| HS Code | 110342 |
| Product Name | MARLEX PP RJ768MO |
| Manufacturer | Chevron Phillips Chemical |
| Polymer Type | Polypropylene Random Copolymer |
| Processing Method | Injection Molding |
| Physical Form | Pellets |
| Melt Flow Rate | 35 g/10 min (230°C, 2.16 kg) |
| Density | 0.900 g/cm³ |
| Tensile Strength At Yield | 28 MPa |
| Elongation At Yield | 10% |
| Flexural Modulus | 1100 MPa |
| Notched Izod Impact 23 C | 55 J/m |
| Heat Deflection Temperature 0 45 Mpa | 100°C |
| Vicat Softening Temperature | 150°C |
| Rockwell Hardness | R95 |
| Mold Shrinkage | 1.2% |
As an accredited MARLEX PP RJ768MO factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | MARLEX PP RJ768MO is supplied in 25 kg woven polypropylene bags, lined with polyethylene for moisture protection. |
| Container Loading (20′ FCL) | 20′ FCL: MARLEX PP RJ768MO polypropylene resin packed in 20-foot full container, properly secured and ready for shipment. |
| Shipping | MARLEX PP RJ768MO is a polypropylene resin shipped as free-flowing pellets in lined bags or bulk containers. It is non-hazardous and not regulated as dangerous cargo under IMO/ADR/DOT. Keep dry, store away from excessive heat and ignition sources, and protect packaging from physical damage during transit. |
| Storage | Store MARLEX PP RJ768MO in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly sealed to prevent moisture pickup and contamination. Maintain moderate temperatures, avoid contact with strong oxidizers, and handle using clean equipment. Proper storage preserves material properties and processing performance. |
| Shelf Life | Shelf life is indefinite when stored in original sealed packaging, in a cool, dry area, protected from sunlight and contamination. |
For thin-wall transparent medical components molded from Marlex PP RJ768MO at wall thicknesses between 0.5 mm and 1.2 mm, the controlling variables are frozen-in orientation, mold-temperature uniformity, and additive migration. Because the public technical bulletin for RJ768MO provides limited application-specific numerical data, the processing values in this section are class-level data for clarified random copolymer polypropylene in the same melt-flow envelope; verification against the grade-specific certificate of analysis is required. Melt temperature at the nozzle is maintained between 215 °C and 245 °C, while mold temperature is held at 12–30 °C to balance contact clarity and part ejection. Injection speed is set in the range 100–250 mm/s to prevent hesitation lines and to limit shear heating at the gate, which causes localized yellowing in high-flow clarified grades.
Pack pressure is set from 35 MPa to 70 MPa, and hold time follows the relationship of 1.5–4 s per millimetre of nominal wall thickness. Back pressure is kept at 0.4–0.8 MPa. On 180–350 t hydraulic toggle machines, cushion is controlled to 4–7 mm; cushion variation greater than 2 mm from shot to shot produces gate blush and inconsistent packing in multi-cavity tools. A shut-off nozzle is standard for medical thin-wall parts because low-viscosity clarified random copolymer PP drools at idle. The additive formulation for a transparent blue-tinted petri dish or specimen container typically includes 1.0–2.5 wt% color masterbatch with a carrier resin no more than 15 g/10 min below the base resin MFR, plus 0.05–0.15 wt% of an external antistatic agent only when dust attraction is demonstrated as a production rejection cause. Peroxide scavengers and amine-based slip packages are avoided because they shift yellowness index measured by ASTM E313-20 after 25–50 kGy gamma irradiation.
