Chapter 4 Plastics Forming and Mold Design（塑料成型工艺及模具）.ppt

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1、Chapter 4 Plastics Forming and Mold Design（塑料成型工艺及模具）（塑料成型工艺及模具）Lesson 13 Summary of PlasticsLesson 14 The Structure of PlasticsLesson 15 Classification and Application of PlasticsLesson 16 Injection MoldingLesson 17 Injection MachineLesson 18 Representative Strcture of Injection MoldLesson 19 Extru

2、sion MoldingLesson 13 Summary of PlasticslPlastics are an important class of materials with an extremely wide range of mechanical,physical,and chemical properties.The first plastics(natural polymers)were produced in the 1860s;however,modern plastics technology(synthetic polymers)began in the 1920s.T

3、hese materials are called plastics,from the Greek plastics meaning they can be molded and shaped.lPlastics are characterized by the following properties:low density,low strength and elastic modulus,low thermal and electrical conductivity,high chemical resistance,and high coefficient of thermal expan

4、sion.They can beBACKNEXTLesson 13 Summary of Plasticslcast,formed,machined,and joined into different shapes and are available in a wide variety of properties,colors,and opacities.Also included in this group of materials are rubbers and elastomers.lBecause of their many unique properties,plastics hav

5、e increasingly replaced metallic components in numerous applications.This trend is explained by considerations with respect to service requirements,strength-to-weight ratio,design and cost of the material,and ease of manufacturing.BACKPREVNEXTLesson 13 Summary of PlasticslWith various additives and

6、reinforcements,plastics are used in a wide range of consumer and industrial products.Some of the major applications are in automotive,electrical and electronic products such as integrated circuits,mechanical equipment,food and beverage containers,packaging,signs,housewares,textiles,safety equipment,

7、toys,appliances,and optical eqmpment.Notes:l1.Plastics are an important class of materials with an extremely wide range of mechanical,physical,and chemicalBACKPREVNEXTLesson 13 Summary of Plasticslpropertiesl译文译文:塑料是一种具有非常广泛的机械、物理和化学性能塑料是一种具有非常广泛的机械、物理和化学性能的重要材料。的重要材料。l2.The first plastics(natural p

8、olymers)were produced in the 1860s;however,modern plastics technology(synthetic polymers)began in the 1920s.l译文译文:最初的塑料最初的塑料(大然聚合物大然聚合物)生产于生产于19世纪世纪60年代年代;但是但是,现代塑料技术现代塑料技术(合成聚合物合成聚合物)出现于出现于20世纪世纪20年代。年代。l解析解析:此句中此句中be produced in译为译为“生产于生产于”。be produced from译为译为“用用制造制造”。BACKPREVNEXTLesson 13 Summar

9、y of Plasticsl3.Plastics are characterized by the following properties:low density,low strength and elastic modulus,low thermal and electrical conductivity,high chemical resistance,and high coefficient of thermal expansion.l译文译文:塑料具有以下特点塑料具有以下特点:低密度、低强度和弹性模量、低低密度、低强度和弹性模量、低导热性和低导电性、高抗化学阻力和高热膨胀系数。导热性

10、和低导电性、高抗化学阻力和高热膨胀系数。l4.They can be cast,formed,machined,and joined into different shapes and are available in a wide variety of properties,colors,and opacities.BACKPREVNEXTLesson 13 Summary of Plasticsl译文译文:塑料能浇铸、成型、机械加工和连成不同的形状塑料能浇铸、成型、机械加工和连成不同的形状,并并且可以具有不同的性能且可以具有不同的性能,颜色和光透性。颜色和光透性。l5.Because of

11、 their many unique properties,plastics have increasingly replaced metallic components in numerous applications.l译文译文:因为具有许多独特的性质因为具有许多独特的性质,塑料在很多应用中已经逐塑料在很多应用中已经逐渐地取代了金属成分。渐地取代了金属成分。l6.This trend is explained by considerations with respect to service requirements,strength-to-weight ratio,design and

12、cost of the material,and ease of manufacturing.BACKPREVNEXTLesson 13 Summary of Plasticsl译文译文:这种趋势可以从以下这些方面进行解释这种趋势可以从以下这些方面进行解释,即产品的服即产品的服务需求、强度和自重的比例、材料的设计和成本以及制造务需求、强度和自重的比例、材料的设计和成本以及制造的简易性。的简易性。l7.With various additives and reinforcements,plastics are used in a wide range of consumer and indust

