This study describes a process technology to maintain or improve the gas barrier property of ethylene vinyl alcohol (EVOH) barrier films after flexing. EVOH and polyethylene-grafted maleic anhydride (PE-g-MA) multi-and microlayer samples with 5, 19, and 35 layers were produced in a coextrusion line. Flexing was performed using a Gelbo flex tester (400 flexes). After flexing, pin hole tests were performed on the film and only those with fewer than two pin holes were retested for oxygen transmission rate (OTR). Pin holes decreased after 400 Gelbo flexes as the number of layers increased. The OTR on these films demonstrated that thin EVOH barrier layers can improve film flex crack resistance. This proves that for a given barrier resin total thickness the flex barrier property can be increased dramatically by microlayering.
Many polymers are extruded through blown film dies to produce both monolayer and multilayer films. A common type of die in use today to produce blown films is the spiral mandrel die. This type of die can be used effectively for many polymers in structures containing up to approximately ten layers. This paper will discuss the development of new technology using a feedblock and layer multipliers in combination with encapsulation technology and a unique film die to produce microlayer blown film structures with significantly larger numbers of layers than can be produced using conventional blown film technology. POLYM. ENG. SCI.,
The current extrusion technology for PVDC polymers is reviewed m detail Items covered include extruder screw design, controlled feeding, and screw temperature control The application of these principles to obtain rates of [185][186][187][188][189][190][191][192][193][194][195]
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