Polyurethane聚氨酯的浇注工艺设计

1、 Chapter 3第三篇Mixing and Casting Polyurethane搅拌和聚氨酯的浇注This chapter is divided into two parts:Basic mixing and castingBackground to mixing and casting这一篇分为两部分：搅拌和浇注的基本知识；搅拌和浇注的背景。The first part covers the steps and equipment required for making a polyurethane part; the second covers more detailed aspe

2、cts of the process.第一部分涵盖了制造聚氨酯件的步骤和设备要求，第二部分涵盖了聚氨酯工艺的更多的细节方面的内容。3.1 Basic Mixing and Casting 搅拌和浇注的基本知识There are two basic ways to mix polyurethane:Machine processingManually这里有两个基本的搅拌聚氨酯的方法：机器搅拌工艺和人工操作。Note: Before any handling of polyurethane chemicals or equipment, all staff and makers must be f

3、amiliar with the occupational Health and Safety requirements for the use of chemicals and machinery as well as all local rules and regulations. Copies of the relevant Material Safety Data Sheets(MSDSs)must be studied and adhered to. Chapter 14 discusses the subject of health and safety in more detai

4、l.注意：在进行聚氨酯的化学试剂或设备的使用前，所有的员工及生产商必须对使用这些化学制品及设备像了解本地政策及习俗一样的熟悉。相关的材料的安全成分表的复印件必须拿来学习并坚持遵守。第14篇就是对健康和安全这一课题的详细讨论。3.1.1 Machining Processing机械制造工艺Machine processing should be carried out using the initial setting given by the raw material and the machine manufacturers. Both the machine and the machine

5、 system must be patible with each other and capable of allowing fine adjustments. 机械的制造工艺应该通过采用聚氨酯原材料商和设备制造商提供的最初设置来进行实施。这些设备和设备系统必须彼此互相兼容且有很周密的调整适应功能。The machine must be large enough for the production to be pleted without a full shutdown and recharge of the system.这个机器设备必须足够大，使得产品在生产过程中不能没有一个完整的断电

6、再充电系统。Machine casting is ideal for one-shot processes where all the ingredients are mixed in a multi-input machine. Some of the ingredients may be preblended, such as the polyols, catalysts, and extenders.机械浇注对于一次浇注成型的工艺来说是可行的，所有的配料都被混合在一个多端输入的机器中。有些配料需要被预混合，像聚氨酯，催化剂以及填充剂。3.1.2 Manually人工操作Basic equ

7、ipment基础设施-Safety gloves, mask, and goggles安全手套，防毒面具以及护目镜-Molds模具-Ovens烤箱-Microwave oven微波炉-Scales电子称-Devacuuming system抽真空系统-Dry nitrogen supply干氮气供应-Mixing container搅拌锅-Stirring paddles搅拌桨-Melting pots for solid curatives(if required)加热固体激活剂的加热罐-Bonding agents 粘结力测试工具-Butane burner丁烷燃烧炉-Trimming k

8、nives修整用的刀具-Machining equipment(if required)机器设备（如果需要）-Measuring and test equipment(as required)测量及检测设备（如果需要）Basic Materials 基本原料-Prepolymers预聚物-Curatives激活剂-Alternative quasiprepolymer system可供选择的预聚化物系统-Mold release 脱模剂-Pigments颜料-Fillers填充剂-Plasticizers增塑剂（塑料桶？）-Cleaning solvents干净的清洁试剂3.1.2.1 Met

9、hod 方法The molding procedure is a multistep process with several steps running in parallel.这个注模过程是一个有多种步骤同时进行的复合工艺。1. Preparation准备a. Clean and bring molds to temperature清理模具并预热模具到一定温度Make any repairs修理完毕Clean surface dirt清理掉表面的灰尘Remove old mold buildup if necessaryHeat to curing temperature加热到固化温度b.

10、 Thaw prepolymers 已溶解的聚氨酯Keep in warm parts of shop 在工厂中保持它的温度Under oven 置于烤箱中Polytetramethylene glycol( PTMEG) based prone to solidify聚丁二醇倾向于固化No center milkiness中心没有乳状浑浊Roll mix to eliminate temperature variations摇晃搅拌时减少温度变化c. Melt curative if necessary加热激活剂使融化如果需要的话Do not overheat不要过热Only suffici

11、ent for day仅够1天足量的即可d. Weigh out prepolymer and curative称量预聚物和激活剂Into clean dry container彻底清理干净装的容器Maximum depth 25% of height最大深度是总深度的25%Can we use more than one container for large pours大的浇注可以使用1个以上的容器e. Bring to correct temperature调到合适的温度Bring to suppliers remended temperature调到供应商建议的温度Use microw

