Chapter 14-Polymer Structures.ppt
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1、1,ISSUES TO ADDRESS., What are the general structural and chemical characteristics of polymer molecules?, What are some of the common polymeric materials, and how do they differ chemically?, How is the crystalline state in polymers different from that in metals and ceramics ?,Chapter 14: Polymer Str
2、uctures,2,What is a Polymer?,Poly mermany repeat unit,Adapted from Fig. 14.2, Callister & Rethwisch 8e.,repeat unit,repeat unit,repeat unit,3,Ancient Polymers,Originally natural polymers were used Wood Rubber Cotton Wool Leather SilkOldest known uses Rubber balls used by Incas Noah used pitch (a nat
3、ural polymer) for the ark,4,Polymer Composition,Most polymers are hydrocarbons i.e., made up of H and C Saturated hydrocarbons Each carbon singly bonded to four other atoms Example: Ethane, C2H6,5,6,Unsaturated Hydrocarbons,Double & triple bonds somewhat unstable can form new bonds Double bond found
4、 in ethylene or ethene - C2H4Triple bond found in acetylene or ethyne - C2H2,7,Isomerism,Isomerism two compounds with same chemical formula can have quite different structures for example: C8H18 normal-octane2,4-dimethylhexane,8,Polymerization and Polymer Chemistry,Free radical polymerizationInitiat
5、or: example - benzoyl peroxide,9,Chemistry and Structure of Polyethylene,Adapted from Fig. 14.1, Callister & Rethwisch 8e.,Note: polyethylene is a long-chain hydrocarbon - paraffin wax for candles is short polyethylene,10,Bulk or Commodity Polymers,11,Bulk or Commodity Polymers (cont),12,Bulk or Com
6、modity Polymers (cont),VMSE: Polymer Repeat Unit Structures,13,Manipulate and rotate polymer structures in 3-dimensions,14,MOLECULAR WEIGHT, Molecular weight, M: Mass of a mole of chains.,high M,Not all chains in a polymer are of the same length i.e., there is a distribution of molecular weights,15,
7、xi = number fraction of chains in size range i,MOLECULAR WEIGHT DISTRIBUTION,Adapted from Fig. 14.4, Callister & Rethwisch 8e.,wi = weight fraction of chains in size range i,Mi = mean (middle) molecular weight of size range i,16,Molecular Weight Calculation,Example: average mass of a class,What is t
8、he average weight of the students in this class: Based on the number fraction of students in each mass range? Based on the weight fraction of students in each mass range?,17,Molecular Weight Calculation (cont.),Solution: The first step is to sort the students into weight ranges. Using 40 lb ranges g
9、ives the following table:,total number,total weight,Calculate the number and weight fraction of students in each weight range as follows:,For example: for the 81-120 lb range,18,Molecular Weight Calculation (cont.),19,Degree of Polymerization, DP,DP = average number of repeat units per chain,DP = 6,
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