Chapter
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Abstract

Polyurethane is a highly versatile polymer that may be used in various types of applications with a wide range of properties. The combination of different types and ratios of isocyanate and polyol allows for the control of the desired end properties. Due to its unique properties, it has found applications in the fields of medical, military, automobile, and aerospace industries. Recently, there has been a prodigious interest in producing polyurethane-based smart polymers, especially shape memory polyurethane (SMPU). This is due to its excellent ability to change shape upon the application of external stimuli such as heat, electric field, magnetic field, and light. The existence of phase-separated structure known as soft- and hard-segment domains contributes toward the shape memory properties of polyurethane. The soft-segment domains are responsible for maintaining the temporary shape, while hard segments fix the permanent shape. This chapter comprehensively aims to address a wide overview of polyurethane-based smart polymer and the chemistry behind the shape memory properties. In addition, this chapter also summarizes the recent studies on the exploration of SMPU using vegetable oils along with petroleum-based polyol and the potential applications of smart polyurethane.

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... 4 SMPUs are widely used and attracted much interest among the researchers due to its versatility as the properties may be tailored by changing its raw materials. 5,6 Most SMPUs are petroleum based. However, due to the fluctuation of petroleum prices and depletion of fossil fuels resources as well as the awareness of the society towards the environmental concern has urged the replacement of petroleum-based polyols with natural oil-based polyol. ...
... 1,2 Palm oil can be modified into palm oil polyol (POP) by means of increasing the number of hydroxyl groups on carbon chain of fatty acids in order to improve its reactivity. 3,4 POP has been widely utilised as raw materials in the preparation of polyurethane (PU) especially the rigid PU foam for various applications. ...
Article
Shape memory polyurethanes (SMPU) are one of the advanced materials that have potential applications in the field of biomedical particularly vascular stent. This paper studies the effect of incorporating palm oil polyol (POP) up to 40% molar ratio in place of petroleum‐based polyol in the preparation of SMPU due to environmental concern. Polycaprolactone diol was utilized as the soft segment while 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol as the hard segments. The SMPU was prepared using two‐step prepolymer method, and the fabricated samples were characterized to study the effect of POP on the thermal properties, tensile, and shape memory behavior of polyurethane. The results obtained have shown that SMPU with incorporation of POP showed good shape fixity (100%) and elongation at break (245%) up to 20% molar ratio of POP. The presence of dangling chains of fatty acid in POP was believed to enhance the flexibility of SMPU molecular chains by acting as a plasticizer. On the other hand, the shape recovery of SMPU remains high even at 40% molar ratio of POP, and the thermal stability of SMPU increased with the addition of POP. It is proposed that the synthesized POP‐based SMPU is a suitable candidate for cardiovascular stent as they possessed desired thermal, mechanical, and shape memory properties.
... Polycaprolactone diol which is biocompatible are widely used as a research material in the production of SMPU for biomedical application as soft segment domains [3]. It initiates the idea of utilizing polycaprolactone diol (PCL) in this work. ...
Conference Paper
Shape memory polymers (SMP) are smart materials with the ability of changing shape when subjected to external stimuli. In this work, the shape memory polyurethane (SMPU) has been synthesized via two step bulk polymerization method by replacing up to 40% molar ratio of petroleum-based polyol using palm oil-based polyols (POP). This effort was done with the purpose of reducing the usage of petroleum-based polyol due to environmental awareness. The main objective is to investigate the effects of different polyol/isocyanate/1,4-butanediol molar ratio in relation to soft-hard segment content towards the mechanical and shape memory properties of the resulting SMPU. The mechanical properties were improved with POP addition and optimum performance of tensile properties were obtained within 35 to 40% of hard segment content. Tensile strength increased with increasing POP content but after 40% of hard segment content, the properties decreased. On the other hand, the modulus significantly reduced with an increase of hard segment content. Crystallinity also decreased with decreasing of polycaprolactone diol (PCL) content as more POP content was added. Shape memory properties of PU 165 is better than PU 154 in terms of the ability to return to its original shape since all of PU 165 samples showed 100% recovery. In general, the addition of palm oil-based polyol showed improvement in mechanical and shape memory properties as compared to pristine SMPU.
