Plastic Packaging: Impact Resistance Testing

In the global food packaging industry, plastic packaging stands as a cornerstone for preserving freshness, ensuring safety and enabling efficient distribution—and impact resistance is the unsung hero that upholds these core functions. For food plastic packaging manufacturers like Zhejiang Hengjiang Plastic Co., Ltd., which specializes in PET/PP food trays, blister packaging and injection-molded food containers, rigorous impact resistance testing is non-negotiable. Food packaging faces countless physical stresses throughout the supply chain: rough handling during transportation, stacking in warehouses, accidental drops at retail stores and even minor knocks during consumer use. A packaging solution with poor impact resistance risks cracking, puncturing or deforming, which not only leads to product spoilage and food waste but also compromises the tamper-proof and airtight properties critical for MAP (Modified Atmosphere Packaging) and VSP (Vacuum Skin Packaging) applications. For food brands, this translates to financial losses, damaged reputations and non-compliance with food safety regulations. For manufacturers, mastering impact resistance testing is the key to delivering reliable, high-quality plastic packaging that meets the stringent demands of the food industry, including BRC and FDA certification standards.

Not all food-grade plastics possess the same impact resistance characteristics, and understanding these differences is the first step in targeted impact resistance testing. Zhejiang Hengjiang Plastic Co., Ltd. focuses on producing packaging from PET (Polyethylene Terephthalate) and PP (Polypropylene), the two most widely used food-grade rigid plastics in the industry, each with unique mechanical properties that shape their impact resistance performance and testing protocols.

PET is a rigid, high-clarity plastic ideal for food trays, hinged containers and pastry boxes. It offers excellent structural stability and impact resistance at room temperature, making it perfect for packaging fresh produce, baked goods and ready-to-eat snacks. However, PET’s impact resistance can decline in low-temperature environments, a critical factor to test for packaging used in refrigerated or frozen food applications. PP, by contrast, is a more flexible plastic with superior low-temperature impact resistance, making it the material of choice for MAP trays, vacuum skin packaging trays and microwave-safe food containers. PP’s durability against sudden shocks and drops—even in cold storage—makes it indispensable for fresh meat, seafood and prepared meal packaging. Both materials undergo specialized impact resistance testing tailored to their molecular structure and end-use applications, ensuring that the final plastic packaging product performs reliably in its intended food supply chain environment.

For thermoformed and injection-molded plastic packaging, the manufacturing process also influences impact resistance. Zhejiang Hengjiang Plastic Co., Ltd. uses advanced automatic blister forming machines and precise injection molding equipment to create uniform wall thickness and seamless structural design—factors that directly boost impact resistance. Testing must account for these manufacturing variables, as inconsistent molding or forming can create weak points that fail under impact.

Impact resistance testing for food plastic packaging adheres to strict industry and international standards, designed to replicate real-world physical stresses and provide quantifiable data on a product’s performance. These standardized methods ensure that test results are reliable, comparable and aligned with food safety and packaging quality certifications such as BRCGS Packaging Materials and FDA 21 CFR 177.1630. The most commonly used testing methods for rigid food plastic packaging (PET/PP trays, containers and boxes) include two core approaches, each targeting different types of impact stress that packaging faces in the supply chain.

Charpy Impact Test is a staple for measuring the brittle fracture resistance of rigid plastic packaging materials and finished products. The test involves striking a notched sample of the plastic packaging (e.g., a PP food tray edge or PET hinged container lid) with a swinging pendulum, measuring the energy absorbed by the sample during fracture. This method is particularly valuable for testing PET packaging, as it identifies potential brittle points that may crack under sudden, sharp impacts—such as a tray being hit by a forklift in a warehouse. For food packaging manufacturers, the Charpy test helps optimize material thickness and design to eliminate weak points, ensuring that even thin-walled PET pastry boxes or cookie trays can withstand routine handling.

Izod Impact Test is closely related to the Charpy test but differs in sample preparation and impact direction, making it ideal for testing plastic packaging with a fixed or clamped design, such as lidded food containers and tamper-proof hinged containers. The sample is held in a vertical clamp, and a pendulum strikes the free, notched end, measuring the energy required to break the material. This test simulates the impact stress of a packaged product being dropped or knocked while the packaging is sealed or clamped, a common scenario for ready-to-eat meal containers and salad boxes. Izod testing is critical for PP MAP trays, as it verifies that the tray’s sealed edges and structural corners—vital for maintaining modified atmosphere—do not break under impact, which would compromise food freshness and shelf life.

Beyond these two primary methods, food plastic packaging also undergoes drop testing for finished products, a practical test that replicates real-world drops from standard heights (e.g., 1m, 1.5m) onto hard surfaces. This test evaluates the entire packaging system’s impact resistance, including seals, lids and structural integrity, and is a mandatory step for packaging used in retail and food service distribution. Zhejiang Hengjiang Plastic Co., Ltd. conducts drop testing on all its finished food packaging products, from 700ml snack containers to 28cm square packaging boxes with lids, to ensure compliance with customer and industry distribution requirements.

