Stone mastic asphalt and open-graded friction course plants introduce high-tenacity polyester staple fiber 6–12 mm in cut length at the downstream side of the aggregate weigh hopper, before the bitumen injection manifold. The fiber is metered through a loss-in-weight feeder to the pugmill at a dosage of 0.2–0.5 wt% of dry aggregate mass, with 0.3 wt% commonly applied in nominal 10 mm SMA wearing course. Dry mixing proceeds for 8–15 s at 160–180 °C, followed by wet mixing for 25–45 s after bitumen addition; exceeding 190 °C is avoided because the polyester fiber begins to soften and can wrap around pugmill shafts, increase torque, and form fiber balls. On twin-shaft pugmills with batch sizes of 2–4 t, the dry-mix interval is extended when aggregate moisture exceeds 1.5% to maintain fiber dispersion before the bitumen spray bar is activated. The relevant test procedures are EN 12697-18 for binder drain-down, AASHTO T 305 for drain-down susceptibility, and EN 13108-5 for SMA mixture specification. Terminal product types include SMA 0/8 and 0/11 wearing courses, open-graded friction courses for airport taxiways, and bridge deck surfacing layers where mastic cohesion and low-temperature crack resistance are specified. Published data for exact pugmill torque escalation at specific binder grades is limited; the upper temperature limit is therefore set by the fiber thermal softening range and observed wrap tendency on production shafts.

Why Is Sheath-Core Co-PET Binder Fiber Used as a Thermal Bonding Matrix for Automotive Interior Trim?

In dry-laid nonwoven lines producing automotive interior trim, a bicomponent polyester staple fiber with a Co-PET sheath and homopolymer PET core is blended with high-tenacity PET or recycled PET base fiber. The sheath melting range of 140–170 °C is deliberately lower than the core softening point of 245–255 °C, allowing thermal bonding without sacrificing fiber structural integrity. The binder fiber is added at 15–30 wt%, with the remaining 70–85 wt% composed of matrix fiber; binder levels below 15 wt% produce insufficient peel strength in the semi-rigid web, while levels above 30 wt% can reduce airflow permeability and increase calender contamination. Carded and crosslapped batts are passed through a through-air oven at 150–190 °C for 20–60 s dwell time; on wide lines of 2.5–3.5 m, the oven temperature profile is staged to avoid sudden sheath melting and uneven density. Flammability conformance is tested under FMVSS 302 and ISO 3795, volatile content is evaluated by VDA 278, and the fiber itself is expected to comply with EU REACH. Production experience on carding machines shows that ambient relative humidity above 60% can cause sheath softening and fiber wrapping on card clothing, so bales are pre-dried at 60–70 °C for 2–3 h before opening. Terminal product types include moldable headliner substrates, door panel padding, parcel shelf covers, and under-carpet acoustic insulators.

In high-temperature baghouse filtration for cement kilns, asphalt mix plants, and coal-fired boiler de-dusting, the filter medium is produced from 100 wt% high-tenacity polyester staple fiber, typically 2.2–6.7 dtex and 38–76 mm cut length, with a needled batt mass of 450–600 g/m² on a scrim of 100–200 g/m². The fiber is carded, crosslapped, and needlepunched at 600–1,200 strokes/min on wide multi-board needlelooms, then the surface is singed and calendered at 170–190 °C to close porosity and improve dust release; an optional PTFE membrane lamination follows. Compliance testing uses ISO 11057 for cleanable filter media pressure drop and dust cake release, while ASTM D6830 provides test protocols for filter media pressure drop characteristics. Continuous service is limited to 130 °C in dry air; the presence of moisture at temperatures above 90 °C accelerates ester hydrolysis, and acid gases such as SO₂ shorten bag life. Terminal product types include pulse-jet filter bags for cement mill dedusting, coal boiler baghouse elements, and asphalt plant dust collectors. Field bag life under variable dust loading is not specifiable from batch tests; published data for specific clinker dust chemistries is limited.

