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Investigating the effects of packaging materials on products
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Hiroko Inoki*, Yuichi Aoki*, Hirokazu Tanaka*, Shigeharu Yamamoto*
Modern packaging materials emit naturally-occurring gas that can corrode the metal parts of the products. To investigate this problem, we developed methods for testing and evaluating the Outgas. Our investigation revealed the source of corrosion to be sulfuration due to hydrogen sulfide (H2S) emitted by the packaging materials. Sulfuration varies with temperature, set-up conditions, and the quantity of the Outgas. To insure product reliability, care must be taken with the type of packaging materials used, the packaging method, and the temperature during shipping.
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With the introduction of the Product Liability law, maintaining and supervising product reliability has become an urgent necessity. Modern products have attained very high levels of product reliability, but product failure may also result from packaging and shipping conditions 1) . Various reports have been published concerning the packaging problem, and awareness has been growing of the impact packaging materials have on the products they contain 2), 3) .
On the other hand, burgeoning concern for environmental problems has resulted in serious efforts to recycle paper and to simplify packaging. Efforts to replace styrofoam with corrugated cardboard as a cushioning material have been gaining ground due to the lack of satisfactory techniques for recycling styrofoam. These changes in packaging can be seen as factors having an impact on the products 4) .
Accordingly, for this report we focused our attention on the corrugated cardboard used in packaging, shipping, and storing products, and we investigated the effects of temperature and various types of corrugated cardboard on products.
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| 2. Test method considerations |
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Sulfuric acid is used in the refinement of pulp, which is the raw material for corrugated cardboard. Residual sulfuric acid ions in the corrugated cardboard produce H2S gas, and this gas is widely known to cause discoloration and degradation 2) . We investigated methods of testing the affects on metal of gases emitted from various kinds of corrugated cardboard.
2-1 Preliminary Test 1: determining specimens
We performed preliminary testing to determine the types of corrugated cardboard and the test pieces to be used in the tests. Table 1 shows test conditions. The test method consisted of holding a test piece between two sheets of corrugated cardboard (60 x 60 mm) and exposing it to high temperature. We selected 80°C with 24-hour exposure for test conditions to reflect the transportation environment encountered by products shipped via sea freight 5) . Table 2 shows test results.
Silver-plated and copper pieces showed discoloration, while no discoloration was observed on aluminum or stainless steel pieces. Therefore, we selected silver-plated pieces for testing to facilitate comparing the different types of corrugated cardboard, as the silver-plated pieces sustained the most severe discoloration. Furthermore, electrical products were strongly affected by corrugated cardboard packaging, while electronic products and office equipment were relatively unaffected. Since there was a tendency for comparable levels of discoloration to occur within the same type of application, we ran this test by making random checks of one or two items in each application category of corrugated cardboard.
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Table 1 Test conditions for Preliminary Test 1
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Corrugated
cardboard
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11 types
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Test
pieces
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Silver-plated, copper,
aluminum, stainless steel
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Test
conditions
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80°C,24h
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Test
conditions
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Table 2 Test results for Preliminary Test 1
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Corrugated cardboard
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Results
(discoloration)
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Application
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Type
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Packaged
item
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Producing
country
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Silver
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Copper
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Electrical
equipment
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A*
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Transformer
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Japan
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B
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Power supply
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Japan
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C*
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Power supply
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Philippines
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D
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Power supply
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Japan
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E
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Instrument
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Japan
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Electronic
parts
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F*
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IC
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Thailand
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G
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IC
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Japan
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H
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IC
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USA
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Office
equipment
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I*
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Printer
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Japan
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J
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Computer
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Malaysia
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K
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Computer
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Singapore
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Note 1: Asterisks ( * ) indicate selected for main test
Note 2: Discoloration severity (as judged by visual inspection)
 …No discoloration  …Moderate discloration
 …Slight discoloration  …Severe discoloration |
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2-2 Preliminary Test 2: set-up condition considerations
We performed testing to determine the discoloration effects of set-up conditions on silver-plated test pieces. The test method consisted of exposing the test pieces to a temperature of 80 for 40 hours, removing the silver-plated test pieces, and visually inspecting both the top and bottom surfaces. Table 3 shows the test methods and results.
A comparison of the surfaces of the silver-plated test pieces showed that surfaces not in contact with the corrugated cardboard were much more severely discolored than contact surfaces. Discoloration is presumed to have progressed due to the silver-plated test pieces being exposed to the convection currents of the gas generated. On the other hand, lack of discoloration on the surfaces in contact may be presumed to have resulted conversely from the lack of exposure to the convection currents. Therefore, the set-up was arranged to facilitate exposure to the convection currents of the gas, promoting ease of evaluation of the corrugated cardboard.
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Table 3 Preliminary Test 2: A comparison of test results under differing conditions
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| Note: "Contact" and "non-contact" indicate the condition of the silver-plated test piece in relation to the corrugated cardboard. |
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| We then tested the four types of corrugated cardboard (A, C, F, & I in Table 2) that had been selected with the preliminary tests. Table 4 shows test conditions, and Fig.1 shows test methods. A weight of 30 g was deemed suitable for determining the level of corrosion caused by corrugated cardboard. Each type of corrugated cardboard was put into 900 mL glass bottles, and then a silver-plated test piece was dangled from the lid, which was sealed. These specimens were then exposed to 40°C or 80°C heat for 100, 200, or 300 hours. The silver-plated test pieces were hung so that they would dangle at a distance of 2 to 3 mm above the corrugated cardboard. Each type of corrugated cardboard was evaluated by observing the appearance of the silver-plated test piece, by EPMA analysis *1 , by contact resistance measurement, and by solderability testing by the wetting balance method. *2
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Table 4 Test conditions
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Fig. 1 Test method
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Test conditions
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40°C?A80°C
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Test time
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100,200,300h
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Corrugated
cardboard
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4types (A,C,F,&I in Table 2)
Weight: 30 g
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Test pieces
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Material: Silver-plated test pieces
Dimensions: 50 x 20 x 0.2 mm
Plating thickness:3μm
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