Self-healing Materials and Shape Memory Polymers

Self-mend Materials and Shape Memory PolymersTopic Area self-healing materials, material body recollection polymers and flash retardant polymers acclivitous Polymer materials Md Hossion ShovonIntroductionThe ability of a tribe to harness nature as thoroughly as its ability to cope up with the challenges posed by it is determined by its complete association of materials and its ability to develop and produce them for various activitys. Advanced Materials ar at the heart of umpteen technological developments that touch our lives. Electronic materials for communication and development technology, optical fibers, laser fibers sensors for the intelligent environment, energy materials for renewable energy and environment, brightness level alloys for better transportation, materials for strategic applications and much. Advanced materials take a shit a wider role to frolic in the upcoming future years because of its multiple uses and lot be of a greater help for whole human ity. Emerging technologies argon those good innovations which represent progressive developments within a field for competitive advantage. proclivity of currently emerge technologies, which contains nearly of the most prominent ongoing developments, advances, and Materials learning and Nanotechnology Innovations atomic number 18 Graphene, Fullerene, Conductive Polymers, Metamaterials, Nanomaterials carbon nanotubes, Superalloy, Lithium-ion batteries, etc. Over the last decade, suffer polymeric materials have been used in biochemical sciences in many ways. Since the term, smart polymeric materials encompasses a wide spectrum of different compounds with unique probable for biological applications,Self-healing Polymers Self-healing polymers are a new class of smart materials that have the capability to repair themselves when they are damaged with out(p) the indispensableness for detection or repair by manual intervention of any kind. Increasing fill for petroleum feedstocks used to produce polymer and the need for polymeric materials with improved act in challenging applications continue to drive the need for materials with all-embracing lifetimes. superstar way to fail the lifetime of a material is to mitigate the appliance leading to failure. In brittle polymers, failure occurs finished twirl brass and extension (1,2) and the ability to repair these cracks when they are save very secondary will prevent further propagation thus extending the lifetime of the material. Emerging self-healing technologies designed to give polymeric materials the capability to arrest crack propagation at an early stage thereby preventing catastrophic failures will go a long way in helping to increase the scene of applications of these materials. With the need for autonomic repair of materials without external intervention thus evident, more(prenominal) recent research has focused on development fully self-healing systems. angiotensin-converting enzyme approa ch to the design of much(prenominal) systems employs the compartmentalization of a reactive healing agent, which is then incorporated into a composite material. Thus, when a crack propagates through the material, it causes the release of the healing agent from the compartment in which it is stored into the crack plane where it solidifies and repairs the material.The commencement exercise basic application of this approach consisted of an epoxy matrix with suspended spy frappe capillaries filled with either cyanoacrylate or a two-part epoxy resin. When a crack propagated through the cured epoxy matrix, the glass capillaries were fractured and the cyanoacrylate monomer or the two-part epoxy in general referred to as healing agents, were released into the crack plane where they reacted and polymerized. A signifi fecal mattert retrieval of the mechanical properties of the samples later on they were al humbleded to heal suggests that the cracked material was effectively repaired by the polymerized healing agent. Since the healing requires only crack propagation as the cancel for the healing mechanism, it represents a truly autonomic or self-healing material. While a successful demonstration of self-healing, the labor-intensive do of manually filling capillaries and distri plainlying them equally throughout the matrix make this approach unsuitable for scale-up.Shape- store PolymersShape-memory polymers are an emerging class of active polymers that have the dual- fig capability. They can change their shape in a predefined way from shape A to shape B when undefended to an appropriate stimulus. While shape B is given by the sign treating step, shape A is determined by applying a process called programming. The shape-memory research was initially gear uped on the thermally induced dual-shape effect. This concept has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive