High Phthalate Plasticizer Content in PVC Cable Sheathing Outside RoHS Boundaries

Flexible PVC cable sheathing compounds formulated with ortho-phthalate ester plasticisers at loadings from 30 phr to 60 phr continue to be manufactured for power, control, and instrumentation cables installed in equipment categories that fall outside the scope of Directive 2011/65/EU as amended by Commission Delegated Directive (EU) 2015/863. The RoHS Annex II entries 7 through 10 restrict bis(2-ethylhexyl) phthalate (DEHP, CAS 117-81-7), benzyl butyl phthalate (BBP, CAS 85-68-7), dibutyl phthalate (DBP, CAS 84-74-2), and diisobutyl phthalate (DIBP, CAS 84-69-5) to a maximum concentration of 0.1 % by weight in each homogeneous material. Because an extruded PVC jacket is a discrete layer that can be separated from the insulation and bedding by mechanical action, it constitutes a homogeneous material under Article 3(20) of the directive, and the 0.1 % threshold is therefore applied to the sheath compound alone, not to the mass of the completed cable. Where the cable is installed as part of a large-scale fixed installation, a large-scale stationary industrial tool, or another excluded system under Article 2(4), the Annex II restriction may not attach to the sheath at all, and the formulation can retain high low-molecular-weight ortho-phthalate contents that would be non-compliant in separately marketed EEE. The same four phthalates are simultaneously subject to Regulation (EC) No 1907/2006 Annex XVII Entry 51, which sets an article-level restriction of 0.1 % by weight in plasticised material from 7 July 2020, but paragraph 4 of Entry 51 creates derogations for purely industrial or agricultural articles, outdoor articles, legacy stock, laboratory measuring devices, aircraft, and certain vehicle applications when specified contact and exposure conditions are met. A cable sheath that sits outside RoHS therefore remains subject to a second regulatory boundary that depends on installation location, accessibility, and the presence or absence of prolonged skin contact with the PVC surface.

Does the 0.1 wt% Homogeneous-Material Restriction Follow the Cable or the Installation Classification?

The classification question is resolved by determining whether the cable assembly is placed on the market as EEE in its own right or supplied solely as a component of an excluded installation. Under Article 2(1) of Directive 2011/65/EU, the directive applies to electrical and electronic equipment listed in Annex I, while Article 2(4)(d) excludes large-scale stationary industrial tools and Article 2(4)(e) excludes large-scale fixed installations. A large-scale fixed installation is a combination of several types of apparatus or devices that is assembled, installed, and intended to be used permanently at a predefined location and de-installed by professionals; a large-scale stationary industrial tool is similarly a machine or system of machines, equipment, and components assembled and installed as a unit for a specific industrial application at a fixed location and operated by professionals. A tray cable, motor lead, or instrumentation cable that is cut, terminated, and fixed within such an installation is not normally placed on the market as an independent EEE at the time the sheath is installed, and therefore the RoHS phthalate concentration does not attach to the jacket. The same polymer compound placed on a separate cable drum for general sale to electrical wholesalers may be in scope because the cable is marketed as EEE in one of the Annex I categories. The consequence is that identical sheath chemistry can be compliant or non-compliant depending on the distribution channel, the end-use classification, and the equipment category, not on the composition of the PVC.

A high phthalate plasticizer content is expressed in parts per hundred resin; for a compound containing 50 phr DEHP, 20 phr ground calcium carbonate, 6 phr calcium-zinc stabilizer/lubricant, and 0.5 phr antioxidant, the DEHP mass fraction is 50 divided by 176.5, or approximately 28.3 wt%. At 40 phr the calculated mass fraction is approximately 24.0 wt%, and at 60 phr it reaches approximately 32.2 wt%. This arithmetic matters because enforcement authorities and manufacturers do not compare phr figures to the RoHS limit; the mass fraction is used. The RoHS threshold of 0.1 wt% is therefore exceeded by a factor of more than 200 in typical high-plasticizer sheathing compounds outside the excluded installation boundary.

Quantitative verification of the phthalate content in a separated sheath layer is performed by solvent extraction and gas chromatography-mass spectrometry according to IEC 62321-8:2017, which is capable of resolving the four restricted ortho-phthalates at concentrations well below the 0.1 % threshold. The method requires mechanical separation of the sheath from the insulation and any fillers, size reduction, extraction, and calibration against certified reference standards for each phthalate. In a non-RoHS cable, the same method can still be used to determine whether the REACH Article 33 communication threshold for SVHCs is exceeded, because DEHP, DBP, BBP, and DIBP are on the Candidate List.

Compound Viscosity, Extruder Torque, and Thermal Shear at High Phthalate Loadings

Dry blending of suspension PVC resin with a K-value of 70 and a high phthalate plasticiser loading is carried out in a hot-cool mixer set, with the PVC and stabiliser first heated to 60 °C before the plasticiser is sprayed through a nozzle at 80 °C to 110 °C. The dry blend becomes free-flowing when the plasticiser is absorbed into the resin grains; batch discharge is typically initiated at 110 °C to 130 °C, depending on the plasticiser solvation rate and the mixer torque curve. A 50 phr DEHP compound requires longer absorption time than a 30 phr compound because the resin particles must swell with a larger volume of ester, and the mix can become pasty if the jacket temperature exceeds 120 °C too early. The cooled dry blend should be stored in sealed vessels at relative humidity below 60 %; if the material is held at higher ambient humidity, surface moisture on filler and resin can generate surface pinholes and die lip build-up during extrusion.

