2- PS/Engineering Resin Blends
The majority of PS blends that belong to this category are mixtures with PPE(Poly phenyl ethylene).
PPE
Discovery of PPE miscibility with PS led to a family of Noryl™
blends, commercialized in 1965.
The PPE/PS blends show the glass transition temperature, Tg = 100 to
210°C, continuously increasing with PPE content. The most often used compositions contain less than 30 wt% of PPE (PPE is about three times
more expensive than PS).
PS/PPE blends have been used as a replacement for PS in applications where higher HDT(Heat deflection temperature) and/or impact strength is required.
These alloys areeasy to foam for the manufacture of, e.g., hot water piping insulation, in automotive applications, etc.
Example 2: Acrylonitrile-Butadiene-Styrene (ABS)
?The first mechanical blends of NBR with SAN(Styrene + Acrylonitrile),known as “type-A ABS,” date from 1936.
?In themid-1940’s, Dow started emulsion polymerizationof “ABS type-G”.
?By the late 1950’s, the highheat ABS were invented.
?Weather-resistant ABS can be obtained either by the incorporation of EVAc(Ethylene-co-vinyl acetate), or by replacing PB with EPDM(Ethylene-co-propylene-co-diene).
1- ABS/PVC Blends
There are several reasons for blending PVC with ABS-type copolymers, viz. to improve processability, mechanical properties, and low-temperature toughness.
Good properties of these blends originate from the miscibility between PVC and SAN-part(Styrene-co-acrylonitrile) of ABS.
PVC
In some commercial blends, viz. Geloy™, ABS may be replaced by ASA(acrylonitrile-co-styrene-co-acrylate) to obtain improved miscibility and weatherability. For enhancement of HDT, SMA(Styrene-co-maleic anhydride) may also be added.
The blends with more than 30 wt% PVC are self-extinguishing, but are more difficult to process.
2- ABS/PC
resistance, but poor to gasoline, aromatic hydrocarbons, esters, ketones and some chlorinated hydrocarbon.
There are many similarities between ABS/PVC and ABS/PC blends. Both are immiscible, having three distinct phases of PVC or PC, SAN, and an elastomer . The blends are compatibilized by the dipole-dipole interactions between PC and SAN, particularly evidentin SAN with? 25 wt% AN. ABS/PC blends can also be compatibilized by incorporation of either acrylic, acidic or epoxy groups.
Example 3:Polyvinylchloride (PVC):
Owing to poor thermal stability of PVC, the high temperature blending must be avoided. Thus only few PVC/engineering resin blends are known.
The first commercial blend of this type is Cylon™. Here PVC is the matrix, and PA (that melts below 215°C!) the dispersed phase. The two
resins were compatibilized using the well known PVC plasticizer — Elvaloy™ (a terpolymer of ethylene, carbon monoxide and acrylics). These soft to semi-rigid alloys were commercialized for wire coating, automotive applications and blow molding. They are flame, abrasion and chemicals resistant, easy to process, and tough.
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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