Influence of the injection molding process on the free volume and its effect on the creep behavior of styrene-acrylonitrile copolymer

• Published in: Mechanics of time-dependent materials Vol. 5; no. 1; pp. 27 - 38
• Main Authors: ENGELSING, K, MENNIG, G
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 2001
• Subjects: Cross-disciplinary physics: materials science; rheology; Deformation, plasticity, and creep; Deformation; material flow; Exact sciences and technology; Materials science; Physics; Rheology; Treatment of materials and its effects on microstructure and properties; Materials testing; Amorphous material; Creep; Cooling rate; Measuring methods; Free volume; Processing time; Amorphous state; Experimental study; Solidification; Lead time; Acrylonitrile copolymer; Molecular orientation; Internal stresses; Injection molding; Aging; Amorphous polymer; Styrene copolymer
• ISSN: 1385-2000; 1573-2738
• DOI: 10.1023/A:1009858702188

Measurements on the creep behavior of injection molded styrene- acrylonitrile copolymer (SAN) samples are described and analyzed. It is shown that the processing conditions have a distinct effect on the tendency to creep and that the differences in creep behavior are mainly due to differences in frozen-in free volume, whereas the different state of molecular orientation and internal stress have only a neglegible effect on the creep behavior. In addition, the time between processing and testing of the material plays an important role for the deformation behavior of the amorphous polymer; this phenomenon is known as physical aging. A slower cooling rate during the solidification of the injection molded part, as well as a longer aging time, lead to a reduced free volume and therefore to a reduced tendency to creep.