Compounding of high-phthalate PVC for cable sheathing is usually performed on a counter-rotating twin-screw extruder with an L/D ratio between 32:1 and 40:1, screw speeds from 300 min⁻¹ to 600 min⁻¹, and barrel set-point temperatures from 140 °C to 180 °C. The presence of 40–60 phr phthalate reduces the melt viscosity substantially, lowers the drive torque compared with rigid PVC, and permits higher throughput for a given gearbox rating; however, the lower viscosity also reduces shear heating and can result in unmelted resin domains if the set temperatures are too low. The melt temperature at the die should be maintained between 170 °C and 195 °C for DEHP- or DIDP-plasticised compounds. Above 200 °C, dehydrochlorination of PVC accelerates, and the phthalate ester can undergo partial hydrolysis at trace moisture levels, producing phthalic acid or monoester intermediates that promote further dehydrochlorination and crosslinking. The extruder should therefore be equipped with a vacuum vent and melt temperature indication at the adapter; the specific mechanical energy input for a 50 phr plasticised compound is generally lower than for rigid PVC, but published data on a specific screw configuration may vary with resin K-value, filler particle size, and screw element layout.

For direct cable sheathing extrusion, a single-screw extruder with an L/D ratio of 25:1 and a compression ratio of 3:1 is commonly used, feeding the pre-compounded pellet or dry blend into a crosshead die that forms the PVC tube over the cable core. The extruder barrel set points are normally staged from 140 °C at the feed section to 175 °C at the metering section, with a head temperature of 185 °C to 195 °C and a stock temperature below 200 °C at the die exit. High plasticizer levels lower die swell compared with rigid PVC, improve surface smoothness at moderate draw-down ratios, but increase tack and can cause blocking on the take-up reel if the water trough temperature exceeds 25 °C. The line speed, screw speed, and crosshead tooling must be balanced so that the melt pressure at the die does not exceed the mechanical rating of the extruder; excessive pressure can cause melt fracture and poor concentricity, while insufficient pressure can lead to voids in the sheath and low adhesion to the bedding.

Representative property ranges for a non-RoHS sheathing compound based on suspension PVC with a K-value of 70, 20 phr ground calcium carbonate, 6 phr calcium-zinc stabilizer package, and 0.5 phr antioxidant are provided below. The values are comparative across DEHP loadings and are not certification data for any commercial cable compound; actual test results depend on resin molecular weight distribution, filler particle size, stabilizer composition, and extrusion conditions. Tensile properties are assessed after conditioning at 23 °C and 50 % relative humidity according to IEC 60811-501, hardness according to ASTM D2240-15e1, brittleness temperature according to ASTM D746-14, and oxygen index according to ASTM D2863-17a.

The data illustrate the property cliff-edge at high phthalate loadings for flame performance and softening; the drop in oxygen index from about 29 to 25 when moving from 40 phr to 60 phr DEHP is a critical processing and selection parameter for cables that must pass the single vertical flame test of IEC 60332-1-2. In such non-RoHS applications, antimony trioxide at 3 phr to 8 phr, chlorinated paraffin, or aluminium hydroxide are often added to offset the fuel contribution of the phthalate, but each addition changes the compound viscosity and the long-term migration behaviour.

The low-temperature flexibility benefit of high phthalate content is measured by cold bend and cold impact tests in IEC 60811-504 and IEC 60811-506, although the brittleness temperature by ASTM D746-14 provides a comparative material property that is widely reported by compound suppliers. A sheath containing 50 phr DEHP may show a brittleness temperature near -25 °C, allowing installation in cold storage or outdoor winter conditions; however, the same compound may fail a cold bend test if the cable core, insulation type, and sheath thickness impose additional strain. The low-temperature gain is accompanied by a reduction in room-temperature hardness and an increase in tack, which can create handling and coiling difficulties on large-diameter reels. Plant data from production-scale single-screw cable lines show that take-up blocking is more frequent when the sheath surface temperature leaving the water trough exceeds 25 °C; chilled water at 10 °C to 15 °C and talc dusting are used as process countermeasures.

A PVC sheath derives intrinsic flame retardancy from its chlorine content, but each increment of phthalate plasticiser reduces the overall chlorine mass fraction, lowers the limiting oxygen index, and increases the fuel load of the outer layer. The single vertical flame test of IEC 60332-1-2 is only a pass/fail test and does not quantify smoke or acid gas release; cable specifications for industrial installations often add smoke density testing according to IEC 61034-2 and halogen acid gas emission according to IEC 60754-1. High plasticizer contents tend to increase smoke density in well-ventilated flaming conditions, while halogen acid gas release remains above the threshold expected for low-smoke zero-halogen alternatives because the backing polymer is still PVC. Compliance outside RoHS therefore does not imply permission to ignore combustion gas and smoke requirements in installation standards or national building codes.

