1、 Chapter 3第三篇Mixing and Casting Polyurethane攪拌和聚氨酯的澆注This chapter is divided into two parts:Basic mixing and castingBackground to mixing and casting這一篇分為兩部分：攪拌和澆注的基本知識；攪拌和澆注的背景。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.第一部分涵蓋了制造聚氨酯件的步驟和設備要求，第二部分涵蓋了聚氨酯工藝的更多的細節方面的內容。3.1 Basic Mixing and Casting 攪拌和澆注的基本知識There are two basic ways to mix polyurethane:Machine processingManually這里有兩個基本的攪拌聚氨酯的方法：機器攪拌工藝和人工操作。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：在進行聚氨酯的化學試劑或設備的使用前，所有的員工及生產商必須對使用這些化學制品及設備像了解本地政策及習俗一樣的熟悉。相關的材料的安全成分表的復印件必須拿來學習并堅持遵守。第14篇就是對健康和安全這一課題的詳細討論。3.1.1 Machining Processing機械制造工藝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. 機械的制造工藝應該通過采用聚氨酯原材料商和設備制造商提供的最初設置來進行實施。這些設備和設備系統必須彼此互相兼容且有很周密的調整適應功能。The machine must be large enough for the production to be pleted without a full shutdown and recharge of the system.這個機器設備必須足夠大，使得產品在生產過程中不能沒有一個完整的斷電

6、再充電系統。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.機械澆注對于一次澆注成型的工藝來說是可行的，所有的配料都被混合在一個多端輸入的機器中。有些配料需要被預混合，像聚氨酯，催化劑以及填充劑。3.1.2 Manually人工操作Basic equ

7、ipment基礎設施-Safety gloves, mask, and goggles安全手套，防毒面具以及護目鏡-Molds模具-Ovens烤箱-Microwave oven微波爐-Scales電子稱-Devacuuming system抽真空系統-Dry nitrogen supply干氮氣供應-Mixing container攪拌鍋-Stirring paddles攪拌槳-Melting pots for solid curatives(if required)加熱固體激活劑的加熱罐-Bonding agents 粘結力測試工具-Butane burner丁烷燃燒爐-Trimming k

8、nives修整用的刀具-Machining equipment(if required)機器設備（如果需要）-Measuring and test equipment(as required)測量及檢測設備（如果需要）Basic Materials 基本原料-Prepolymers預聚物-Curatives激活劑-Alternative quasiprepolymer system可供選擇的預聚化物系統-Mold release 脫模劑-Pigments顏料-Fillers填充劑-Plasticizers增塑劑（塑料桶？）-Cleaning solvents干凈的清潔試劑3.1.2.1 Met

9、hod 方法The molding procedure is a multistep process with several steps running in parallel.這個注模過程是一個有多種步驟同時進行的復合工藝。1. Preparation準備a. Clean and bring molds to temperature清理模具并預熱模具到一定溫度Make any repairs修理完畢Clean surface dirt清理掉表面的灰塵Remove old mold buildup if necessaryHeat to curing temperature加熱到固化溫度b.

10、 Thaw prepolymers 已溶解的聚氨酯Keep in warm parts of shop 在工廠中保持它的溫度Under oven 置于烤箱中Polytetramethylene glycol( PTMEG) based prone to solidify聚丁二醇傾向于固化No center milkiness中心沒有乳狀渾濁Roll mix to eliminate temperature variations搖晃攪拌時減少溫度變化c. Melt curative if necessary加熱激活劑使融化如果需要的話Do not overheat不要過熱Only suffici

11、ent for day僅夠1天足量的即可d. Weigh out prepolymer and curative稱量預聚物和激活劑Into clean dry container徹底清理干凈裝的容器Maximum depth 25% of height最大深度是總深度的25%Can we use more than one container for large pours大的澆注可以使用1個以上的容器e. Bring to correct temperature調到合適的溫度Bring to suppliers remended temperature調到供應商建議的溫度Use microw

