From raw material to finished product: The journey of plastic pallets

In the vast system of modern logistics industry, plastic pallets, although seemingly low-key, play a crucial role and are undoubtedly the heroes behind the scenes. Whether it's the mountains of goods piled up in large storage centers or the logistics trucks shuttling on city roads, plastic pallets are indispensable. It is like a reliable partner, silently carrying goods and ensuring efficient and smooth logistics transportation. According to relevant data, in the current booming development of e-commerce, every journey of express packages from warehouses to consumers is likely to be assisted by plastic pallets, which have a high coverage rate in the logistics process.

Have you ever been curious about how these ubiquitous plastic pallets have gradually transformed from raw materials into practical logistics tools? What kind of magical craftsmanship endows them with sturdy and durable characteristics? Don't worry, let's delve into the world of plastic pallet production together and explore the truth.

1、 Raw materials: selection of cornerstone

（1） Analysis of Common Raw Materials

In the production of plastic pallets, polypropylene (PP) and polyethylene (PE) are the two main players and the most commonly used raw materials. Polypropylene, a thermoplastic, has attracted much attention for its outstanding mechanical properties and heat resistance. It has high hardness and strong rigidity, making PP plastic pallets stable and not easily deformed when carrying heavy objects. It is very suitable for handling and storing heavy goods in warehousing and logistics. Moreover, PP has good chemical stability and is "immune" to most acid, alkali, and salt solutions, which makes it highly effective in special industries such as chemical engineering. In some chemical storage and transportation scenarios, PP plastic pallets ensure the safe storage and transportation of chemicals due to their corrosion resistance. In addition, PP has a relatively low density, making the produced pallets lighter and easier for workers to handle, reducing labor intensity. However, PP plastic pallets are not perfect either. Their low temperature resistance is poor and they are prone to becoming fragile in low temperature environments, which limits their use in low-temperature places such as cold storage.

Polyethylene is another widely used raw material with excellent flexibility and impact resistance. PE plastic pallets are like "anti hit players" that can effectively cushion external impacts and are not easily broken. This feature makes them particularly suitable for working in environments with frequent collision risks, such as logistics transfer centers that frequently load and unload goods. Moreover, PE has excellent low-temperature resistance, even in cold storage with temperatures as low as -40 ° C, it can maintain good flexibility and function normally. In the fields of food processing and cold chain logistics, goods often need to be stored and transported in low-temperature environments, and PE plastic pallets can perfectly handle it, ensuring the freshness and safety of food. However, the mechanical properties of PE plastic pallets are relatively average, with low tensile strength. They are prone to deformation when carrying heavy objects for a long time, and their hardness is not high. They are also prone to scratches and wear during use.

（2） Pre treatment of raw materials

After selecting the raw materials, the pre-treatment process is crucial. Firstly, granulation treatment should be carried out to crush and granulate large plastic raw materials through professional equipment, making them into uniform small particles. This process is like crushing large stones into small ones, which not only facilitates subsequent processing in the injection molding machine, but also ensures that the raw materials are more uniform when heated and melted, thereby ensuring the quality stability of the plastic tray. Imagine if the raw materials are of different sizes, there may be over heating in some areas and under heating in others during the injection molding process, resulting in uneven performance of the tray.

During granulation treatment, it is also necessary to ensure the purity of the raw materials. Manufacturers will use various screening and impurity removal equipment to remove impurities from raw materials, even the smallest foreign objects may affect the quality of plastic pallets. For example, if metal debris is mixed into the raw materials during injection molding, these debris may damage the internal structure of the tray, causing cracks or even fractures during use. In order to further ensure quality stability, strict quality testing will be conducted on raw materials, including testing of their physical and chemical properties. Only raw materials that meet the standards can enter the next production process.

2、 Production process: The magic of shaping trays

（1） Injection molding process

The injection molding process can be regarded as the "main force" in the production of plastic pallets and is widely used. The entire process is like an orderly and precise performance. Firstly, the pre treated plastic pellets are fed into the barrel of the injection molding machine, where they undergo a high-temperature "baptism". The temperature inside the barrel is usually precisely controlled within a certain range according to the type of plastic, such as 180-230 ° C for polypropylene (PP) and 160-220 ° C for polyethylene (PE). Under the action of high temperature, plastic particles gradually melt and become a melt with good fluidity, as if endowed with flowing vitality.

