When Fragrance-Containing Cream Jars Require Both Clarity and Stress-Crack Resistance

Clear outer shells for oil-in-water and water-in-oil cream formulations are produced from Kumho Petrochemical SAN 330NI as a direct replacement for general-purpose polystyrene in tools that require higher resistance to aliphatic cream bases and repeated cap tightening torque. The material is introduced at 100 wt% virgin pellet in high-gloss transparent jars and at 85–90 wt% virgin with 10–15 wt% regrind derived from sorted sprues, runners, and hot-runner drops in opaque inner collars or secondary caps. A SAN-carrier colour masterbatch is metered at 1.5–2.5 wt%; masterbatch loadings above 3.0 wt% raise injection-moulded haze from approximately 2.0% to 5.5–6.5% when tested per ASTM D1003-13, so side-feed gravimetric dosing is preferred over hand-mix additions. The moulding process is multi-cavity injection moulding on machines with clamp forces between 5,000 kN and 6,500 kN, reciprocating screw L/D ratios of 20:1–22:1, and non-return ring clearances held below 0.10 mm to prevent melt backflow and short-shot variability. Melt temperature is controlled at 230–250°C, mould temperature at 35–55°C, and holding pressure is profiled from 70% to 90% of peak injection pressure to suppress sink marks at hinge bosses and thread roots. Pre-drying in desiccant dryers at 80°C for 2–4 hours to a residual moisture level of ≤0.05 wt% per ISO 15512:2019 is required when ambient relative humidity exceeds 60%; batches left in open hoppers without drying exhibit splay and silver streaks in hot-runner tools. The relevant compliance assessment includes REACH Regulation (EC) No 1907/2006 substance screening, EU Packaging and Packaging Waste Directive 94/62/EC heavy metal limits with a total cadmium, lead, mercury, and hexavalent chromium sum below 100 mg/kg, and chemical compatibility testing of the moulded article under ISO 175:2010 using emulsion and alcohol-water simulants representative of the finished cosmetic formulation. Terminal finished product types include transparent cream jars, outer caps, lipstick tube casings, compact bases, and fragrance gift-set covers. On production floor data from multi-cavity tools, tunnel gates positioned in non-visible recesses below the base plate reduce gate blush at injection velocities below 45 mm/s; velocity settings above 50 mm/s are associated in high-flow SAN technical bulletins with increased melt-front turbulence, visual weld lines, and reduced clarity at the gate boundary.

Clear sump bodies and filter bowls for point-of-use water treatment systems are moulded from transparent styrene-acrylonitrile copolymer when the housing must retain dimensional stability under intermittent hydrostatic pressure, resist mineral scale accumulation, and avoid stress whitening around threaded ports. For wetted pressure-bearing walls and threads, the polymer is used at 100 wt% virgin; regrind is excluded from these zones because the notch sensitivity of styrenic copolymers concentrates stress at weld lines and thread roots. Regrind may be introduced at ≤5 wt% only into non-wetted overmoulded knobs or external grips, and the recycled fraction must be dried to ≤0.03 wt% moisture before blending. Compliance for potable water contact is evaluated under NSF/ANSI 61 extraction testing, US FDA 21 CFR 177.1040 for acrylonitrile-styrene copolymers, and EU Regulation (EU) No 10/2011 with the overall migration limit of 10 mg/dm². Structural acceptance uses tensile yield strength measured per ASTM D638-14 and flexural modulus per ASTM D790-17 on dry-as-moulded specimens; hydrostatic burst validation is performed on complete housings after 1,000 h water contact at 23°C and after thermal cycling from 5°C to 45°C. The downstream production process is injection moulding with sequential valve-gated hot-runner manifolds, screw L/D of 20:1, shot size maintained between 30% and 70% of barrel capacity, melt temperature 240–255°C, and mould temperature 50–70°C to reduce residual orientation. Threads are formed by unscrewing cores or collapsible cores rather than thread splits to avoid flash at the sealing shoulder; hydraulic core pulls and position monitoring prevent mould damage during ejection. A 1.2 kg filter bowl in a 2,500 kN machine typically cycles at 60–90 s, with cooling time limited by the thickest thread boss rather than the bowl sidewall. Terminal finished products are clear filter sumps, replacement bowls for under-sink and countertop filtration units, and transparent housings for low-pressure point-of-use systems. SAN 330NI is not specified for continuous service above 70°C or for hot-water pressure vessels; polysulfone or polyamide 66 is required in those conditions. Assembly adhesives containing ketones, esters, or aromatic hydrocarbons are incompatible with SAN under hoop stress and cause environmental stress cracking in threaded regions, particularly when thread engagement torque exceeds 10 N·m on 50 mm diameter closures.