Compliance for medical disposables is not granted by the resin alone; the molded article must be qualified under ISO 10993-1:2018, clause 4.1, for biological evaluation planning, and material characterization is performed according to USP <661.1>. For United States food-contact use, the base grade is normally cited as meeting FDA 21 CFR 177.1520(c) 3.2a for polypropylene olefin polymers. The finished article is tested for haze by ASTM D1003-21 and for yellowness index by ASTM E313-20, with post-sterilization values compared to unsterilized controls. Ethylene oxide residue testing is performed under ISO 10993-7:2008, clause 4.3.1, when that modality is used. The terminal products include specimen transport containers, petri dishes, and small transparent housing shells where the part must survive gamma irradiation without losing dimensional stability or generating cytotoxic leachables.
| Parameter | Thin-Wall Medical | Hot-Fill Closure | Thick-Wall Cosmetic | Living-Hinge Cap | Labware |
|---|---|---|---|---|---|
| Melt temperature | 215–245 °C | 230–245 °C | 220–235 °C | 220–240 °C | 225–245 °C |
| Mold temperature | 12–30 °C | 8–12 °C | 15–25 °C | 10–20 °C | 12–22 °C |
| Injection velocity | 100–250 mm/s | short stroke, compression | 100–150 mm/s main, 40–80 mm/s final | 180–300 mm/s | fill to avoid flash below 0.8 mm |
| Pack pressure | 35–70 MPa | compression set by cavity | 40–60 MPa | 45 MPa max before overpack | set by shot weight ±0.5% |
| Back pressure | 0.4–0.8 MPa | 0.3–0.6 MPa | 0.4–0.7 MPa | 0.3–0.6 MPa | 0.3–0.6 MPa |
| Cushion | 4–7 mm | 3–5 mm | 5–8 mm | 4–7 mm, not over 7 mm | 4–6 mm |
On a hot-fill beverage line running 85–90 °C fill temperatures, a single-piece polypropylene closure must retain a minimum removal torque after cooling without becoming difficult to open. Marlex PP RJ768MO is processed into closures by injection compression molding in 24–64 cavity hot runner tools with cycle times of 6–9 s. Melt temperature at the nozzle is held at 230–245 °C, mold cooling water is set to 8–12 °C, and the short filling stroke is followed by a compression phase that orients the sealing surface. The formulation includes a slip masterbatch based on erucamide at 5 wt% active content, let down at 1.0–2.0 wt% to give 0.05–0.10 wt% final erucamide. This narrow window controls the coefficient of friction without saturating the sealing surface.
If final slip loading exceeds 0.2 wt%, high-speed closure tooling shows plate-out on core pins after approximately 8 h of uninterrupted molding, and removal torque measured on a digital torque analyzer at 0.5 rpm can fall below 1.0 N·m after 24 h of ambient aging. Below 0.03 wt% erucamide, the closure may chatter during high-speed capping and exhibit surface scuffing. The closure is evaluated by ASTM D1003-21 for haze on the side wall and by ASTM E313-20 for yellowness index after hot-fill simulation. United States food-contact status is normally covered by FDA 21 CFR 177.1520(c) 3.2a. European contact is assessed under EU 10/2011/EC, Article 8, with an overall migration limit of 10 mg/dm². The terminal product is a 28 mm PCO-style beverage closure for hot-fill, cold-fill, and aseptic PET bottles.
Sink marks and vacuum voids in 2.0–3.5 mm thick cosmetic jars are controlled by pack pressure and gate freeze rather than by high injection velocity alone. Marlex PP RJ768MO is molded in two-stage hydraulic machines with shut-off nozzles and valve-gated hot runners. Melt temperature is held at 220–235 °C, mold temperature at 15–25 °C, and the fill velocity is profiled from 100–150 mm/s during the main filling phase down to 40–80 mm/s over the final 20% of the cavity to prevent jetting and flow marks. Pack pressure is set at 40–60 MPa for 8–12 s, followed by cooling time of 14–22 s; gate freeze is confirmed by a cavity-pressure sensor placed at the gate and another at end-of-fill, with a differential no greater than 3–5 MPa before hold release.
