Effect of strain level on stress relaxation and recovery behaviors of isotactic biaxially oriented polypropylene films

Abstract

The long-term recovery process and the changes in the uniaxial tensile properties and in the structure of isotactic biaxially oriented polypropylene (i-boPP) films after pre-extended at strain levels ranging from 1% up to 130% at room conditions were examined by using tensile testing, Fourier transform infrared spectroscopy/attenuated total reflectance, atomic force microscopy, and X-ray diffraction methods. It is significantly observed that the pre-extended i-boPP films at strain levels from 1% to 6% recovered completely back to their initial lengths and tensile properties. However, the i-boPP films showed a very slow recovery process and obtained very high remaining deformations changing with time which indicates irreversible structural processes after they were extended at higher strain levels. In order to predict the remaining deformation or length and the characteristics of the recovery process at any time, the linear equation of strain with respect to log time was proposed. The reasons for the changes in the tensile properties, the morphology, and the structure of the pre-extended i-boPP films were examined in detail.

Crystallization, Mechanical, and Antimicrobial Properties of Diallyl Cyanuric Derivative-Grafted Polypropylene

“…Polypropylene (PP) is an engineering thermoplastic polymer widely employed in textiles, pipes, automobiles, and many other fields due to its several advantages, including chemical resistance, ease of processing, low price, and excellent production performance. − The research and development of high-performance and high-value-added PP plastic remains a major challenge for both academy and industry. Improvement of the crystalline properties, thermal stability, electrical conductivity, and flame-retardant properties of PP has also been introduced to increase its range of applications. − Particularly, plastics are susceptible to bacterial contamination and can act as important sources for cross-infection and cross-contamination during usage and storage. The transmission of microorganisms could be minimized by introducing antimicrobial functions.…”

Quantitative relation between the relaxation time and the strain rate for polymeric solids under quasi‐static conditions

“…The relaxation time is an essential physical quantity in the viscoelastic constitutive model; it reflects the hysteresis of the microstructure of polymeric materials under external loading . The dependence of the relaxation times on the shear (or strain rate) has been studied extensively for viscoelastic fluids in the past.…”