ASTM D832-07(2012)
- standard by ASTM International, 12/01/2012
- Standard Practice for Rubber Conditioning For Low Temperature Testing
- Category: ASTM
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Full Description
Property | Crystallization | Glass Transition |
Physical effects | Becomes stiff (hard) but not necessarily brittle | Becomes stiff and brittle |
Temperature-volume relation | Significant decrease in volume | No change in volume, but definite change in coefficient of thermal expansion |
Latent heat effect (4, 5, 8) | Heat evolved on crystallization | Usually no heat effect, but definite change in specific heat |
Rate (2, 4, 6, 7, 8) | Minutes, hours, days, or even months may be required. In general, as temperature is lowered, rate increases to a maximum and then decreases with increase in deformation. Rate also varies with composition, state of cure, and nuclei remaining from previous crystallizations, or from compounding materials such as carbon black. | Usually rapid; takes place within a definite narrow temperature range regardless of thermal history of specimen. May be limited rate effect (2) |
Temperature of occurrence | Optimum temperature is specific to the polymer involved. | Very wide limits, depending on composition |
Effect on molecular structure | Orientation of molecular segments; random if unstrained, approaching parrallelism under strain | Change in type of motion of segments of molecule |
Materials exhibiting | Unstretched polymers including natural rubber (low sulfur vulcanizates), chloroprene, Thiokol A polysulfide rubber, butadiene copolymers with high butadiene content, most silicones, some polyurethanes. Butyl rubbers crystallize when strained. Straining increases rate of crystallization of all of the above materials. | All |
Product Details
- Published:
- 12/01/2012
- Number of Pages:
- 4
- File Size:
- 1 file , 74 KB
- Note:
- This product is unavailable in Russia, Ukraine, Belarus
Document History