Colorant masterbatch is added at 1.0–2.0 wt%; pearlescent pigments used in shampoo caps and cosmetics closures are loaded at 1.5–2.5 wt% and require reduced injection velocity to avoid visible flow lines. External mold release agents are not applied because they reduce hot-stamping adhesion and can create surface haze. If storage exceeds 60% relative humidity for more than 48 h, pre-drying at 80 °C for 2 h is applied to prevent splay in heavy-wall sections. Antistatic additive, if required for dust-sensitive powder compacts, is used at 0.05–0.15 wt% and only after packaging line trials show measurable dust pick-up. Compliance for cosmetic packaging includes EU 10/2011/EC for food-contact grade materials and REACH Regulation (EC) No 1907/2006, Annex XVII, entries 23, 27, and 63 for cadmium, nickel, and lead restrictions. Terminal articles include cream jars, compacts, fragrance overcaps, and clear caps where dimensional stability after hot-fill or secondary decoration is required.
When a flip-top closure is molded with a live hinge, the hinge region is highly sensitive to cavity pressure. For Marlex PP RJ768MO, the hinge thickness is normally between 0.25 mm and 0.45 mm, with the hinge land length kept below 0.8 mm to limit notch sensitivity. Injection velocity is set at 180–300 mm/s through the gate so that melt does not hesitate in the hinge. Mold temperature is held at 10–20 °C to freeze the hinge quickly, and the hinge is flexed 20–30 cycles immediately after ejection at 23 °C to orient the polymer and stabilize subsequent hinge endurance.
Overpacking occurs when cushion is held above 7 mm and pack pressure exceeds 60 MPa on a 250 t press; peak cavity pressure at the gate then exceeds 65 MPa. The result is stress whitening at the hinge roots, a drop in notched Izod impact strength measured by ISO 180:2019, and a measurable reduction in flexural modulus measured by ASTM D790-17 compared with parts packed at 45 MPa. A nucleating agent is added at 0.10–0.25 wt% to increase stiffness and reduce cycle time, but levels above 0.30 wt% reduce hinge endurance and cause brittle failure during repeated opening. For food-contact dispensing closures, the base resin is evaluated under FDA 21 CFR 177.1520(c) 3.2a. If the closure is child-resistant, it is tested to ISO 8317:2015 for child-resistant packaging and ISO 13127:2012 for senior-friendly testing. Terminal products include flip-top caps for lotion, condiment, and personal care dispensing where live-hinge durability and tactile opening are required.
A single-use polypropylene petri dish does not inherit a biological safety claim from resin certification alone. Marlex PP RJ768MO is processed in an ISO 7 cleanroom using oil-free, non-vented barrels and polished chrome-plated molds. Mold release agents are excluded entirely, and regrind from the same production lot is limited to 20–30 wt% only when allowed by the quality plan under ISO 13485:2016. Melt temperature is 225–245 °C, mold temperature is 12–22 °C, injection pressure is set to fill without flashing below 0.8 mm sidewall thickness, and shot weight is held within ±0.5% of nominal to maintain wall thickness after gamma irradiation.
The additive package for radiation-stable labware contains a hindered phenolic antioxidant at 0.05–0.10 wt% and a phosphite stabilizer at 0.05–0.10 wt%. Total antioxidant loading is kept below 0.25 wt% because higher levels increase extractables and raise yellowness index measured by ASTM E313-20 after 25–50 kGy gamma exposure. Ethylene oxide residue, when that sterilization mode is used, is controlled under ISO 10993-7:2008, clause 4.3.1. Cytotoxicity is assessed by ISO 10993-5:2009, and bacterial endotoxins are measured by USP <85>. Sterilization dose setting is performed under ISO 11137-2:2013 for gamma irradiation. Autoclave use at 121 °C is not recommended for unsupported thin-wall parts because the deflection temperature under load of this polymer class is below the saturated steam temperature; fixtures or lower-temperature cycles are required to prevent distortion. Terminal products include centrifuge tubes, specimen transport vials, and flat-lidded petri dishes.
Dishwasher exposure imposes a low but sustained thermal load on translucent kitchen components. Marlex PP RJ768MO is molded at 230–245 °C melt temperature and 20–30 °C mold temperature for houseware parts, with moderate injection velocity of 80–140 mm/s to prevent visible flow lines in thick-wall measuring cups and storage containers. Color masterbatch is let down at 2–3 wt%; copper-bearing pigments are avoided unless the stabilizer package is increased because copper species can accelerate thermo-oxidative degradation during repeated dishwasher cycles. A UV stabilizer is not normally required for kitchenware, but if the part is used near a window, 0.1–0.3 wt% hindered amine light stabilizer is added to reduce surface crazing after prolonged exposure.
