Material Strength and Durability

Transcription

1 Material Strength and Durability What Does it Mean for Flexible SBS Materials Dhuanne Dodrill Rollprint Packaging Products, Inc.

2 Stress or Force/area (psi) Stress-Strain Curves Elastic Limit Strain or Elongation (%)

3 Stress or Force/area (psi) Stress-Strain Curves Ultimate Tensile Strength Elastic Limit Strain or Elongation (%)

4 Stress-Strain Curves Ultimate Tensile Strength Units are independent of thickness Pounds per square inch (psi) Megapascal (MPa) Force needed to break the material is directly proportional to its thickness Material Tensile Strength (psi) PET (oriented) 44,000 Nylon (oriented) 37,000 Nylon (cast) 9000 LDPE 3100 Thickness (in.) Breaking Force (lb f )

5 Stress-Strain Curves Ultimate Tensile Strength Units are independent of thickness Pounds per square inch (psi) Megapascal (MPa) Force needed to break the material is directly proportional to its thickness Material Tensile Strength (psi) Thickness (in.) Breaking Force (lb f ) PET (oriented) 44, Nylon (oriented) 37, Nylon (cast) LDPE

6 Stress or Force/area (psi) Stress-Strain Curves Ultimate Tensile Strength Elastic Limit Strain or Elongation (%) Elongation

7 Stress-Strain Curves Elongation Value is independent of thickness Highly dependent upon sample preparation Neither ultimate tensile strength nor elongation is highly predictive of performance

8 Stress or Force (psi) Stress-Strain Curves Young s Modulus Elastic Limit Strain or Elongation (%)

9 Stress or Force (psi) Stress-Strain Curves Elastic Limit 2% Secant Modulus 0 2 Strain or Elongation (%)

10 Stress or Force (psi) Stress-Strain Curves Elastic Limit Strain or Elongation (%)

11 Stress or Force/area (psi) Stress-Strain Curves opet (550,000) Below Elastic Limit opa (260,000) PA (125,000) HDPE (80,000) LDPE (25,000) EVA (13,000) Strain or Elongation (%)

12 Stress or Force/area (psi) Stress-Strain Curves opet (550,000) Below Elastic Limit opa (260,000) PA (125,000) HDPE (80,000) LDPE (25,000) EVA (13,000) Strain or Elongation (%)

13 Durability Puncture Resistance Blunt Sharp Abrasion Resistance Cut Resistance Flexural Durability Tear Resistance Initiated Unitiated

14 Blunt Puncture Resistance

15 Puncture Resistance Blunt ASTM D1709: Dart Drop X

16 Puncture Resistance Blunt ASTM D1709: Dart Drop Method A: 38mm (1.5 ) diameter dart 0.66m (26 ) height Method B: 51mm (2 ) diameter dart 1.5m (60 ) height Report Impact Failure Weight 50% of test specimens fail under impact Bruceton staircase method used to calculate

17 Puncture Resistance Blunt ASTM D1709: Dart Drop ASTM F1306: Slow Penetration 3.2mm diameter hemispherical probe Sample test diameter of 34.9mm Crosshead speed 25 mm/min (1in/min)

18 Puncture Resistance Blunt ASTM D1709: Dart Drop ASTM F1306: Slow Penetration ASTM D3420: Pendulum Impact Procedure A: 60mm sample Impact head ½ radius / 1 diameter Procedure B (Spencer): 89mm sample Impact head ½ radius / ¾ diameter

19 Puncture Resistance Impact Strength of opet as a Function of Film Thickness

20 Puncture Resistance Impact Strength of Laminates Material Impact Strength (kpa) PET 800 PE Sealant 100

21 Puncture Resistance Impact Strength of Laminates Material Impact Strength (kpa) PET 800 PE Sealant 100 PET / PE Sealant 225

22 Puncture Resistance Impact Strength of Laminates Material Impact Strength (kpa) Cast Nylon >1500 PE Sealant 100

23 Puncture Resistance Impact Strength of Laminates Material Impact Strength (kpa) Cast Nylon >1500 PE Sealant 100 Nylon / PE Sealant 175

