Polymer architecture via abstraction of a hydrogen, can create a mid-chain growth site. Branching can be quantified by the branching index. An effect related to branching is chemical crosslinking - the formation of covalent bonds between chains. Crosslinking tends to increase T and increase strength and toughness. Among other applications, this process is used to strengthen rubbers in a process known as vulcanization, which is based on crosslinking by sulfur. Car tires, for example, are highly crosslinked in order to reduce the leaking of air out of the tire and to toughen their durability. Eraser rubber, on the other hand, is not
Rubber toughening viable option for practical applications in architecture and car manufacturing as a substitute for glass when high transparency is necessary. Incorporating a rubber filler phase increases the toughness. Such fillers need to form strong interfacial bonds with the PMMA matrix. In applications where optical transparency is important, measures must be taken to limit light scattering. It is common in toughening PMMA, and in other composites, to synthesize core-shell particles via atom-transfer radical-polymerization that have an outer polymer layer that has properties similar to those of the primary phase that increases the particle’s adhesion to the matrix. Developing PMMA compatible core-shell