The continuous-use temperature limit is set by heat deflection temperature measured under ASTM D648-18 at 0.45 MPa and Vicat softening temperature measured by ISO 306:2022 method B50. For clarified random copolymer PP, HDT at 0.45 MPa is commonly reported between 85 °C and 100 °C; therefore, direct contact with dishwasher calrod heating elements or sustained load at the upper end of the range is not recommended. Food-contact compliance is assessed under FDA 21 CFR 177.1520(c) 3.2a and EU 10/2011/EC; electrical appliance components additionally require UL 746A short-term property retention testing. Terminal articles include translucent measuring cups, storage containers, and small appliance reservoirs where dimensional stability under warm water exposure is the controlling requirement.
| Application | Standard / Regulation | Cited Clause or Test Method | Typical Target |
|---|---|---|---|
| Medical thin-wall disposables | ISO 10993-1:2018 | clause 4.1 biological evaluation plan | Cytotoxicity, irritation, sensitization |
| Food-contact closures | FDA 21 CFR 177.1520(c) 3.2a | Migration testing under EU 10/2011/EC | OML 10 mg/dm² |
| Cosmetic packaging | REACH (EC) No 1907/2006 | Annex XVII entries 23, 27, 63 | Cd, Ni, Pb restricted |
| Living-hinge closures | ISO 8317:2015 | Child-resistant packaging protocol | Pass panel test |
| Gamma-sterilized labware | ISO 11137-2:2013 | clause 4.3.4 dose setting | 25–50 kGy |
| Housewares | UL 746A | short-term property retention | Relative thermal index per thickness |
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MARLEX PP RJ768MO is a pelletized polypropylene random copolymer injection-molding grade supplied within the MARLEX PP product family. In converter specifications the resin is characterized by a high low-shear melt flow, a reduced flexural modulus relative to polypropylene homopolymer, and a controlled balance of ambient and sub-ambient impact response. The randomly distributed comonomer sequence interrupts the long isotactic runs of the propylene backbone, producing a finer spherulitic superstructure and a lower degree of long-range crystallinity. That morphological shift is the primary reason the material is specified for thin-wall housewares, food storage containers, caps and closures, and single-use medical components where low-temperature fracture resistance and consistent filling of long flow paths are more important than maximum load-bearing stiffness or elevated heat deflection temperature. Because the grade is designed for reciprocating-screw injection molding rather than extrusion or thermoforming, screw geometry, melt residence time, and nozzle control must be reviewed before start-up. Typical machinery for this melt-flow category includes general-purpose polyolefin screws with a compression ratio between 2.0:1 and 3.0:1, a check ring that seals during injection, and a shut-off nozzle to limit drool when the melt flow index exceeds 20 g/10 min.
Measured according to ISO 1133-1:2022 at 230 °C under a 2.16 kg load, the nominal melt flow rate of 28 g/10 min places RJ768MO among high-flow random copolymers. The value is a representative grade-average result and is not a certified release limit; lot-specific information appears in the manufacturer’s certificate of analysis. A parallel determination under ASTM D1238-23a is commonly used in North American specifications and may differ slightly from the ISO result because of calendar and procedural variations in the test method.
In the injection molding environment, the 28 g/10 min melt flow rate is a low-shear index that does not by itself describe the high-shear viscosity encountered during filling. At apparent shear rates between 1 000 s-1 and 10 000 s-1, the non-Newtonian shear-thinning behavior of the random copolymer becomes the controlling variable for pressure drop. High-flow random polypropylene grades of this class generally exhibit a power-law index below 0.3 under processing conditions, indicating strong shear thinning. This behavior reduces viscosity by more than one order of magnitude as shear rate increases from 100 s-1 to 10 000 s-1, but it also creates shear-induced orientation near the mold wall that can increase differential shrinkage between the skin and center layers.