Article
Full-text available
Segmented thermoplastic polyurethanes (TPUs), which consist of an amorphous soft segment from 1,3-butanediol and hexamethylene diisocyanate (HDI) and a crystalline hard segment from 4,4′-bis-(6-hydroxy hexoxy)biphenyl and tolylene 2,4-diisocyanate were synthesized. Their thermal and mechanical properties, shape memory effect, utilizing amorphous soft segment domain as reversible phase and crystalline hard segment domain as frozen phase, were examined. The reversibility observed on repeated deformation was improved as the magnitude of deformation was reduced and the hard segment content was increased, or by crosslinking with excess HDI.
Article
Full-text available
Vegetable oil-based shape-memory polyurethane networks are an emerging class of bio-based functional materials with great potential applications. In this study, a series of different structural soybean oil polyols were synthesized, and utilized to fabricate polyurethane networks by reacting with 1,6-diisocyanatohexane. The soybean oil-based polyurethanes (SOPUs) were characterized with differential scanning calorimetry (DSC), dynamic mechanical tests (DMA), tensile testing, shape-memory testing, and atomic force microscopy (AFM). It was found that SOPUs with a preserved triglyceride structure were fixed in a temporary shape at −20 °C, while others were fixed in temporary shapes at 4 °C. Although the recovery speeds were different, all the samples could completely regain their permanent shapes at 37 °C (human body temperature). Furthermore, different SOPUs exhibited different surface structures, which might provide the materials with additional values.
Article
Full-text available
Vegetable oils are excellent but very heterogeneous renewable raw materials for polyols and polyurethanes. This review discusses the specific nature of vegetable oils and the effect of their structures on the structure of polyols and polyurethanes. One section is dedicated to polyols for rigid and flexible foams and methods of their preparation such as direct oxidation of oils, epoxidation followed by ring opening, hydroformylation, ozonolysis, and transesterification. The next section deals with preparation and structure‐property relationships in polyurethanes from different groups of polyols, different isocyanates, and different degrees of crosslinking. The final section covers the environmental aspects of bio‐based polyurethanes, i.e., thermal stability, hydrolytic stability, and some aspects of biodegradability.
Article
Full-text available
Shape-memory polymers (SMPs) have attracted significant attention from both industrial and academic researchers due to their useful and fascinating functionality. This review thoroughly examines progress in shape-memory polymers, including the very recent past, achieved by numerous groups around the world and our own research group. Considering all of the shape- memory polymers reviewed, we identify a classification scheme wherein nearly all SMPs may be associated with one of four classes in accordance with their shape fixing and recovering mechanisms and as dictated by macromolecular details. We discuss how the described shape- memory polymers show great potential for diverse applications, including in the medical arena, sensors, and actuators.
Book
Looking beyond the traditional applications of polyurethanes (PUR), Polyurethanes as Specialty Chemicals presents a different approach to polyurethane chemistry by examining a range of new products and new research for both environmental and medical applications. This book is also the first in its field to provide useful design tools for product designers to customize the foam surface. The author examines extraction methods and biodegradability of polyurethanes for removing pollutants from air and groundwater and for sanitation/wastewater treatment. Thomson also explores the behavior of polyurethanes in a biological environment, covering a broad spectrum of applications that includes artificial organs, chelating agents for pharmaceuticals, and delivery systems for skin care products and cosmetics. The in-depth treatment of biochemical processes and cellular interaction includes tissue response, cell adhesion, 3D cell scaffolding for cell propagation, the immobilization of enzymes, and the production of proteins. Other topics of interest include agricultural applications and the use of PUR as an analytical/diagnostic system for testing toxicity without the use of animals. Destined to become indispensable in its field, Polyurethanes as Specialty Chemicals explores conventional PUR and its composites - emphasizing formulations, reticulated foams and hydrophilics - as versatile structures that can be used for specific design objectives in environmental and medical applications.