When a Non-RoHS Sheath Falls Within REACH Annex XVII Entry 51 and the Industrial-Use Exemption Is Not Self-Executing

RoHS exclusion does not extinguish the article-level restriction in Regulation (EC) No 1907/2006 Annex XVII Entry 51. Paragraph 3 of Entry 51 prohibits placing on the market articles containing DEHP, DBP, BBP, or DIBP individually or in any combination at a concentration equal to or greater than 0.1 % by weight of the plasticised material after 7 July 2020, unless a paragraph 4 derogation applies. For a PVC sheath containing 50 phr DEHP, the plasticised material is the entire sheath compound because the polymer matrix is plasticised throughout; the calculated 28.3 wt% DEHP therefore violates paragraph 3 unless the article-level derogation is established. Paragraph 4(a) exempts articles solely for industrial or agricultural use or solely for outdoor use only when the plasticised material does not come into prolonged contact with human skin or mucous membranes. A cable installed in a locked motor control room of a steel mill may satisfy this condition if access is limited to maintenance personnel and the cable is not used as a temporary extension lead; a cable routed through a public parking garage or hospital corridor may not satisfy the condition because cleaning, inspection, and building maintenance can involve routine skin contact. The burden of documenting the exemption rests with the entity placing the cable on the market, and the assessment must be performed at article level, not at installation level.

The following compliance matrix summarises the overlap between RoHS and REACH restrictions for the four ortho-phthalates most relevant to PVC cable sheathing.

The matrix demonstrates that a non-RoHS cable sheath containing a high loading of a high-molecular-weight phthalate such as diisodecyl phthalate or diisononyl phthalate may avoid the Entry 51 prohibition entirely, because those substances are not restricted in general articles and are only constrained in toys and childcare articles under Entry 52. Diisodecyl phthalate and diisononyl phthalate are therefore common replacement plasticisers in cable sheathing where high flexibility and low fogging are required, with loadings of 40 to 60 phr, while the restricted low-molecular-weight ortho-phthalates are retained only in applications where a specific REACH derogation can be documented or where the cable is outside the EU market and outside RoHS-style enforcement regimes.

High-molecular-weight phthalates differ from DEHP in solvation kinetics and migration behaviour. Diisodecyl phthalate absorbs more slowly into PVC resin during dry blending and generally requires a jacket temperature 5 °C to 10 °C higher than DEHP to reach an equivalent free-flowing dry blend. The higher molecular weight lowers volatility, reduces mass loss in activated carbon testing, and improves retention of elongation after heat ageing at 100 °C for 168 h according to IEC 60811-401 or equivalent test programs. The processing window narrows at the upper end: the melt viscosity of a DIDP compound is higher than that of a DEHP compound at the same loading, so screw torque and die pressure increase, and the risk of exceeding the gearbox limit must be evaluated before a direct drop-in substitution.

Migration of the plasticiser affects adjacent cable materials even when regulatory phthalate limits do not apply. In a non-RoHS cable, the PVC sheath is frequently in direct contact with a chlorinated polyethylene or ethylene-propylene rubber insulation or bedding layer. Low-molecular-weight ortho-phthalates migrate into the adjacent elastomer because the solubility parameters are close; the elastomer swells, softens, and may lose mechanical strength after long service at conductor temperatures above 70 °C. The extent of migration is assessed by mass loss to an adsorptive medium under ASTM D1203-22 or by mechanical property changes after oven ageing of the full cable in accordance with IEC 60811-401. The use of high-molecular-weight phthalates such as DIDP or DPHP reduces migration because the molecular diffusion coefficient is lower, but no phthalate system is entirely migration-free, and cable designers must consider the compatibility of the sheath with adjacent connector gaskets, cable clamps, and cable ties manufactured from rigid polystyrene or polycarbonate.

An EPR-insulated 0.6/1 kV power cable with a high-phthalate PVC sheath installed as part of a non-RoHS large-scale stationary industrial tool in a hot-rolling mill enters service with the jacket compound containing 30 wt% diisodecyl phthalate, 15 phr antimony trioxide, and 20 phr calcium carbonate by mass. The production batch is verified for tensile strength and elongation before extrusion in accordance with IEC 60811-501, and the finished cable is subjected to a vertical flame test in accordance with IEC 60332-1-2. The installation is fixed, accessible only to trained operators, and not placed on the EU market as a separate EEE, so the RoHS Annex II phthalate concentration does not attach; if the formulation instead contained DEHP at a calculated 28.3 wt%, the Article 33 communication threshold would be exceeded and the REACH Entry 51 paragraph 3 restriction would require an industrial-use derogation. The manufacturer therefore retains a phthalate-plasticised PVC sheath by using a non-restricted high-molecular-weight phthalate and documents the absence of the four restricted ortho-phthalates in the homogeneous jacket layer.