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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging

Verification Tests for Barrier Property of Starch-based Biodegradable Packaging
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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging - 1

Verification Tests for Barrier Property of Starch-based Biodegradable Packaging It’s estimated that approximately 35% of deterioration accidents of food during guarantee period are caused by inferior packaging materials. Meanwhile, about 65% of the food packages are with hidden dangers. Barrier property is one of the key indexes for the evaluation of the properties of packaging materials and shelf life periods of the packed contents. Correspondingly, the barrier property testing of biodegradable packaging material, a newly developed material in recent years, has become a research focus of the packaging quality inspection institutions. This thesis introduces the significance of barrier property testing of biodegradable packaging films, starch-based biodegradable plastics and the complete verification process of its barrier property by Labthink. The thesis hopes to provide guidance for barrier property testing for manufacturers of biodegradable packaging materials. Keywords: biodegradable, packaging films, barrier property, oxygen, water vapor, Labthink 1. Significance for Testing With the increasing consciousness of environmental protection, white pollution, a new threat for environment after the green house effect, has become a focus of the whole society. As the most effective way to solve white pollution, the development and application of biodegradable plastics has drawn great attention. In order to apply various kinds of biodegradable films to packaging industry, their barrier properties need to be evaluated, especially for packaging of food, pharmaceutical and every day-use articles. Some packaging materials have excellent barrier property that can prevent gas from entering into the package and follow-up oxidization or mildewing. On the contrary, some packaging materials have excellent gas permeability or water vapor permeability that helps gas exchange between the packaging materials. Therefore, water vapor transmission tests or gas transmission tests for various biodegradable packaging films are of great importance for property evaluation and further development of biodegradable packaging materials. 2. Starch-based Biodegradable Materials Starch is a kind of polysaccharide compound, the widely-used natural biodegradable macromolecular compound. Starch-based plastics refer to the plastics with starch or its derivatives in ingredients, which can be further categorized into starch-filled plastics and full-starch plastics. As to degradability, it can be categorized into starch-filled non-full-biodegradable disintegrable plastics and the full-biodegradable plastics whose main ingredient is starch-based biodegradable resin. Starch-based biodegradable packaging materials mainly include starch packaging material and raw starch & protein film packaging materials. Since starch is a kind of multi-hydroxyl natural rigid high polymer material, its defects, including moisture absorption, brittleness and difficulties to plasticization, have impeded the application of starch materials. Now, how to improve the toughness of starch-based biodegradable plastics, its moisture resistance and machinability have become the research focuses on biodegradable plastics. www.labthinkinternational.com.cn

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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging - 2

144 Wuyingshan Road, Jinan, P.R.China At present, no specific testing standard for water vapor transmission or gas transmission property of biodegradable plastics has been issued. Thus, Labthink made a barrier property testing on full-starch biodegradable film based on ASTM D 1434(differential pressure method) and ASTM E 96 (weight method) in its Permeability Laboratory. The sample is a full-starch biodegradable film with a thickness of approximately 380um, as shown in Fig 1. The testing instrument is Labthink PERME VAC-V2 Gas Permeability Tester and Labthink PERME W3/0120 Water Vapor...

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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging - 3

3. Verification Tests for Barrier Property by Labthink 3.1 Gas Transmission Rate Testing According to ASTM D1434, the specimen should be placed in the 23℃ dry environment for 48 hours. High pure oxygen is needed; uniform area should be selected without wrinkles, folds, pinholes or other defaults. First, prepare, with the sampler, three pieces of samples and filter papers respectively, as shown in Fig. 4. Before placing samples, smear proper sum of vacuum grease uniformly over the area which is 2mm away from the fillister, so that the sealing performance of the system can be confirmed....

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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging - 4

Fig. 6 3.2 Water Vapor Transmission Test Prepare samples as per ASTM E96. When cutting the samples, uniform area should be selected without wrinkles, folds, pinholes or other defaults as well as dirt or water. Prepare 3 samples (as shown in Fig. 7) with sample cutter. Clean and dry the water vapor permeation cup before placing the sample onto it. Dry state of the cup is a must. Then, fill this preconditioned cup with distilled water until water surface is 19± 6mm away from the sample. Take care not to splash the water onto the thread of screw, so as not to influence the testing results....

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Verification Tests for Barrier Property of Starch-based Biodegradable Packaging - 5

Fig. 8 4. Conclusions It can be verified from the testing results that full-starch biodegradable film has excellent barrier property against oxygen, yet poor barrier property against water vapor. Thus, modification is needed if it’s to be applied as a kind of packaging material. A case in point is the full-starch thermoplastic starch, the production mechanism of which is to turn starch molecules into disorderly distributed structures, and then, forms into thermoplastic starch that has thermoplastic property. The structure of starch molecules changes, yet its chemical structure remains...

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