The ability of a polymer to sustain a mechanical load depends on the strength of covalent bonds and the forces between the molecules. In an amorphous system much of the load is carried by van der Waals interactions and random coil entanglements between chains. However, if a substantial fraction of the polymer chains can be aligned in the load-bearing direction, a larger portion of the load can be transmitted to the main-chain covalent bonds.
Orientation effect on crystline process and this crystline linked with density this effect on structure of polymer. Extrusion blow moulded film usually receives biaxial orientation. During blowing ,the diameter of the extruded tube is increased, and this causes the structure of the film to be oriented perpendicular to the extrusion direction . orientation should take place below the melting temperature when the polymer is crystline so that the crystals are oriented. Orientation of polymer must be performed at temperature between glass transition and melting temperature .Biaxial orientation is desirable to orient films in planner direction ,parallel and perpendicular to the flow.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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