Until the 1950’s, PS was produced in small quantities — the resin was
brittle, thermally unstable, with poor solvent and scratch resistance. The main use of styrene was in the manufacture of styrenics, viz. Buna-S, SBR, or ABS.
Common PS is atactic and amorphous. It has good optical clarity, low dielectric loss factor, modulus E = 3.2 GPa, strength ? = 45-65 MPa,
density ? = 1050 kg/m3, and CUT (Continuous use temperature) = 50-70°C.
Because of brittleness and low chemical resistance the demand for neat PS has decreased, and except for foaming, PS is rarely used.
PS can also be polymerized into crystalline forms: isotactic (iPS) or syndiotactic (sPS) with Tm = 230 or 272°C, respectively.
The high-impact PS, HIPS, has been known since 1911. In the USA,
Ostromislensky [1924, 1926-28] patented copolymerization of styrene with “rubber, balata or other elastic and plastic gum”.
HIPS product
PS is miscible with several polymers, viz. polyphenyleneether (PPE), polyvinylmethylether (PVME), poly-2-chlorostyrene (PCS), polymethylstyrene (PMS), polycarbonate of tetramethyl bisphenol-A (TMPC),etc.
PS is immiscible with PMMA, PMA, polyethylacrylate (PEA), polybutylacrylate (PBA),or PBMA
1- PS/Commodity Resin Blends
The most common immiscible PS blends are those prepared to improve the impact strength of PS or its copolymers, viz. HIPS or SBR.
Table: Toughening of PS
It was reported that incorporation of 0.1-18 vol% of either acrylic or olefinic elastomer particles (e.g., in HIPS) into a thermoplastic (viz. PE, PP,PS, etc.) resulted in excellent control of the foaming process .
PS is one of the most frequently foamable thermoplastic resin.
Recently blends containing ? 50 wt% PS (MW = 200 kg/mol) and acrylic copolymers were described as particularly useful for the manufacture of low density foams.
The presence of copolymer facilitated foaming, but it reduced the
foam compressive strength. The best balance was obtained using about 22 wt% of the copolymer.
2- PS/Engineering Resin Blends
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 .
|