Paper made from hydroxyapatite (HAP) nanowires is flame-resistent, in stark contrast to commercial cellulose-based paper. Credit: Chinese Academy of Sciences; Ying-Jie Zhu.
Fahrenheit 451? How about Fahrenheit 2012?
A group of scientists at Shanghai Institute of Ceramics, Chinese Academy of Sciences recently reported in Chemistry – A European Journal that they have developed nonflammable, flexible, and nontoxic paper out of hydroxyapatite (Tm=2012ºF).
Traditional paper is made from plant-based cellulose pulp and consumes a huge amount of natural resources and contributes to a large proportion of anthropogenic waste. The chemical stability of cellulose-based paper degrades over time or environmental conditions. Also, it is highly flammable, which complicates the ability to safely store archival printed documents.
Working to avoid these less desirable qualities of organic paper, scientists have been searching for inorganic paper alternatives for years. Previous innovations improved stability but consequently increased pollution and waste.
Hydroxyapatite is promising for papermaking because it is abundant, biocompatible, and nontoxic (it is the primary component of bones and teeth). However, hydroxyapatite is not very flexible due to the formation of short nanorods and nano needle structures. The Chinese scientists have now solved this problem, too, with a new solvothermal synthesis technique to synthesize ultralong nanowires of hydroxyapatite.
Ying-Jie Zhu, lead researcher on the study, described the new synthesis in a press release: “We have developed a new method, based on the use of a different reagent, which is calcium oleate. In this way we obtain HAP ultralong nanowires, with lengths of tens of micrometers and very high aspect ratios (>100). The as-prepared ultralong nanowires are highly flexible and can be bent or rolled without being broken.”
The scientists then made the nanowires into paper by simply suction-filtering nanowire-spiked solutions through a Büchner filter. The result is a sort of “super paper”—the authors show that it is strong, flexible, and heat- and flame-resistant. Although the paper is durable, adding sodium silicate as a binder can further strengthen the paper, the authors report.
Perhaps most importantly, the scientists could easily write and print on the paper, suggesting the material would be excellent for long-term archival storage of important documents. As a bonus, the paper is also highly adsorbet for organic pollutants, such as chloroform and toluene, and could potentially be used for pollution mitigation efforts.
Feature image credit: gfpeck; Creative Commons License.