12、ave for smaller amount 可使用微波炉来加热较小的量f. Degas脱气Use vacuum pot使用真空罐Approximately 6KPa(28”Hg)vacuum真空压强在6Kpa(28”Hg)Break vacuum if too foamy如果太多的气泡需要停止抽真空2. Mixing 搅拌a. Add pigment to prepolymer 将颜料添加到聚氨酯中Some pigments need to be predispersed into the prepolymer 有些颜料需要提前加到聚氨酯中分散开b. Add curative to prep

13、olymer in gentle stream将激活剂缓缓加入到聚氨酯中Add to mixing container in a stream连续不断的将激活剂加到搅拌的容器Pour along one edge沿着一个边倾倒c. Mix using zigzag motion or cross-blending使用曲折的动作曲线来交错双向搅拌Do not whip in air不要在空气中搅拌Clean prepolymer from edges and corners into mix聚氨酯的边边角角都要进行搅拌Clear mixes must be streak free搅拌器要清理干净

14、Pigments must be pletely dispersed颜料必须完全地在聚氨酯中扩散开d. Degas again再次脱气If required degas again provided there is sufficient pot life倘若在有效的适用期内要求再次脱气3. Pouring浇注a. Add to mold in thin stream将原料成细股状浇入模具中Rate of pouring must not block inlet in mold浇注时不能大股地注入到模具中Increase height to prevent blockage during po

15、uring在浇注过程中逐渐地增加高度来防止浇注过程中的中断b. Polyurethane must flow down mold and displace air upward聚氨酯必须流入模具中并使得空气往上排出Mold fill should be from bottom up.模具的浇注需从底部往上面来浇满All surfaces must be wetted with no adhering air bubbles.所有的覆膜面都不能有气泡附着在表面。c. Air must not be trapped in mold 空气绝对不能残留在模具中Mold must be titled a

16、nd/or rotated for undercuts to be pletely filledd. Polyurethane should not fold on itself聚氨酯不能靠自己来混合Polyurethane that is gelling can fold over on itself and cause fault linese. Pouring must be pleted in time for air bubbles to escape before material gels浇注要及时完成，因为要在材料固化之前使材料中的气泡跑出Gel point can be de

17、termined by drawing a thread from surface, using piece of wire with diameter of a paper clipUse a” soft” butane flame to pop surface bubbles用较柔的丁烷火焰将件表面的气泡燃烧掉Always keep flame moving要一直让火焰不断移动4. Curing固化a. Place filled mold in oven将注满的模具放入烤箱Oven set to approximately 10°C higher than initial mix

18、 material temperature烤箱设置到比原料混合搅拌时的温度高10°CPolyurethane must be not heat up or cool mold聚氨酯不能温度太高或模具的温度太低b. Demold when part have sufficient strength当零件有足够的强度时可以进行脱模Normally 1 to 2 hours (See suppliers remendation)通常是1到2小时（详见供应商的建议）MDI-based systems may be hard but still brittlec. Remove any maj

19、or flash and sprues 除去任何主要的浇注飞溅和浇注口结渣Use sharp knife使用锋利的刀子Material not as tough as when fully cured材料不如充分固化后坚硬d. Prepare mold for next pour 为下一次的浇注准备模具Recoat mold with mold release重新在模具上涂上脱模剂This is not always necessary as often more than one casting can be made这个操作不需要经常进行因为不止进行一次浇注Keep hot for nex

20、t run 为下一轮的浇注保持温度5. Post curing后固化a. Return part to oven for 8 to 18 hours for full 将件重新放入烤箱进行818小时的充分固化Follow supplier remendations for time and temperature根据供应商的要求来设定时间及温度Cycle is normally overnight一个循环一般是一整晚Very hard materials need extra postcure to overe brittleness很硬的件需要额外的后固化来克服脆性b. Final clea

21、ning of flash lines and sprues最后的飞溅的清理和浇注熔渣Remove extra flash with knife or by grinding用刀子将飞溅割掉或通过打磨Clean item清理项c. Any postmolding machining脱模后的机加工Machine dimension to size 机加工到要求尺寸Remember thermal expansion注意受热膨胀3.2 Background to Mixing and Casting搅拌和浇注的基础3.2.1 Introduction 说明The mixing of polyure

22、thane ponents is to plete chemical reactions that convert the various ingredients to viable products with known properties. There are four main points that must be adhered to:聚氨酯成分的搅拌是完成将化学反应转化成各种我们需要的性能的产品材料。这里有必须坚持的四点内容：Everything dry and keep dry after use(see 3.2.1.1)在完成使用后所有的东西要保持干燥（详见3.2.1.1）C

23、orrect weights of all ingredients所有的配料称量要准确Correct temperatures of ingredients, molds and curing temperatures and times配料温度，模具温度以及固化温度和时间要正确Correct mixing and casting techniques正确的搅拌和浇注技巧These are the basic requirements to produce satisfactory products这些是工厂生产出合格产品的基本要求。3.2.1.1 Dryness of System系统的干燥