Book
Polyurethanes in Biomedical Applications studies the use of polyurethanes in implanted medical devices. This analysis describes the concepts of polymer science, the manufacture of polyurethanes, and the biological responses to implant polyurethanes, reflecting the developments in biomaterials science and the interdisciplinary nature of bioengineering.
Article
Thermal-responsive shape-memory polyurethane consists of two phases, a thermally reversible phase for maintaining a transient shape and fixed phase structure for recovering the original shape. The use of shape memory polyurethane in clothing is a novel concept. The aim of this paper is to introduce the application of shape memory polyurethane to smart clothing, whose thermal insulation value could be change depending on the change of temperature of the external environment to give comfort regardless of weather change. Thus a review on the shape memory polyurethane is introduced: the mechanism of the shape memory polyurethane is described; the difference between ordinary polyurethane and shape memory polyurethane, the research on shape memory polyurethane and its potential application to smart garment are summarized; the work being carried out in the Hong Kong Polytechnic University are also introduced.
Chapter
In addition to the well-established classes of polyurethane elastomers, a variety of chemically modified varieties have been marketed commercially designed for specific applications. An account of some of these is now given.
Article
Until recently a product made from a cast or injection moulded polyurethane has always been more expensive than a similar one made from a conventional rubber or plastic and hence its use was only justified by complicated long term cost-performance calculations. Whilst this remains the situation for most types of PUs, it is also now possible using the automated reaction injected molding (RIM) process to make products which are cost competitive with other rubbers and plastics and which also possess superior properties. Hence, especially in the automotive field PU usage is rapidly increasing. This review is organized into materials followed by application technology.
Article
Problem statement: This study was carried out for the characterization of epoxidized and non-epoxidized fatty diethanolamides by High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC). Approach: The fatty diethanolamides were synthesized by reacting 40% (w/w) of Epoxidized Palm Olein (EPOo) with 60% (w/w) Refined Bleached Deodorized Plam Kernel Olein (RBDPKOo) with Diethanolamine (DEA) at 110°C for 5 h. Results: The identities of the peaks were established by secondary standards that were derived from pure methyl esters. HPLC separated major non-epoxidized diethanolamide compounds, namely C10:0, C12:0, C14:0, C16:O, C18:1 and C18:0 and the molecular weights of the compounds were dentified by Liquid Chromatography-Mass Spectrometry (LC-MS). Conclusion: GC provided a more complete separation for the non-epoxidized diethanolamides, epoxidized diethanolamides, glycerol, Diethanolamine (DEA) and some minor compounds from the self-condensation of DEA and diethanolamides. Gas Chromatography-Mass Spectrometry (GC-MS) elucidated the chemical structure of the epoxidized diethanolamides.
Article
The catalytic effects of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and pyridine on the ring-opening reaction between epoxidized soybean oil and fatty acids from castor oil in a solvent free process were investigated using differential scanning calorimetry and were analyzed using both model-free and model-fitting methods. The resulting biopolyols from this reaction with epoxidized soybean oil, and similarly prepared polyols from epoxidized linseed oil, were characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. Polyurethane films were prepared by step-growth polymerization of the biopolyols with isophorone diisocyanate and were characterized by dynamic mechanical analysis, thermogravimetric analysis, and tensile tests. Polyurethanes from polyols manufactured with DBU as catalyst exhibited higher glass transition temperatures, tensile strength, and Young’s modulus than polyurethanes from polyols manufactured using a catalyst-free method, which was attributed to the more homogeneous structure of their cross-linked network.Keywords: Epoxidized soybean oil; Differential scanning calorimetry; Reaction kinetics; Thermoset polymers; Activation energy; Renewable chemicals
Article
In this study, a series of bio-based polyols were prepared from olive, canola, grape seed, linseed, and castor oil using a novel, solvent/catalyst-free synthetic method. The bio-based triglyceride oils were first oxidized into epoxidized vegetable oils with formic acid and hydrogen peroxide, followed by ring opening reaction with castor oil fatty acid. The molecular structures of the polyols and the resulting polyurethane were characterized. The effects of cross-linking density and the structures of polyols on the thermal, mechanical, and shape memory properties of the polyurethanes were also investigated.
