5. Plastics – from chemistry to performance Polymer Chemistry Material microstructure Material properties Product Performance

7. ‹ #› Bonding Energy & Distance Bond energy Bond length

12. Mechanical Properties - stiffness Amorphous stiffness temperature T g T g – glass transition temperature

13. Mechanical Properties - stiffness Temperature stiffness Semi crystalline T g T m – melt temperature T m

14. Mechanical Properties - stiffness T m T m T g stiffness Temperature Amorphous plastic Semi crystalline plastic

15. Physical Properties 15%GF Polyester, PBT 1400 nylon 6/6 13%GF Density 0.0509 lb/in ³ 0.0444 lb/in ³ Water Absorption 0.1 % 1.1 % Linear Mold Shrinkage 0.005 in/in 0.006 in/in

16. Plastic Mechanical Properties

20. Stress/Strain Curve Linear Elastic Material

26. Tensile Testing Results Stress vs Strain For plastics the rate of stress applied affects the material’s response

31. Mechanical Response as a function of Time ‹ #› F F F time input  time displacement

32. Elastic Solid Model ‹ #› F F   k Spring constant or stiffness k

33. Elastic Solid – Microstructural Behavior ‹ #› The applied force straightens polymer chain segments F F The polymer chain segments return back to a more disorder and stable configuration when force is removed

37. Cone and Plate cone polymer

38. Stress and Shear Rate Polymer melt stationary plate moving plate force Shear stress

41. Rheometry Experiments Experiment H Re-Grind PC Melt Rheology at 550 o F

45. Viscous Fluid Model F F  d  dt C Viscous Damping Constant

47. The plastic part is subjected to a tensile force The plastic part is increases its length L, when the force is removed it will not spring back – this a permanent deformation The plastic part is increases its length L F F L o , original length F F L new = L o +  L L new = L o +  L permanent

49. Viscoelastic Solid Model F   (t) time

50. Viscoelastic Solid, Microstructural Behavior Polymer chain segments are stretched by the force, this is the elastic element of the model As the Polymer chain segments are stretched there is friction between these chain segments – this is the viscous damping element When the force is removed, the chains return to the original state – during this motion, there is also friction Heat is generated

51. General Viscoelastic Model F C E K E C P K E – elastic stretching of chain segments C E – friction between chain segments (very small) C P – friction between complete polymer chains

52. Maxwell Viscoelastic Model F K E C P K E – elastic stretching of chain segments C P – friction between complete polymer chains

57. time Tension in a part Relaxation curves Increasing temps Initial Tension t o Length after time t o 1 2 3 3 2 1

58. l Stress Relaxation

66. Dynamic Mechanical Analysis From TA Instruments

67. Dynamic Mechanical Analysis

68. Dynamic Mechanical Analysis From TA Instruments

69. Dynamic Mechanical Analysis From TA Instruments

70. Dynamic Mechanical Analysis Viscous elastic response From TA Instruments

71. Viscous elastic response

72. Viscous elastic response

74. Dynamic Mechanical Analysis

77. From TA Instruments

78. From TA Instruments

79. Creep Viscoelastic Model  (t) time Critical time For this load, there has not been enough time to start the viscous motion F C E K E Permanent Deformation – creep For this load, the viscous motion has started

85. Creep – time, temp loads

90. Depends on material ability to absorb energy Stress/strain curve Area underneath Stress/strain curve is the measure of impact  strain  stress

92. Degree of Crosslinking & Toughness Tough Strong

93. Small Additives Get between Polymer chains This increases d and can make the degrade properties Example – excess of colorant can weaken a plastic part

98. Melt Flow Rate Test Apparatus: Resin

99. Melt Flow Index # grams of flow per 10 minutes Weighted Plunger Barrel Molten Pellets Extrudate Orifice Heater Band Dynisco LMI 4000 Len Czuba August 2006

102. Tensile Strength Test Apparatus:

104. Impact Resistance Test Apparatus: Len Czuba August 2006

106. Impact Resistance Test Specimen: Len Czuba August 2006

114. Load and Material Interaction Failure probability

115. Load ave = 6000, std dev = 1000 PET ave = 12000, std dev = 1000 Example - Material Properties & Loads

116. Load ave = 6000, std dev = 2000 PET ave = 12000, std dev = 1000 Solution 1 - use the same part for another application

117. Load ave = 6000, std dev =1000 PET ave = 12000, std dev 1500 Solution 2 - get cheaper materials

118. Load ave = 6000, std dev = 1000 Regrind PET ave = 9500, std dev = 1200 Solution 3 - get cheaper materials, use regrind

119. 25% regrind 75% virgin Solution 4 - get cheaper materials, use regrind + virgin

120. Solution 4 - get cheaper materials, use regrind + virgin

121. Solution 4 - get cheaper materials, use regrind + virgin

123. Solution 5 - Redesign Part Existing cross section New cross section

125.  = Mc / I new