Last Updated on: 26th November 2021, 09:48 am
For the last 30 years, plastisol inks have been a pillar of the textile screen printing industry. While in certain applications such as high solids acrylic (HSA), silicones, discharge, and modern water-based inks, innovations are common, plastisols are still the go-to option for most of the impressed sportswear industry.
The plastisol screen-printing inks manufactured today come from a wide variety of performance factors. Each product line typically is designed to address a specific screen-printing application, including:
- Soft-hand applications
- Athletic-printing applications
- High-elongation fabrics
- Photographic reproduction
- Nylon and synthetic applications
- Special effect applications
Unlike the ink lines from the past, today, most plastisols are manufactured straight from the bottle as ready-to-use goods. While that is the case, there is also a wide variety of chemical modifications required to improve the output of the ink depending on the desired results of the final product.
Here, let’s look at the currently accessible modifications for plastisol screen printing, as well as their advantages, disadvantages, and any caution that should be added while using them.
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Plastisol Ink Additives for Application in Screen Printing:
The following plastisol additives you must use to optimize your screen printing process.
1. Soft-hand Extenders:
Soft-hand Extender is one of the most common additives on the market. Moreover, initially designed to minimize the athletic look of the prints.
Many decorators used coarser mesh counts and excessive ink films before the onset of high-tension screen printing, resulting in the introduction of soft-hand extensors to help minimize that effect.
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Such extenders are particularly useful when printing light-colored garments. As the soft-hand extenders are lower in viscosity, it improves the movement and penetrates the ink film through the cloth.
Keeping in mind that you want the ink film on the fabric’s surface and not being driven too much into the garment, higher-tension screens also contribute to this effect.
There is no actual limit to how much an opaque plastisol can be added to a soft-hand extender, as long as you know that the overall opacity of the ink will decrease as the extender-to-ink ratio increases.
2. Viscosity Reducers:
A viscosity reducer is the most common additive employed by many plastisol screen printers and can be of great help when properly employed. There are two basic types of viscosity reducers in plastisol printing applications: straight plasticizer reducers and curable reducers.
The former can be effective if correctly used and calculated according to the guidelines of the supplier.
The trouble with straight plasticizer reducers was that many printers wouldn’t accurately calculate the necessary volume. Which sometimes culminated in an unnecessarily plasticized ink that wouldn’t cure accurately and a finished print with low washability properties.
Back in the 1980s, when there was a discovery of curable reducers.
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This form of viscosity reducer is a liquid plasticizer with a balanced amount of resin. It allows for a proper cure for the reduced ink. This eliminates the danger of poor washability of a subsequent trans paper.
Thus enabling screen printers to change the ink as per their preference.
It would be best if you take caution because the application of an unnecessary amount of curable reducer will result in low visibility. Most importantly, if the viscosity of the ink becomes too small.
As for every plastisol additive, you must strictly adhere to the manufacturer’s instructions for proper mixing directions.
3. Flash Additives:
The goal of this form of plastisol additive is to reduce the flash time for normal plastisol inks. Responsive to heat and susceptible to scorching, flash additives are helpful when printing on polyester or tri-blends.
This minimizes the fabric when printing on tri-blends. Exposure to sunlight can further reduce the likelihood of bruises. On the other hand, polyester fabrics do not tend to scorch as easily as tri-blends. Still, the risk of sublimating polyester coloring — which only promotes the potential for dye sublimation or migration — should be taken into account.
Therefore, you may benefit from the final product from any heat mitigation that may implement into the cycle.
Depending on the manufacturer, you can apply flash additives to a typical plastisol up to 10 per cent by weight.
Again, obedience to the manufacturer’s mixing instructions is often necessary.
4. Foil-Release Additives:
Any plastisol textile screen printer who has ventured into the special-effects realm of foil applications has experienced working with foil-release additives. As foil had an inherent ability to stick to plastisol ink film’s surface, the ink must be modified to reject the foil’s bonding characteristics.
Foil applications can be tricky due to several variables within the process, including:
- Plastisol brand
- Ink-film thickness on the fabric
- Foil brand
- Amount of foil-release additive in the ink
- Heat-transfer time, temperature, and pressure
It’s not unusual to spend time upfront conducting research and development tests to find the optimal combination of parameters to produce consistent results.
The best starting point is with the manufacturer’s recommendations. It is for both the amount of foil-release additive and the foil-transfer instructions.
Furthermore, you may need to adjust the additives to achieve optimal, repeatable results.
5. Nylon-Catalyst Additives:
Synthetic materials such as nylon have an incredibly smooth woven coating instead of the coarse, knitted coating of a T-shirt. It makes it much more challenging to attach a plastisol ink to the cloth correctly.
Its effect amplifies on a waterproof product, such as Scotchgard. It allows the need for a solvent for nylon imperative.
Nylon-catalyst additives not only will enhance a plastisol’s bonding capabilities to a nylon woven fabric’s surface but also will lower the ink’s core temperature.
It is an advantage, as many synthetic fabrics like nylon can’t withstand the full curing temperatures of 320°F required for standard plastisols.
6. High-Elongation Additives:
Currently, people are using high-elongation speciality inks and additives across several different ink lines.
The high-elongation liquid and liquid additives are very effective when printing on fabrics such as spandex and lycra.
It is necessary to avoid dyed fabrics containing polyester while dealing with such materials because high-elongation additives can facilitate dye migration.
While regular plastisol inks have a reasonable degree of elongation, fabrics such as spandex and Lycra need the ink without cracking to provide an elongation factor of up to 300 percent.
The percentage of additive or clear to add to a standard ink will vary among manufacturers. Mixing instructions — as with any additive — should be strictly followed to achieve the best results.
Given the fact that you intend to print plastisol inks straight from the bottle. Therefore, you may come across various circumstances where they may require different adjustments to increase the efficiency of the ink depending on application and substratum.
Once it comes to adding in such ingredients, try to obey the supplier’s instructions to obtain optimal performance.
Many screen printers started using these six plastisol ink additives as it makes screen printing work easier. As viscosity reduces, color enhancers and reduce wastage.
These additives result in a properly finished print, while you must follow the manufacturer’s instructions to measure the required amount.
What is plastisol ink made of?
Plastisol ink is made up of plasticizing emulsion particles of PVC particles. It is recommended to use plastisol inks for printing on colored fabrics.
Which one is better; plastisol or water-based?
Plastisol inks give vibrant prints, especially on darker garments. They feel stiffer. At the same time, water-based ink is thin and suitable for light-colored garments.
Are plastisol inks safe?
Plastisol inks are made from polyvinyl chloride that reacts with other chemicals to form dioxins. Dioxins are toxic chemicals that affect health. So, plastisol inks must be handled carefully and kept out of children.
At what temperature does plastisol ink cure?
Plastisol ink cures at a temperature of 300 – 330º F.