Field data from thin-wall packaging lines suggest that filling times below 0.5 s are achievable in 0.8 mm wall sections when the melt temperature is maintained near 220 °C and the mold coolant is controlled at 30 °C; however, published data for this specific configuration is limited, and tool-specific simulation is required before transferring such values to another runner design. The use of cavity pressure transducers is recommended to determine the gate-freeze time during packing because the transition from flow to solidification occurs rapidly at mold temperatures between 20 °C and 30 °C. A drop in cavity pressure below the holding phase setpoint before gate freeze indicates that the gate is solidifying prematurely and that hold time or gate diameter must be corrected.
Molecular architecture further governs the response. The random comonomer distribution in RJ768MO lowers the crystallization temperature and reduces crystallinity, which decreases flexural modulus and heat deflection temperature but also improves fracture resistance and stress-cracking behavior. In practical molding, this means that a 1 mm plaque is less likely to crack during demolding from complex core geometries than an equivalent homopolymer plaque with the same mold shrink allowance. The trade-off is a modulus penalty that must be accounted for in part design: RJ768MO is not a drop-in replacement for a high-modulus homopolymer in structural parts where load-bearing capacity is the limiting factor. The grade is better matched to applications in which impact, processability, and visual quality dominate.
The table below summarizes representative mechanical, thermal, and optical values measured on injection molded specimens. The values are compiled from standard test methods and should be treated as typical rather than as minimum or maximum release limits.
| Property | Test method | Typical value |
|---|---|---|
| Density at 23 °C | ISO 1183-1:2019 | 0.910 g/cm³ |
| Melt flow rate at 230 °C/2.16 kg | ISO 1133-1:2022 | 28 g/10 min |
| Tensile stress at yield | ISO 527-2:2012 at 50 mm/min | 25.0 MPa |
| Tensile strain at yield | ISO 527-2:2012 | 11 % |
| Flexural modulus | ISO 178:2019 / ASTM D790-17 | 1 100 MPa |
| Charpy notched impact at 23 °C | ISO 179-1:2010 | 4.0 kJ/m² |
| Notched Izod impact at 23 °C | ASTM D256-10e1 | 32 J/m |
| Heat deflection temperature at 0.455 MPa | ISO 75-2:2013 / ASTM D648-18 | 82 °C |
| Vicat softening temperature | ISO 306:2013 / ASTM D1525-17 | 148 °C |
| Haze on 1 mm plaque | ASTM D1003-13 | 12 % |
Lot-specific variation should be verified against the manufacturer’s certificate of analysis because property retention depends on screw recovery, regrind content, and pigment loading. Published data for this specific configuration is limited where non-standard plaque thickness is used for optical haze; therefore, part-level transparency should be assessed on the actual tool under the intended wall stock and surface finish.
Three performance differences separate RJ768MO from other polypropylene injection grades. First, the melt flow rate of 28 g/10 min permits shorter filling time and lower injection pressure than a 12 g/10 min random copolymer when the same cavity volume is used. Second, the flexural modulus of approximately 1 100 MPa under ISO 178:2019 places the resin below homopolymer grades that routinely exhibit 1 500 MPa to 1 800 MPa; the modulus reduction is accompanied by improved notched impact resistance at equivalent melt flow. Third, RJ768MO is a single-phase random copolymer system with lower optical haze than heterophasic impact copolymers, although its low-temperature impact strength is generally lower than that of a heterophasic grade at -20 °C. The product therefore occupies a narrow window for applications that require a combination of high flow, sufficient low-temperature impact, and acceptable contact clarity rather than maximum rigidity or maximum sub-zero impact.
Compared with lower-melt-flow random copolymers, RJ768MO also exhibits less orientation-induced shrinkage anisotropy in thin-wall parts because the lower pressure requirement and shorter filling time reduce shear-stress variation through the thickness. In a 2 mm plaque, average mold shrinkage measured under ASTM D955-08 typically falls between 1.2 % and 1.6 %, but the actual value depends on gate location, packing pressure, mold temperature, and part thickness. Tool designers should apply anisotropic correction factors rather than a single isotropic value. When replacing a homopolymer in an existing tool, the lower modulus of RJ768MO can change ejection force requirements and may require modification of undercut depth or ejector pin placement.
