The Ultimate Guide to Grades Craftech Industries, 2013 8 Dock Street, Hudson, NY 12534 Website: www.craftechind.com Blog: info.craftechind.com/blog of Nylon E-mail: [email protected] Phone: 518-828-5001 or 800-833-5130 Fax: 518-828-9468 2 Introduction 3 Descriptions of Nylon Grades 6 Nylon Properties Chart INTRODUCTION Nylon is a generic term for a family of thermoplastic polymers. The first to be commercially developed was Nylon 6,6 by a team of researchers at DuPont® headed by Wallace Hume Caruthers in the 1930s. Nylon 6,6 is a polyamide fiber derived from a diamine and a dicarboxylic acid. The numerical nomenclature of nylons is derived by the number of carbon atoms in the diamine and those in the dibasic acid monomers used in manufacturing the particular type of nylon. Thus Nylon 6,6 has 6 C diamine and 6 C diacid. There is a large number of polyamide materials available to produce nylon as there is a large variety of diamines and dicarboxylic acids. Grades such as nylon 6, nylon 6,6 as well as 4,6; 5,10; 6,10; 6,12; 11 and 12 are some of the more common. Nylons are semi-crystalline polymers meaning they have both crystalline and amorphous regions. Nylons are chemically resistant to organic solvents and weak alkalis. They have good chemical resistance to weak acids, alcohols, and hydrocarbons. However nylon may dissolve in phenols, strong alkalis and strong acids. It is also attacked by UV radiation. Nylon does not perform well if submerged in water over time as it is hygroscopic, meaning that it tends to absorb water. This also reduces its electrical resistance. Nylon is not susceptible to molds, insects or fungi. Nylon is one of the most common polymers. It is used in a wide variety of applications including but not limited to fishing line, tires, ladies’ stockings, and parachute material, bearings, textiles, and flak jackets, as well as carpet, musical strings for a variety of instruments, toothbrushes, rope, hair combs, pipes, gears and machine screws. The frame of the modern Glockmeister™ hand gun is made of a nylon composite. Even the flag planted on the moon by Neil Armstrong was made of nylon. Some nylon grades are also realized by the use of additives. Here are some examples of additives that can improve performance: • Elevated temperatures cause molecular weight degradation in unmodified nylon. Heat stabilizers can be added so nylon can be used at elevated temperatures. • Nylon is naturally abrasion resistant. However, to improve its performance in bearing applications molybdenum disulphide (MoS2) is added to increase lubricity. • Nylon that is glass-filled improves structural and impact strength as well as rigidity. • Nylon can also be carbon-filled and this composite excels over the base resin and glass-filled resin with improved tensile and flexural strength, lower expansion, better dimensional stability, and improved thermal and electrical conductivity. • While nylon degrades over time when exposed to UV light adding carbon black reduces degradation from sunlight. • Carbon fiber may be added to make nylon anti-static or conductive. • Color can be added to nylon. 2 • Nylons typically have a UL 94 V-2 rating. A flame resistance material such as a halogenated derivative is added to obtain a UL 94 V-0 rating. • Oil, PTFE, and silicon are less commonly added. • Other additives are included to achieve improved performance in various applications. DESCRIPTIONS OF NYLON GRADES Nylon 6 and Nylon 6,6 Let’s start with two of the most common types of this material; Nylon 6 and Nylon 6,6. As indicated above Nylon 6,6 was developed in the United States by DuPont®. In order to compete, Nylon 6 was developed by Paul Schlack at the German company IG Farben. Nylon 6,6 and Nylon 6 dominate the market. Nylon 6 is the most popular nylon in Europe and elsewhere while nylon 6,6 is preferred in North American markets. The properties of Nylon 6,6 and Nylon 6 are almost indistinguishable. The major difference between the two is that Nylon 6 has a considerably lower melting point then Nylon 6,6. Its melting temperature is 428°F (220°C) and for Nylon 6,6 is it 509°F (265°C.) This lower melting point can be a disadvantage, for example in textiles where fabric made from Nylon 6 has to be ironed carefully to avoid damage. Nylon 6 and Nylon 6 fiber filled: Polycaprolactam. (C6H11NO)n Nylon 6 is a homopolymer and is made by the ring opening polymerization of caprolactam. HO Nylon 6 is made by heating caprolactam to about 250°C in 5-10% water in an – [ N – C – (CH2)5 ] – inert atmosphere of nitrogen for 4-5 hours. The