companys on the molecu lar level. Finally, polymers are introduced that can be multifunctional. Besides their dual-shape capability, these active materials are biofunctional or biodegradable. Potential applications for much(prenominal) materials as active medical devices are highlighted. Shape-memory polymers are dual-shape materials belonging to the group of actively moving polymers. They can actively change from a shape A to a shape B. Shape A is a temp shape that is sustained by mechanical deorganization and subsequent fixation of that deformation. This process to a fault determines the change of shape shift, resulting in shape B, which is the permanent shape. In shape-memory polymers reported so far, heat or light has been used as the stimulus. Using irradiation with infrared light, application of electric fields, alternating magnetized fields, or immersion in water, indirect actuation of the shape memory effect has also been realized. The shape-memory effect only relies on the molecular computer architecture and does not require a specific chemical structure in the repeating units. in that respectfore, intrinsic material properties, e.g. mechanical properties, can be familiarized to the need of specific applications by variation of molecular parameters, such as the type of monomer or the comonomer ratio.An employment of a cross-linked polymer net live synthesized by poly attachment of monofunctional monomers with low molecular weight or oligomeric cross-linkers has been realized in polyurethanes by the supplement of trimethyl owl to the reaction mixture.The reaction of tetra-functional silanes, working as net points, with oligomeric silanes, which work as spacers and to which two distinct benzoate- ground mesogenic groups have been attached, results in a formation of a main-chain smectic-C elastomer38. In contrast to other fluid-crystalline elastomers, which display a shape-changing conduct and have been compared to shape-memory polymers recently, these elastomers hav e shape-memory properties. The cross-linking process during synthesis defines the permanent shape. The shape-memory effect is triggered by the thermal passage of the liquid-crystalline domains. In the programming process, the polymer network is heated to the identical state of the liquid crystalline domains, stretched or twisted, and then cooled below the clearing transition temperature of the smectic-C mesogens. Upon reheating over this clearing transition, the permanent shape can be recovered. In contrast to shape-changing liquid crystalline elastomer systems, these polymers display shape-memory behavior because the liquid crystalline moieties work as a switch. In shape-changing liquid-crystalline elastomers, the molecular figurehead of the single liquid crystals is converted into a macroscopic movement some other class of thermoplastic shape memory polymers with Trans = Tg are polyesters. In copolyesters base on poly(-caprolactone) and poly (butylene terephthalate), the poly (butylene terephthalate) segments act as physical cross-linkers25. The shape-memory capability can also be added to a polymer using a polymer-analogous reaction. A polymer-analogous reaction is the application of a standard organic reaction (like the reduction of a ketone to an alcohol) to a polymer having several of these reactive groups. An example is the polymer-analogous reduction of a polyketone with NaBH4/THF, which results in a poly(ketone-co-alcohol). The polyketones are synthesized by late transition metal catalyzed polymerization of propene, hex-1-ene, or a mixture of propane and hex-1-ene with CO. The Tg of this polymer is directly related to the degree of reduction, which can be ad retributoryed by the amount of NaBH4/THF. The most promising shape-memory material is a partly reduced poly (ethene-co-propane-co-carbon oxide), which displayed a course-separated morphology with hard microcrystalline ethylene/CO-rich segments within a softer amorphous polyketone ethylene-pro pene/CO-rich matrix. The crystalline domains of this material work as physical cross-linkers. This results in an elastic behavior above Tg because the glass transition temperature (Trans = Tg) is related to the switching phase. Partial reduction of the material allows control of Tg, which can be adjusted from below room temperature to 75C.Flame-retardant Polymers dismission-safe polymers are polymers that are resistant to degradation at high temperatures. There is need for crowd out-resistant polymers in the construction of small, enclosed spaces such as skyscrapers, boats, and planing machine cabins. In these tight spaces, ability to escape in the event of a evict is compromised, increasing fire risk. In fact, some studies report that virtually 20% of victims of airplane crashes are killed not by the crash itself but by ensuing fires. Fire-safe polymers also find application