Recently, several people have come to ask: Will plastic pallets freeze in cold storage? Will it break easily when thrown outdoors in winter? Compared to wooden pallets, which one is more valuable? At the end of the day, it's all about one question: can a tray bought at a high price work well in temperatures below minus ten or twenty degrees Celsius.
Nowadays, cold chain is becoming increasingly popular, from fresh produce to vaccines, and the requirements for trays in low-temperature environments are also increasing. Here are some of my own observations and summaries, hoping to help friends who are struggling with selection.
1, Plastic is afraid of cold, not all plastics are afraid
Let's first explain a principle: when plastics become brittle at low temperatures, there is actually a threshold called the "glass transition temperature". You can understand it as every type of plastic having its own 'freezing point' - once the temperature exceeds this point, the molecular chains cannot move, the material changes from soft and tough to hard and brittle, and can crack upon impact.
For example, ordinary polypropylene (PP) has a freezing point of around minus 10 ° C. In winter in the north, it is easy to exceed this limit outdoors or in cold storage. The freezing point of high-density polyethylene (HDPE) is as low as minus 120 ° C, making it a naturally frost resistant material.
2, Two common materials, one cold resistant and one cold sensitive
HDPE: The "cow tendon bottom" in cold storage
HDPE has high density and dense structure, and its biggest feature is toughness and resistance to cold. It can maintain elasticity and not crack in an environment of minus 40 ° C. More extreme data suggests that pure HDPE can withstand temperatures as low as minus 60 ° C. Industrial grade HDPE pallets can be used for a long time in cold storage at temperatures ranging from minus 30 ° C to minus 40 ° C. The key is that forklifts are inevitably bumped, and HDPE is as tough as beef tendon, so it won't explode if bumped - this is particularly important in cold storage.
PP: Hardcore who is afraid of cold
PP is much lighter than HDPE (with a density 20%~30% lower), has higher rigidity and hardness, and is also heat-resistant. It can be cooked and sterilized at over 100 degrees Celsius without any problems, making it suitable for high-temperature workshops and food heating scenarios. But its weakness is the low temperature difference. It becomes brittle below minus 10 ° C and should never be stored in a cold storage.
Summary in one sentence: HDPE is selected for cold storage, PP is used for high-temperature workshops, and the ambient temperature environment is free. If the situation is reversed, placing the PP tray in a cold storage at minus 18 ° C will soon result in cracks or even direct breakage, which is not worth the loss.
After rewriting in this way, common phrases such as "don't sell the key" and "come to the conclusion first" in the original text were removed, and the narrative order and metaphorical approach were changed. At the same time, all key data (glass transition temperature, -40 ° C, -60 ° C, etc.) and comparative conclusions were retained. Hope it meets your requirements.
3, Plastic pallets vs wooden pallets: a 'head-on battle' in low-temperature environments
Many companies are accustomed to using wooden pallets, thinking they are cheap and convenient. But in low temperature environments, the gap arises.
Plastic pallets can maintain stable performance in environments ranging from -25 ℃ to 40 ℃, while wooden pallets are prone to moisture absorption and expansion at low temperatures, leading to an increased risk of cargo damage. The surface smoothness of plastic pallets far exceeds that of wooden pallets, which can reduce cargo damage rates by 15% -20%. The comprehensive advantages of plastic pallets in cold chain scenarios are more prominent: wooden pallets are prone to moisture absorption and mold growth, do not meet the hygiene requirements of food cold chain, are prone to cracking in low temperature environments, and have a short service life.
A detailed test comparison data shows that wooden pallets can withstand temperatures ranging from -30 ℃ to+40 ℃, but are prone to cracking at low temperatures; Poor moisture and mold resistance, may absorb moisture and mold. In contrast, plastic trays have good moisture and mold resistance, do not absorb moisture, and are not easily cracked at low temperatures.
The difference in service life is also significant: the average service life of wooden pallets is usually 2-3 years, while high-quality new HDPE pallets can have a service life of 5-8 years, which is 3-4 times that of wooden pallets. A certain cold chain logistics enterprise has reduced fuel consumption by 12% in a single transportation by replacing wooden pallets with plastic pallets, improved manual handling efficiency by 30%, and reduced comprehensive annual operating costs by more than 60%.
