On the overdrawing of melt‐spun isotactic polypropylene tapes

Abstract

The morphology and mechanical properties of melt-spun and post-drawn isotactic polypropylene (iPP) tapes have been studied in order to examine their dependence on the post-draw ratio applied. Special attention is focused on the characterization of the so-called overdrawing behavior of the tapes; at a certain draw ratio, a change of the optical appearance of the tape from transparent to opaque is observed. Overdrawing is accompanied with changes in the mechanical properties, surface, and morphology of the tapes. For postdraw ratios without overdrawing, and for highly overdrawn tapes, the variation in the mechanical properties measured is very small, but for slightly overdrawn tapes, a large scattering of mechanical properties has been measured. In the latter case, this behavior is related to the start of internal delamination of the tapes during post drawing. It is shown that strongly overdrawn tapes have excellent mechanical properties, in particular, high specific stiffness and strength.

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

“…This tape displays a wider azimuthal spread suggesting crystals with poorer orientation, which is an unusual phenomenon. However, occasionally this occurs when the sample is "over-drawn" at a temperature that is too low [30]. An "over-drawing" regime was observed for the tape with DR = 8 drawn at 90 °C.…”

“…Schimanski et al [30] found that for PP tapes with DR > 10, an "over-drawing" regime existed where tapes changed from transparent to opaque. They also observed that the crystal orientation increased rapidly with increasing DR at first, but started to decrease for DR > 10.…”

Failure behaviour of self-reinforced polypropylene at and below room temperature

“…The drawing process enhances the molecular orientation of the PP, which improves the mechanical properties in the drawing direction [4,5]. These fibres or tapes are then woven in the preferred configuration [6][7][8] and compacted at elevated temperature and pressure into a self-reinforced sheet.…”

“…The influence of the drawing process parameters on the mechanical properties of the PP tapes and the influence of the processing parameters on the mechanical properties of the final SRPP were extensively studied [4,5,[22][23][24]. However, these studies do not explain the impact behaviour of SRPP at low temperature.…”

Synergistic Reinforcement of Highly Oriented Poly(propylene) Tapes by Sepiolite Nanoclay

“…More recently, a lot of interest has also been shown in highlydrawn PP tapes, in particular for application as ''selfreinforced'' or ''all-PP'' composites, where both reinforcement and matrix are made from the same polymer. Remarkable achievements in this field [37][38][39][40][41][42][43][44][45][46][47][48][49] led to commercialised products such as Curv 1 or PURE 1 and its licence Tegris 1 .…”