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T-14
4. Belt width greater than O.D. of pulley – This condition creates an abnormal
degree of lateral travel.
5. Belt length – The greater the ratio of length/width of the belt, the less the tendency
to move laterally.
II. In the Belt
1. Direction of the lay of the cords in the belt. See Figure 18.
2. Twist of the strands in the cord. See Figure 16.
6.4 Characteristics Of Belt Body Materials
Basic characteristics of the three most often used materials are shown in Table 2. The
tabulated characteristics give rise to the following assessment of these materials:
Natural Rubber
• High resilience, excellent compression set, good molding properties
• High coefficient of friction; does not yield good ground finish
• High tear strength, low crack growth
• Can withstand low temperatures
• Poor oil and solvent resistance; unable for ketones and alcohol
• Ozone attacks rubber, but retardants can be added
Neoprene
• High resilience
• Flame resistant
• Aging good with some natural ozone resistance
• Oil and solvent resistance fair
Polyurethane
• Excellent wear resistance, poor compression set
• Low coefficient of friction
• Oil and ozone resistance good
• Low-temperature flexibility good
• Not suitable for high temperatures
Table 2 Comparison of Different Belt Body Materials*
Common Name
Natural Rubber
Neoprene
Urethane, Polyurethane
Chemical Definition
Durometer Range (Shore A)
Tensile Range (p.s.i.)
Elongation (Max. %)
Compression Set
Resilience – Rebound
Abrasion Resistance
Tear Resistance
Solvent Resistance
Oil Resistance
Low Temperature Usage (°F)
High Temperature Usage (°F)
Aging Weather – Sunlight
Adhesion to Metals
Polyisoprene
20 – 100
500 – 3500
700
Excellent
Excellent
Excellent
Excellent
Poor
Poor
–20° to –60°
to 175°
Poor
Excellent
Polychloroprene
20 – 95
500 – 3000
600
Good
Excellent
Excellent
Good
Fair
Fair
+10° to –50°
to 185°
Good
Good to Excellent
Polyester/Polyether Urethane
35 – 100
500 – 6000
750
Poor
Good
Excellent
Excellent
Poor
Good
–10° to –30°
to 175°
Excellent
Fair to Good
* Courtesy of Robinson Rubber Products