{"id":950,"date":"2026-06-19T14:22:37","date_gmt":"2026-06-19T06:22:37","guid":{"rendered":"https:\/\/bastone-petrochem.com\/?p=950"},"modified":"2026-06-14T07:45:06","modified_gmt":"2026-06-13T23:45:06","slug":"what-additives-are-used-polypropylene","status":"publish","type":"post","link":"https:\/\/bastone-petrochem.com\/es\/what-additives-are-used-polypropylene\/","title":{"rendered":"\u00bfQu\u00e9 aditivos se utilizan en el polipropileno"},"content":{"rendered":"\n

A PP COA might list “1500 ppm phenolic AO + 1000 ppm phosphite + 500 ppm slip” and look like a complete additive package. Whether those numbers are correct depends on whether the grade is heading into a hot-water pipe, a UV-exposed woven bag, or a clear yogurt cup.<\/p>\n\n\n\n

PP is chemically vulnerable in a way most thermoplastics are not. The tertiary carbon on every repeat unit is the preferred site for radical oxidation. A stripped-down PP resin<\/a> embrittles within months of melt processing and faster outdoors.<\/p>\n\n\n\n

Why PP Needs Additives in the First Place<\/h2>\n\n\n\n

Polypropylene without stabilizers<\/a> loses molecular weight in hours under processing-temperature shear. The tertiary C-H bond on each propylene repeat unit dissociates roughly 80 kJ\/mol weaker than a polyethylene secondary C-H. PP forms hydroperoxides much faster during extrusion and injection molding.<\/p>\n\n\n\n

Chain scission follows, MFI drifts upward, and the part either cracks in service or fails an Izod requalification six months in.<\/p>\n\n\n\n

Three vulnerabilities drive the package design. Thermal-oxidative attack during melt processing (220-280 \u00b0C) is handled by an antioxidant pair.<\/p>\n\n\n\n

UV photo-oxidation in outdoor service is handled by HALS or UV absorbers. Surface and processing behavior \u2014 slip, antistat, clarity \u2014 is handled by smaller-volume functional additives.<\/p>\n\n\n\n

\"Diagram<\/figure>\n\n\n\n

Antioxidant Additives: Phenolic Primary plus Phosphite Secondary<\/h2>\n\n\n\n

The default PP antioxidant system is a phenolic primary plus a phosphite secondary, run at 1000-2500 ppm total (0.1-0.25 wt%) for general-purpose grades. Irganox 1010<\/a> is the most common phenolic. Irgafos 168 is the most common phosphite.<\/p>\n\n\n\n

The two work at different points in the oxidation chain. Irgafos 168 preferentially decomposes hydroperoxides during processing. Irganox 1010 captures free radicals long-term in service and governs how the resin ages in storage.<\/p>\n\n\n\n

Real-world ratios skew much further toward phosphite than textbook examples suggest. A measured PP film sample analyzed in ACS Omega in 2020 showed Irganox 1010 at 220 wppm and Irgafos 168 at 1580 wppm.<\/p>\n\n\n\n

That roughly 7\u00d7 phosphite-to-phenolic ratio reflects how much processing-protection load Irgafos carries on high-shear extrusion lines. For long-term thermal stability alone, Irganox 1010 in the 500-1000 ppm window is typical.<\/p>\n\n\n\n

\"Laboratory<\/figure>\n\n\n\n

UV Stabilizers and HALS for Outdoor Service<\/h2>\n\n\n\n

PP that sees sunlight \u2014 woven bags, agricultural film, garden furniture, automotive exterior trim \u2014 needs a hindered amine light stabilizer (HALS) at 0.1-0.5 wt% (1000-5000 ppm). Chimassorb 944 is the most common HALS for general outdoor PP.<\/p>\n\n\n\n

Tinuvin 622 at 0.3% is a common alternative in fiber. Severe UV exposure pushes loading to 2.0 wt%.<\/p>\n\n\n\n

HALS works differently from the antioxidants above. A UV absorber dissipates incident UV as heat and depletes as it works.<\/p>\n\n\n\n

HALS traps free radicals through a nitroxyl-radical regeneration cycle, so the stabilizer cycles rather than being consumed. One-time shield vs self-healing armor.<\/p>\n\n\n\n

USPTO patent 8721946 documents automotive interior PP at 1000-2500 ppm HALS on top of 400-2400 ppm phenolic AO plus 500-1500 ppm phosphorus AO. That HALS top-up over the producer baseline is what most outdoor and automotive grades look like.<\/p>\n\n\n\n

\"Outdoor<\/figure>\n\n\n\n

Slip and Antistat Agents<\/h2>\n\n\n\n

Two surface-acting families share the same bloom mechanism but different jobs \u2014 slip controls film friction; antistat dissipates charge on molded parts.<\/p>\n\n\n\n

Slip agents<\/h3>\n\n\n\n

Slip agents lower the coefficient of friction on PP film so wound rolls unwind cleanly. Erucamide and oleamide are the standard fatty amides at 500-2000 ppm.<\/p>\n\n\n\n

