The critical surface tension of polypropylene (PP) is a measure of the highest surface tension of a liquid that can wet the polymer. It is crucial for understanding and predicting how PP will interact with other materials, especially in applications like coatings, adhesives, and printing. Generally, the critical surface tension of polypropylene is around 29-31 dynes/cm. This relatively low value indicates that PP has a somewhat hydrophobic surface, making it challenging to adhere to or print on without surface treatment. Techniques like corona treatment, plasma treatment, or the application of a primer are often used to increase the surface energy of PP, improving adhesion and wetting properties. Understanding this property is essential for engineers and designers who work with polypropylene to ensure the compatibility and efficacy of PP in various applications.

In the context of zircon (ZrSiO4), the strength of the Si-O (silicon-oxygen) bond is generally stronger than that of the Zr-O (zirconium-oxygen) bond. The ionic radius of Zr is larger than that of Si, leading to a less effective overlap in the Zr-O bond compared to the Si-O bond. Consequently, the Si-O bond exhibits stronger covalent character and, as a result, greater bond strength. This difference in bond strength is crucial for the stability and durability of the zircon structure, making it resistant to high temperatures and chemical corrosion. Thus, within the zircon lattice, SiO bonds play a pivotal role in its renowned properties.

In 1791. titanium was discovered.