Lab A: Shrink Packaging
Lab A: Shrink Packaging Group 6: Lai Saeteurn, Ting Chen Patrick Schuiteman, Charlotte Thomas PKG323-005 November 15, 2012 _________________________________________
Purpose: The objective of this experiment is to investigate the relationship between temperature and percent shrinkage of shrink film. Measuring Instrument and Sensitivity: Shrink Tunnel Micrometer, +/- 0.01 mm
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Data: Table 1: Film Shrinkage Temp. (°F) 225
Film Direction CD MD CD MD CD MD
275 325
lf (mm) 0.146 0.263 0.240
Li (cm) 10 10 10 10 10 10
Lf (cm) 3.9 5.3 3.1 2.7 3.0 2.6
ΔL (cm) 6.1 4.7 6.9 7.3 7.0 7.4
Percent Shrinkage 61% 47% 69% 73% 70% 74%
Compound Error (%) 11.3% 10.7% 11.3%
Table 2: Percent Shrinkage Temp. (°F) 225 275 300 325
Cross Direction Sp (%)
Machine Direction Sp (%)
61% 69% 69.5% 70%
47% 73% 73.5% 74%
Table 3: Tray Dimensions Lt (cm) Wt (cm) Dt (cm)
22 11 1.3
Table 4: Results of Shrink Package Trials
1
Film Dimensions Lf x Wf (cm) 47 x 30
2
35 x 28
Trial #
Results Very Wrinkly, Bubbly, Loose Less Wrinkly, Tighter
3
Figure 1: Cross Direction Sp vs. Temperature
CD Precent Shrinkage (%)
85 75 65 55 45 35 25 15 70
120
170
220
270
320
370
270
320
370
Temperature (°F)
Figure 2: Machine Direction Sp vs. Temperature
MD Precent Shrinkage (%)
85 75 65 55 45 35 25 15 70
120
170
220 Temperature (°F)
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Calculations: (0.6 mil LDPE shrink film) 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 = (
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + ) 𝐿!"# 𝐿!"# 𝐿!""
𝑉! = 𝐿! ∗ 𝐿! ∗ 𝑙! 𝑉! = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .001524 𝑐𝑚 = 1.524𝑒 !! 𝑐𝑚! 𝑉! !!"°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0146 𝑐𝑚 = 1.46𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !!"°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 11.3% 3.9 𝑐𝑚 5.3𝑐𝑚 0.146 𝑚𝑚
𝑉! !"#°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0263 𝑐𝑚 = 2.63𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !"#°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 10.7% 3.1 𝑐𝑚 2.7 𝑐𝑚 0.263 𝑚𝑚
𝑉! !"#°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0240 𝑐𝑚 = 2.40𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !"#°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 11.3% 3.0 𝑐𝑚 2.6 𝑐𝑚 0.240 𝑚𝑚
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Conclusion and Discussion: According to calculations it indicates that after exposure to experimental shrink tunnel temperatures there are changes in film volume. As LDPE shrink film undergoes three different temperature settings, the film shrinks (each time) causing the volume (and thickness) to increase by a small percentage. In example, the film at 225°F increased in volume from 1.524𝑒 !! 𝑐𝑚! to 1.46𝑒 !! 𝑐𝑚! . The effect of shrinkage of the volume of the film is due to the molecules rearranging when exposed to heat, thus causing variations in thickness and volume throughout the shrunk film. In addition, the conveyor belt speed affects the overall percent shrinkage, the slower or faster the belt runs the more or less time the plastic samples are exposed to heat. In other words, there is a direct correlation between shrink percentage as it is affected by thickness and volume. A well-designed shrink package should contain minimal wrinkles, have a tight and snug wrap, no holes or pockets of air. Excessive shrink film can cause air to be sealed into the package causing bubbles and wrinkles, these flaws are the result of poor shipping conditions, defective product(s) and much more. In the experiment, the results from Table 4 indicate that two trials were performed to find proper dimensions to shrink wrap a 22 cm x 11 cm x 1.3 cm product. In the first trial dimensions of 47 cm x 30 cm were used; a large enough surface area that looked visibly appropriate. After the first trial went through the shrink tunnel it was observed that a large amount of air was trapped in the package, there were large wrinkles, and loose film. It was determined that the film dimensions were far too big, thus leading to the second trial of 35 cm x 28 cm. After the second trial observations showed that the film had a relatively snug fit on the product, minimal to no wrinkles, and did not contain any trapped air or bubbles. Although two trials were performed it can be assumed that further trial would produce more efficient results. From this experiment, it can be concluded that shrink packaging can be easily pierced or torn if in contact with sharp objects or products that can snag onto it (and tear). Therefore, products such as knives, certain children’s toys, hardware tools, or any products with very pointy corners could not benefit from shrink packaging, as it does not provide product or shipping protection.