24、Raw materials are normally supplied with moisture content of less than 0.05%. The presence of moisture in the system will result in fine bubbles throughout the entire pour. These bubbles are very small and evenly dispersed. Included air bubbles are larger and more randomly dispersed.原材料通常提供时含水量低于0.0

25、5%. 含水量的多少在整个浇注系统中会导致气泡的产生。这些通常气泡比较小且均匀分布。也不包含比较大而且不均匀分布的气泡。All containers must be flushed with dry nitrogen gas prior to resealing after use .Normal mercial pressed nitrogen is dry enough with a dew point of at least -40°C.在使用过后这些的容器要提前用干氮填平进行再次密封。通常商业用的压缩氮气是足够干燥的且露点至少在-40°C。Some curative

26、s such as BDO are very hygroscopic and must be handled with care to prevent the absorption of any moisture.有些激活剂像丁二醇容易吸湿并且必须要很小心地保护防止吸收到任何的水分。3.2.2 Basic Requirements基本要求3.2.2.1 Molds模具Molds for casting polyurethane parts can be made from a wide range of materials. The most important factor is that

27、they must be impervious to moisture and not contain any moisture. The other main criterion is that they must not be thermoplastic at the processing temperature. Some of the main materials used to make molds include the following:浇注聚氨酯的模具可以由多种的材料做成。最重要的表现是它们不受潮湿的影响不会吸收水分。另一个主要的标准是在工艺过程的升温中不能是热塑性的。制作模

28、具的主要原料一般包括以下的几种：Polyurethane 聚氨酯Aluminum铝Epoxy (filled and unfilled) 环氧树脂（填充的或未填充的）Silicones （either encased or backed）硅胶Steel 钢Hard thermoplastics 硬的热性塑料Polyester resins聚酯树脂Polyurethanes, silicones, and epoxies are very useful for making molds of objects that need to be reproduced.聚氨酯，硅胶和环氧树脂对于需要重新

29、制作产品模具的是非常有用的材料。Molds must be cost effective. A mold may be made in a single piece or in any number of parts with or without inserts. The following are some main factors to be considered in making a mold:模具的成本要非常划算。一个模具可以是单独的一件整体或者是由若干数量的带金属或不带金属的零件构成。下面是制作模具应该要考虑到的主要方面：Value of part being made 被制作的

30、件的价值Number of parts to be produced要生产的产品的数量Finish of part 产品的完成数量Accuracy of size of finished casting 完成的铸件的尺寸的精确度Positions and nature of any undercuts任何的咬边的位置和特点Size and shape of inserts金属件的尺寸和形状Any holes in molding 模具中的任何孔Positions allowable for pour holes and vents 浇注允许的浇注孔或排气孔的位置Available pot li

31、fe of polyurethane 聚氨酯的有效使用期Polyurethane shrinks anywhere between 0% and 2% on curing depending on the grade and the cure circle. Room temperature cure can have zero shrinkage. The normal range of shrinkage is 1% to 1.5%.聚氨酯在固化过程中，任何地方的收缩率根据级别和固化周期的不同在0%到2%之间。在室温情况下固化收缩率为0.正常的收缩X围是1%到1.5%。Shrinkage

32、is three dimensional. The amount in thin sections may not always be noticeable.收缩是立体的。在比较薄的件上收缩并不是很明显。3.2.2.2 Design Factors设计因素The following are some points that should be taken into account when design a mold:下面是在设计模具时应该考虑在内的几点：Allow a slight draw on long parts to allow for removal if possible-1/2

33、 to 1°可以允许在长点的件上有1/2到1°的斜度从而方便从模具中拔出。Undercuts cannot be pulled out切入的不易被拉出来Visible areas are best from molded surfaces从模具面上得到的可视区是最好的If the shrinkage of the system is uncertain, make the mold on the smaller limits. If part is too small, material can normally be removed from the mold.如果这个系

34、统的收缩率不确定，要将模具做到小公差。如果零件太小，材料通常是可以从模具中取出的。-Adding material to the mold is expensive.向模具中添加原料是很昂贵的。For molds in two halves pour one half, cure, mold, release, and then pour the second half.Molds with an undercut-make vertical casting slit into two vertical halves with scalpel or other thin, sharp knif

35、e. Make tight-fitting outer mold to keep the two halves together.因为模具要用来浇两个半片的件，需要先浇注1半，预热，装模，脱模 然后再浇注另一半。More details are given in Chapter 5. 在第5部分会给出更多的细节。3.2.2.3 Equipment 设备The size and plexity of the equipment needed depend on the nature of the products being produced.根据生产的产品特性来决定需要的设备的规格及复杂程度。Weighing equipment称量设备 -Electronic scales are the most monly used电子称是最常用的-The weight range to suit weighing prepolymer for hand processing is 5 to 30 kg maximum in at