Di-iso-nonyl Phthalate DINP

What Limits DINP Content in 75°C PVC Insulation Compounds?

Compounds rated for 75°C service under IEC 60227-3 and UL 62 are generally plasticized with DINP at 40-60 phr, with the upper boundary set by exudation resistance rather than tensile failure. On a production-scale twin-screw extruder with L/D 25:1-30:1, DINP (CAS 68515-48-0) is injected into the PVC dry blend at barrel temperatures 160-180°C through heated positive-displacement pumps. The dry blend is prepared in a high-speed mixer to 120°C and cooled to 50°C before extrusion. A common processing failure occurs when melt temperature exceeds 185°C at the vacuum port: the Ca-Zn stabilizer system is depleted rapidly and amber discolouration appears in the finished jacket. Exudation testing according to ASTM D3291 under compression at 70°C for 24 h indicates that a 50 phr DINP compound with 3 phr epoxidized soybean oil remains dry, while a 65 phr DINP compound frequently develops an oily film when aged for 7 days at 70°C and 95% RH. Mechanical properties measured on dumbbells cut from pressed sheets according to ASTM D638 are typically 15-20 MPa tensile strength and 200-300% elongation at break for a K-value 70 suspension PVC resin at 50 phr DINP. The same compound typically shows Shore A hardness 80-85 when tested to ASTM D2240 after 15 s dwell.

In calendered vinyl flooring wear layers, DINP is charged to the high-speed mixer at 40-55 phr on the basis of the suspended PVC resin; the dry blend reaches 120°C before dropping into a 75 L Banbury intensive mixer. After discharge at 160°C, the melt is transferred to a two-roll mill and then to a four-roll inverted-L calender where roll temperatures are held between 150°C and 170°C. The wear layer is calendered to a thickness of 0.5-0.7 mm and then laminated to the foam core. DINP selection in this layer is governed by surface lacquer adhesion and resistance to permanent indentation. The finished resilient floor covering is assessed under EN 649, which does not prescribe plasticizer type but does impose the requirement that dimensional stability and residual indentation be evaluated after conditioning. In export documentation, the presence of DINP at levels above 0.1% by weight in plasticized material is not relevant to EN 649 flooring; however, if the same wear layer is later converted into a toy or childcare article that can be placed in the mouth, the restriction in REACH Annex XVII Entry 52 applies. Production records from continuous calendering lines indicate that plasticizer migration into the backside adhesive layer becomes measurable when the wear layer contains more than 55 phr DINP and the floor covering is stacked at 40°C for 30 days. For this reason the upper loading is commonly limited to 50 phr unless a barrier lacquer is applied. The foam core beneath the wear layer typically uses a higher DINP loading of 60-70 phr together with 2-4 phr azodicarbonamide blowing agent and 40-80 phr calcium carbonate filler. Thermal stabilizers used in the foam core are selected from zinc octoate or Ca-Zn systems to prevent premature decomposition of the blowing agent at the gelation temperature of 140-160°C.

Automotive PVC plastisol underbody sealants based on DINP function as thixotropic coatings that must remain sprayable at high shear while resisting sag during oven gelation. A production formula consists of 100 phr PVC paste resin with a K-value of 66-70, 60-90 phr DINP, 100-140 phr surface-treated calcium carbonate, 3-6 phr calcium oxide moisture scavenger, and 2-5 phr blocked isocyanate adhesion promoter. The plastisol is applied by airless spray at 120-180 bar through a 0.3-0.6 mm tip, then gelled and cured at 180-200°C for 10-15 min. Brookfield viscosity measured at 25°C with spindle No. 6 at 20 rpm typically falls between 3,000-7,000 mPa·s, while the high-shear viscosity at 1,000 s⁻¹ measured on a cone-and-plate rheometer is below 1,000 mPa·s. A critical process boundary is filler moisture: if the calcium carbonate moisture content exceeds 0.1%, water reacts with the blocked isocyanate during cure and forms pinholes in the cured film. The calcium carbonate is therefore pre-dried at 105°C for 2 h before dispersion. Viscosity drift is tested by stored material at 40°C for 7 days; an increase above 15% indicates incomplete blocking of the isocyanate or migration of the plasticizer onto the filler surface. The gelation profile is measured by differential scanning calorimetry at 10°C/min, with the PVC gelation endotherm observed between 120°C and 140°C and the cure exotherm above 180°C. After curing, the sealant is conditioned 7 days at 70°C and tested for tensile properties according to DIN 53504; elongation retention above 80% relative to the unaged control is commonly specified. Peel adhesion to electrodeposition-coated steel after 14 days water immersion at 40°C is specified above 5 N/mm according to ISO 11339.