The trade-off is bloom-rate control. Too low and the COF stays high. Too high and you get plate-out on the chill roll.<\/p>\n\n\n\n

Erucamide is also one of the fastest-degrading additives in PP processing, alongside Irgafos 168. Akoueson et al. in Science of the Total Environment (2023) and ACS Omega (2020) both measured these two as the highest-degradation-rate species under typical extrusion conditions.<\/p>\n\n\n\n

Push the extruder 20 \u00b0C hotter than the data-sheet target and the in-part erucamide concentration after processing can already sit well below the nominal. The 1500 ppm spec assumes a controlled process window, not infinite headroom.<\/p>\n\n\n\n

Antistat agents<\/h3>\n\n\n\n

Antistat agents \u2014 typically glycerol monostearate (GMS) or ethoxylated amines at 500-2000 ppm \u2014 manage static charge on injection-molded parts and fibers. The mechanism is similar to slip in that the additive blooms to the surface. Antistat is omitted in food-contact PP where migration is regulated.<\/p>\n\n\n\n

Clarifier and Nucleator Additives for Clear PP<\/h2>\n\n\n\n

For clear PP cups, jars, and thin-wall packaging, sorbitol-based clarifiers like Millad NX 8000<\/a> and Millad 3988 run at 0.2-0.25 wt% (2000-2500 ppm). Organophosphate nucleators like Milliken HPN-68 and NJStar NU-100 run lower at 0.1-0.15 wt%.<\/p>\n\n\n\n

Nucleators do a different job. They raise crystallization temperature without targeting transparency, which speeds injection cycle time.<\/p>\n\n\n\n

New-generation nucleators are roughly 3\u00d7 more efficient than legacy sodium benzoate. Milliken documented a 39.8% cooling-time reduction with HPN-68 in injection molding.<\/p>\n\n\n\n

\"Clear<\/figure>\n\n\n\n

Less-Common PP Additives: Flame Retardants, CR Peroxide, Color Masterbatch<\/h2>\n\n\n\n

Three families round out the typical PP additive package, with much wider loading ranges.<\/p>\n\n\n\n

    \n
  • Flame retardants<\/strong> \u2014 Brominated systems like BDDP with antimony trioxide synergist run at 5-10 wt% to hit UL 94 V-0 or V-2. Halogen-free mineral systems (ATH, Mg(OH)\u2082) need 15-30 wt% for the same rating, and at those loadings mechanical properties change measurably.<\/li>\n<\/ul>\n\n\n\n
      \n
    • Controlled-rheology peroxide<\/strong> \u2014 DHBP (Luperox 101) at 200-600 ppm at the extruder visbreaks the resin to raise MFI and narrow molecular-weight distribution. Producer-side chemistry, generating the “CR” grade variants in supplier catalogs.<\/li>\n<\/ul>\n\n\n\n
        \n
      • Color masterbatch<\/strong> \u2014 Letdown ratio 1-4 wt% depending on pigment loading in the carrier. Color arrives as a separate pellet stream fed at the throat; the base-resin COA additive note does not include it.<\/li>\n<\/ul>\n\n\n\n

        The Producer Baseline: What Additives Already Ship in PP Pellets<\/h2>\n\n\n\n

        The most useful mental model for reading a PP additive note on a COA is the two-layer one: producer baseline plus compounder top-up. State-owned Chinese producers \u2014 Sinopec, PetroChina (including the Dushanzi complex), and CNOOC \u2014 ship general-purpose PP grades with a baseline antioxidant and slip package added at the polymerization plant.<\/p>\n\n\n\n

        A typical baseline for a homopolymer like PetroChina T30S or a random copolymer like PetroChina Dushanzi T4401 lands at 800-1500 ppm phenolic AO, 800-1500 ppm phosphite, and 500-1500 ppm slip. The compounder layers more on top depending on end-use.<\/p>\n\n\n\n

        For outdoor: 1000-5000 ppm of HALS, often 2-5\u00d7 the baseline stabilizer total. For clear injection: 2000-2500 ppm of sorbitol clarifier. For automotive interior: the HALS + slip package above.<\/p>\n\n\n\n

        The COA additive note describes the producer baseline. The TDS for a compounded grade describes the full package.<\/p>\n\n\n\n

        \"Reading<\/figure>\n\n\n\n

        What COA Readers Most Often Misjudge<\/h2>\n\n\n\n

        The mistake I see most often is treating the producer’s baseline phenolic + phosphite + slip note as the full additive package, then specifying an outdoor or automotive part against it. That baseline is correct for a generic injection-molded indoor part. It is not correct for anything that sees UV, sustained heat, or a slip-critical film line.<\/p>\n\n\n\n

        Read the COA additive note for what it is \u2014 the producer baseline. Ask the compounder for the full TDS, including the HALS, UV absorber, clarifier, or specialty top-up that brings the package to the end-use spec. A loading that is normal for an injection cup is wrong for a woven bag in Riyadh sunlight.<\/p>\n\n\n\n