Next, we enter the high-pressure injection stage. The screw of the injection molding machine is like a strongman, rapidly injecting molten plastic into the mold cavity with extremely high pressure. This pressure is quite astonishing, usually reaching tens to hundreds of megapascals. The strong pressure drives the melt to quickly fill every corner of the mold, accurately shaping the shape of the tray. At this moment, the mold is like a magical "magic box" that determines the final shape of the tray.

After the mold cavity is filled, it enters the cooling and shaping stage. The cooling system begins to function by circulating water or other cooling media to remove the heat from the mold and plastic melt, gradually cooling and solidifying the plastic. This process is like "cooling and shaping" the tray, transforming it from a soft melt into a sturdy finished product. The control of cooling time is crucial as it directly affects the quality and production efficiency of pallets. If the cooling time is too short, the tray may not fully solidify, resulting in deformation, unstable dimensions, and other issues; If the cooling time is too long, it will reduce production efficiency and increase costs. Generally speaking, the cooling time will be adjusted based on factors such as the thickness and size of the tray, as well as the characteristics of the plastic, usually ranging from tens of seconds to a few minutes.

The advantages of injection molding process are very significant. Its production efficiency is extremely high, and it can quickly produce a large number of plastic pallets, which is crucial for meeting the large-scale demand in the market. Moreover, injection molded trays have high dimensional accuracy and can be strictly controlled within a small tolerance range. The surface quality is also very good, smooth and even, without the need for excessive subsequent processing. In addition, this process also has strong adaptability and can produce trays of various shapes and structures, whether they are flat, grid, or trays with different structures such as Sichuan, Tian, and Jiujiao at the bottom, they can be easily handled. However, there are also some shortcomings in the injection molding process. The high cost of molds is a major pain point, and the production cost of a set of molds may reach tens of thousands or even hundreds of thousands of yuan, which is a considerable expense for some small businesses. Moreover, the investment in injection molding equipment is also significant, requiring a large production space. At the same time, this process has high requirements for raw materials, and the quality and performance of raw materials will directly affect the quality of pallets. The injection molding process is suitable for producing plastic pallets with complex structures, high dimensional accuracy requirements, and large batch sizes. It is widely used in industries such as food and beverage, chemical and pharmaceutical, and logistics.

（2） Blow molding process

The blow molding process has unique charm and principles. Its first step is to extrude the tube blank. The plastic raw material is put into the extruder, heated and melted, and then extruded through a specific die head to form a tubular shaped blank. This blank is like a 'hollow semi-finished product', laying the foundation for subsequent molding.

Subsequently, it enters the crucial stage of blow molding. Quickly place the just extruded hot billet into the blow molding mold, and then introduce compressed air into the billet. Under the action of high-pressure air, the billet rapidly expands like a blown up balloon, tightly adhering to the inner wall of the mold, thus forming the shape of a tray. Just like when blowing a balloon, the air expands the balloon and makes it stick to the mold. After the tray cools and solidifies, the mold is opened, and a complete blow molded tray is born.

There are significant differences between blow molding process and injection molding process. From the perspective of product structure, blow molded trays are mostly hollow structures, which makes them relatively lightweight and also have good cushioning performance. And injection molded trays are usually solid. In terms of molds, blow molding molds are relatively simple and cost-effective, which makes them advantageous in some cost sensitive application scenarios. Injection molds are more complex and require higher precision. The advantages of blow molding technology are also prominent. It can produce larger sized pallets to meet the needs of handling and storing large goods. Moreover, blow molded trays have good impact resistance. When subjected to external impact, the hollow structure can effectively absorb and disperse the impact force, reducing tray damage. In addition, due to the low cost of blow molding molds, the blow molding process can also adapt well to the production needs of small batches and customized trays.

（3） Introduction to other processes

In addition to the two main processes mentioned above, there are also vacuum forming and extrusion forming methods. Vacuum vacuum forming method is to use vacuum suction to adsorb the heated and softened plastic sheet onto the surface of the mold, thereby forming. This process equipment and mold have lower costs and are suitable for producing trays with relatively simple shapes and low strength requirements. For example, some small pallets used for display or lightweight item handling. However, the wall thickness of vacuum formed trays is uneven and the strength is relatively weak.

The extrusion molding method is to use the extrusion effect of a screw or plunger to force the melted polymer material through the die under pressure, thereby forming a tray with a constant cross-section. This process is currently less widely used in China and only appears in a few places. Its characteristics are high production efficiency and the ability to produce continuously, but the shape of the product is relatively simple, mainly suitable for producing trays with specific cross-sectional shapes.

