尼龙成型指导E.doc

d ® Zytel nylon resin Start with DuPont Table of Contents Chapter 1 Page Chapter 6 Page General InformationÊ . 2 Composition and Properties. 2 Physical Form . 2 Containers . 2 Chapter 2 The Injection Molding ProcessÊ . 4 Processing Characteristics. 4 Melting or Softening Temperature . 4 Energy Requirements . 4 Melt Viscosity . 4 Stability and Behavior at Melt Temperature . 5 Cycle Time . 5 Shrinkage . 5 Chapter 3 The Injection Molding MachineÊ . 6 Machine Melt Capacity . 6 Screw Design . 6 Nonreturn Valve . 6 Nozzle . 6 Nozzle Shutoff Valve . 6 Hydraulic System . 7 Injection Pressure . 7 Clamping Capacity . 8 Temperature Control. 8 Chapter 4 Machine Operating ConditionsÊ . 9 Cylinder Temperature Profile . 9 Melt Temperature. 9 Nozzle Temperature . 9 Injection Pressure . 10 Injection Rate . 11 Screw Forward Time. 11 Overall Cycle. 11 Screw Speed. 11 Back Pressure . 13 Mold Temperature . 13 Start-Up. 13 Shutdown. 14 Purging . 14 Chapter 5 Handling of Molding ResinÊ . 15 Effects of Moisture and Contamination on Molding Resin. 15 Handling Regrind . 16 Drying . 17 How To Obtain Optimum ToughnessÊ . 19 Selection of Zytel ®Ê . 19 Molding Zytel ® 3189, 408L and ST801 for Toughness . 19 Part Design. 19 Chapter 7 Interrelationship of Part Design, Molding Conditions, Resin Selection and Mold DesignÊ . 20 Thickness of Section . 20 Ribs and Strengthening Members . 21 Bosses . 21 Fillets and Radii . 21 Undercuts. 22 Chapter 8 Mold DesignÊ . 23 Sprue BushingÊ . 23 Runner Design . 23 Gate Design . 23 Mold Cooling . 25 Venting . 25 Undercuts. 25 Runnerless MoldsTypes and Terms. 26 Chapter 9 DimensionsÊ . 28 Mold ShrinkageÊ . 28 Post-Mold Shrinkage. 29 Effects of Moisture and Temperature on Dimensions . 29 Dimensional Tolerances . 30 Chapter 10 Quality ControlÊ . 34 Resin Specifications . 34 Specifications on Molded Parts . 34 Chapter 11 Troubleshooting Guide for Zytel ® Nylon ResinsÊ . 36 Chapter 12 Operating PrecautionsÊ . 38 Handling of Zytel ® Nylon ResinsÊ . 39 Slipping Hazards . 39 Spontaneous Ignition. 39 Chapter 1 Zytel ® Nylon Resins for Injection Molding Composition and Properties Zytel ® nylon resins are thermoplastic polyamides having properties that place them high on the list of engineering plastics. Zytel ® nylon resins are tough and withstand repeated impact. They are highly resistant to abrasion and to most chemicals. Molded articles retain their shape at elevated temperatures, are strong in thin sections and have low coefficients of friction. Many of the compositions, including Zytel ® 101L, are classified by Underwriters' Laboratories. Also, flame retardant nylons qualify- ing for the UL94 V-1 and 94 V-0 are under con- tinuing development. The principal Zytel ® nylon resins may be divided by chemical composition into four basic groups 66 nylon, 612 nylon, 6 nylon and copolymersall of which may be modified to give special proper- ties. Resins in any of these groups may also be made with different molecular weights. Properties such as melting point, water absorption and modu- lus of elasticity are determined primarily by the type of nylon. Impact resistance is determined by the type of modifier used (if any) and molecular weight of the nylon. Melt viscosity is determined mainly by molecular weight. Additives of various kinds may be used to enhance properties (e.g., mold release, screw retraction). Zytel ® nylon resins may be reinforced with glass fibers to increase their tensile strength, stiffness, and dimensional stability, but this Molding Guide is limited to a discussion on unreinforced nylons. For information on glass-reinforced Zytel ® resins and Minlon ® mineral reinforced resin, contact your DuPont representative. The commercially coded Zytel ® nylon resins are listed and described in Figure 1. In addition, there are some experimental resins, coded "FE," designed to have specific attributes. These resins are on commercial trial and, if found suitable, will be given full commercial designation. Information concerning current Zytel® nylon "FE" resins can be obtained from your DuPont representative. Physical Form Most Zytel ® nylon resins are supplied as right cylinder pellets of approximately 2.3 × 2.6 mm (0.090 × 0.100 in). A few are supplied in a rectan- gular cut, approximately 3.2 × 3.2 × 3.2 mm (0.125 × 0.125 × 0.125 in). Containers ® Most Zytel nylon resins are packaged in 25-kg (55.1-lb) net weight pinch-pack bags, foil coated with the innerply laminated with polyethylene resin. Certain nylon resins are available in other packages: Corrugated boxes with polyolefin liner, 750 kg (1,653 lb) net weight or more. Disposable four-way entry pallets used for 40-bag units and on bulk corrugated boxes. Overall dimensions on palletized loads: Bags: 109 × 127 × 137 cm high (43 × 50 × 54 in high) Boxes: 107 × 122 × 109 cm high (42 × 48 × 43 in high) 2 Figure 1. Zytel ® Nylon Molding Resins Designation Description Characteristics and Major Uses 66 NylonsMelt at 262°C (504°F)Stiff and strong over a wide range of temperature. Excellent toughness and chemical resistance. Zytel ® 101 Zytel ® 101L Zytel ® 101F Zytel ® 132F Zytel ® 103HSL, 103FHS General Purpose Unlubricated General Purpose Lubricated General Purpose Fast Cycle General Purpose Nucleated, Fast Cycle Heat Stabilized Lubricated Zytel ® 105 BK010A Zytel ® 122L Zytel ® 42A Weather Resistant Hydrolysis Resistant High Viscosity for Extrusion Basic 66 nylon. Unmodified 66 nylon of medium viscosity. The industry standard. A 66 nylon lubricated for improved machine feed and mold release characteristics. Widely used in injection molding for mechanical parts, consumer products, etc. A non-nucleated 66 nylon for optimum molding performance. 