For food plastic packaging manufacturers, impact resistance testing is not a one-time quality check but an integrated part of the entire production process—from raw material sourcing to finished product delivery. Companies like Zhejiang Hengjiang Plastic Co., Ltd., which operates a 100K-class GMP clean workshop and has a dedicated laboratory area, implement a multi-stage testing protocol to ensure consistent impact resistance across all products, leveraging advanced manufacturing and testing equipment to maintain high standards.

Raw Material Testing is the first line of defense. Before PET and PP sheet rolls are fed into automatic sheet making machines, they undergo impact resistance testing to verify that the raw material meets the manufacturer’s specifications and food-grade standards. This step prevents subpar materials from entering production, as the quality of the plastic resin directly determines the final packaging’s impact resistance. For example, recycled food-grade PP must pass additional impact tests to ensure that the recycling process has not compromised its mechanical properties.

In-Process Testing occurs during thermoforming and injection molding, where random samples are taken from the production line and tested for impact resistance. This real-time testing allows manufacturers to identify and correct production variables—such as temperature, pressure or mold design—that may reduce impact resistance. For instance, if a batch of PET food trays fails a Charpy impact test, technicians can adjust the blister forming machine’s temperature to optimize the plastic’s molecular structure and restore impact resistance. Zhejiang Hengjiang Plastic Co., Ltd.’s team of 10 technical managers oversees in-process testing, ensuring that production remains aligned with quality standards and that any deviations are addressed immediately.

Finished Product Testing is the final and most comprehensive stage, where packaged products (or empty packaging simulating filled conditions) undergo a full suite of impact resistance tests, including Charpy, Izod and drop testing. Only products that pass all tests are certified for delivery, and test data is documented to comply with BRC, FDA and SGS certification requirements. For custom packaging solutions—such as personalized pastry boxes or meat roll packaging containers—finished product testing is tailored to the customer’s specific distribution and use cases, ensuring that the packaging meets unique impact resistance needs.

Continuous Improvement Through Testing Data is a critical final step. Manufacturers analyze impact resistance test data over time to identify trends, such as a specific PP tray design that consistently performs poorly in low-temperature drop tests, and use this information to refine product design and manufacturing processes. This data-driven approach not only improves the impact resistance of existing products but also informs the development of new packaging solutions, such as high-impact CPET (Crystalline PET) trays for high-temperature food applications, a growing focus for the food packaging industry.

Impact resistance testing is inextricably linked to the food safety certifications that are mandatory for food plastic packaging manufacturers operating in global markets. Certifications such as BRCGS Packaging Materials, FDA 21 CFR 177.1630 and SGS testing all require rigorous proof of a packaging product’s mechanical integrity—of which impact resistance is a key component. For manufacturers like Zhejiang Hengjiang Plastic Co., Ltd., which exports 30% of its products to Asia, South America, North America and Europe, passing impact resistance testing is a prerequisite for obtaining and maintaining these certifications, which are trusted by food brands and regulatory bodies worldwide.

BRCGS Packaging Materials certification, in particular, places strict emphasis on packaging durability and performance, as poor impact resistance can lead to food contamination and spoilage—violations of the certification’s food safety principles. The BRCGS audit process includes a review of a manufacturer’s impact resistance testing protocols and data, ensuring that testing is standardized, documented and integrated into quality management systems. Zhejiang Hengjiang Plastic Co., Ltd.’s recent BRCGS audit (2025) verified that its thermoformed PP boxes and injection-molded PET trays meet all mechanical performance requirements, including impact resistance, a key factor in the audit’s positive outcome with no deviations.

FDA 21 CFR 177.1630 certification, which governs food-grade plastic materials in the United States, requires that plastic packaging not only be non-toxic but also structurally sound. Impact resistance testing ensures that packaging does not crack or deform under normal use, as a damaged package can lead to chemical leaching (even from food-grade plastics) and food contamination. SGS testing, such as the chloroform-soluble extractives test conducted on Zhejiang Hengjiang Plastic Co., Ltd.’s PET trays in 2025, is often paired with impact resistance testing to provide a comprehensive assessment of packaging safety and performance, giving food brands confidence in the products they use.

In addition to formal certifications, impact resistance testing also helps manufacturers meet customer-specific food safety requirements. For example, meat processors require plastic meat trays with high impact resistance to prevent contamination from broken packaging during the processing and distribution of raw meat, while bakery brands need pastry boxes that can withstand stacking without deforming—protecting both the product and its presentation. By prioritizing impact resistance testing, manufacturers ensure that their plastic packaging not only complies with global certifications but also meets the unique food safety needs of every customer.