High-Impact Polystyrene

For many applications, the homopolymer of styrene is too brittle. To overcome that, many different approaches were originally tried. These included use of high molecular weight polymers, use of plasticizers, fillers (glass fiber, wood flour, etc.), deliberate orientation of the polymeric chains, copolymerization and addition of rubbery substances. Effect of plasticizers is too severe for practical use, and use of high molecular weight polymers exhibits only marginal improvement. Use of fillers, though beneficial, is mostly confined to United States. Orientation is limited to sheets and filaments, and copolymerization usually lowers the softening point too much. Addition of rubbery materials, however, does improve the impact resistance of polystyrene. This is done, therefore, extensively. The most common rubbers used for this purpose are butadiene–styrene copolymers. Some butadiene homopolymers are also used but to a lesser extent. The high-impact polystyrene is presently prepared by dissolving the rubber in a styrene monomer and then polymerizing the styrene. This polymerization is either done in bulk or in suspension. The product contains styrene–butadiene rubber, styrene homopolymer, and a considerable portion of styrene-graft copolymer that forms when polystyrene radicals attack the rubber molecules. The product has very enhanced impact resistance. Past practices, however, consisted simply in blending a mixture of polystyrene and rubber on a two-roll mill, or in a high shear internal mixer, or passing through an extruder. The impact strength of the product was only moderately better than that of the unmodified polymer. Another procedure was to blend polystyrene emulsion latex with a styrene–butadiene rubber emulsion latex and then to coagulate the two together. The product is also only marginally better in impact strength than styrene homopolymer. This practice, however, may still be in existence in some places. In high-impact polystyrene, the rubber exists in discrete droplets, less than 50 mm in diameter. In effect the polymerization serves to form an oil in oil emulsion [199] where the polystyrene is in the continuous phase and the rubber is in a dispersed phase. The graft copolymer that forms serves to “emulsify” this heterogeneous polymer solution [200]. Commercial high-impact polystyrene usually contains 5–20% styrene–butadiene rubber. The particle size ranges from 1 to 10 mm. High-impact polystyrene may have as much as seven times the impact strength of polystyrene, but it has only half its tensile strength, lower hardness, and lower softening point.

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اخبار العتبة العباسية المقدسة

شعبة الحرم الشريف تستعد لاستقبال زائري النصف من شهر شعبان

العتبة العباسية المقدسة تنشر لافتات الفرح بمناسبة ذكرى ولادة الإمام المهدي (عجّل الله فرجه)

العتبة العباسية المقدسة تفتتح التسجيل لتأدية الزيارة بالنيابة في ليلة النصف من شعبان

قسم المقام يعلن جاهزيّته لاستقبال زائري النصف من شعبان

المزيد

الآخبار الصحية

الصحة العالمية تكشف حقيقة انتشار فيروس نيباه خارج الهند

متى يصبح محيط الخصر "مؤشر خطر"؟

دراسة تكشف دور "العوامل الوراثية" في تحديد عمر الإنسان

رائحة كريهة في الجسم.. "علامة خفية" أخطر مما تتصور

المزيد

الآخبار التكنلوجية

مايكروسوفت تكشف عن الجيل الثاني من شرائحها للذكاء الاصطناعي

خرافة "ثمانية أكواب يوميا".. كم من الماء يحتاج جسمك فعليا؟

هل توجد حياة خارج كوكبنا؟.. اكتشاف جديد يثير اهتمام العلماء

اكتشاف الخلايا المسؤولة عن فقدان ذاكرة الطفولة

المزيد

مواضيع ذات صلة

Thermoplastic and Thermoset Acrylic Resins

Acrylic Elastomers

Polymerizations of Acrylic and Methacrylic Esters

Polymers of Acrylic and Methacrylic Esters

ABS Resins

Polymers from Substituted Styrenes

Polystyrene Prepared by Ionic Chain-Growth Polymerization

Preparation of Polystyrene by Free-Radical Mechanism

GR-N Rubber

GR-S Rubber

Cyclopolymerization of Conjugated Dienes

Special Polymers from Dienes