A study on crystalline residual stress of the iPP surface layer in Al/iPP/Al under the influence of microwave irradiation

Abstract

AbstractThe residual stress of the iPP surface layer in Al/iPP/Al under the influence of microwave irradiation was investigated by thin film (TF)‐X‐ray diffraction (XRD). Depending on the irradiation time, we calculated the macro residual stress, micro stress, and lattice static distortion stress. The results show that the macroscopic residual tensile stress of irradiated iPP samples dropped from about 12 MPa to 4 MPa. D(300) (the β crystal phase) becomes larger from about 4 to 10 nm as the irradiation time increased, and the β‐form iPP becomes more perfect. However, for theα‐form phase, D(110) remains almost stable. Moreover, the microscopic distortion coefficient ε(300) that decreases from approximately 0.03 to 0.018, becomes smaller than ε(110) parallel to the irradiation time, so the microscopic stress of the β‐crystal is decreased. In addition, the lattice static distortion energy of the α‐form greatly increases from 2 to 6 MPa, but the lattice static distortion energy of the β‐crystals remains constant at about 1.5 MPa and is much smaller than that of the α‐crystals at the same irradiation time. These calculated results are in good agreement with that of the crystallinity and order parameter of the β‐crystals of the TF‐XRD. The lattice distortion energy is a major portion of the plastic deformation, therefore, it suggests that the lattice static distortion energy is the main cause of α → β crystalline transformation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3759–3765, 2004