13、rial products.l译文译文:塑料含有各种添加剂和增强相塑料含有各种添加剂和增强相,广泛地应用于生活用广泛地应用于生活用品和工业制品中。品和工业制品中。l8.Some of the major applications are in automotive,electrical and electronic products such as integrated circuits,mechanical equipment,food and beverageBACKPREVNEXTLesson 13 Summary of Plasticslcontainers,packaging,sig

14、ns,housewares,textiles,safety equipment,toys,appliances,and optical equipment.l译文译文:塑料主要应用于汽车产品、电气和电子产品中塑料主要应用于汽车产品、电气和电子产品中,例如例如集成电路、机械装备、食品和饮料罐、包装、标记、家用集成电路、机械装备、食品和饮料罐、包装、标记、家用器皿、纺织品、安全装置、玩具、器具和光学设备。器皿、纺织品、安全装置、玩具、器具和光学设备。l解析解析:此句中此句中some of the major applications are in译为译为“塑料主要应用于塑料主要应用于”。BACKP

15、REVLesson 14 The Structure of PlasticslPlastics are composed of polymer molecules and various additives.Polymers are long-chain molecules(also called giant molecules or macromolecules),which are formed by polymerization;that is,linking and cross-linking of different monomers.MonomerslA monomer is th

16、e basic building block of polymers.The word mer(from the Greek meros,meaning part)indicates the smallest repetitive unit,similar to the term unit cell in crystal structures.Thus,polymer means many mers or units.Monomers are organic materials.They includeBACKNEXTLesson 14 The Structure of Plasticslca

17、rbon atoms joined in covalent bonds(electron sharing)with other atoms such as hydrogen,oxygen,nitrogen,fluorine,chlorine,silicon,and sulfur.lA typical monomer is the ethylene molecule shown in Fig.14-1(a).These molecules can be made to attach themselves to other ethylene molecules by a chemical reac

18、tion involving heat,pressure,and a catalyst.In this reaction,the double bonds between the carbon atoms open and the molecules arrange themselves in a long line Fig.14-1(b).BACKPREVNEXTLesson 14 The Structure of PlasticslThe polymer shown in Fig.14-1(b)is called a linear polymer because structure.The

19、 number of molecules in this chain(length of chain)is known as the molecular weight.A linear molecule does not mean that it is straight.These molecules(chain are of different lengths and their arrangement is amorphous without any long-range order.This arrangement is often described as a bowl of spag

20、hetti,or worms in a bucket,all intertwined with each other.Because of the differences in the length of the chains,the molecular weight of a polymer is determined on a statistical basis.BACKPREVNEXTLesson 14 The Structure of PlasticsBondinglAlthough within each long-chain molecule there is covalent b

21、onding(primary bonds),no such intermolecular bonding exists between different chains.The bonds between different chains(intramolecular),and between the overlapping portions of the same chain,are known as secondary bonds.Secondary bonds are van der Waals bonds,hydrogen bonds,and ionic bonds.Secondary

22、 bonds are all much weaker than the covalent bonds within the chain.BACKPREVNEXTLesson 14 The Structure of PlasticslThe difference in strength between the two bonds is on the order of one to two orders of magnitude.This difference is important,because it is the weaker secondary bonds that determine

23、the overall strength of the polymer.(Thus,for instance,an object is only as strong as its weakest part.)lIf the repeating units in a chain are all of the same type,the macromolecule is known as a homopolymer.However,in order to obtain certain special properties,two or three different types of monome

24、rs can be combined in a polymer.These are known as copolymers and terpolymers,respectively.BACKPREVNEXTLesson 14 The Structure of PlasticsBranching and LinkinglThe properties of a copolymer depend not only on the two monomers,but also on their arrangement in the molecular structure(Fig.14-2).Branchi

25、ng,for instance,interferes with the relative movement of the molecules and affects the resistance to deformation.Another kind of chain is cross-linking Fig.14-2(c),which is spatial(three-dimensional)network structure with adjacent chains tied together.Cross-linking has great influence on the propert

26、ies of the polymer,such as in the vulcanization of rubber.BACKPREVNEXTLesson 14 The Structure of PlasticslThermoplastics,such as acrylic,nylons,polyethylene,and polyvinyl chloride,are linear-chain molecules.Thermosetting plastics,such as epoxies,phenolics,and silicones,have cross-linked chains.An ex