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Purpose: The objective of this experiment is to investigate the relationship between temperature and percent shrinkage of shrink film. Measuring Instrument and Sensitivity: Shrink Tunnel Micrometer, +/- 0.01 mm
2
Data: Table 1: Film Shrinkage Temp. (°F) 225
Film Direction CD MD CD MD CD MD
275 325
lf (mm) 0.146 0.263 0.240
Li (cm) 10 10 10 10 10 10
Lf (cm) 3.9 5.3 3.1 2.7 3.0 2.6
ΔL (cm) 6.1 4.7 6.9 7.3 7.0 7.4
Percent Shrinkage 61% 47% 69% 73% 70% 74%
Compound Error (%) 11.3% 10.7% 11.3%
Table 2: Percent Shrinkage Temp. (°F) 225 275 300 325
Cross Direction Sp (%)
Machine Direction Sp (%)
61% 69% 69.5% 70%
47% 73% 73.5% 74%
Table 3: Tray Dimensions Lt (cm) Wt (cm) Dt (cm)
22 11 1.3
Table 4: Results of Shrink Package Trials
1
Film Dimensions Lf x Wf (cm) 47 x 30
2
35 x 28
Trial #
Results Very Wrinkly, Bubbly, Loose Less Wrinkly, Tighter
3
Figure 1: Cross Direction Sp vs. Temperature
CD Precent Shrinkage (%)
85 75 65 55 45 35 25 15 70
120
170
220
270
320
370
270
320
370
Temperature (°F)
Figure 2: Machine Direction Sp vs. Temperature
MD Precent Shrinkage (%)
85 75 65 55 45 35 25 15 70
120
170
220 Temperature (°F)
4
Calculations: (0.6 mil LDPE shrink film) 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 = (
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + ) 𝐿!"# 𝐿!"# 𝐿!""
𝑉! = 𝐿! ∗ 𝐿! ∗ 𝑙! 𝑉! = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .001524 𝑐𝑚 = 1.524𝑒 !! 𝑐𝑚! 𝑉! !!"°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0146 𝑐𝑚 = 1.46𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !!"°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 11.3% 3.9 𝑐𝑚 5.3𝑐𝑚 0.146 𝑚𝑚
𝑉! !"#°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0263 𝑐𝑚 = 2.63𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !"#°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 10.7% 3.1 𝑐𝑚 2.7 𝑐𝑚 0.263 𝑚𝑚
𝑉! !"#°" = .1 𝑐𝑚 ∗ .1 𝑐𝑚 ∗ .0240 𝑐𝑚 = 2.40𝑒 !! 𝑐𝑚! 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐸𝑟𝑟𝑜𝑟 !"#°" =
0.1 𝑐𝑚 0.1 𝑐𝑚 0.1 𝑚𝑚 + + = 11.3% 3.0 𝑐𝑚 2.6 𝑐𝑚 0.240 𝑚𝑚
5
Conclusion and Discussion: According to calculations it indicates that after exposure to experimental shrink tunnel temperatures there are changes in film volume. As LDPE shrink film undergoes three different temperature settings, the film shrinks (each time) causing the volume (and thickness) to increase by a small percentage. In example, the film at 225°F increased in volume from 1.524𝑒 !! 𝑐𝑚! to 1.46𝑒 !! 𝑐𝑚! . The effect of shrinkage of the volume of the film is due to the molecules rearranging when exposed to heat, thus causing variations in thickness and volume throughout the shrunk film. In addition, the conveyor belt speed affects the overall percent shrinkage, the slower or faster the belt runs the more or less time the plastic samples are exposed to heat. In other words, there is a direct correlation between shrink percentage as it is affected by thickness and volume. A well-designed shrink package should contain minimal wrinkles, have a tight and snug wrap, no holes or pockets of air. Excessive shrink film can cause air to be sealed into the package causing bubbles and wrinkles, these flaws are the result of poor shipping conditions, defective product(s) and much more. In the experiment, the results from Table 4 indicate that two trials were performed to find proper dimensions to shrink wrap a 22 cm x 11 cm x 1.3 cm product. In the first trial dimensions of 47 cm x 30 cm were used; a large enough surface area that looked visibly appropriate. After the first trial went through the shrink tunnel it was observed that a large amount of air was trapped in the package, there were large wrinkles, and loose film. It was determined that the film dimensions were far too big, thus leading to the second trial of 35 cm x 28 cm. After the second trial observations showed that the film had a relatively snug fit on the product, minimal to no wrinkles, and did not contain any trapped air or bubbles. Although two trials were performed it can be assumed that further trial would produce more efficient results. From this experiment, it can be concluded that shrink packaging can be easily pierced or torn if in contact with sharp objects or products that can snag onto it (and tear). Therefore, products such as knives, certain children’s toys, hardware tools, or any products with very pointy corners could not benefit from shrink packaging, as it does not provide product or shipping protection.
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