High-Modulus Polyester Staple in Needlepunched Geotextile Hydraulic Transmissivity

For drainage and separation geotextiles, the input raw material is 100 wt% high-modulus polyester staple, sourced as virgin or recycled PET with a linear density of 3.3–17 dtex and fiber length 50–120 mm. The finished nonwoven geotextile mass per unit area ranges from 200 g/m² for separation layers to 1,000 g/m² for heavy protection and reinforcement composites; no binder or resin addition is used, so the formulation addition ratio is the full substrate fiber composition. Production involves bale opening, fine-opening and blending, carding, crosslapping to a predetermined lap count, and needlepunching at 300–800 strokes/min with barbed needles. On wide 4.5 m needlelooms, the drafting rate and needle penetration depth are adjusted to maintain consistent tensile isotropy. Conformity is established under ISO 10318 for terminology and classification, ISO 10319 for tensile properties, ISO 11058 for water permeability perpendicular to the plane, ISO 12236 for static puncture resistance, and EN 13249 for road-related geotextile requirements. Terminal product types include separation geotextiles placed between subgrade and aggregate, drainage composites with geotextile bonded to a dimpled core, landfill liner protection mats, and erosion-control blankets. A significant limitation is alkaline hydrolysis; polyester geotextiles are not recommended for permanent contact with saturated calcium hydroxide solution or fresh concrete because pH values above 12.5 at 25 °C can reduce molecular weight over time.

Spunbond PET Carrier Web Shrinkage Control During Polymer-Modified Bitumen Membrane Production

In continuous roofing membrane manufacturing, a spunbond polyester carrier web is unwound and drawn through a preheating zone set at 120–160 °C before entering the bitumen impregnation nip. The carrier is 100 wt% PET spunbond with a mass per unit area of 150–250 g/m²; the finished membrane bitumen compound add-on is typically 1.5–3.0 kg/m², so the carrier represents 10–20 wt% of the final membrane mass depending on surfacing. The process includes controlled web tension, pre-shrinking behavior of the carrier, immersion in oxidised or polymer-modified bitumen at 160–190 °C, calendering to achieve target thickness, and immediate cooling before sand or slate release. Specifications for the finished product are referenced to EN 13707 for reinforced bitumen sheets for roof waterproofing and ASTM D5147 for sampling and testing modified bituminous sheet material. Preheating above 180 °C can cause edge curl and width loss; converting lines therefore hold the web temperature below this threshold for not more than 30 s. Terminal product types include mechanically fastened cap sheets, self-adhered base sheets, torch-on membranes, and reinforced underlayments.

When Sheath-Core PET Binder Fiber Replaces Latex in Air-Laid Absorbent Core Binding

In air-laid absorbent core production for disposable hygiene and adult incontinence products, a bicomponent polyethylene terephthalate/co-polyethylene terephthalate sheath-core fiber with sheath melting at 130–160 °C is dry-blended with cellulosic fluff pulp and superabsorbent polymer. The binder fiber is metered at 10–20 wt% of total dry furnish; below this range the thermally bonded core has insufficient wet tensile strength, and above 20 wt% the fiber can reduce liquid strike-through speed and create a stiff panel. The blended furnish is formed on a perforated air-lay drum at line speeds of 150–400 m/min, then transferred through a through-air oven at 140–170 °C for 20–40 s; the sheath melts and forms bond points at fiber intersections while the PET core maintains the matrix. Liquid strike-through time is tested under EDANA NWSP 070.3.R1, mass per unit area and thickness under ISO 9073-1 and ISO 9073-3, and nonwoven classification under ISO 9092. Terminal product types include acquisition distribution layers, absorbent core wrap strips, feminine hygiene core wrap, and adult incontinence barrier leg cuff reinforcement. A stated operational boundary is that thermal bonding temperatures above 170 °C can scorch cellulose and reduce wet strength; line operators therefore monitor oven profile and surface temperature rather than raising dwell time to compensate.