Harbinger Times

Shanghai, China – November 13, 2026 – When buying High Impact Polystyrene (HIPS) sheet rolls for thermoforming, impact resistance is one of the properties worth checking. But what does the number on a technical datasheet actually tell you?

HIPS is tougher than general-purpose polystyrene (GPPS) because it contains a rubber-modified structure that improves its ability to absorb impact. This makes it suitable for food trays, electronic component inserts, industrial packaging, and other thermoformed products that need to withstand regular handling.

However, a higher impact strength value does not automatically mean a better sheet. Buyers need to understand the test method and consider how the material will perform after thermoforming.

1. What Does HIPS Impact Resistance Measure?

One commonly used method is the notched Izod impact test, specified in ASTM D256.

A pendulum strikes a notched plastic specimen, and the energy absorbed during fracture is measured. The result indicates how well the material resists impact under the specified test conditions.

Typical reporting units include:

• J/m (joules per meter)

• kJ/m² (kilojoules per square meter)

• ft·lb/in (foot-pounds per inch)

These units are not directly interchangeable, so buyers should check the test method before comparing supplier data.

For general industry reference, HIPS notched Izod values commonly fall around 60–210 J/m, depending on the grade and formulation. This is an indicative range, not a guaranteed specification for thermoforming sheet rolls.

The key point: A higher value generally indicates better impact resistance in that particular test. It does not directly predict how much impact a finished tray or container can withstand.

2. Why Impact Test Results Can Differ Between Suppliers

Two HIPS suppliers may report different impact strength values even when both products are described as high-impact material.

Several factors can explain the difference.

Test method: Notched and unnotched impact tests measure different material behavior. Their results should not be compared directly.

Specimen thickness: Impact results depend on specimen dimensions and notch geometry. Resin datasheets may also use injection-molded specimens rather than extruded sheet samples.

Testing temperature: HIPS can behave differently at lower temperatures. This matters for refrigerated or frozen-food applications.

Material formulation: Rubber content and polymer formulation influence the balance between impact resistance, stiffness, and processing behavior.

When comparing suppliers, ask for the test standard, specimen type, thickness, and testing temperature. This makes the reported figures much more useful.

3. Does Impact Resistance Change After Thermoforming?

Yes. The mechanical performance of a thermoformed product can differ from that of the original flat sheet.

During thermoforming, the heated HIPS sheet stretches across the mold. Material thickness is redistributed, particularly around deep-drawn corners and sidewalls.

Three factors deserve attention:

• Wall thickness: Excessive stretching can create thin areas that are more vulnerable to cracking.

• Heating conditions: Uneven heating may cause inconsistent material distribution.

• Product design: Sharp corners and sudden changes in geometry can create stress concentration points.

For this reason, a good flat-sheet impact result does not guarantee that every formed product will perform equally well.

If impact resistance is critical, test samples from the actual thermoformed product under realistic handling conditions.

4. Choosing HIPS Sheet for Different Applications

Different applications require different balances of toughness, stiffness, and formability.

For electronics applications, electrical properties should also be considered separately from mechanical impact resistance.

For example, PULIXIN offers:

• Antistatic HIPS: Typical resistance of 10⁹–10¹¹ Ω.

• Conductive HIPS: Typical resistance of 10⁴–10⁶ Ω.

Both options are available for applications requiring specific electrostatic protection.

5. What Should Buyers Check Before Ordering HIPS Sheet Rolls?

From a sheet manufacturer’s perspective, impact strength is only one part of material selection. Buyers should also check:

1. Impact test data: Confirm the test standard, specimen type, and testing conditions.

2. Thickness consistency: Uneven sheet thickness can affect forming and finished-part performance.

3. Thermoforming compatibility: Check whether the material runs reliably on your existing production line.

4. Material options: Confirm whether standard, antistatic, conductive, or customized grades are available.

5. Batch consistency: Stable material properties are important for continuous production.

At PULIXIN, we manufacture HIPS sheet rolls for downstream thermoforming applications.

Our general product specifications include:

The appropriate grade depends on the application, forming conditions, and required mechanical properties. Specific impact resistance values should be confirmed for the selected material grade.

Conclusion

Impact resistance numbers help buyers compare HIPS materials, but they should never be considered in isolation.

Check the test method and conditions, then evaluate how the sheet performs during actual thermoforming. For most buyers, consistent thickness, reliable forming behavior, and suitable toughness are more valuable than simply choosing the material with the highest datasheet number.

The right HIPS sheet is the one that performs consistently in your production process and meets the requirements of your finished product.

Frequently Asked Questions1. What is a good impact strength for HIPS?Typical industry reference values for notched Izod impact strength are around 60–210 J/m. Actual results depend on the material grade and test conditions.2. Is HIPS more impact-resistant than GPPS?Yes. HIPS contains a rubber-modified structure that improves toughness and reduces brittleness compared with GPPS.3. Does higher Izod impact strength mean better thermoforming performance?Not necessarily. Impact strength measures resistance to a specific impact test. Formability also depends on material formulation, heating conditions, thickness, and product design.4. Can HIPS be used for electronic component trays?Yes. Standard HIPS can be used for general applications, while antistatic and conductive HIPS grades are available when electrostatic protection is required.5. What should I request from a HIPS sheet supplier?Ask for impact test data, material thickness, test conditions, available grades, and sheet specifications. For critical applications, conduct a production trial using your actual thermoforming equipment.

About us

Pulixin Packaging Materials (Shanghai) Co., Ltd. was established in 2009 in Shanghai. Its registered capital is RMB 20.8 million and area is more than 20,000 square meters. We are a manufacturer and seller of PP, PS, PET sheets etc . Our company owns 12 PET/PP/PS co-extruded production lines which import from Europe , and 2 coating production lines. Our production volume has been more than 40,000 metric tons per year. Our company products are mainly used in packaging for electronics, food, toys, cosmetics, medical, toys, printing and other industries.

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