Hydrochromic Pigment

They work by chemical reaction and physical reaction.

Generally, hydrochromic pigments are humidity-dependent, which change colors in response to the ambient humidity. This is a kind of physical reaction related to hygroscopicity. Hydrochromic pigments are mostly composed of moisture-absorbing agents (e.g. calcium chloride and potassium chloride) and color-changing agents (e.g. phenolphthalein and barium iodide).

Due to poor hygroscopicity of moisture-absorbing agents, hydrochromic pigments have original colors at low humidity. As the ambient humidity rises, moisture-absorbing agents will absorb more water molecules, which will change the molecular structure of color-changing agents, thus changing the moisture absorption spectrum of pigments and leading to different colors.

Indicators in wet dressings are another type of hydrochromic pigments, such as red hydrochromic indicators in Vaseline gauze dressings. They are usually made through chemical reaction. For example, red indicators containing bromophenol blue is made by acid-base neutralization reaction in water. Changes in the molecule structure of bromophenol blue in the neutralization reaction will lead to changes in moisture absorption and colors. Accordingly, indicators change from red to other colors in water.

In addition to the above two, there are some special hydrochromic pigments, such as capsuled color-changing agents, which react with water as capsules are broken and thus change colors. This is often applied to ensure the stability and controllability of hydrochromic pigments.

In short, the properties of hydrochromic pigments are related to the hygroscopicity, chemical reaction or physical reaction of raw materials. Due to the hygroscopicity and chemical reaction, hydrochromic pigments change colors in the presence of water molecules, which are widely applied in many fields.

1. Hydrochromic Toys

Hydrochromic pigments are widely applied in toys. Most of toys contain color-changing fillings which change colors immediately if touched with wet hands, thus leading to more fun and surprise for children.

2. HydrochromicPrinting

Hydrochromic pigments are crucial in printing. Hydrochromic inks are widely applied in bills, trademarks, seals and the like to prevent forgery and tampering. The security of bills can be enhanced as they are checked for water scrubbing.

3. Hydrochromic Textile

Hydrochromic fabrics are widely used in textile, such as a lot of swimwear and raincoats. They change colors immediately when they are exposed to water, reminding users that they are wet. They have both practical and decorative effects.

4. Environmental monitoring

Hydrochromic materials are widely used in environmental monitoring. For example, waterproof labels made of hydrochromic paper are used to monitor water leakage of buildings, bridges and other structures. Hydrochromic paper indicates water leakage as they change color immediately in water.

Hydrochromic inks change colors due to special properties of modified pterimide compounds (main raw materials). Pterimide compounds are organic molecules with special fluorescent properties and high hydrophilicity. Their molecule structures change in water, thus leading to color changes.

1. Advantages, shortcomings and applications of hydrochromic inks
2. Hydrochromic inkadvantages

Hydrochromic inks have excellent anti-counterfeiting effects to prevent fake goods in the market and protect the legitimate rights and interests of consumers. Meanwhile, they are helpful to effectively curb illegal activities, such as piracy and counterfeiting. They have high coloring power to facilitate identification.

2. Hydrochromic inkShortcomings

Hydrochromic inks are applicable to a limited extent. They are usually used in watermark paper, anti-counterfeiting labels, etc. They must not be directly applied in ordinary paper, plastics, etc. In addition, they cannot be prepared with simple processes and low costs.

2. Hydrochromic inkApplications

Hydrochromic inks are widely applied in anti-counterfeiting materials, watermark paper, anti-piracy materials, anti-counterfeiting labels, etc. For instance, they are suitable for bankbooks and drafts in banks; stamps in postal services; insurance documents, bills, security documents, trademarks and seals of insurance companies, etc.