1. Bleaching:
* Purpose: To remove lignin and other impurities from paper pulp, making it whiter and brighter.
* Chemicals: Chlorine dioxide, hydrogen peroxide, sodium hypochlorite.
* Process: The pulp is treated with a bleaching agent in a controlled environment.
2. Sizing:
* Purpose: To make paper less absorbent and more resistant to ink feathering.
* Chemicals: Starch, rosin, synthetic polymers.
* Process: The sizing agent is added to the pulp during papermaking or applied to the finished paper surface.
3. Coating:
* Purpose: To improve the smoothness, gloss, and printability of paper.
* Chemicals: Clay, calcium carbonate, titanium dioxide, polymers.
* Process: A thin layer of coating material is applied to the paper surface.
4. Dyeing and Printing:
* Purpose: To add color and patterns to paper.
* Chemicals: Dyes, pigments, inks.
* Process: Dyes are dissolved in water and applied to paper, while pigments are suspended in a binder and applied using various printing techniques.
5. Chemical Treatments for Specialty Papers:
* Water resistance: Treated with waxes, resins, or polymers to repel water.
* Grease resistance: Treated with silicone compounds or other grease-repelling agents.
* Fire resistance: Treated with fire retardants like ammonium phosphate or boric acid.
* Antimicrobial properties: Treated with biocides to prevent microbial growth.
6. Degradation and Recycling:
* Purpose: To break down paper fibers and reuse them in new paper products.
* Chemicals: Sodium hydroxide (NaOH) and other chemicals used in the pulping process.
* Process: Paper is mechanically and chemically processed to separate fibers from lignin and other materials.
7. Aging and Degradation:
* Purpose: Natural process that changes paper's physical and chemical properties over time.
* Chemicals: Oxygen, humidity, pollutants.
* Process: Exposure to these factors leads to paper discoloration, embrittlement, and deterioration.
These are just a few examples of how paper can be chemically changed. The specific method and chemicals used depend on the desired properties and the intended application of the paper.
