Shape memory natural rubber

Abstract

Charles Goodyear discovered the vulcanization of natural rubber (NR) 170 years ago and transferred the gooey natural compound into the first representative of an entirely new class of materials; the elastomers. Thenceforth, NR was intensively explored and was used for countless products to date. All the more surprising, it was found recently that NR exhibits superior and unexpected properties whenever it is cross-linked to a degree smaller than 0.4% which is fairly below the commonly used 1%-2%. This article gives a brief overview on the exceptional properties of lightly cross-linked NR, named shape memory natural rubber (SMNR), including the cold programmable shape memory effect, storing of extremely large strain, energy and cold, and its capability to sense and memorize environmental parameters.

Shock‐ and Energy‐Absorption Capability of Cold‐Programmable Shape Memory Polymers

“…Cold‐programmable shape memory polymers (SMPs) like shape memory natural rubber (SMNR) and lightly cross‐linked syndiotactic polypropylene (x‐sPP) might be promising candidates for mimicking the properties of spider dragline silk. This is due to the crystallization‐inhibition of these polymers and that they transform themselves from a fully amorphous, rubber‐like into a semicrystalline, high modulus state upon stretching to large elongations and retain the latter after removing the stretching force.…”

The Influence of Bleached Jute Fiber Filler on the Properties of Vulcanized Natural Rubber

“…Vulcanized natural rubber has several properties that are superior to those of synthetic rubbers, such as high elasticity and high tensile strength 1,2 . Such properties make it an exceptional material for use in several technological products 2 .…”

“…Such properties make it an exceptional material for use in several technological products 2 . However, there has been growing interest in the substitution of the synthetic fillers, which are widely used in industrially manufactured rubber composites, by natural fillers that are extracted from a renewable sources because of the sustainability of natural rubber [3][4][5] .…”

Thermo‐/moisture‐responsive shape‐memory effect of poly(2‐ethyl‐2‐oxazoline) networks

“…[1][2][3][4] While most stimuli-responsive materials are limited to a change of a certain physical or chemical property, shapememory materials react on a suited trigger by changing their shape. 5,6 Especially shape-memory polymers (SMPs) 7-10 distinguish themselves by high stored strains [11][12][13][14][15] and remarkable amounts of stored mechanical energy, 12,16 tunable trigger temperature, 17,18 narrow trigger ranges, 19 cold-programmability, 15,20 heating rate sensitivity, 21 and various options for triggering such as UV-/IRradiation, 22,23 mechanical stress 17,18 and even solvents 24,25 or moisture. 26 One way to realize an SMP with excellent properties, that is, high fixity ratio, high recovery ratio, and high strain storage, is to crosslink the thermoplastic polymers.…”

“…Applying only light crosslinking right at the borderline between thermoplastic and elastomer, referred to as critical crosslinking, ensures a high stretchability of the resulting network and leaves the original properties of the thermoplastic almost unaffected. 11,15,17,18,27 An interesting class of thermoplastics for realizing SMPs are poly(2-alkyl-2-oxazoline)s (POx), because they offer a variety of exceptional properties, such as solubility in water and hydrophobic solvents, a lower critical solution temperature (LCST), a broad range of glass transition temperatures (T g s), and biocompatibility. [28][29][30][31][32][33] These properties can be tailored by altering the length of the alkyl substituent during synthesis.…”