The short answer
Injection-grade HIPS typically runs about 3–15 g/10 min melt flow at 200°C / 5 kg, 1.03–1.05 g/cm³ density and 85–210 J/m (1.6–3.9 ft·lb/in) notched Izod. Higher impact costs stiffness and some heat. Higher flow fills thin walls but usually lowers stiffness and heat. Producers do not publish rubber content, so compare notched Izod, flexural modulus and gloss. Stress-crack-resistant grades for refrigeration are mostly sheet grades.
Have a part number or drawing callout?
Paste it as written. A polymer chemist will tell you which grade it calls for, suggest equivalents and quote it by email.
This page covers HIPS for injection molding. For the clear, unmodified version see GPPS vs. HIPS, and for typical values see polystyrene properties. Two grade pages show the range: Styron 478, a North American injection grade, and TotalEnergies 7240, a European sheet grade. If HIPS is not tough or heat resistant enough, see ABS vs. HIPS.
Typical spec window
| Property | Typical range | Test method |
|---|---|---|
| Melt flow | About 3–15 g/10 min for injection grades; sheet grades about 2–4 | ASTM D1238 or ISO 1133, 200°C / 392°F, 5 kg |
| Density | 1.03–1.05 g/cm³ / 0.0372–0.0379 lb/in³; most sheets list 1.04 | ASTM D792 or ISO 1183 |
| Notched Izod, 23°C / 73°F | 85–210 J/m / 1.6–3.9 ft·lb/in | ASTM D256 |
| Tensile strength | 16–36 MPa / 2,300–5,200 psi | ASTM D638 |
| Flexural modulus | About 1.4–2.3 GPa / 200,000–340,000 psi | ASTM D790 |
| Heat deflection, 1.8 MPa | 70–94°C / 158–201°F; annealed bars read higher | ASTM D648 |
| Vicat softening | 93–106°C / 199–222°F | ASTM D1525 |
| Gloss, 60° | Grade-specific; high-gloss grades list about 90–94, matte grades much lower | ASTM D523 |
| Flammability | HB for standard grades | UL 94 |
Typical ranges from 2026 North American data sheets from AmSty, TotalEnergies and INEOS Styrolution. Your grade's own data sheet and the lot COA are what count.
What it’s used for
- Appliance housings and small appliance parts
- Electronics housings and covers
- Toys and housewares
- Lids and refrigeration parts
- Medical disposables and housings (check USP Class VI by grade)
- Thin-wall trays and parts (high-flow grades)
How to tell grades apart
- Impact class. Current North American sheets we checked do not use a medium-impact label: AmSty lists its grades simply as HIPS, and TotalEnergies splits its list into high impact and super high impact. By the data, grades fall in three bands: about 85–107 J/m (1.6–2.0 ft·lb/in), stiffer and glossier, such as Styron 478 and TotalEnergies 825; about 112–150 J/m (2.1–2.8), such as Styron 414 and Styrolution PS 5600; and about 160–210 J/m (3.0–3.9), such as TotalEnergies 945E.
- Rubber content. HIPS gets its toughness from polybutadiene rubber grafted into the polystyrene. Producers do not publish the rubber percentage, so compare notched Izod, falling dart where listed, flexural modulus and heat deflection instead.
- Flow. High-flow grades of about 13–15 g/10 min (Styron 414 and TotalEnergies 830) fill thin walls. Some trade away stiffness and heat: Styron 414 lists a 206,000 psi flexural modulus, against 300,000 psi for Styron 478 at 6 g/10 min.
- Gloss. High-gloss grades such as TotalEnergies 825 and 830 list 60° gloss of 90–94; matte grades run much lower. Some grades combine high gloss with high impact, such as TotalEnergies 945E (gloss 90, about 171 J/m). Approve gloss on real parts.
- Stress-crack resistance. Standard HIPS can crack in contact with fats, oils and foam blowing agents. Stress-crack-resistant (ESCR) grades such as TotalEnergies 960E, AmSty A-TECH 1170 and Styrolution PS 5400 exist, but nearly all are sheet extrusion grades with melt flow of about 2–4.
- Flame retardant. Standard grades are UL 94 HB. Flame-retardant HIPS is a separate family, and none of the current AmSty or TotalEnergies North American grade lists we checked includes one. If a drawing calls for one, send it and we will check sources.
What to put on your RFQ or PO
- Melt flow with the condition. 200°C / 392°F and 5 kg, nominal value and range.
- Impact. Notched Izod (ASTM D256) and, if your parts are drop tested, falling dart where the producer lists it.
- Stiffness and heat. Flexural modulus and heat deflection or Vicat, if the part carries load or sits near heat.
- Gloss. A 60° gloss value or an approved sample part.
- Chemical exposure. Any contact with fats, oils, cleaners or foam insulation, so we can check stress-crack resistance.
- Color. By code or match, and whether you add masterbatch.
- Agency. The producer's FDA letter (21 CFR 177.1640), UL 94 HB file and color, or USP Class VI, as your part needs.
- COA values to check. Melt flow and impact on each lot, and color values for pre-colored resin.
- Packaging and quantity. Gaylords or 25 kg (55 lb) bags, total quantity and release size.
A polymer chemist reviews every request and checks the grade against your process before we quote. Every prime lot from our suppliers ships with a COA, and orders start at one gaylord.
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- Same melt flow, impact and gloss from another producer. The closest swap. For example, TotalEnergies 825 and Styrolution PS 5600 are grades to check against Styron 478; both run higher flow. INEOS Styrolution is closing its Channahon, Illinois polystyrene plant in Q4 2026, so confirm the supplying plant before you qualify a Styrolution grade.
- A North American sheet grade. For imported sheet HIPS such as TotalEnergies 7240, buyers in the U.S. and Canada usually qualify a locally made grade.
- ABS. More heat, toughness, gloss and chemical resistance at a higher price. See ABS vs. HIPS.
- GPPS or a GPPS/HIPS blend. Stiffer and cheaper, with less impact. See GPPS vs. HIPS.
- PP impact copolymer. Lighter (about 0.90 g/cm³) and more chemical resistant, but it shrinks more, so a HIPS tool usually will not mold it to size. See PP impact copolymer.
Common processing problems
- Cracks near oils, fats or foam insulation: environmental stress cracking
- Yellowing and lost impact from overheating: heat discoloration
- Flow lines and gloss bands: flow lines
- Dimples over ribs and bosses: sink marks
- Shade shifts between lots: color inconsistency
Common questions
What melt flow HIPS do I need for injection molding?
Start from the grade that runs your mold now, at 200°C / 5 kg. Most injection grades sit between about 3 and 8 g/10 min. Thin-wall parts use high-flow grades of about 13–15, which can give up stiffness and heat. Sheet grades run lower, about 2–4.
What is the difference between medium-impact and high-impact HIPS?
It is a matter of notched Izod and stiffness. Lower-impact grades of about 85–107 J/m are stiffer and often glossier. Grades above about 160 J/m take drops better but are usually less stiff. Current North American data sheets mostly label all of these high impact, so compare the numbers.
How much rubber is in HIPS?
Producers do not publish rubber content on their data sheets. Compare the properties the rubber controls instead: notched Izod, falling dart, flexural modulus, heat deflection and gloss.
Does HIPS need to be dried?
Usually not. Dry only regrind, resin stored in humid conditions or pellets with condensation, at about 71–75°C / 160–167°F for 1–2 hours. Keep the melt at or below about 250°C / 482°F, since the rubber degrades with heat.
Tell us the grade you run now
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province