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HIPS

Poliestireno de Alto Impacto

HIPS·Polystyrenes·Amorphous

HIPS (High Impact Polystyrene) is the "tough sibling" of GPPS: same PS backbone but with 5–15% dispersed polybutadiene that absorbs impact energy. Result: it loses GPPS transparency (becomes opaque matte), but gains 5–10× more impact resistance, keeping the low cost and easy processing typical of the polystyrene family.

Dominant application #1: refrigerator and freezer liners — most white interiors of household refrigerators and freezers worldwide are thermoformed HIPS (vacuum forming). Application #2: yogurt cups and thermoformed food-packaging containers. It's also the material of choice for cheap hangers, disposable food trays, low-cost toys, and budget automotive interiors. You know it by trade names: Styron HIPS (Trinseo), Styrolution PS Impact (INEOS), SABIC PS-HI.

Here we compile the reference ranges from the PDS, plus questions that come up over and over on the shop floor: HIPS vs GPPS vs ABS, thermoforming vs injection, food-safe, unbeatable costs. Share your experience in the comments — ranges shift by manufacturer and butadiene content, and collective discussion is what gets us out of the jams.

The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.

This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.

These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.

General Properties

Chemical StructureAmorphous
Specific Gravity (Density)1.04:1
L/D Ratio18 – 24
Compression Ratio2 – 3
Tonnage Factor3.09 – 6.18kN/cm²
Thermal Diffusivity0.0683mm²/s
Max Shear Rate40,0001/s
Shrinkage0.2 – 0.8%
Regrind30%
Heat Deflection (HDT) @ 1.82 MPa74°C
Glass Transition (Tg) @ 10°C/min91°C
Vicat Softening @ 50N85°C

Drying

Drying Temperature60 – 79°C
Drying Time1 – 4h
Recommended Moisture0.5%
Recommended Dryer TypeAir
Dew Point-40°C

Temperatures

Melt218 – 246°C
Nozzle221 – 232°C
Front221 – 232°C
Middle210 – 221°C
Rear204 – 216°C
Demolding54 – 82°C
Mold (Cooling)38 – 71°C
Feed Throat10 – 49°C

Processing

Back Pressure4.8 – 8.3bar
Screw Speed40 – 90RPM
Injection SpeedMedium – High
Barrel Occupancy25 – 75%
Injection Pressure700 – 1,000Pbar
Holding Pressure175 – 800Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter3.05 – 6.1mm
Gate Diameter0.76 – 1.52mm
Gate Area0.46 – 1.82mm²
Wall Thickness1.19 – 4.5mm

Venting

Depth (Vent Depth)0.0203 – 0.0508mm
Land (Vent Land)0.508 – 1.02mm
Width (Vent / Clearance)3.05 – 10.2mm
Relief (Relief Channel)0.127 – 0.254mm

Frequently asked questions

HIPS is **GPPS modified with rubber**: 5–15% polybutadiene (or styrene-butadiene copolymer) dispersed as small particles in the PS matrix. The rubber **breaks transparency** (becomes opaque matte) but provides an **impact-absorption mechanism** — rubber particles act as stress concentrators that dissipate energy without propagating fractures. Density 1.04 g/cm³, 0% transparency (opaque), impact strength 50–150 J/m (vs 20 J/m for GPPS).
**HIPS wins on**: cost (20–30% cheaper than ABS), processing ease (lower temperature, faster cycle), superior thermoforming (deep draws, sharp lines), surface printability. **ABS wins on**: tensile strength (40–50 vs 20–40 MPa), notched Izod impact (200–400 vs 50–150 J/m), stiffness, dimensional stability, use temperature, chemical resistance. Rule of thumb: **cost-driven + thermoforming + non-structural** → HIPS. **Rigid housing + repeated impacts + premium finish** → ABS. Refrigerators are HIPS because they're thermoformed and don't take impact. Electronics housings are ABS because they get knocked around and need to hold tolerances.
The white interior liner of fridges/freezers is thermoformed HIPS for **5 reasons**: (1) **Excellent thermoforming** — complex deep draws in one operation, uniform walls, sharp lines for compartments, (2) **Low-temperature toughness** — butadiene rubber maintains toughness at –20°C (GPPS would shatter), (3) **Low cost** — a fridge liner is several m² of plastic; HIPS is half the price of ABS, (4) **Chemical resistance** to foods and household cleaners, (5) **FDA food-safe**. Typical liner thickness: 1.5–3 mm from extruded sheet.
**Unique combination**: (1) rigidity to hold container shape, (2) moderate impact (won't crack on squeeze or drop), (3) cheap sheet thermoforming (millions per hour), (4) **matte surface** ideal for direct offset print or IML (in-mold labeling), (5) FDA food-grade. Applications: **yogurt cups** (Danone, Yoplait extensive HIPS users), **meat/poultry trays** in supermarkets, **take-away clamshells**, **microwaveable trays** (not repeat-heat but single-use OK), **disposable cutlery**. Recycle codes: #6 (PS), same problem as GPPS — technically recyclable, practically tough.
**Usually no**, but **drying helps** for pigmented or cosmetic-surface grades. HIPS absorbs very little moisture (<0.1%) thanks to its polystyrene nature, but the butadiene rubber can trap micro-moisture. **General recommendation**: routine production in temperate climates → no drying. Cosmetic or premium pigmented parts → **light drying 60–80°C × 2 h**. **Premium fridge liners**: mandatory drying (visual defects across 1 m² are unacceptable). Tropical climate or material open >1 day: preventive drying.
The PDS marks **38–71°C** — similar to GPPS and ABS. **Hot** (60–70°C) = better gloss and surface reproduction (matters if printing/painting), lower residual stress, longer cycle. **Cold** (38–50°C) = shorter cycle, higher output, ideal for high-volume disposables (cups, trays). For HIPS sheet thermoforming: tooling is typically aluminum with vacuum, ambient or light 40–50°C heating depending on geometry.
Shrinkage **0.4–0.7%**, similar to GPPS and ABS, isotropic (no significant directionality as it's amorphous). Advantage: predictable tolerances, no significant warpage in large flat parts. For precise parts (not HIPS's strong suit): consider multiple gates, uniform walls, balanced cooling. **Post-shrinkage** minimal if processed well.
**No**, same as GPPS — HIPS yellows and embrittles under UV in **6–12 months** outdoors. Not the choice for outdoor use — **use ASA or UV-stabilized PP instead**. However, UV-stabilized HIPS exists (with HALS) for semi-outdoor apps like dashboard instrument panels, electronics housings exposed to indirect light. For outdoor toys or garden furniture meant to last >1 year, not HIPS.
**Yes, FDA and EFSA approve** food-grade HIPS for normal food contact use. Same considerations as GPPS and general PS: micro-migration of residual styrene monomer, increases with heat and fats. **Recommendation**: HIPS is safe for **cold disposable use** (yogurt, salads, cold trays) — millions of tons used this way globally without documented issues. For repeated hot use (microwave, hot coffee), prefer food-grade PP. **FDA limit is 0.1 mg/L** in water — commercial HIPS products are well below.
**HIPS wins on**: rigidity (cup holds shape through transport and stacking), IML ease (non-waxy surface), faster thermoform cycle (huge advantage at 100k+ cups/hour), cost. **PP wins on**: higher food-safety (no residual styrene monomer), real recyclability (PP #5 vs PS #6 which barely anyone accepts), microwave use, better with hot products. **2026 trend**: regulatory pressure on PS is pushing **much yogurt production from HIPS to PP** especially in Europe. Traditional yogurt (cold dessert): HIPS still dominant. Premium or "natural" yogurt: more and more PP.

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