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To obtain barrier properties such as oxygen, aromatic hydrocarbons, water vapour and chemical resistance, PVdc is coated on polyamide or other plastics films such as PVC and PP. This requires several coating passes (at least 5-6). Besides, the equipment for coating is expensive, and this capital investment for coating equipment increases the coating cost.
A new technology has been developed, in which PVdc is coextruded with polyamide. The experimental results indeed show a very promising future for this new technique for barrier films. PVdc provides an economical solution compared to EVOH, and also offers longer shelf life before use. PVdc also offers enhanced barrier properties at higher relative humidity compared to EVOH. PVdc film is also softer compared to EVOH.
Another interesting technology of encapsulation of barrier resins is now available. For larger throughput, encapsulation process is essential. Besides, it provides uninterrupted processing run. Encapsulation is a process in which less thermally sensitive material surrounds the thermally sensitive material in the feed block prior to entering the main die. This prevents a contact of barrier resin with metal wall in the die.
Some experiments illustrate an improvement of barrier properties with PVdc coextrusion with polymers such as LDPE, LLDPE, HDPE , PA and PP.
Coextruded PVdc films will be ideal for packaging of aromatic spice, beverage, dairy product, dry food, freezer meat, pharmaceutical product. |
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