66 nylons nucleated for fast molding cycles. Stiffer and stronger than unmodified nylons at some sacrifice in toughness. New, improved heat-stabilized 66 nylons designed to retard embrittlement at high service temperatures. Have 130°C ULratings for electrical use. Lubricated for improved machine feed and mold release. Zytel ® 103FHS is fast cycling version. Contains well-dispersed carbon black for outstanding resistance to weathering. Stabilized to resist hydrolysis and oxidation in long-term exposure to hot water. Lubricated for improved machine feed and mold release. For extrusion into rod, tubing and complex shapes. Can be molded into parts requiring high impact resistance. Toughened 66 NylonsMelt at 262°C (504°F). Added toughness and flexibility. Zytel ® 408L, 408HS 408 BK010 Zytel ® 450HSL, BK152 Zytel ® 3189, 3189HSL General PurposeHeat Stabilized, Weather Resistant Heat Stabilized General Purpose Superior toughness and moldability at some sacrifice in strength and stiffness. Economy grade. Similar to Zytel ® 408L. Superior toughness/stiffness, balance, outstanding flow and processibility. Super Tough Nylons. Highest impact strength of any engineering thermoplastic. Zytel ® ST801, ST801HS, ST801 BK010 General PurposeHeat Stabilized, Weather Resistant Zytel ® ST800L, ST8000HSL, General PurposeHeat ST800HSL BK010 Zytel ® ST811HS Zytel ® ST901L Stabilized, Weather Resistant General Purpose Outstanding toughness. Good moldability. Some sacrifice in strength and stiffness. Similar to Zytel ® ST801. Economy grades. Super tough nylon 6. Highest toughness even at low temperatures. General PurposeAmorphous Low shrinkage and warpage. Properties relatively unaffected by Characteristics moisture. Excellent combination of stiffness and toughness. 612 NylonsMelt at 218°C (424°F)Low moisture absorption and excellent dimensional stability. Zytel ® 151L Zytel ® 158L Zytel ® 153HSL Zytel ® 157HSL BK010 General PurposeLubricated General PurposeLubricated Heat StabilizedLubricated A 612 nylon lubricated for improved machine feed and mold release. Higher melt viscosity and greater toughness than Zytel ® 151L. Lubricated for improved machine feed and mold release. Heat-stabilized Zytel ® 158L to retard embrittlement at high service temperatures. Primarily for wire jacketing. Weather and Heat Resistant Contains well-dispersed carbon black for outstanding resistance to Lubricated Flame Retardant NylonUL 94 V-O Rating Zytel ® FR10 General Purpose weathering. Heat stabilized. Lubricated for improved machine feed and mold release. UL 94 V-0 down to 0.71 mm (0.028 in) in natural and black color. Miscellaneous ProductsCopolymers, Blends, Plasticized Resins, Unextracted Nylon 6 Zytel ® 91AHS Zytel ® 109L Plasticized Nylon Copolymer General PurposeColor Stabilized, Nucleated, Lubricated High flexibility and toughness. Primarily for extrusion but may be molded into hammer heads, etc. Easy processing at the expense of stiffness and high temperature properties. Excellent for heavy section moldings. 3 Chapter 2 The Injection Molding Process The injection molding of thermoplastic resins is a well-known and widely practiced science. It constitutes a major processing technique for converting nylon into a variety of end-use products. In basic terms, the process involves heating the solid molding powder to melt it, then transferring it to a mold and holding it under pressure until it freezes, or solidifies. Plastic molding compounds represent a range of chemical types. Each type has its own specific processing characteristics which must be consid- ered and understood before it can be successfully molded. The information in this book is intended to provide guidance in the injection molding of unreinforced Zytel ® nylon resins, which are chemi- cally classified as polyamides. Processing Characteristics The physical and chemical properties of a plastic dictate the way in which it must be molded. Among these are: Melting or softening temperature Energy content (specific heat and latent heat) Melt viscosity Stability and behavior at melt temperatures Freezing rate, crystallization rate, and cycle time Shrinkage Melting or Softening Temperature Most Zytel ® nylon resins are crystalline materials with melting points higher than those of many other thermoplastic materials. However, some are noncrystalline and have softening temperatures, not true melting points. Melting points of Zytel ® nylon resins are compared with those of other plastic materials in Figure 2. Energy Requirements Zytel ® nylon resins must be heated to their process- ing temperatures before they can be molded (see Figure 3). Crystalline materials such as Zytel® 101L and acetal resins can require greater energy input than amorphous or noncrystalline resins because considerable energy is needed just to coalesce the ordered structure. The heat energy required for doing this is known as heat of fusion Figure 2. Melting Points of Plastic Materials Melting or Softening Temperature Type Polyethylene (low density) Polystyrene Acetal (homopolymer) ® Zytel 151L (612 nylon) Polycarbonate Zytel ® 101L (66 nylon) Zytel ® 408L, 3189 (modified 66 nylons) Zytel ® ST801 °C 105 168 175 218 221 262 262 262 °F 221 334 347 424 430 504 504 504 Figur