Yes, plastisol can go bad or, more accurately, change in quality and usability over time. Its useful life is directly influenced by its specific formulation and how it's stored.
Plastisols are designed to be stable, but like many chemical compounds, they will most likely undergo changes over time. These changes can affect their performance, printability, and final cure characteristics. To maintain optimal quality, it's crucial to use plastisol materials on a first-in, first-out (FIFO) basis as quickly as possible.
What Makes Plastisol Change Over Time?
The longevity and stability of plastisol are not universal; they vary significantly based on several factors:
- Specific Formulation: Different plastisol inks are made with varying plasticizers, resins, pigments, and additives. Each formulation has its own inherent shelf life, with some being more stable than others. For instance, high-opacity inks or those with specialized additives might have different aging characteristics than standard colors.
- Storage Conditions: Environmental factors play a critical role. Exposure to extreme temperatures, humidity, and direct sunlight can accelerate the degradation process. Heat can cause plasticizers to migrate or evaporate, altering the ink's viscosity and texture.
- Contamination: Introducing foreign substances, such as dust, lint, solvents, or even other types of ink, can compromise the plastisol's stability and performance.
- Air Exposure: While plastisol doesn't "dry" in the air like water-based inks, prolonged exposure can still lead to changes, such as skinning or the absorption of moisture, which can affect flow and print quality.
Signs of Deteriorated Plastisol
Recognizing when plastisol has gone bad is important to prevent printing issues and ensure quality results. Here are common indicators:
| Sign of Deterioration | Description | Impact on Printing |
|---|---|---|
| Increased Viscosity | The ink becomes noticeably thicker, more gummy, or stiff, making it difficult to stir or pass through the screen mesh. | Leads to poor flow, inconsistent ink deposit, difficult screen clearing, and blurry prints. |
| Separation | Components of the ink (pigments, plasticizers) begin to separate, forming layers, or developing clear liquid on top or bottom. | Results in inconsistent color, poor opacity, and uneven texture. |
| Graininess/Grit | The ink feels gritty or contains small, hard particles when rubbed between fingers, indicating pigment agglomeration or contamination. | Can clog screens, cause pinholes, and lead to a rough print surface. |
| Color Shift | The color appears duller, darker, or has an off-hue compared to fresh ink, due to pigment degradation or separation. | Inaccurate color matching and inconsistent branding. |
| Poor Adhesion/Cure | Even after proper curing temperatures, the ink may remain tacky, crack easily, or fail to adhere properly to the substrate. | Durability issues, prints wash out or crack, leading to product returns. |
| Unusual Odor | A strong, chemical, or rancid smell, indicating degradation of components or bacterial growth (though less common with plastisol). | While not directly affecting print, it's a sign of chemical instability. |
Best Practices for Extending Plastisol Shelf Life
To maximize the useful life of your plastisol inks and ensure consistent printing results, adhere to these practices:
- Implement FIFO: Always use your oldest stock first. This prevents inks from sitting too long and developing issues.
- Proper Storage Environment:
- Store plastisol in a cool, dry place. Ideal temperatures typically range from 65-85°F (18-29°C).
- Avoid extreme temperature fluctuations, which can cause plasticizer migration.
- Keep containers tightly sealed to prevent air exposure and contamination.
- Store away from direct sunlight or any other heat sources.
- Maintain Cleanliness:
- Use clean utensils when stirring or scooping ink.
- Avoid introducing lint, dust, or other debris into the ink.
- Do not mix different ink types or brands unless specifically recommended by the manufacturer.
- Inspect Before Use: Before each use, visually inspect the ink for any signs of separation, thickening, or contamination. Stir thoroughly to re-incorporate any settled components.
By understanding how plastisol ages and implementing proper storage and handling techniques, you can significantly extend its useful life and maintain high-quality printing standards.
