The performance differences between high-density polyethylene (HDPE) medicinal ointment boxes and low-density polyethylene (LDPE) boxes stem from their fundamentally different molecular structures. HDPE molecules have linearly arranged chains with very few branches, allowing for tight packing and a highly crystalline structure. In contrast, LDPE molecules have numerous long and short branches, resulting in a looser molecular arrangement and significantly reduced crystallinity. This structural difference directly determines their significant differences in mechanical properties, thermal properties, barrier properties, and processing adaptability.
Regarding mechanical properties, high-density polyethylene medicinal ointment boxes exhibit superior strength and rigidity. Their high crystallinity gives the material greater hardness and impact resistance, making them less prone to deformation or breakage even under significant external forces, suitable for containing solid ointments or in applications requiring frequent opening and closing. In contrast, LDPE boxes, due to their higher degree of molecular chain branching, are softer. While they offer strong impact resistance, their rigidity is insufficient, making them more susceptible to deformation from compression or impact. They are more suitable for packaging highly fluid liquid ointments or in applications requiring flexibility.
The differences in thermal properties are equally significant. High-density polyethylene medicinal ointment boxes have a higher melting point and superior heat resistance, maintaining structural stability at higher temperatures and resisting softening and deformation due to temperature increases. They are suitable for packaging medicines requiring high-temperature sterilization or storage in warm environments. Low-density polyethylene boxes have a lower melting point and weaker heat resistance, making them prone to softening or even melting at high temperatures. Therefore, they are more suitable for packaging ointments stored under refrigeration or at room temperature, preventing packaging failure due to temperature fluctuations.
Barrier properties are another key area of difference between the two. High-density polyethylene medicinal ointment boxes have a denser molecular arrangement, providing stronger barrier properties against water vapor and oxygen. This effectively prevents ointments from deteriorating due to moisture absorption or oxidation, extending their shelf life. This characteristic makes them an ideal packaging choice for ointments requiring long-term storage or those sensitive to environmental conditions. Low-density polyethylene boxes have a looser molecular structure and relatively weaker barrier properties. While they can meet general short-term storage needs, their protective effect may be insufficient for medicines requiring strict moisture and oxidation prevention.
In terms of processing adaptability, both have their advantages due to their different molecular structures. High-density polyethylene medicinal ointment boxes have poorer flowability, requiring higher temperatures and pressures during processing. However, the molded products exhibit high dimensional stability, making them suitable for producing complex, high-precision packaging containers, such as threaded medicine bottles or irregularly shaped boxes. Low-density polyethylene boxes have lower melt viscosity, better processing flowability, and are easily blow-molded or injection-molded into thin-walled products, such as hoses or film packaging. They also offer higher production efficiency and lower energy consumption, making them more suitable for large-scale production.
Regarding chemical stability, high-density polyethylene medicinal ointment boxes exhibit excellent resistance to most acids, alkalis, and solvents. Even with prolonged contact with the chemical components of pharmaceuticals, they are unlikely to react, ensuring drug safety. While low-density polyethylene boxes have good chemical stability, they may swell or degrade upon contact with certain organic solvents or strong oxidizing agents. Therefore, it is necessary to select appropriate packaging materials based on the drug's composition.
In practical applications, high-density polyethylene medicinal ointment boxes, due to their high strength, heat resistance, and strong barrier properties, are often used to contain solid ointments, creams, or drugs requiring long-term storage, such as dermatological medications and topical ointments. Its sealing and stability effectively protect the quality of medicines and reduce losses during transportation and storage. Low-density polyethylene boxes, due to their softness and ease of processing, are more often used for packaging liquid ointments, ophthalmic preparations, or medicines that require squeezing, such as eye drops and hand creams. Their flexibility makes them easy for consumers to use, and their lower cost makes them suitable for large-scale production.
