4 (four) is the natural number following 3 and preceding 5.
Printing is a process for reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The earliest known form of printing as applied to paper was woodblock printing, which appeared in China before 220 A.D. Later developments in printing technology include the movable type invented by Bi Sheng around 1040 AD and the printing press invented by Johannes Gutenberg in the 15th century. The technology of printing played a key role in the development of the Renaissanceand the scientific revolution, and laid the material basis for the modern knowledge-based economy and the spread of learning to the masses.
A rubber band (also known as an elastic band, gum band or lacky band) is a polymer with viscoelasticity (having both viscosity and elasticity) and very weak inter-molecular forces, generally having low Young's modulus and high failure strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanisates. Each of the monomers which link to form the polymer is usually made of carbon, hydrogen, oxygen or silicon. Elastomers are amorphous polymers existing above their glass transition temperature, so that considerable segmental motion is possible. At ambient temperatures, rubbers are thus relatively soft (E~3MPa) and deformable. Their primary uses are for seals, adhesives and molded flexible parts. Application areas for different types of rubber are manifold and cover segments as diverse as tires, shoe soles, and damping and insulating elements. The importance of rubbers can be judged from the fact that global revenues are forecast to rise to US$56 billion in 2020. not in citation given.
Polymer that displays rubber-like elasticity. Rubber like solids with elastic properties are called elastomers. Polymer chains are held together in elastomers by weak intermolecular forces. These weak binding forces permit the polymers to be stretched. Natural rubber, neoprene rubber, buna-s and buna-n are elastomers.