Elevate Bottled Water Packaging: Wankai's High-Performance PET WK-801 and WK-801L

Why PET Replaced Glass and Metal

Before PET bottles gained popularity in the late 1970s and early 1980s, glass bottles and metal cans were the primary packaging choices for water. While glass is inert and maintains water quality, it is heavy, fragile, and energy-intensive to produce. Metal cans are lightweight but can lead to metal ion migration and do not visually convey the quality of the water. The complex manufacturing processes of metal cans also result in higher production costs. As a result, PET has emerged as the preferred material for bottled water packaging.

Wankai New Materials Co., Ltd. provides two varieties of bottle-grade PET resins, WK-801 and WK-801L, each with distinct intrinsic viscosities(IV) to cater to global customer needs. These resins are highly regarded for their excellent processability, food-grade safety, high strength, and transparency.

Two IV Options for Water Packaging

In international trade, understanding the HS codes for bottle-grade PET resins is essential, as tariff rates can vary based on intrinsic viscosity (IV). PET granules are classified into two HS codes: 3907.69.10 for resins with an IV below 0.78 dL/g, suitable for standard water bottles and lightweight packaging, and 3907.61.10 for resins with an IV of 0.78 dL/g or higher, commonly used in high-strength packaging solutions such as large-capacity containers and premium bottled beverages.

Intrinsic viscosity plays a crucial role in determining the processing and performance characteristics of PET resins, affecting flow behavior, mechanical strength, and product quality. Higher IV resins, like Wankai’s WK-801 (IV 0.8±0.02 dL/g), are engineered for applications requiring superior mechanical strength, impact resistance, and dimensional stability, making them ideal for large-capacity water bottles or premium product lines. Conversely, lower IV resins such as WK-801L (IV 0.77±0.02 dL/g) offer improved flowability during injection and blow molding, resulting in faster cycle times, smoother preform surfaces, and reduced energy consumption.

By providing these two IV options, Wankai ensures flexibility for manufacturers to select the optimal resin for their production needs, achieving a balance between product performance, production efficiency, and cost-effectiveness, ultimately catering to diverse market demands in water packaging.

Excellent Processability of WK-801 and WK-801L

Wankai's water bottle-grade PET resins, WK-801 and WK-801L, feature stable molecular weights and distributions, along with exceptional crystallization properties, ensuring outstanding performance across various processing conditions. 

Utilizing solid-state polymerization equipment from Polymetrix, equipped with Honeywell's DSC central control system, Wankai guarantees that all control points employ high-precision instruments and control valves for advanced design and reliable operation.

The content of terminal carboxylic acids is crucial in determining the polymer's molecular weight, directly affecting the plasticity and processability of bottle-grade PET resins. By effectively managing terminal carboxylic acid levels, Wankai enhances the flowability, melting temperature, and processing temperature of PET, ensuring exceptional performance under varying processing conditions.

After solid-state polymerization, WK-801 and WK-801L achieve intrinsic viscosities of 0.8±0.02 and 0.77±0.02, respectively, with terminal carboxylic acid contents below 28 mmol/kg. The moderate intrinsic viscosities provide excellent flowability during injection and blow molding, enhancing production efficiency. Additionally, the low terminal carboxylic acid content improves plasticity and transparency while reducing brittleness. This compatibility allows WK-801 and WK-801L to be used with various molding equipment, enabling manufacturers to select optimal processing conditions based on their needs. Consequently, this increases production efficiency and minimizes equipment changeover and adjustment times, while keeping energy consumption during processing low, effectively reducing overall production costs.

Balance Between High Strength and Transparency

The high strength of bottle-grade PET is essential for its widespread use in packaging. WK-801 and WK-801L achieve excellent mechanical properties, allowing bottles to withstand high pressure and impact while minimizing breakage during transport and storage. Wankai optimizes production processes to improve the density of molecular chains, enhancing tensile and compressive strength.

Additionally, by maintaining a terminal carboxylic acid content below 28 mmol/kg, the plasticity of the bottle preforms is improved, reducing brittleness and ensuring excellent strength across various temperatures. This not only preserves bottle integrity but also extends product shelf life, meeting market demands for durability and safety.

Through stringent quality control and standardized production processes, WK-801 and WK-801L deliver consistent high-strength performance across various specifications and usage environments, meeting the market's high demands for safety and durability.

Beyond strength, high transparency is crucial for bottled water packaging, enabling consumers to assess the water quality visually. Wankai achieves this balance by optimizing polymerization parameters and employing proprietary IPA esterification and low-temperature polymerization technologies, which enhance polymer flowability and transparency while maintaining strength.

Color stability is another key factor. Wankai uses a real-time color analyzer for dynamic adjustments during production, ensuring the L-value (whiteness/transparency) remains above 83 and the b-value (yellow/blue index) stays below -0.5. This efficient system ensures consistent quality, minimizes resource waste, and meets the visual standards of downstream customers.

Food Contact Safety of WK-801 and WK-801L

The food-grade safety of WK-801 and WK-801L stems from Wankai New Materials Co., Ltd.'s unique de-aldehyde process and stringent quality control measures, ensuring that these products not only comply with national standards in China but also meet international standards such as the EU REACH regulation, (EU) No 10/2011, and the US FDA 21 CFR 177.1630 requirements for food-grade polyester resins.

During the production of WK-801 and WK-801L PET resins, acetaldehyde—a volatile and potentially toxic byproduct—can form due to high-temperature oxidation, catalysts, or side reactions. Its presence in PET raw materials directly influences the acetaldehyde content in finished bottles, with studies showing a nonlinear correlation between the two under consistent production conditions.

Wankai minimizes acetaldehyde formation during solid-state polymerization of bottle-grade PET resins by using nitrogen as an inert gas to prevent oxidative and thermal degradation. To ensure high nitrogen purity, the production facilities employ a nitrogen purification system (NPV unit) that removes impurities like ethylene glycol and water. The purified nitrogen is then recycled, keeping acetaldehyde content below 0.7 μg/g, meeting Wankai’s internal standards and GB/T 17931 requirements.

After the solid-state polymerization reaction, the acetaldehyde content meets the requirements for food packaging. To further ensure the safety of bottle-grade polyester resins, Wanke's Quality Center employs headspace gas chromatography to test acetaldehyde levels. In addition to controlling acetaldehyde, Wankai’s Quality Control Center regularly tests for heavy metal content and other harmful substances to ensure strict safety compliance.

Conclusion

Wankai addresses the increasing demand for bottled water with its high-performance bottle-grade PET resins, WK-801 and WK-801L, which excel in processability, strength, transparency, and food safety. By offering two IV options tailored for both high-strength packaging and faster production cycles, Wankai provides manufacturers with flexible solutions. As the market shifts towards safer and more sustainable packaging, Wankai remains dedicated to innovation and quality, driving the sustainable development of PET materials while delivering cost-effective and eco-friendly choices.