Polymer blend (PB): Mixture of at least two macromolecular substances, polymers or copolymers, in which the ingredient content is above 2 wt%.
Types of polymer blends:
1- Miscible polymer blend: Polymer blend, homogenous down to the molecular level, associated with the negative value of the free energy of mixing: ?Gm ? ?Hm? 0, and a positive value of the second derivative: ?2?Gm/??2 > 0. It is a single –phase structure , has properties of average values between the values of properties of its components and has one Tg.
2-Immiscible polymer blend: A blend exhibits more than two phases. It is a blend whose free energy of mixing; ?Gm ? ?Hm > 0
Usually, has two Tg s , since the two components are phase separated.
Miscible PB Immiscible PB
Scientists often measure the Tg of a blend to find out if it is miscible or immiscible. If two Tgs are found, then the blend is immiscible. If only one Tg is observed , then the blend is likely to be miscible.
3-Homologous polymer blend: Mixture of two or more fractions of the same polymer each of which has different molecular weight distribution.
4-Isomorphic polymer blend: Polymer blend of two or more different semi-crystalline polymers are miscible in the crystalline state as well as in the molten state.
5-Compatible polymer blend: An immiscible blend is called compatible if it is useful blend wherein the inhomogeneity (caused by different phases) is on a small enough scale not to be apparent in use.
OR:
Blends that miscible in a certain useful range of composition and temperature, but immiscible in others.
Most compatible blends are immiscible and can be made compatible only by a variety of compatibilization techniques. When the interface
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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