On the development of uniaxially‐oriented PET tapes for weaving, woven tape fabrics, and their applications

Abstract

This article reports the development of weavable, uniaxially‐oriented PET tape, and woven‐tape fabric. Fabric from uniaxially‐oriented polypropylene (PP) tape has been commercially produced since the 1960s, and it is the dominant material for flexible industrial packaging, carpet backing, geotextiles and self‐reinforced composites. Attempts had been made over the same period to produce similar poly(ethylene terephthalate) (PET) tape fabric, knowing that it would offer superior performance over PP due to PET's higher stiffness and strength, lower creep, abrasion resistance, and higher temperature capability. However, these attempts could not be translated into industrial production because the PET tapes had a tendency to splinter when subjected to sudden pulls and twists in the weaving loom. This was solved here by blending polymeric additives such as 2% polycarbonate (PC) and 2% linear low‐density polyethylene (LLDPE). Transmission electron microscopy of the oriented tapes showed the 2% PC formed a profusion of nano ellipsoids that adhered well to the PET matrix, and these prevented axial cracks from running through in a brittle manner. The LLDPE formed larger domains with poorer adhesion, but it imparted resistance to splitting from twists and axial folding. The combination of PC and polyolefin imparted a synergistic toughening of the tape. POLYM. ENG. SCI., 59:E120–E132, 2019. © 2018 Society of Plastics Engineers

The splitting tendency of uniaxially‐orientedPETtapes investigated with nano‐indentation, nano‐scratch, differential scanning calorimetry, and X‐ray

“…[3][4][5][6] Bashir et al described the industrial method of manufacture of weavable PET tapes. [6] Amorphous PET tapes were slit from a cast film and uniaxially drawn 5× to 6× and heat set under tension at 240 C. The heat setting increases the crystallinity and the strength, and also provides resistance to shrinkage for subsequent use of the fabric at high temperature. The approach in effect is similar to the one used to produce PET fibers and filaments.…”

“…Toughening additives were needed to make the PET tapes weavable at industrial speeds. [4][5][6] Attempts to make PET tape weavable involved trying inorganic fillers and polymeric additives [7] as toughening agents. Minor amounts of linear low density polyethylene with octene comonomer (C8 LLDPE), [4] or 2% polycarbonate (PC) + 2% C6 LLDPE, [5] imparted weavability.…”

“…A small decrease in tenacity was traded off for a large increase in the tensile impact strength. [6] Additives add expense and of course contaminate the recycling stream. The polyolefin additives induce haze in the PET tape and fabric.…”

“…A full scale, direct weaving operation would require 1 MT of tape and hence it is prohibitively expensive. In the previous work, [6] three combined tests were used to gauge the weavability of a tape composition. These were [1] tensile impact strength of the tape [2] ; nature of the fracture surface (axial splintering or puckered); and [3] axial splitting on axial folding.…”

“…These tests are easier to use than the three combined methods. [6] Nano-scratch testing is widely used in the coatings and paint industry but it has not been used to gauge splitting of uniaxially-oriented tapes. By making scratches parallel and perpendicular to the tape axis, a simple correlation could be found with tapes likely to split.…”