Why Do an Eraser and a Scale Stick Together After Being Stored in a Pencil Case?
Have you ever tried to separate a stuck eraser and scale after placing them in a pencil case for a long time? If so, you're not alone. This phenomenon is not uncommon and is often due to a combination of factors related to the material composition of the eraser and scale, dust and debris, heat and humidity, and pressure. In this article, we will explore these factors in detail, providing a comprehensive understanding of why this happens and how to prevent it.
Material Composition and Stickiness
Many erasers are made from rubber or a similar polymer, which can become sticky or tacky over time, especially if they are of lower quality. This stickiness can cause them to adhere to other surfaces. Additionally, the scale is typically formed by mixing a variety of organic polymers such as polystyrene (PS), polymethyl methacrylate (PMMA), also known as plexiglass, and polypropylene (PP). On the other hand, the formulation of plastic erasers is usually composed of PVC and other compounds, plasticizers, fillers, stabilizers, and processing aids. The use of plasticizers significantly affects the properties of rubber. By increasing the distance between molecules, plasticizers reduce intermolecular attraction, making the material softer. However, uneven mixing and insufficient plasticization during the production process can lead to small bubbles and scratches, which are difficult to avoid.
Dust and Debris Accumulation
Over time, dust, pencil shavings, and other debris can accumulate on the surfaces of both the eraser and the scale. This accumulation can create a slightly adhesive layer that makes them stick together. The sticky residue from the eraser can interact with other surfaces, including the scale, leading to adhesion.
Effects of Heat and Humidity
Storage conditions play a crucial role in determining whether the eraser and scale will stick together. If the pencil case is stored in a warm or humid environment, the heat can cause the rubber in the eraser to soften, increasing the likelihood of adhesion. Additionally, humidity can promote the degradation of materials, making them more sticky. These environmental factors exacerbate the stickiness of the rubber and can further contribute to the adhesion issue.
Pressure and Deformation
When the pencil case is tightly packed, the pressure can cause the eraser to deform slightly, leading to adhesion with the scale. This deformation can be particularly noticeable if the eraser is placed in a tight space or if it is in contact with the scale for an extended period. The deformation can cause molecular-level changes that increase the likelihood of sticking.
Prevention and Maintenance
To prevent the eraser and scale from sticking together, consider storing them separately or using protective covers. Protective covers can help reduce the buildup of dust and debris and protect the surfaces from environmental factors. Additionally, properly storing the pencil case in a cool, dry place can help maintain the integrity of the rubber and other materials, reducing the likelihood of stickiness.
Conclusion
The stickiness between an eraser and a scale after prolonged storage in a pencil case is often due to material composition, dust and debris, heat and humidity, and pressure. Understanding these factors can help you use the eraser and scale more effectively and prevent unnecessary frustration. By taking appropriate preventive measures, you can ensure that your writing and drawing tools stay in top condition.