What Limits Impact Performance in Clear Blender Jar Moulding?

Transparent blender jars, juicer bowls, and refrigerator crisper drawers are moulded from SAN 330NI when food-contact clarity must be retained after repeated dishwasher exposure and low-temperature impact against ice or frozen fruit. The recommended formulation for a clear blender jar is 100 wt% virgin resin; regrind is limited to ≤10 wt% in transparent sidewalls and ≤20 wt% in opaque base adapters, provided the notched Izod impact strength measured per ASTM D256-10 remains within the supplier specification for the virgin lot. A food-contact-approved colour masterbatch is added at 1.0–2.0 wt% only when tinted jars are specified; pigments that increase haze above 4.0% per ASTM D1003-13 are rejected for transparent bowls. The production process is thick-wall injection moulding with wall sections between 4 mm and 6 mm, melt temperature 230–250°C, mould temperature 40–60°C, and valve-gated hot runner systems to eliminate sprue vestiges on the bowl interior. Screw L/D ratios of 20:1 with a compression ratio of 2.0–2.5:1 are used; shot weights are kept between 40% and 60% of barrel capacity to reduce residence time and yellowing. Post-mould annealing at 70–80°C for 1–2 hours reduces residual stress around thick bosses and thread starts, which is critical for blender jar bases where impact loads concentrate at transition radii. The terminal finished product types include clear blender jars, extractor bowls, coffee machine water reservoirs, refrigerator crisper drawers, and transparent storage containers for small household appliances. Compliance for repeated food contact requires US FDA 21 CFR 177.1040, EU Regulation (EU) No 10/2011, and GB 4806.7-2023 for plastic food-contact materials; appliance-level safety is evaluated under IEC 60335-1:2020. Operational boundaries are defined by the combination of low temperature impact and dishwashing chemistry: SAN 330NI is not microwave-safe and should not be exposed to dishwasher drying cycles above 65°C for extended periods because repeated thermal shock after aggressive detergent contact can initiate microcracks at gate vestiges and weld lines.

Trigger Sprayer Closure Moulding and Solvent Compatibility Limits

Trigger sprayer bodies, lotion pump closures, and dispensing heads for household and personal care liquids are moulded from SAN 330NI because the acrylonitrile component increases resistance to aqueous surfactant solutions and diluted glycol ether solvents compared with polystyrene. The resin is used at 100 wt% virgin in the primary chemical-contact body and nozzle housing; regrind is restricted to ≤10 wt% in non-contact external shrouds, colour-matched overmouldings, or dust caps. Colour concentrate based on a styrene-acrylonitrile carrier is metered at 1.5–2.0 wt% for opaque grades, while transparent sprayer bodies are processed without pigment to maintain visual inspection clarity. The downstream process is multi-cavity injection moulding on hot-runner tools with valve-gate control, melt temperature 235–250°C, mould temperature 40–60°C, and holding pressure maintained until gate freeze to prevent dimensional drift in snap-fit closure skirts. Screw L/D is typically 20:1 with a non-return ring clearance below 0.10 mm; injection speed is profiled to prevent jetting in elongated nozzle sections. Terminal finished product types include trigger sprayer bodies, lotion pump bases, dispensing caps, overcaps, and aerosol collar components. Compliance is assessed under REACH Regulation (EC) No 1907/2006, EU Packaging and Packaging Waste Directive 94/62/EC, and the heavy metal limits of 100 mg/kg total for lead, cadmium, mercury, and hexavalent chromium. Solvent compatibility is validated by immersion testing per ISO 175:2010 in representative surfactant systems containing 1–5 wt% non-ionic surfactant and 0.5–2.0 wt% glycol ether. The operational boundary is sharply defined: continuous contact with concentrated esters, ketones, or aromatic hydrocarbon-based cleaning solvents is not recommended because these media plasticise the SAN matrix and reduce hoop stress retention in threaded closure seals. Published data for this specific grade under aggressive solvent immersion is limited; each cleaning formulation should be tested in the finished closure geometry rather than on generic tensile bars.

