Premium
Anisotropy in injection‐molded ethylene‐propylene‐diene rubbers. Part II: Disks delaminated by a water‐jet cutting technique
Author(s) -
Lavebratt Håkan,
Stenberg Bengt
Publication year - 1994
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760341108
Subject(s) - materials science , anisotropy , composite material , natural rubber , ethylene propylene rubber , compression molding , molding (decorative) , jet (fluid) , polymer , swelling , mold , copolymer , optics , physics , thermodynamics
Anisotropy and molecular orientation are well known phenomena in the field of thermoplastics, but only a few studies have described anisotropy in rubber materials. It has been shown that injection molding gives rise to a higher degree of anisotropy than compression molding. The anisotropy in the rubber material was strengthened by carbon black and is presumably due to molecular orientation. This paper describes the anisotropy of injection‐molded ethylene‐propylene‐diene rubbers. The two polymers had different molecular weight distributions and thus different rheological properties. The compounds were injected into center‐gated 4mm thick disks. The disks were subsequently split into three layers using a water‐jet cutting technique. Measurement of mechanical and swelling properties in the different layers and directions showed that the anisotropy varied through the thickness of the disk. By X‐ray scattering it was shown that rubber molecules had a preferred direction and thus, that the anisotropy was probably predominantly due to molecular orientation created during the mold filling.