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Date: 12-1-2020
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Date: 29-9-2017
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Date: 25-2-2016
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POLYACETALS
Polyacetals are among the aliphatic polyether family and are produced by the polymerization of formaldehyde. They are termed polyacetals to distinguish them from polyethers produced by polymerizing ethylene oxide, which has two -CH2- groups between the ether group. The polymerization reaction occurs in the presence of a Lewis acid and a small amount of water at room temperature. It could also be catalyzed with amines:
Polyacetals are highly crystalline polymers. The number of repeating units ranges from 500 to 3,000. They are characterized by high impact resistance, strength, and a low friction coefficient.
Articles made from polyacetals vary from door handles to gears and bushings, carburetor parts to aerosol containers. The major use of polyacetals is for molded grades.
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مخاطر خفية لمكون شائع في مشروبات الطاقة والمكملات الغذائية
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"آبل" تشغّل نظامها الجديد للذكاء الاصطناعي على أجهزتها
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الزائرون يحيون ليلة الجمعة الأخيرة من شهر ربيع الآخر عند مرقد أبي الفضل العبّاس (عليه السلام)
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