Some common examples are carboxymethyl cellulose CMC , cationic and anionic hydroxyethyl cellulose EHEC , modified starch , and dextrin. In sizing , the strength and printability of paper is increased. Sizing also improves the hydrophilic character, liquid spreading, and affinity for ink. Starch is the most common sizing agent. Cationic starch and hydrophilic agents are also applied, including alkenyl succinic anhydride ASA and alkyl ketene dimers AKD.
Cationic starch increases strength because it binds to the anionic paper fibers. When starch exceeds the amount the fibers can bind to, it causes foaming in the production process as well as decreased retention and drainage. Surface modification makes paper hydrophobic and oleophilic.
Three different plasma-solid interactions are used: Plasma activation is where species in the plasma like ions, electrons, or radicals are used to chemically or physically modify the surface. Lastly, plasma coating is where material is coated to the surface in the form of a thin film. Plasma coating can be used to add hydrocarbons to surfaces which can make a surface non-polar or hydrophobic. The specific type of plasma coating used to add hydrocarbons is called plasma enhanced chemical vapor deposition process or PCVD.
An ideal hydrophobic surface would have a contact angle of degrees to water. This means that the hydrocarbons lie flat against the surface creating a thin layer and preventing dampening water absorption. However, in practice it is fine or even preferred to have a low level of dampening water absorption because of a phenomenon that occurs when water settles at the surface of paper.
A number of factors can influence the pH of a paper. Residual acids from processing, rosin or alum sizing, fillers used to create bulk, oils used to make paper transparent, optical brighteners, atmospheric sulfur dioxide, and the presence of lignins can all result in a pH of 4.
Recent study has shown that even the purest cotton papers will become slightly acidic, even though they left the mill at pH ranging between 6. This may be due to the nature of the paper itself, or because of exposure to air polluted with sulfur dioxide and oxides of nitrogen-common pollutants caused by the burning of fossil fuel-which turn water molecules into sulfuric acid and nitric acid.
Buffered papers are often slightly alkaline with a pH around 8. A pH moderately higher than 7 is not considered harmful in paper. The two situations where pH information is vital is in the case of paper and boards used for archival storage and framing, and in watercolor papers.
Materials used to help preserve artwork should have the highest standards. The whiteness of watercolor paper is another important factor because as paper acidifies it usually yellows. With the exception of watercolor papers, it is generally considered unnecessary in papers made with percent cotton because most percent cotton papers will acidify only slightly and stop.
It is becoming more commonplace to buffer wood-pulp art papers and boards to slow down, not stop, the discoloration and embrittlement process. The problem of maintaining a nonacidic pH with even percent cotton watercolor papers is the need to add a size to reduce absorbency. Alum is a combination of sulfates, which tend to acidify the paper, leaving it sometimes with a pH as low as 4. Exactly how much damage to a paper will be caused by a specific amount of acidity is debatable.
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The main ways chemistry is used in creating paper is when the lignin is dissolved in the water and taken from the cellulose. The next way chemistry is used is when the fibrils from the cellulose bond together to form a compact structure called paper.
Paper chemicals designate a group of chemicals that modify the properties of paper. These chemicals can be used to alter the paper in many ways, including changing its color and brightness, or by increasing its strength and resistance to water.
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The two situations where pH information is vital is in the case of paper and boards used for archival storage and framing, and in watercolor papers. Materials used to help preserve artwork should have the highest standards. The Institute of Paper Chemistry was established in as a partnership between Lawrence College (now Lawrence University) and the local paper industry. It was a graduate institute for training paper chemists, organized by Lawrence but financed by the paper industry.