4, Technological Upgrade: How to Make Plastic Trays More Frost Resistant
The answer is affirmative. The low temperature resistance of plastic pallets can be further optimized in various ways.
At the material formulation level, by adding nanoscale toughening agents and introducing elastic particles into HDPE, the low-temperature impact strength can be significantly improved. Currently, there are technologies in the industry that can increase the impact strength of pallets by more than 20% at -40 ℃, while maintaining material rigidity and meeting international cold chain transportation standards. Common additives also include toughening agents and plasticizers, where the softening temperature and brittleness temperature of plasticizers decrease, while elongation, flexibility, and flexibility increase; Antifreeze can reduce the brittleness temperature, enhance flexibility and flexibility.
At the structural design level, the "Chuanzi structure+reinforcing ribs" design can effectively reduce the risk of cracking caused by local stress by increasing the support area at the bottom of the pallet, dispersing the pressure on the goods. In addition, trays with double-sided structures or built-in steel pipes can disperse stress points and increase wall thickness, which also helps improve low temperature resistance.
It is worth mentioning that the selection of color masterbatch can also affect the low-temperature resistance of the tray - the compatibility between the carrier resin and the base plastic (such as polyethylene) is crucial, and mismatched formulations may lead to a significant decrease in low-temperature performance.
5, Real case: See how companies use it
Just talking about theory is not interesting, let's take a look at a few practical cases.
A frozen food enterprise used flat nine legged plastic pallets. After continuous use at -18 ℃ for 3 years, there were no cracks or deformations on the surface of the pallets, and the loss rate of goods decreased by 12%. Another fresh food e-commerce company has reduced the spoilage rate of goods from 1.2% to 0.3% after adopting customized cold chain trays. This improvement is largely due to the stable low-temperature performance of HDPE trays in -18 ℃ cold storage, which, combined with the tray structure, promotes even distribution of cold air and effectively avoids quality problems caused by local temperature differences.
In the field of pharmaceutical cold chain, vaccine transportation has extremely strict requirements for temperature and environment. A test conducted by a multinational pharmaceutical company showed that using plastic pallets to transport insulin preparations reduced the damage rate by 72% compared to traditional wooden pallets, and the pallets themselves can withstand high-temperature steam disinfection at 121 ℃, achieving more than 200 cycles of use. In the testing of JD Asia's No.1 warehouse, a certain type of pallet maintained stable performance even in extreme environments ranging from -30 ℃ to 80 ℃, resulting in a 35% increase in sorting efficiency and a significant decrease in cargo damage rate.
6, Practical selection suggestions
Pallets made of new HDPE raw materials are preferred. The recycled materials have broken and aged due to many impurities, which not only reduce the anti-aging performance by more than 50%, but also may release harmful substances. The food and pharmaceutical industries also need to confirm that the pallets have passed FDA food contact certification or comply with GB 4806.7 standards, and require suppliers to provide third-party SGS or TUV testing reports.
Choose the appropriate tray type based on actual needs - double-sided trays are suitable for shelf storage and high-strength stacking, Sichuan style trays are convenient for forklifts to enter four directions and suitable for high turnover scenarios, and nine legged trays are lightweight and suitable for ground ox handling and flat stacking.
It is recommended to reserve 10% -15% of the budget for large cold storage and choose modified HDPE special cold chain pallets. Key operating points: Before entering the cold storage from room temperature, gradually cool down the pallets in the buffer zone to avoid sudden temperature changes; When loading goods, evenly distribute the weight to prevent local stress concentration; Regularly rinse with high-pressure water guns and professional cleaning agents to maintain hygiene and extend lifespan.
The core of the performance of plastic pallets in low-temperature environments is one sentence: choose the right materials and use the right methods. HDPE is the best choice for low-temperature scenarios. With reasonable selection and maintenance, it can become a very reliable assistant in cold chain logistics. I hope this article can help friends who are struggling with the selection of low-temperature logistics.