27、ample of cross-linking is the vulcanization of rubber for automobile tires,each tire being one giant molecule.lPlastics made of linear chain structures are called thermoplastics,and those made of cross-linked chain are called thermosetting plastics,or simply,thermosets.BACKPREVNEXTLesson 14 The Stru

28、cture of PlasticsNotes:l1.Plastics are composed of polymer molecules and various additives.l译文译文:塑料由聚合分子和各种添加剂组成。塑料由聚合分子和各种添加剂组成。l解析解析:此句中此句中are composed of译为译为“由由组成组成”。l2.Polymers are long-chain molecules(also called giant molecules or macromolecules),which are formed by polymerization;that is,link

29、ing and cross-linking of different monomers.l译文译文:聚合体是长链分子聚合体是长链分子(也称巨大分子或高分子也称巨大分子或高分子),它是通它是通过聚合形成的过聚合形成的,即单体的结合和交联。即单体的结合和交联。BACKPREVNEXTLesson 14 The Structure of Plasticsl解析解析:此句中此句中which在句中引导非限制性定语从句。在句中引导非限制性定语从句。that is的意思是的意思是“即即,就是就是,换句话说换句话说,就是说就是说,更确切地说更确切地说”,也也可以说成可以说成that is to say。l3.

30、The word mer(from the Greek meros,meaning part)indicates the smallest repetitive unit,similar to the term unit cell in crystal structures.l译文译文:mer这个词这个词(来自希腊语的来自希腊语的meros,意思是意思是“部分部分”)表表示最小的重复个体示最小的重复个体,与晶体结构中的术语与晶体结构中的术语“单位晶格单位晶格”相相似。似。l解析解析:句中句中unit cell的意思是的意思是“晶胞晶胞,单胞单胞,格子单位格子单位,单位单位晶格晶格,单位粒子单位

31、粒子”。Be similar to“与与相似相似”。BACKPREVNEXTLesson 14 The Structure of Plasticsl4.These molecules can be made to attach themselves to other ethylene molecules by a chemical reaction involving heat,pressure,and a catalyst.l译文译文:这些分子可以通过加热、加压和添加催化剂的化学这些分子可以通过加热、加压和添加催化剂的化学反应过程反应过程,把它们自己依附在其他乙烯分子上。把它们自己依附在其他

32、乙烯分子上。l解析解析:句中句中attach to的意思是的意思是“使依附使依附,把把放在放在”。l5.A linear molecule does not mean that it is straight.l译文译文:线型分子并不意味着它是直的。线型分子并不意味着它是直的。l解析解析:此句中此句中mean译为译为“意味意味”。BACKPREVNEXTLesson 14 The Structure of Plasticsl6.Although within each long-chain molecule there is covalent bonding(primary bonds),no

33、such intermolecular bonding exists between different chains.The bonds between different chains(intramolecular),and between the overlapping portions of the same chain,are known as secondary bonds.l译文译文:虽然在每个长链分子之间有一个共价键虽然在每个长链分子之间有一个共价键(主键主键),但是但是在不同的链之间则不存在这种分子间的共价键。在相同链在不同的链之间则不存在这种分子间的共价键。在相同链之间的重

34、叠部分存在的键被称为次键。之间的重叠部分存在的键被称为次键。l7.If the repeating units in a chain are all of the same type,the macromolecule is known as a homopolymer.BACKPREVNEXTLesson 14 The Structure of Plasticsl译文译文:如果一条分子链中的重复单元都是同如果一条分子链中的重复单元都是同-类型类型,那么这那么这种高分子称为均聚物。种高分子称为均聚物。l8.The properties of a copolymer depend not onl

35、y on the two monomers,but also on their arrangement in the molecular structure(Fig.14.2).l译文译文:共聚物的性能不仅决定于两个单体共聚物的性能不仅决定于两个单体,也取决于它们在也取决于它们在分子结构中的排列分子结构中的排列(图图14-2)l解析解析:此句中此句中depend.on译为译为“决定于决定于,被被决定决定,以以为条件为条件,视视而定而定”。BACKPREVLesson 15 Classification and Application of PlasticslPlastic are genera

36、lly divided into the categories of thermoplastic and thermosets plastic.ThermoplasticslWe noted earlier that,in the amorphous structure of a polymer,the bonds between adjacent long-chain molecules(secondary bonds)are much weaker than the covalent bonds:primary bonds)within each molecule.Hence,it is