Article
Hyperbranched polyurethanes were synthesized from poly(ε-caprolactone) diol as a macroglycol, butanediol as a chain extender, a monoglyceride of a vegetable oil (Mesua ferrea, castor, and sunflower oils separately) as a biobased chain extender, triethanolamine as a multifunctional moiety, and toluene diisocyanate by a prepolymerization technique with the A2 + B3 approach. The structure of the synthesized hyperbranched polyurethanes was characterized by 1H-NMR and X-ray diffraction studies. M. ferrea L. seed-oil-based polyurethane showed the highest thermal stability, whereas the castor-oil-based one showed the lowest. However, the castor-oil-based polyurethane exhibited the highest tensile strength compared to the other vegetable-oil-based polyurethanes. All of the vegetable-oil-based polyurethanes showed good shape fixity, although the castor-oil-based polyurethane showed the highest shape recovery. Thus, the characteristics of the vegetable oil had a prominent role in the control of the ultimate properties, including the shape-memory behaviors, of the hyperbranched polyurethanes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39579.
Article
The effect of soft segment molecular weight and chemical structure on the morphology and final properties of segmented thermoplastic polyurethanes containing various hard segment contents has been investigated from the viewpoint of the degree of microphase separation. Vegetable oil-based polyesters and corn sugar-based chain extender have been used as renewable resources. The synthesis has been carried out in bulk without catalyst using a two-step polymerization process. Physicochemical, thermal and mechanical properties, and also morphology, have been studied using Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, X-ray diffraction and mechanical testing. Chemical structure and molecular weight of polyols strongly affect the properties of the synthesized segmented thermoplastic polyurethanes. An increase in soft segment molecular weight leads to an increase of the degree of soft segment crystallinity and microphase separation, thus giving enhanced mechanical properties and higher thermal stability. Copyright © 2012 Society of Chemical Industry
Article
Segmented polyurethanes have been synthesized employing polyols derived from renewable resources, semicrystalline or amorphous in nature, as soft segment, and an aliphatic (1,6-hexamethylene diisocyanate, HDI) or aromatic (4,4′-diphenylmethane diisocyanate, MDI) diisocyanate and 1,4-butanediol (BD) as hard segment using two-step bulk polymerization procedure. The effect of soft and hard segment structure and hard segment content on thermal, mechanical and shape memory properties has been studied by means of differential scanning calorimetry, tensile tests and tensile tests performed using a thermal chamber.
Article
One of the obvious shortcomings of bio-based shape memory polyurethanes (Bio-SMPUs), which usually use natural oil based polyols as the soft segment, is their low mechanical strength because the long dangling chains (six to eight carbons) in these polyols prevent the Bio-SMPUs from deep micro-phase separation, and consequently deteriorate their mechanical properties. In this work, we prepared a bio-based polyester diol for the soft segment, in which short side chains (CC) were used to tune the transition temperature and the morphology of the Bio-SMPUs. The moderate concentration of short branch chains barely affects the micro-phase separation, and the mechanical properties of the Bio-SMPUs are quite satisfactory. With the same 70 wt% soft segment content, the tensile strength in this work is 13.2 MPa, while the one using ricinoleate-based soft segments reported 2.8 MPa. Through proper shape memory programming, the synthesized Bio-SMPUs show good shape memory properties with a shape fixing rate of greater than 98% and a shape recovery rate of 85% in the first cycle and greater than 90% in the following cycles. This study provides a framework for developing bio-based SMPUs with high mechanical and good shape memory properties at the same time.