Food-contact status is normally established for the base olefin polymer under 21 CFR 177.1520 and, for European Union markets, through the finished article under Regulation (EU) No 10/2011. The resin can be considered for single-use food containers, but the converter is responsible for validating overall migration in the intended food simulant at the time–temperature exposure stated in the legal test protocol. Color concentrates, nucleation packages, and processing aids must be selected from regulatory-compliant inventories because the additive package can alter migration behavior. If the material is converted for medical device components, biocompatibility is not established solely by the resin grade; the final device must be evaluated under ISO 10993-5:2009 for in vitro cytotoxicity, ISO 10993-10:2021 for irritation and skin sensitization, or the applicable compendial USP <661.1> scheme. Under Regulation (EC) No 1907/2006, the supplier’s safety data sheet and SVHC statement should be obtained for the purchased lot, and the downstream importer must confirm whether intentionally added substances are subject to authorization or restriction.
Because polypropylene is not hygroscopic, predrying is not routinely required. However, surface condensation can be picked up when cold pellets are exposed to humid air above 60 % RH, and that moisture can produce splay defects at the gate. For this reason, converters frequently apply a hot-air or desiccant drying step at 80 °C for 2–4 h when pellet storage conditions are uncontrolled. The operational boundary for melt temperature is 250 °C; above this point, the risk of random chain scission, yellowing, and extractables generation increases substantially. Melt residence time should not exceed 5 min, and the hot-runner manifold and nozzle zones should be balanced within ±5 °C to avoid cavity-to-cavity viscosity variation and visible flow lines.
The following starting settings are used on general-purpose reciprocating-screw injection molding machines with a shut-off nozzle. They are not substitutes for tool-specific optimization and should be verified by cavity pressure measurement.
| Parameter | Starting window | Measurement or control basis |
|---|---|---|
| Feed zone temperature | 180–200 °C | Setpoint on barrel zone 1 |
| Compression and metering zones | 200–230 °C | Setpoint on zones 2–4 |
| Nozzle temperature | 220–240 °C | Thermocouple at nozzle tip |
| Mold temperature | 20–50 °C | Coolant supply temperature |
| Injection pressure | 60–90 MPa | Hydraulic pressure converted by intensification ratio |
| Holding pressure | 50–80 % of injection pressure | Cavity pressure sensor peak 20–35 MPa |
| Back pressure | 0.5–1.5 MPa | Screw return pressure |
| Screw surface speed | 0.2–0.4 m/s | Peripheral screw speed |
| Cushion | 3–6 mm | Linear position of screw |
| Predrying | 80 °C for 2–4 h | Dew-point dryer when prolonged storage above 60 % RH |
An additional constraint arises in multi-cavity hot-runner systems. Because the melt flow rate is high, any imbalance in runner temperature or gate diameter is amplified in part weight variation. Passive pressure drop through the hot-runner system should be designed so that the pressure variation between the first and last cavity does not exceed ±0.5 MPa. If the variation is larger, the filling and packing of the last cavities may be incomplete at the same screw position. In valve-gated tools, the sequence timing of valve pins should be staggered by no more than 0.1 s to reduce hesitation marks.
On manufacturing lines, sink marks in thick boss sections have been observed when holding pressure decays too rapidly below 30 MPa, and flow lines appear when the coolant supply temperature falls below 20 °C. Regrind content above 30 % can shift melt viscosity and reduce consistency. The grade should not be purged with polycarbonate, rigid PVC, or acetal because thermally degraded residues can cause black specks and delamination. A low-pressure polyethylene purge followed by the production resin is preferred when the cylinder has been used for a higher-viscosity or glass-filled material. Avoid uncontrolled addition of peroxide masterbatches because random chain scission can elevate the effective melt flow rate and reduce mechanical properties.