37、the strength of the secondary bonds that determines the overall strength of the polymer.Linear and branched polymers have weak secondary bonds.BACKNEXTLesson 15 Classification and Application of PlasticslIf we now raise the temperature of this polymer above the glass-transition temperature,we find t

38、hat it becomes softer and easier to form or to mold into a shape.The mobility of the long molecules(thermal vibrations)increases at Trt and above.If this polymer is now cooled,it returns to its original hardness and strength.In other words,the process is reversible.lPolymers that exhibit this behavi

39、or are known as thermoplastics.Typical examples are acrylics,nylon,polyethylene,and polyvinyl chloride.BACKPREVNEXTLesson 15 Classification and Application of PlasticsThermosetslWhen the long-chain molecules in a polymer are cross-linked in a three-dimensional(spatial)network,the structure becomes i

40、n effect one giant molecule with strong covalent bonds.Cross-linking is done by the polymerization processes.Because of the nature of the bonds,the strength and hardness of such a polymer is not affected by temperature.lThese polymers are known as thermosets because,during polymerization under heat

41、and pressure,the network is completed and the shape of the part is permanentlyBACKPREVNEXTLesson 15 Classification and Application of Plasticslset(curing).Unlike in thermoplastics this reaction is irreversible and the polymer cannot be recycled.However,if the temperature is increased sufficiently th

42、e thermosetting polymer begins to decompose,char,and degrade.Thermosetting polymers do not have a sharply defined glass-transition temperature.Commonly,thermosetting resins become rubbery and compliant across a narrow temperature range.lThe response of a thermosetting plastic to temperature can be l

43、ikened to boiling an egg or baking a cake.Once theBACKPREVNEXTLesson 15 Classification and Application of Plasticslcake is baked and cooled,repeating it will not change its shape,and if the temperature is too high,it will burn.On the other hand,the response of a thermoplasticlcan be likened to ice c

44、ream.It can be softened,refrozen,and resoftened a number of times.It can be molded into shapes,frozen,and then softened again to be remolded into a different shape.lA typical example of a thermosetting plastic is phenolic,which is a product of the reaction between phenol and formaldehyde.Typical pro

45、ducts of this polymer are the handles on cooking pots and pans and electricalBACKPREVNEXTLesson 15 Classification and Application of Plasticscomponents such as switches.lThe polymerization process for thermosets generally takes place in two stages.The first one is at the chemical plant,where the mol

46、ecules are partially polymerized into linear chains.The second stage is at the parts-producing plant,where the cross-linking is completed under heat and pressure during the molding of the part.lThermosetting plastics generally possess better mechanical,thermal,chemical,and electrical resistance and

47、better dimensional stability than thermoplastics.BACKPREVNEXTLesson 15 Classification and Application of PlasticsNotes:l1.Plastics are generally divided into the categories of thermoplastics and thermosets plastics.l译文译文:塑料塑料-般分为热塑性塑料和热固性塑料两大类。般分为热塑性塑料和热固性塑料两大类。l2.We noted earlier that,in the amorph

48、ous structure of a polymer,the bonds between adjacent long-chain molecules(secondary bonds)are much weaker than the covalent bonds(primary bonds)within each molecule.l译文译文:我们在前面已经提到过我们在前面已经提到过,在聚合物的分子结构中在聚合物的分子结构中,相相邻的长链分子之间的键邻的长链分子之间的键(次键次键)的结合力要弱于长链内部分的结合力要弱于长链内部分子之间的共价键子之间的共价键(主键主键)。BACKPREVNEXTL

49、esson 15 Classification and Application of Plasticsl解析解析:句中句中that是从属连词是从属连词,引导宾语从句引导宾语从句,作动词作动词note的宾的宾语。语。much weaker中中much放在形容词的比较级之前表程度放在形容词的比较级之前表程度,译为译为“得多得多”。l3.If we now raise the temperature of this polymer above the glass-transition temperature,we find that it becomes softer and easier to f

50、orm or to mold into a shape.l译文译文:如果现在提高这种聚合体的温度至玻璃化转换温度如果现在提高这种聚合体的温度至玻璃化转换温度之上之上,我们会发现聚合体变得更软且更容易成型或模塑成我们会发现聚合体变得更软且更容易成型或模塑成型。型。l解析解析:此句含有一个此句含有一个if引导的条件状语从句引导的条件状语从句,另外主句中还另外主句中还包含一个由包含一个由that引导的宾语从句引导的宾语从句,作作find的宾语。的宾语。BACKPREVNEXTLesson 15 Classification and Application of Plasticsl4.When the