resultant chemical reaction causes the caprolactam to polymerize. A polyamide is formed with six carbon atoms derived from the caprolactam monomer hence its name Nylon 6. Nylon 6 is slightly less crystalline that Nylon 6,6 and it absorbs moisture more rapidly. Thus as moisture and temperature increase Nylon 6 absorbs water more rapidly and loses strength faster. It isHO the second most widely used polyamide in the U.S. Adding fibers such as glass or carbon fiber to this materialH can result in HO O greater tensile strength. See the properties chart below for details. – [ N – C – (CH2)5 ] – – [ N – (CH2)6 – N – C – (CH2)4 – C ] – Nylon 6,6 and Nylon 6,6 fiber-filled: Polyhexamethylene adiamide. (C12H22N2O2)n Nylon 6,6 is made by the polycondensation of the two monomers hexmethylene diamine and adipoyl chloride. It is the most commercially important polyamide and is the strongest of the nylons over the widest range of H HO O temperature and moisture. Additionally, it exhibits no – [ N – (CH2)6 – N – C – (CH2)4 – C ] – appreciable flow below its melting point. Glass reinforced H HO O grades result in a material with tensile strengths up to 32,000 psi which is approximately 200 times higher than the base resin. Additionally– [ N glass-filled – (CH2 )6nylon – N – C – (CH2)8 – C ] – has a higher deflection temperature resulting in increases from 160°F to 500°F (71°C to 260°C). H HO O 3 H HO O – [ N – (CH2)6 – N – C – (CH2)10 – C ] – – [ N – (CH2)6 – N – C – (CH2)8 – C ] – H HO O – [ N – (CH2)6 – N – CHO – (CH2)10 – C ] – – [ N – C – (CH2)10 ] – HO – [ N – C – (CH2)10 ] – HO HO Nylon 4,6: (C10H22N2O4) This nylon is made by a condensation reaction– [ N between – C – dipic (C Hacid2) 5and ] – 1,4-diaminobutane. It can be made from renewable substances instead– [ ofN hydrocarbons. – C – (CH With2)5 ]a – heat deflection temperature of 285°C (545°F), Nylon 4,6 is able to withstand extreme heat. It has a continuous operating temperature of 155°C/135°C (330°F/275°F) and a UL 94V HB rating. This nylon has better heat resistance and mechanical properties at elevated temperature than Nylon 6 or Nylon 6,6. Nylon 4, 6 also has a symmetrical chain structure that leads to a high degree of crystallinity and rapid crystallization. This is what gives it better retention of stiffnessH and creep resistanceHO over a O HO wider range of temperatures as well as heat aging resistance. It isH often used in sewingHO the seams for O airbags where hot inflation gases can cause intense short term– [ heatingN – (CH of the2 )threads.6 – N –Nylon C –4,6 (CH is 2)4 – C ] – – [ N – C – (CH2)5 ] – also known under the trade name Stanyl®. – [ N – (CH2)6 – N – C – (CH2)4 – C ] – Nylon 5,10: This is a copolymer made from pentamethylene diamine and sebacic acid. It thus has 5 C diamine and 10 C diacid. Nylon 5,10 was studied by Carothers before Nylon 6,6. While it has superior properties it was more expensive to produce. H HO O Nylon 6,10 and Nylon 6,10 glass-filled: H HO O (C16H30O2N2) Nylon 6,10 is made by the condensation of H – [ NHO – (CH2)6 – N – CO – (CH2)4 – C ] – hexamethylene diamine and sebacic acid. It has lower – [ N – (CH2)6 – N – C – (CH2)8 – C ] – water absorption rate than nylon 6, or nylon 6,6. Because – [ N – (CH2)6 – N – C – (CH2)8 – C ] – it performs better in water, nylon 6,10 is used to make tooth brushes and bristles and monofilaments for other products. Nylon 6,10 can be fiber-filled for greater strength. H HO O Nylon 6,12 and Nylon 6,12 glass-filled: H HO O (C18H34O2N2) Nylon 6,12 is produced by the – [ N – (CH ) – N – C – (CH ) – C ] – 2 6 H HO2 10 O polycondenstion of hexamethylene diamine and adipic – [ N – (CH2)6 – N – C – (CH2)10 – C ] – acid. This material is also a low moisture absorbing nylon. – [ N – (CH2)6 – N – C – (CH2)8 – C ] – The addition of methylene to the polyamide results in a hydrophobic, water-resistant product with half the water absorption of Nylon 6,6. Nylon 6,12 becomes stiffer and more rigid when saturated with water. Nylon 6,12 also has higher temperature ratings than nylon 6,6. When strength is required, nylon 6,12 can be modified by adding glass fibers. HOH HO O Nylon, molybdenum disulphide (MoS2) filled: This compound has increased surface HO– [ N – (CH2)6 – N – C – (CH2)10 – C ] – lubricity and wear resistant over unfilled nylon. Also the addition of –molybdenum [ N – C –disulphide (CH2)10 allows ] – for lower surface friction, increased surface hardness, increased heat– resistance, [ N – C as – well (C asH 2higher)10 ] – tensile strength and improved dimensional stability than unfilled grades.