as adhesives in aerospace materials, insulation for electronics and in military materials such as try t enting. many fire-safe polymers naturally exhibit an intrinsic resistance to bunk, while others are synthesized by incorporating fire-resistive additives and fillers. Current research in developing fire-safe polymers is focused on modifying various properties of the polymers such as ease of ignition, rate of heat release, and the growing of smoke and toxic gases. Standard methods for testing polymer flammability vary among countries in the united accedes usual fire tests include the UL 94 small- kindle test, the ASTM E 84 Steiner Tunnel, and the ASTM E 622 National Institute of Standards and Technology (NIST) smoke chamber. look into on developing fire-safe polymers with more desirable properties is concentrated at the University of Massachusetts Amherst and at the national Aviation Administration where a long-term research program on developing fire-safe polymers was begun in 1995. The Center for UMass/Industry Research on Polymers (CUMIRP) was ceremonious in 1980 in Amher st, MA as a concentrated bunch up of scientists from two academia and industry for the purpose of polymer science and engineering research. positive the flammability of different materials has been a subject of interest since 450 B.C. when Egyptians attempted to reduce the flammability of woodwind by soaking it in potassium aluminum sulfate (alum). Research on fire-retardant polymers was bolstered by the need for new types of synthetic polymers in World War II. The combination of a halogenated paraffin and antimony oxide was found to be successful as a fire retardant for canvas tenting. Synthesis of polymers, such as polyesters, with fire retardant monomers were also true around this time..Additives are divided into two basic types depending on the interaction of the additive and polymer. Reactive flame retardants are compounds that are chemically construct into the polymer. They usually contain heteroatoms. Additive flame retardants, on the other hand, are compounds that are not covalently bound to the polymer the flame retardant and the polymer are just physically mixed together. Only a few elements are organism widely used in this field aluminum, phosphorus, nitrogen, antimony, chlorine, bromine, and in specific applications magnesium, coat and carbon. One prominent advantage of the flame retardants (FRs) derived from these elements is that they are relatively easily to manufacture. The most important flame retardants systems used act either in the gas phase where they remove the high energy radicals H and OH from the flame or in the solid phase, where they shield the polymer by forming a charred bottom and thus protect the polymer from being attacked by oxygen and heat. Flame retardants based on bromine or chlorine, as considerably as a number of phosphorus compounds act chemically in the gas phase and are very high-octane. Others only act in the condensed phase such as metal hydroxides (aluminum trihydrate, or ATH, magnesium hydroxide, or MDH, and boehmite), metal oxides and salts ( surface borate and zinc oxide, zinc hydroxystannate), as well as expandable graphite and some nanocomposites (see below). Phosphorus and nitrogen compounds are also effective in the condensed phase, and as they also may act in the gas phase, they are kind of efficient flame retardants. Overviews of the main flame retardants families, their mode of action and applications are given in. Besides providing satisfactory mechanical properties and renewability, natural fibers are easier to obtain and much cheaper than man-made materials. Moreover, they are more environmentally friendly. Recent research focuses on application of different types of fire retardants during the manufacturing process as well as applications of fire retardants (especially intumescent coatings) at the finishing stage.A good example for a very efficient phosphorus-based flame retardant system playacting in the gas and condensed phases is aluminum diethyl phosphonate in conj unction with synergists such as melamine polyphosphate (MPP) and others. These phosphonates are mainly used to flame retard polyamides (PA) and polybutylene terephthalate (PBT) for flame retarded applications in electrical engineering/electronics (EE).These are well illustrated by the investigations on glass fiber reinforced polyamide 66 flames retarded with red phosphorus (PA 66-GF/Pr), which demonstrate these charming characteristics Figure 1 shows the thermal and thermo-oxidative decomposition of PA 66-GF/Pr in comparison to PA 66-GF, as well as the performance in strobilus shape calorimeter experiments. For both materials, decomposition is characterized by at least three different processes, which potently overlap for PA 66-GF and are clearly separated for PA 66-GF/Pr. whatsoever decomposition processes