It is famous for its abrasive resistance, toughness, and low cost. Figure 1: Static vs dynamic friction Friction coefficients of thermoplastics against steel. %PDF-1.5 �; What kind of plastic? The coefficient of friction testing helps to determine two values, i.e. Rubber in contact with other surfaces can yield friction coefficients from 1 to 2. It is important to evaluate the coefficient of friction, wear rate, and pressure velocity limitations of the material. Example - Friction Force The friction force of a 100 lb wooden crate pushed across a concrete floor with friction coefficient of 0.62 can be calculated as: Ff = 0.62 (100 lb) = 62 (lb) 1 lb = 0.4536 kg Example - Car Stopping Distance A car with mass 2000 kg drives with speed 100 km/h on a wet road with friction coefficient 0.2. The value of μs is generally higher than the value of μk for a given combination of materials. 1.1 This test method covers determination of the coefficients of starting and sliding friction of plastic film and sheeting when sliding over itself or other substances at specified test conditions. Coefficient of friction, ratio of the frictional force resisting the motion of two surfaces in contact to the normal force pressing the two surfaces together. Most dry materials in combination have friction coefficient values between 0.3 and 0.6. The coefficient of friction is required in calculating tightening torques and resulting bolt tensile forces and stress and in calculating the resulting friction between the connected surfaces. Fig.11.5 shows that the friction coefficient of rubber, plastics depend on the sliding speed. The interface friction coefficients for soil sliding on 12-inch (305-mm) square, 2-inch (51-mm) thick coupons of PE4710 high density polyethylene (HDPE) were measured in the laboratory by a direct shear <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> <> %���� Ultra High Molecular Weight Polyethylene is another thermoplastic that exhibits a very low coefficient of friction, along with 10 times the resistance to abrasion than carbon steel. Low coefficient of friction Near-zero moisture absorption. Values outside this range are rarer, but teflon, for example, can have a coefficient as low as 0.04. DESIGN COEFFICIENT TABLES Hazen-Williams Friction Factor (C) Pipe Material Values for C Range High/Low Average Value Typical Design Value Plastic, PVC, Polyethylene pipe or tubing 160/150 150-155 150 Cement or mastic lined iron or steel pipe 160/130 148 140 Copper, brass, lead, tin or glass pipe or tubing 150/120 140 130 Static and Kinetic coefficient of friction . Below are provided a small number of values showing approximate values of friction coefficients to be used for steel screw fastened connections. "�? Is the rubber subject to other forces? 4 0 obj Is this in atmosphere, water, vacuum, some other environment? PTFE's coefficient of friction is 0.05 to 0.10, which is the third-lowest of any known solid material (BAM being the first, with a coefficient of friction of 0.02; diamond-like carbon being second-lowest at 0.05). UHMW (Polyethylene) Redco™ Ultra High Molecular Weight Polyethylene (UHMWPE) has extremely low moisture absorption, a very low coefficient of friction, is self lubricating and is highly resistant to abrasion (10 times more resistant to abrasion than carbon steel). The coefficients of dynamic friction for a low-density polyethylene resin are presented in this paper as a function of the surface temperature, pressure, and velocity. @. The versatility of polyethylene has made it a popular plastic for countless industrial applications that require durability, low friction, and chemical resistance. For example, static friction can prevent an object from sliding down a sloped surface. Coefficient of Friction, Plastics to Steel Static 0.30 0.30 Dynamic 0.28 0.28 Coefficient of Friction, Plastics to Plastic Static 0.76 0.76 Dynamic 0.44 0.44 Thermal Properties DSC Melting Point Homopolymer 320 - 329 °F 160 - 165 °C Copolymer 275 – 318 °F 135 – 159 °C Specific Heat (@ 23°C) 70 … In addition to PTFE, the classic bearing and wear materials made of polyimide, PEEK, PPS, Nylon, Acetal and Polyester are also known for their good sliding friction properties. The coefficient of friction between two materials in relative sliding may depend on contact pressure, surface roughness of the relative harder contact surface, temperature, sliding velocity and the type of lubricant whether the level of contamination. The table below is from Barrett, "Fastener Design Manual," NASA Reference Publication 1228, 1990: The table below is from MIL-HDBK-60, "Threaded Fasteners - Tightening to Proper Tension," 1990: Affordable PDH credits for your PE license, Barrett, "Fastener Design Manual," NASA Reference Publication 1228, 1990, MIL-HDBK-60, "Threaded Fasteners - Tightening to Proper Tension," 1990. x��][s�r~w��ü�j��9�gR.ֱ)_;r���y�i��/:�:���bи��.3@2S�X�����读�p���v���j�|������ջ�_�����q���ק//o6�������Y�����ן~r�5i�v��뷟~B�N��4B��Q��m^�釾y����O?�����O?�X5�4��������5_�pޜF�|���>�͡9 ���Rn �d�$U��"��?��k�0�s�p�d�v� k�@���.o����C���IZ���W-�_��տo���Z*���&����\��˛5_]Ǿ�uC�[���bEb�~$����ه��X�]��FT���=�h+�8���23r't��75����]i�9�_���L�Wf���ѿ�v�#�zt���k�w�In��1�\�GZã �-��׊�Q�����#��^�O��kBW6�����k�*(������ �Y�^���'lu��ѿ��� ���Pԗ� � 2 0 obj Much has been The coefficient of friction testing is done to determine the easiness with which two facades when placed in contact with each other are able to slide on one another. Low polyurethane coefficient of friction is desirable for applications that want sliding to occur. COF depends on the nature of the materials and surface roughness. It is also self-lubricating with extremely low moisture absorption, and it has the highest impact strength of any thermoplastic polymer presently on the market. The friction force is the force exerted by a surface when an object moves across it - or … (a) Oleic acid; (b) Atlantic spindle oil (light mineral); (c) castor oil; (d) lard oil; (e) Atlantic spindle oil plus 2 percent oleic acid; (f) medium mineral oil; (g) medium mineral oil plus ½ percent oleic acid; (h) stearic acid; (i) grease (zinc oxide base); (j) graphite; (k) turbine oil plus 1 percent graphite; (l) turbine oil plus 1 percent stearic acid; (m) turbine oil (medium mineral); (n) olive oil; (p) palmitic acid; (q) ricinoleic acid; (r) dry soap; (s) lard; (t) water; (u) rape oil; (v) 3-in-1 oil; (w) octyl alcohol; (x) triolein; (y) 1 percent lauric acid in paraffin oil. The procedure permits the use of a stationary sled with a moving plane, or a moving sled with a stationary plane. Here is an excellent discussion on friction coefficients, plus a comprehensive table of friction coefficients.. ... Coefficient of Friction - Static (Polished Steel) ASTM D-1894 --- .15 - .20 Friction force develops between contacting surfaces of two bodies and acts to resist relative motion between the bodies. Coefficient of Friction 0.29 0.29 Thermal Properties DSC Melting Point Homopolymer 275 °F 135 °C Copolymer 230 – 273 °F 110 – 134 °C Specific Heat (@ 23°C) 2.25 kJ/kg °K Heat of Fusion Homopolymer 245 kJ/kg Copolymer 140 – 232 kJ/kg Thermal conductivity Homopolymer 0.49 W / m °K Nevertheless, for the two data points furthest from the regression line (PP and PVC), if we were to use COF to predict surface energy, we’d be off by more than 10 and 8 dynes/cm, respectively. It is also important to consider the coefficient of thermal expansion of the plastic, particularly if it is to be used in contact with a mating metal part. 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