24 Puncture Resistance Blunt Lower Modulus Better energy absorption Better blunt puncture resistance Thickness impacts performance Impact not readily predictable test Combining materials impacts performance NOT additive test

25 Sharp Puncture Resistance

26 Puncture Resistance Sharp ASTM D3420 Pendulum Impact can be modified Material sharp puncture performance tracks with abrasion resistance NOT with dull puncture

27 Durability Puncture Resistance Abrasion Resistance

28 Abrasion Resistance

29 Abrasion Resistance

30 Abrasion Resistance New Abrasion Resistance Test Method under development at ASTM Uses a reciprocating linear abrading device

31 Abrasion Resistance New Abrasion Resistance Test Method under development at ASTM 1 mm hemispherical needle stylus 1 inch travel 30 cycles/minute Variable weight

32 Abrasion Resistance Cycles to Failure as a Function of Film Thickness at Different Applied Loads unoriented Nylon 2 mil PA 1 mil PA 0.75 mil PA

33 Abrasion Resistance Cycles to Failure as a Function of Film Thicknesses at Different Applied Load at 5% EVA

34 Abrasion Resistance Cycles to Failure as a Function of Applied Load at Different Film Thicknesses unoriented Nylon 2 mil PA 1 mil PA 0.75 mil PA

35 Abrasion Resistance As applied load increases, cycles to failure decreases exponentially As film thickness increases, cycles to failure increase exponentially Combining materials impacts performance Additives can impact performance dramatically

36 Durability Puncture Resistance Abrasion Resistance Cut Resistance

37 Cut Resistance

38 Cut Resistance No Standard Test Method Material performance follows patterns of sharp puncture and abrasion

39 Durability Puncture Resistance Abrasion Resistance Cut Resistance Flexural Durability

40 Flexural Durability

41 Flexural Durability Creases Yielding

42 Flexural Durability ASTM F392: Gelbo Flex Measures resistance to repetitive strain Twisting motion followed by crushing motion 45 cycles/minute

43 Flexural Durability ASTM F392: Gelbo Flex Measures resistance to repetitive strain Five conditioning flex levels A. Full flex for 2700 cycles B. Full flex for 900 cycles C. Full flex for 270 cycles D. Full flex for 20 cycles E. Partial flex for 20 cycles

44 Flexural Durability ASTM F392: Gelbo Flex Measures resistance to repetitive strain Five conditioning flex levels A. Full flex for 2700 cycles B. Full flex for 900 cycles C. Full flex for 270 cycles D. Full flex for 20 cycles E. Partial flex for 20 cycles Not very predictive Possibly because typically combined with abrasion issues

45 Durability Puncture Resistance Abrasion Resistance Cut Resistance Flexural Durability Tear Resistance

46 Tear Resistance Initiated (propogation) ASTM D1922: Pendulum Method (Elmendorf) ASTM D1938: Trouser Tear

47 Tear Resistance Initiated ASTM D1922: Elmendorf ASTM D1938: Trouser Tear Unitiated ASTM D1004 Graves

48 Tear Resistance Initiated (notched) material requires less force than unitiated material to tear Orientation impacts tear resistance MD and TD values will differ There is not a direct linear relationship between thickness and tear resistance The better the bond between combined materials, the lower the tear resistance

49 Relative Durability Stable Webs Puncture Tear Abrasion Cut Blunt Sharp Unititated Initiated Flex opet opp opa PA Ranking: 0 (least resistance) 4 (highest resistance)

50 Relative Durability Sealant Webs Puncture Tear Abrasion Cut Blunt Sharp Init. Prop. Flex Sealability HDPE MDPE LLDPE LDPE EVA mpe Ionomer Ranking: 0 (least resistance) 4 (highest resistance)

51 Relative Durability Ideal material choices dependent upon type of failure Combining materials dramatically impacts durability properties Many failures modes are due to a combination of effects TEST

52 Questions Dhuanne Dodrill Rollprint Packaging Products