When DINP Replaces DIDP in Single-Ply Roofing Membrane Calendering

The replacement of a higher-molecular-weight phthalate with DINP in a single-ply PVC roofing membrane narrows the calender operating window because DINP volatility becomes measurable at roll temperatures near 180°C. Membrane producers typically run the mix on a 75-90 L Banbury line at 160-175°C, then feed a four-roll calender with roll temperatures 165-185°C. The membrane is reinforced with a polyester scrim and is calendered to total thickness 1.2-1.5 mm, with the top and bottom PVC layers containing 45-60 phr DINP and 5-10 phr epoxidized soybean oil. Volatile loss measured according to ASTM D1203 Method A for 24 h at 87°C is typically below 1.5% in a well-stabilized DINP compound, but roll smoke is observed earlier than with DIDP under the same calender conditions. Product specifications are checked against ASTM D4434 and EN 13956; these standards define minimum breaking strength, elongation, tear resistance and dimensional stability after heat ageing. The primary incompatibility is direct contact with solvent-based bitumen primers: aromatic and aliphatic fractions extract DINP from the membrane surface, causing stiffening and shrinkage. A separation fleece or inorganic barrier is required where the membrane is bonded to asphalt substrates. Published comparative long-term ageing data for DINP versus DIDP in EN 13956 membranes is limited; plant-level records from northern European installations indicate that the practical upper service temperature for a DINP-plasticized membrane should not exceed 70°C unless additional plate-out control and surface stabilization are applied.

Maintaining Foam Cell Stability in Synthetic Leather Base Coats

For compact and foamed synthetic leather base coats, DINP is used in PVC plastisols at loadings between 70-80 phr per 100 phr paste resin. The foaming system is based on azodicarbonamide at 2-4 phr, with activation adjusted by zinc oxide at 0.5-1.5 phr. The plastisol is knife-over-roll coated onto release paper or polyester fabric in two passes, with a first compact skin layer of 0.10-0.15 mm wet thickness and a second foamed layer of 0.20-0.35 mm wet thickness. The oven is divided into three zones: the first zone at 140-150°C to initiate gelation, the second zone at 190-210°C to decompose the blowing agent, and the third zone at 180-190°C to fuse the surface. The critical process boundary is the relationship between plastisol gelation and blowing agent decomposition. If the compound gels too early, the gas cannot expand the cell structure; if the compound gels too late, the gas escapes and the foam collapses. DINP solvates the paste resin more slowly than DEHP, shifting the gelation temperature upward by approximately 5-10°C under the same heating rate. This shift can be compensated by reducing the plasticizer content to 65 phr or by adding 5-10 phr of a fast-fusing extender plasticizer. The expanded layer is tested for hardness using ISO 7619-1, with typical Shore A values of 35-50 depending on expansion ratio. The final coated fabric is assessed for dry and wet rub fastness according to ISO 105-X12, because plasticizer exudation lowers rub fastness.

Extruded gasket and industrial hose profiles formulated with DINP are processed on single-screw extruders with L/D ratios of 24:1 to 30:1 and a compression ratio of 3:1. The dry blend is made from a K-value 65-70 suspension PVC resin, 60-75 phr DINP, 30-60 phr calcium carbonate, 4-6 phr Ca-Zn stabilizer, and 0.5-1.0 phr stearic acid external lubricant. The die temperature is set at 175-190°C, and the extruder head pressure is maintained below 250 bar to prevent plate-out. Extrudate swell becomes measurable when the DINP content exceeds 70 phr, requiring a shorter die land length or higher melt temperature. The extruded profile is cooled in a water spray unit at 20-30°C and cut to length. Compression set is determined according to ASTM D395 Method B after 22 h at 70°C; a 60 Shore A compound at 65 phr DINP typically shows compression set of 35-50%, while a 75 Shore A compound at 50 phr DINP shows 45-60%. Heat ageing in a forced-air oven at 100°C for 168 h normally produces a Shore A hardness increase of less than 5 points if the stabilizer package contains a hindered phenolic antioxidant. Exposure to ASTM IRM 903 oil at 23°C for 24 h according to ASTM D543 causes volume loss above 15%, indicating that DINP-plasticized profiles are unsuitable for continuous petroleum contact.