3、 Quality Inspection: Guardian of Quality

（1） Size and deviation detection

Accurate size is crucial for plastic pallets, as it directly affects their compatibility with other logistics equipment. During the inspection, the staff will use various high-precision measuring tools, such as tape measures, vernier calipers, etc. Taking a tape measure as an example, its accuracy can usually reach millimeter level, which can accurately measure the length, width, and height of the tray. For the fork hole size of the pallet, including length, width, and depth, strict control is necessary to ensure that it can perfectly match the forklift. Imagine if the fork hole size is too small, the fork of the forklift cannot be inserted smoothly, which will lead to difficulties in loading and unloading goods and seriously affect logistics efficiency; However, if the size of the fork hole is too large, the fit between the pallet and the fork will not be tight during transportation, which poses a safety hazard.

During the measurement process, the actual measured values will be carefully compared with the design standards and customer requirements. Generally speaking, the allowable size deviation of plastic pallets is controlled within a small range. For example, the length and width deviation of the tray may be required to be controlled within ± 5mm, and the height deviation may be controlled within ± 3mm. Only pallets with dimensional errors within the specified allowable range can seamlessly connect with shelves, handling equipment, etc. during storage and transportation, improving the efficiency and safety of logistics operations.

（2） Load and strength testing

Load and strength testing is a key step in evaluating the quality of plastic pallets, mainly through simulating actual usage scenarios. During the static load test, a certain weight of load will be evenly placed on the tray and maintained for a period of time, usually 24 hours or even longer. During this process, the staff will closely observe the deformation of the tray, such as whether the panel of the tray is concave, whether the bottom support structure is bent or deformed, and whether there is any damage, such as cracking, fracture, etc. Through static load testing, it is possible to accurately understand the maximum weight that a pallet can withstand in a stationary state, which is of great reference significance for stacking and storing goods in a warehouse.

The dynamic load test simulates the dynamic situation of the pallet during transportation, loading and unloading. Will use forklifts or other handling equipment to perform multiple loading and unloading operations on pallets with a certain weight of goods, allowing the pallets to undergo actions such as lifting, moving, and lowering. During this process, focus on the load-bearing capacity and structural stability of the tray in motion, and observe whether there are any deformation, breakage, or other issues with the tray. Because in actual logistics operations, pallets are often subjected to dynamic impact forces, dynamic load tests can effectively test the performance of pallets in such situations.

If the pallet is used for shelf storage, a shelf load test is also required. Place the pallet on the shelf, load a certain weight of goods, and observe the load-bearing capacity and deformation degree of the pallet on the shelf. When storing on shelves, pallets not only have to bear the weight of the goods, but also the pressure of the shelf crossbeam, as well as the complex forces such as vibration during the storage and retrieval process. Therefore, shelf load testing is crucial to ensure the safe use of pallets in the shelf environment.

（3） Other performance tests

In addition to size and load related testing, performance testing such as corrosion resistance and temperature resistance of pallets cannot be ignored. In corrosion resistance testing, trays that may come into contact with chemical substances are soaked in a solution of a certain concentration of acid, alkali, salt, etc. After a period of time, the corrosion of the tray is observed. For example, in the chemical industry, pallets often come into contact with various corrosive chemicals. If the corrosion resistance is poor, the pallets will be corroded and damaged, leading to cargo leakage and causing safety accidents.

Temperature resistance testing is divided into high temperature resistance and low temperature resistance testing. During the high temperature resistance test, the tray is placed in a high-temperature environment, usually set at a temperature of 50-80 ° C or even higher, to observe whether the tray undergoes deformation, softening, and other phenomena. And the low temperature resistance test is to place the tray in a low temperature environment, such as -20-40 ° C commonly found in cold storage, to detect whether the tray will become brittle or crack. In cold chain logistics, goods need to be stored and transported in a low-temperature environment, which requires pallets to have good low-temperature resistance to ensure the safety and stability of the entire logistics process.

4、 Personalized customization: meeting diverse needs

In today's diversified market environment, personalized customization services for plastic pallets are increasingly favored by enterprises. Different industries and enterprises have different demands for plastic pallets, and personalized customization can accurately meet these diverse needs, making plastic pallets better adapt to the production and logistics processes of enterprises.