12、ave for smaller amount 可使用微波爐來加熱較小的量f. Degas脫氣Use vacuum pot使用真空罐Approximately 6KPa(28”Hg)vacuum真空壓強在6Kpa(28”Hg)Break vacuum if too foamy如果太多的氣泡需要停止抽真空2. Mixing 攪拌a. Add pigment to prepolymer 將顏料添加到聚氨酯中Some pigments need to be predispersed into the prepolymer 有些顏料需要提前加到聚氨酯中分散開b. Add curative to prep

13、olymer in gentle stream將激活劑緩緩加入到聚氨酯中Add to mixing container in a stream連續不斷的將激活劑加到攪拌的容器Pour along one edge沿著一個邊傾倒c. Mix using zigzag motion or cross-blending使用曲折的動作曲線來交錯雙向攪拌Do not whip in air不要在空氣中攪拌Clean prepolymer from edges and corners into mix聚氨酯的邊邊角角都要進行攪拌Clear mixes must be streak free攪拌器要清理干凈

14、Pigments must be pletely dispersed顏料必須完全地在聚氨酯中擴散開d. Degas again再次脫氣If required degas again provided there is sufficient pot life倘若在有效的適用期內要求再次脫氣3. Pouring澆注a. Add to mold in thin stream將原料成細股狀澆入模具中Rate of pouring must not block inlet in mold澆注時不能大股地注入到模具中Increase height to prevent blockage during po

15、uring在澆注過程中逐漸地增加高度來防止澆注過程中的中斷b. Polyurethane must flow down mold and displace air upward聚氨酯必須流入模具中并使得空氣往上排出Mold fill should be from bottom up.模具的澆注需從底部往上面來澆滿All surfaces must be wetted with no adhering air bubbles.所有的覆膜面都不能有氣泡附著在表面。c. Air must not be trapped in mold 空氣絕對不能殘留在模具中Mold must be titled a

16、nd/or rotated for undercuts to be pletely filledd. Polyurethane should not fold on itself聚氨酯不能靠自己來混合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澆注要及時完成，因為要在材料固化之前使材料中的氣泡跑出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用較柔的丁烷火焰將件表面的氣泡燃燒掉Always keep flame moving要一直讓火焰不斷移動4. Curing固化a. Place filled mold in oven將注滿的模具放入烤箱Oven set to approximately 10°C higher than initial mix

18、 material temperature烤箱設置到比原料混合攪拌時的溫度高10°CPolyurethane must be not heat up or cool mold聚氨酯不能溫度太高或模具的溫度太低b. Demold when part have sufficient strength當零件有足夠的強度時可以進行脫模Normally 1 to 2 hours (See suppliers remendation)通常是1到2小時（詳見供應商的建議）MDI-based systems may be hard but still brittlec. Remove any maj

19、or flash and sprues 除去任何主要的澆注飛濺和澆注口結渣Use sharp knife使用鋒利的刀子Material not as tough as when fully cured材料不如充分固化后堅硬d. Prepare mold for next pour 為下一次的澆注準備模具Recoat mold with mold release重新在模具上涂上脫模劑This is not always necessary as often more than one casting can be made這個操作不需要經常進行因為不止進行一次澆注Keep hot for nex

20、t run 為下一輪的澆注保持溫度5. Post curing后固化a. Return part to oven for 8 to 18 hours for full 將件重新放入烤箱進行818小時的充分固化Follow supplier remendations for time and temperature根據供應商的要求來設定時間及溫度Cycle is normally overnight一個循環一般是一整晚Very hard materials need extra postcure to overe brittleness很硬的件需要額外的后固化來克服脆性b. Final clea

21、ning of flash lines and sprues最后的飛濺的清理和澆注熔渣Remove extra flash with knife or by grinding用刀子將飛濺割掉或通過打磨Clean item清理項c. Any postmolding machining脫模后的機加工Machine dimension to size 機加工到要求尺寸Remember thermal expansion注意受熱膨脹3.2 Background to Mixing and Casting攪拌和澆注的基礎3.2.1 Introduction 說明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:聚氨酯成分的攪拌是完成將化學反應轉化成各種我們需要的性能的產品材料。這里有必須堅持的四點內容：Everything dry and keep dry after use(see 3.2.1.1)在完成使用后所有的東西要保持干燥（詳見3.2.1.1）C