Two-piece transparent tumblers, salad bowls, and refrigerator storage containers are injection moulded from SAN 330NI when the part must resist staining from tomato oil, tea, coffee, and citrus juices while maintaining glass-like clarity at ambient food-service temperatures. The body is moulded at 100 wt% virgin resin for visible surfaces; sorted regrind from sprues and rejected pre-colour parts is added at ≤20 wt% in opaque bases, foot rings, or outer shells only after drying to ≤0.05 wt% moisture. Food-contact colour masterbatch is metered at 1.5–2.0 wt% in tinted versions, but transparent tumblers are typically produced without masterbatch to hold total luminous transmittance above 88% per ASTM D1003-13. The downstream process is high-cavitation injection moulding on stack moulds with 32–64 cavities, melt temperature 230–250°C, mould temperature 40–50°C, and cycle times between 15 s and 25 s depending on wall thickness and stack layout. Ejector pins are positioned in non-visual base rims to avoid push marks on the transparent sidewall; polishing of cavity surfaces to SPI A-1 finish is required for acceptable gloss. Terminal finished product types include stackable drinkware, serving bowls, refrigerator storage boxes, and clear compartments for domestic water dispensers. Compliance for food contact is based on US FDA 21 CFR 177.1040, EU Regulation (EU) No 10/2011, and GB 4806.7-2023; the product is not approved for microwave reheating or for continuous dishwasher drying above 65°C because repeated hot-air drying after alkaline detergent exposure can produce microcracking around injection gate remnants. Published data for SAN 330NI under repeated domestic dishwasher cycles is limited; processors supplying retail kitchenware typically validate one year of cyclical dishwasher simulation on production tooling before release.

Can SAN 330NI Replace PMMA in Low-Load Display Glazing?

SAN 330NI is selected for indoor point-of-sale display panels, audio equipment dust covers, vending machine display windows, and transparent electronics housings where impact load is low and PMMA price or processing stability is not acceptable. The compound is processed at 100 wt% virgin resin with 1.0–2.0 wt% antistatic masterbatch to reduce dust attraction on display surfaces; regrind is limited to ≤10 wt% in non-visual structural ribs or rear mounting bosses. Injection moulding is performed on polished cavity surfaces with surface roughness below Ra 0.05 µm, melt temperature 230–250°C, mould temperature 60–80°C, and low-to-moderate injection velocity to avoid silver streaks and flow lines across large flat windows. Hot-runner valve gates are positioned at the edge of the visible face, and holding pressure is ramped downward before gate freeze to prevent birefringence at the gate boundary. Terminal finished product types include transparent display glazing, dust covers for audio and laboratory instruments, vending machine front panels, and clear covers for low-voltage electrical enclosures. Compliance is assessed under UL 94 HB flammability classification, RoHS Directive 2011/65/EU, IEC 62368-1:2023 for audio/video and ICT equipment enclosures, and REACH Regulation (EC) No 1907/2006. The operational boundary is defined by surface durability: SAN 330NI does not match PMMA in Taber haze retention after 100 cycles under ASTM D4060-19, and it is not recommended for outdoor display glazing where ultraviolet exposure and windborne abrasion are continuous. Published comparative abrasion data for this specific grade under ASTM D4060-19 is limited; PMMA remains the reference material for high-clarity display applications requiring the lowest possible Taber haze increase.