Stress‐induced crystallization of biaxially oriented polypropylene

Abstract

ABSTRACT:The hot stretching of thick, extruded sheets at high temperatures is a very important process in the production of finished biaxially oriented polypropylene (BOPP) films with special inner structures. Through a simulation of hot stretching in the machine direction (MD) of the processing of BOPP films, it was found that at high temperatures, the stretching ratio greatly influenced the obtained crystalline structure, as observed by differential scanning calorimetry (DSC). Also, in MD hot stretching, the crystallinity increased by an average of 20%. Wide-angle X-ray diffraction patterns of extruded sheet samples with and without stretching confirmed the structural changes shown by DSC, and the results proved that ␤-crystal modification did not occur during the MD hot-stretching process.

Characterization of a Pearlescent Biaxially Oriented Multilayer Polypropylene Film

“…A shoulder corresponding to the melting of small crystallites was observed at all heating rates. This shoulder was also observed for biaxial oriented polypropylene by previous investigators [18]. The melting temperature shifts to higher temperatures as the rate of heating was increased.…”

“…where ∆H m is the melting enthalpy of the samples, J/g; ∆H 0 f is the heat of PP fusion at 100 % crystallinity, corresponding to 207 J/g [18].…”

Gas transport and thermal characterization of mono‐ and di‐polyethylene films used for food packaging

“…Commercial BOPP films have special inner structures obtained by the stretching of the thick, extruded sheets at high temperatures in the machine direction and in the transverse direction. 6 To obtain high-performance films with superior properties, layering two or more different materials in a single structure is necessary. Polyamide (PA) has frequent use as a component in these multilayer film structures 7 because of its unique combination of mechanical strength, puncture resistance, transparency, thermal stability, oxygen and aroma barrier, and thermoformability.…”

Effect of Temperature and Mechanical Stress on Barrier Properties of Polymeric Films Used for Food Packaging

“…Its advantageous properties include low density, no toxicity, good moisture resistance, good mechanical strength, and dimensional stability and printability. Commercial BOPP films have special inner structures obtained by the stretching of the thick, extruded sheets at high temperatures in the machine direction and in the transverse direction [7]. Polyamide has frequent use as a component in these multilayer film structures [8] due to its unique combination of mechanical strength, puncture resistance, transparency, thermal stability, O 2 and aroma barrier, and thermoformability.…”