23、orrect weights of all ingredients所有的配料稱量要準確Correct temperatures of ingredients, molds and curing temperatures and times配料溫度，模具溫度以及固化溫度和時間要正確Correct mixing and casting techniques正確的攪拌和澆注技巧These are the basic requirements to produce satisfactory products這些是工廠生產出合格產品的基本要求。3.2.1.1 Dryness of System系統的干燥

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.原材料通常提供時含水量低于0.0

25、5%. 含水量的多少在整個澆注系統中會導致氣泡的產生。這些通常氣泡比較小且均勻分布。也不包含比較大而且不均勻分布的氣泡。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.在使用過后這些的容器要提前用干氮填平進行再次密封。通常商業用的壓縮氮氣是足夠干燥的且露點至少在-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.有些激活劑像丁二醇容易吸濕并且必須要很小心地保護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:澆注聚氨酯的模具可以由多種的材料做成。最重要的表現是它們不受潮濕的影響不會吸收水分。另一個主要的標準是在工藝過程的升溫中不能是熱塑性的。制作模

28、具的主要原料一般包括以下的幾種：Polyurethane 聚氨酯Aluminum鋁Epoxy (filled and unfilled) 環氧樹脂（填充的或未填充的）Silicones （either encased or backed）硅膠Steel 鋼Hard thermoplastics 硬的熱性塑料Polyester resins聚酯樹脂Polyurethanes, silicones, and epoxies are very useful for making molds of objects that need to be reproduced.聚氨酯，硅膠和環氧樹脂對于需要重新

29、制作產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:模具的成本要非常劃算。一個模具可以是單獨的一件整體或者是由若干數量的帶金屬或不帶金屬的零件構成。下面是制作模具應該要考慮到的主要方面：Value of part being made 被制作的

30、件的價值Number of parts to be produced要生產的產品的數量Finish of part 產品的完成數量Accuracy of size of finished casting 完成的鑄件的尺寸的精確度Positions and nature of any undercuts任何的咬邊的位置和特點Size and shape of inserts金屬件的尺寸和形狀Any holes in molding 模具中的任何孔Positions allowable for pour holes and vents 澆注允許的澆注孔或排氣孔的位置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%.聚氨酯在固化過程中，任何地方的收縮率根據級別和固化周期的不同在0%到2%之間。在室溫情況下固化收縮率為0.正常的收縮X圍是1%到1.5%。Shrinkage

32、is three dimensional. The amount in thin sections may not always be noticeable.收縮是立體的。在比較薄的件上收縮并不是很明顯。3.2.2.2 Design Factors設計因素The following are some points that should be taken into account when design a mold:下面是在設計模具時應該考慮在內的幾點：Allow a slight draw on long parts to allow for removal if possible-1/2

33、 to 1°可以允許在長點的件上有1/2到1°的斜度從而方便從模具中拔出。Undercuts cannot be pulled out切入的不易被拉出來Visible areas are best from molded surfaces從模具面上得到的可視區是最好的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.如果這個系

34、統的收縮率不確定，要將模具做到小公差。如果零件太小，材料通常是可以從模具中取出的。-Adding material to the mold is expensive.向模具中添加原料是很昂貴的。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.因為模具要用來澆兩個半片的件，需要先澆注1半，預熱，裝模，脫模 然后再澆注另一半。More details are given in Chapter 5. 在第5部分會給出更多的細節。3.2.2.3 Equipment 設備The size and plexity of the equipment needed depend on the nature of the products being produced.根據生產的產品特性來決定需要的設備的規格及復雜程度。Weighing equipment稱量設備 -Electronic scales are the most monly used電子稱是最常用的-The weight range to suit weighing prepolymer for hand processing is 5 to 30 kg maximum in at