Our "Understanding Plastic Property Charts" series now includes an environmental performance section. We've already thoroughly covered mechanical, thermal, processing properties, addressing issues of product durability, high-temperature resistance, ease of molding. However, in actual use, products face complex environments such as sun and rain, alternating high and low temperatures, and contact with water, oil, and detergents. This can lead to fading and aging, or even cracking and deformation. Therefore, it's crucial to consider two core indicators: weather resistance and chemical properties.
These two directly determine product's lifespan and applicable scenarios—weather resistance refers to its "resistance to aging in natural environments," while chemical properties refer to its "resistance to corrosion from various media." Especially for cups, kettles, small kitchen appliances, and outdoor plastic parts, both indicators must be considered when selecting materials. Today, we'll use a combination of text and images to thoroughly explain definitions, testing, and material selection logic, along with key comparisons and practical techniques for immediate application!

1. Core Definition: Weather resistance refers to ability of plastics to resist long-term effects of natural environmental factors and maintain stable appearance and performance.
Natural environmental factors mainly include: ultraviolet (UV) radiation, alternating high and low temperatures, humidity/rain, oxygen/ozone. Among these, UV radiation is core culprit for plastic aging (it damages plastic molecular chains, leading to degradation). In simple terms: Plastics with good weather resistance will not significantly fade, powder, or become brittle even after 1-3 years of outdoor exposure; plastics with poor weather resistance will lose their toughness and crack easily after a few months of exposure, their appearance will yellow and fade.
Units/Evaluation Methods: There is no fixed unit. Industry often evaluates weather resistance by performance retention rate after aging tests (e.g., tensile strength, impact strength retention ≥50%) or aging time (e.g., UV aging resistance 1000h, 2000h). The higher value, the better weather resistance.
2. Typical Manifestations of Plastic Aging
From appearance to performance, aging gradually deteriorates. Cups, kettles, small kitchen appliances, and outdoor items require special attention:
Appearance: Yellowing, fading, loss of gloss, surface powdering, cracking;
Performance: Sharp drop in impact strength, becoming brittle and easily broken, decreased flexural strength, loss of toughness;
Structural: Deformation, warping, loosening of fasteners (due to material shrinkage/embrittlement caused by molecular chain degradation).
3. Core Testing Methods: Accelerated Aging Test Simulating Natural Environment (with National Standards)
Natural aging tests take several years. Accelerated aging tests, a common industry standard, quickly predict weather resistance. There are two core categories, both with national standards:
(1) Xenon Lamp Weathering Test (most common, GB/T 16422.2, corresponding to ISO 4892-2)
Test Logic: A xenon lamp simulates full spectrum of sunlight (including ultraviolet and visible light), combined with temperature, humidity, and a spray system to simulate a natural environment of "sun exposure + rain + high and low temperatures," continuously irradiating sample.
Evaluation Criteria: After irradiation for a specified time (e.g., 500h, 1000h, 2000h), the appearance changes (color difference, chalking grade) and mechanical property retention rate of sample are tested to determine weather resistance level.
(2) Ultraviolet (UV) Aging Test (Focusing on ultraviolet light, GB/T 16422.3, corresponding to ISO 4892-3)
Test Logic: A UV lamp is used to simulate ultraviolet bands (UV-A/UV-B) in sunlight. Combined with condensation, this simulates UV aging in a humid environment, focusing on testing plastic's resistance to UV degradation.
Applicable Scenarios: Primarily used to evaluate resistance of plastics to ultraviolet light; suitable for rainless, high-UV environments.