are shifted to spurn temperatures so that the decomposition region is broadened. There is only a small increase in thermal stability for the final decomposition step. Therma l decomposition changes from a one-step decomposition to a two-step decomposition characteristic. In fire tests, PA 66-GF/Pr is an effective charging material, achieving a clear reduction in THE and HRR in the cone calorimeter, as well as the highest self-extinction classification V-0 in the UL 94, whereas in the chance of PA 66-GF all of the polymeric material is consumed so that only the glass fibers remain. Thermo-oxidative decomposition of PA 66 was concluded to occur in cone calorimeter experiments before ignition when a black skin is built up, and during afterglow after flame-out, when a further decrease in tummy occurs accompanied by CO production. During the forced-flaming between ignition and flame-out, a stable flame rules out a major influence of oxygen on the decomposition during pyrolysis. The mass loss after flaming combustion and the burning time are used to estimate an average effective pyrolysis temperature. This temperature was estimated by the necessary analog ous isothermal thermos gravimetry with the same mass loss in the burning time. This is a very rough estimation, of course, since the sample in the cone calorimeter, which is characterized by a temperature profile developing over time, is described by a constant temperature independent of place and time. However, since the specimens investigated were rather thin (2.8 mm) and contained boggy filler, and because the fire residue was rather homogenous, the values summarized in Table 3 reasonably estimate the effect. The pyrolysis temperature for PA 66-GF is controlled by the decomposition temperature of the polymer and remains more or less constant for all irradiations used. The calculated temperature is higher than-but still close to-the temperature characteristic for the maximum mass loss rate in thermos gravimetry, and the temperature increases slightly with increasing irradiation. The PA 66 is consumed nearly in all by the pyrolysis zone running through the sample. The approximate d pyrolysis temperature of PA 66-GF/Pr is characterized by the decomposition temperature of the first decomposition step and thus crucially lower than the temperatures concluded for PA 66-GF.SummaryThe development and characterization of self-healing synthetic polymeric materials have been inspired by biological systems in which damage triggers an autonomic healing response. This is an emerging and fascinating area of research that could significantly extend the working life and safety of the polymeric components for a broad lean of applications The past decade has witnessed remarkable advances in stimuli-responsive shape memory polymers (SMPs) with strength applications in biomedical devices, aerospace, textiles, civil engineering, bionics engineering, energy, electronic engineering, and household products. Shape memory polymer composites (SMPCs) have further enhanced and broadened the applications of shape memory polymers. In addition to reinforcement, SMPCs can enable or enhanc e thermal stimuli-active effects, novel shape memory effect, and new functions. Many thermal stimuli-responsive effects have been achieved such as electroactive effect, magnetic-active effect, water-active effect, and photoactive effect. The typical examples of novel shape memory effects are multiple shape memory effect, spatially controlled shape memory effect, and two-part shape memory effects. In addition, new functions of SMPCs have been observed and systemically examine such as stimuli-memory effect and self-healing. Flame retardancy of polymeric materials is conducted to provide fire protection to flammable consumer goods, as well as to mitigate fire growth in a wide range of fires. Incorporating flame-resistant additives into polymers became a common and relatively cheap way to reduce the flammability of polymers, while synthesizing intrinsically fire-resistant polymers has remained a more expensive alternative, although the properties of these polymers are usually more eff icient at deterring combustionReferencesFame, Fire and Materials http//onlinelibrary.wiley.comA review of stimuli-responsive shape memory polymer composites http//www.sciencedirect.comEmerging Areas of Materials Science and Nanotechnology http//materialsscience.conferenceseries.comSchartel, Bernhard Phosphorus-based Flame Retardancy Mechanisms-Old Hat or a scratch Point for Future DevelopmentBraun, U. Balabanovich, A.I. Schartel, B. Knoll, U. Artner, J. Ciesielski, M. Dring, M.Perez, R. Sandler, J.K.W. et al. Influence of the Oxidation State of Phosphorus on the Decomposition and Fire Behaviour of Flame-Retarded Epoxy resin Composites. Polymer 2006, 47, 8495-8508Perez, R. 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