 140 (60) 374 (190) 455 (235) 158 (70) 194 (90) Table 1 shows a comparative chart of the properties of nylon 6 and nylon 66. Several noticeable differences between the properties of nylon 6 and 66 can be seen. Process temperatures of nylon 66 are higher than nylon 6 because the melting point of nylon 66 is approxi- mately 510°F (266°C) versus 460°F (238°C) for nylon 6. Nylon 66 offers higher rigidity or flexural properties combined with excellent thermal properties, especially Deflection Temperature Under Load (DTUL), allowing nylon 66 to withstand high- er mechanical loading than nylon 6. This guide will focus on VYDYNE® nylon 66 resins and how to design for their use in a variety of end-use applications. What is Nylon? – continued Dual Number Nylons Hexamethylene Diamine + Adipic Acid = NYLON 66 Hexamethylene Diamine + Sebacic Acid = NYLON 610 Hexamethylene Diamine + Dodecanoic Acid = NYLON 612 5 Comparing Nylon to Other Engineering Thermoplastics Amorphous Polymers Amorphous polymers consist of polymer molecules having no ordered structure. Figure 4 shows the structure of a typical amor- phous polymer uploads/Geographie/ vydyne-processing-guide.pdf

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