 

1. Core Definition: Chemical properties refer to ability of plastics to resist long-term contact with various chemical media without swelling, cracking, deformation, or performance degradation. Media that cups, kettles, and small kitchen appliances come into daily contact with are a core consideration, mainly divided into food-grade media and general-purpose media, directly affecting product safety and durability:
Food-grade media: Water (cold/boiling water), vinegar, soy sauce, cooking oil, milk, fruit juice, alcohol (low concentration);
General-purpose media: Detergent, dishwashing liquid, soapy water, disinfectant (low concentration);
Special media: Organic solvents (alcohol, acetone, less frequent contact), acid and alkali solutions (high concentration, rare). Evaluation Method: No fixed unit; industry judges performance based on changes after contact with media – divided into four levels: "no impact, slight swelling, significant deformation, cracking and dissolution." No impact/slight swelling is considered acceptable (food-grade must comply with national standard GB 4806.7 for plastics in contact with food).
2. Typical Deterioration Manifestations of Plastics After Contact with Media
Degree of deterioration varies with type of media and contact time. Significant deterioration must be strictly avoided for food contact parts such as cups and jugs:
Slight Deterioration: Sticky surface, slight swelling (small increase in volume), recoverable after drying, no significant change in performance;
Moderate Deterioration: Deformation, hardening/softening (due to changes in molecular structure caused by media penetration), decreased mechanical properties;
Severe Deterioration: Cracking, dissolution, leaching of harmful substances, product unusable, safety risks present (strictly prohibited for food contact parts).
3. Core Testing Methods: Immersion Test (Food grade requires additional migration test, mandatory according to national standards)
(1) General Chemical Performance Test: Room Temperature/High Temperature Immersion Test (Industry-widely applicable)
Test Logic: Process plastic sample into a standard test piece, completely immerse it in target medium (such as boiling water, edible oil, detergent solution), set specified temperature (room temperature 25℃/boiling water 100℃) and time (24h, 72h, 168h), remove and air dry, observe appearance and test mechanical properties;
Evaluation Criteria: No deformation, cracking, or stickiness in appearance, and a mechanical property retention rate ≥80% are considered qualified.
(2) Food-grade Specific Test: Migration Test (Mandatory Requirement of GB 4806.7)
Test Logic: For plastics intended for food contact, immerse them in food simulants (water, 3% acetic acid, 10% ethanol, olive oil, simulating different food types) according to national standards. Test migration amount of harmful substances (such as heavy metals, plasticizers, volatile organic compounds) in immersion solution at specified temperatures and times.
Core Requirement: Migration amount must be lower than national standard limit; otherwise, it cannot be used for food contact parts (cups, kettles, inner liners, tableware, etc.).

 

Different plastics exhibit significant differences in weather resistance and chemical properties. Modification (such as UV-resistant modification, food-grade modification) will significantly improve corresponding properties. Glass fiber reinforcement has virtually no impact on chemical properties but will slightly reduce weather resistance (requires UV-resistant modification). Following are industry-standard data. Food-grade modified materials must be additionally labeled as conforming to GB 4806.7; select materials directly according to specifications!

Key principle summary: For food contact parts, prioritize PP, PC, HDPE, and food-grade TPE, all of which can pass GB standards ABS is strictly prohibited from food contact use under 4806.7 certification.
Outdoor/exposed parts must use UV-resistant modified materials (PP/PC/HDPE can all be UV-resistant modified). Unmodified materials experience short-term aging.
For high-temperature media contact parts (boiling water/high-temperature oil), choose PP, PC, or PPS.
HDPE and TPE are only suitable for low-temperature media.

