| 摘要 |
Polypropylene carrier layer is perforated 1 - 2 mm at 1 - 12 cm. centre distances and sealed with a polyethylene film. - Oxygen can thus permeate through the carrier and the sealing layer but moisture is kept out. - The melting point of the carrier is higher than the sealant so that at weld points this flows well right over the join and forms a tight seal. - When used for meat trays, these pref. have ribs underneath to allow oxygen to permeate and travel round here and thus preserve the colour of the product.
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