Towards an understanding of the heat distortion temperature of thermoplastics

Abstract

A systematic understanding of the heat distortion temperature (HDT) of amorphous and semi-crystalline polymers is possible through a direct correlation with the modulustemperature behavior. For amorphous polymers, the precipitous drop in modulus at the glass transition temperature makes the HDT a well-defined, reproducible and predictable property. Furthermore, the addition of reinforcing fillers has a negligible effect on the HDT of the amorphous polymer. For semi-crystalline polymers, however, the exact opposite may hold true. The modulus exhibits a "plateau" region between the glass transition and the melting transition. Hence the HDT often is difficult to predict, is sensitive to thermal history and may be greatly increased through the addition of fillers. More importantly, the HDT may not be an accurate measure of the upper use temperature for semi-crystalline polymers in loadbearing situations since considerable stiffness may still be retained even upon exceeding the HDT.

Polymeric Nanocomposites for Automotive Applications

“…Nanofillers, however, are not expected to impart many of the property losses of conventional fillers because smaller particles produce less stress concentration. [6] The heat-distortion temperature of NCH nanocomposite was enhanced dramatically with respect to Nylon 6 by addition of 5 % clay (65 to 110 C) as compared to 30 % mineralfilled Nylon 6 (65 to 120 C). [10] However, the unusual enhancement for the NCH is probably due to the unique nature of the in-situ reactively intercalated product and may not be as dramatic in other polymeric matrices.…”

“…This reality has driven the development of numerous approaches to enhance the properties of conventional materials. [6] Examples of these approaches include structural plastics, alternative metals and alloys, reinforcing fillers, and glass fiber composites. Each of these approaches has limitations.…”

Kenaf‐fiber‐reinforced poly(lactic acid) used for electronic products

“…The reason is that the inorganic fillers prevent the deformation of molded pieces of these plastics 13 and promote the crystallization of the plastics on the surface of the fillers. The kenaf fiber probably has the same synergistic effect as inorganic fillers in improving heat resistance and stiffness.…”

Glass‐Rubber Transition Behavior

“…The HDT is defined as the temperature at which a 100 mm length, 3 mm thick specimen bar at 1.82 MPa in a three-point bending mode deflects 0.25 mm. Young's modulus at the HDT is 0.75 Gpa (133,134). For unfilled polymers, both the Vicat and the HDT tests usually record a temperature just above the glass transition temperature, or for melting conditions, just below the temperature of final disappearance of crystallinity.…”