Core of controlling weather resistance and chemical properties is "scenario matching + modification optimization". Based on actual usage scenarios of cups/pots/small kitchen appliances, following techniques can be directly implemented to avoid aging and corrosion risks!
✅ Tip 1: Determine Weather Resistance Requirements Based on Usage Environment
Outdoor Use / Exposed Parts (e.g., outdoor cups, exposed outer shells of small kitchen appliances): UV-resistant modified materials are mandatory, with priority given to UV-resistant PP/PC/HDPE. Requirements include resistance to xenon lamp aging ≥1000h and no significant fading.
Indoor Use / Internal Parts (e.g., inner liners of cups and kettles, internal supports of small kitchen appliances): Unmodified materials are acceptable; UV resistance modification is not required, reducing costs.
✅ Tip 2: Determine Chemical Performance Requirements Based on Contact Media
Food Contact Parts (cup body, inner liner, inner ring of lid): Food-grade modified materials are mandatory, conforming to GB 4806.7. PP/PC is preferred, resistant to boiling water and various food media. ABS is prohibited.
Non-Food Contact Parts (outer shell, handle, decorative parts): Ordinary materials are acceptable. Parts in contact with detergents must be resistant to low concentrations of detergents (ABS/PP/PC are all acceptable).
✅ Tip 3: Optimized Modification and Combination for a Balanced Performance and Cost
Outdoor + Food Contact Components (e.g., outdoor water bottles): UV-resistant modified PP/PC + food-grade modified PP/PC, offering both weather resistance and safety, with the highest cost-effectiveness;
Outdoor + Load-Bearing Components (e.g., outdoor cup handles): Glass fiber reinforced + UV-resistant modified PP, balancing rigidity and weather resistance, preventing aging and breakage;
High Transparency + Outdoor Components (e.g., high-transparency outdoor cups): UV-resistant modified PC, maintaining transparency while improving weather resistance.
✅ Tip 4: Manufacturing Process Assistance to Enhance Product Weather Resistance
Surface Coating/Lamination: Applying a UV-resistant coating or lamination to plastic surface physically isolates ultraviolet rays and rainwater, improving weather resistance (suitable for materials with poor weather resistance, such as ABS shells);
Wall Thickness Optimization: Appropriately increasing wall thickness (≥2.5mm) for outdoor components reduces UV damage to internal molecular chains, delaying aging.

❌ Myth 1: Equating "high temperature resistance" with "boiling water resistance (chemical property)"
For example, ABS can withstand temperatures up to 80℃, but it cannot withstand prolonged contact with boiling water, which will cause it to become sticky and deform. High temperature resistance is a thermal property, while boiling water resistance is a chemical property; the two are not directly related.
❌ Myth 2: Using unmodified materials directly for outdoor/exposed parts
For example, unmodified PP will yellow and become brittle after 3 months of outdoor exposure to sunlight. UV-resistant modification must be done beforehand; do not omit this step to save cost.
❌ Myth 3: Food-grade modified materials do not need to comply with national standards
All plastics used in food contact must be clearly labeled as conforming to GB 4806.7. Materials without this label, even if claimed to be "food-grade," still pose a risk of leaching.
❌ Myth 4: UV-resistant modified materials can resist all aging
UV-resistant modification mainly protects against ultraviolet rays. Outdoor parts also need to consider alternating high and low temperatures and rain. It is recommended to combine this with surface coating for double protection.
❌ Myth 5: PC material can withstand prolonged contact with high-concentration alcohol.
PC is resistant to low-temperature, low-concentration alcohol, but prolonged contact with high-concentration alcohol (≥75%) will cause slight swelling, affecting performance. Cups and bottles should avoid being filled with high-concentration alcohol.
❌ Myth 6: Glass fiber reinforced materials do not require UV-resistant modification.
Weather resistance of glass fiber reinforced materials is slightly worse than that of pure materials. For outdoor use, glass fiber reinforced PP/PC still needs UV-resistant modification; otherwise, it will accelerate aging and cracking.

Weather resistance and chemical properties are core guarantees for long-term durability and safe use of plastic products, especially for cups and bottles (food contact + daily use), small kitchen appliances (multi-media contact + partial exposure), and outdoor plastic parts (full-environment aging). When selecting materials, both weather resistance and chemical properties must be considered in conjunction with mechanical and thermal properties.
Remember core logic: for outdoor use, look at UV resistance and weather resistance; for food contact, look at chemical properties according to GB 4806.7; for special scenarios, make targeted modifications (UV resistance/food grade); combine this with appropriate production process optimization to ensure that product remains stable in complex environments for a long time and significantly reduce after-sales risks.