Article
Shape-memory polymers (SMPs) have wide range of applications due to their ability to sense environmental stimuli and reshape from a temporary shape to a permanent shape. Plant oil-based polymeric materials are highly concerned in recent years in consideration of petroleum depletion and environmental pollution. However, plant oil-based polymers are rarely investigated regarding their shape-memory characteristics though bio-based SMPs are highly desired nowadays. In this study, a series of soybean oil-based shape-memory polyurethanes (SSMPUs) are prepared through a mild chemo-enzymatic synthetic route, and their properties are fully characterized with tensile testing, DSC, dynamic mechanical analysis (DMA), and shape-memory testing. Results show that SSMPUs are soft rubbers with tensile strength in the range of 1.9–2.2 MPa and glass transition temperature in the range of 2–5°C, and possess good shape recoveries at RT when stretching ratio is 10, 20, and 30%, respectively. This work would promote the development of high-value-added plant oil-based shape-memory polyurethanes. Practical applications: Using annual renewable plant oil as feedstock, the synthesized SSMPUs show good shape recovery properties, which will make them applicable as potential alternatives to petroleum-based shape-memory materials. The simple and mild preparation process also contributes to the further exploration of plant oil to value-added functional materials.
Article
Coatings tailored to corrosion protection of metallic substrates are of the utmost relevance to ensure reliability and long-term performance of coated parts as well as the product value of the coated materials. Presently, there is a strong emphasis on the development of advanced functional and smart coatings for corrosion protection in different technological applications. On the one hand, there is a need for more advanced coatings for conventional applications and, on the other hand, there is a need to answer the requirements of several new Hi-Tech applications. Thus, this review highlights the most recent trends in the field of functional coatings for corrosion protection of metallic materials in a wide range of technical applications. Emphasis is given to self-healing coatings and smart coatings combining multiple functionalities for increased corrosion protection. Recent developments on the introduction of functionalities based on encapsulation of corrosion inhibitors, anti-fouling agents and superhydrophobic additives or modification of organic and hybrid matrices via chemical manipulation are reviewed. Special attention is dedicated to functional coatings for corrosion protection of bioresorbable metallic implants that have an important impact in biomedical applications.
Article
The bio-based hyperbranched polyurethanes (HBPUs) have generated immense interest as advanced shape memory materials. In the present investigation, HBPUs were synthesized from poly(ε-caprolactone)diol as a macroglycol, butanediol as a chain extender, monoglyceride of Mesua ferrea L. seed oil as a bio-based chain extender, triethanolamine as a branch-generating moiety (at different percentages), and toluene diisocyanate by a prepolymerization technique using A2 + B3 approach. The structure of the synthesized HBPU was characterized by different techniques. Nuclear magnetic resonance (proton) study indicated the formation of highly branched structure with degree of branching 0.9. The increment of thermal stability from 225 to 260°C and melting point from 50 to 53.5°C with the increase of triethanolamine content was observed. Tensile strength 4–8 MPa, elongation at break 614–814%, impact resistance 0.8–0.95 m, and scratch hardness 2–6 kg increased with the increase of multifunctional moiety content from 0 to 5 wt%. The shape recovery ratio increased with the increase of multifunctional moiety content from 0.21 to 0.95. Thus, the studied HBPUs have the potential to be used as advanced thermoresponsive shape memory materials. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Article
Biobased polymeric materials are gaining increasing attention in biomedical areas. Here, we report a new class of biocompatible polyurethanes prepared from soybean oil-based polyol that was synthesized by ring-opening reaction of epoxidized monoglyceride (EMG) with lactic acid. By adjusting the molar ratio of hydroxyl to isocyanate group and the content of chain extender, soybean oil-based polyurethanes with tensile strength of 9.30–27.1 MPa and elongation at break of 74.1–110.7% were prepared, while usual lipid-based polyurethanes with the same 1,6-diisocyanatohexane as reactant hardly have tensile strength higher than 5 MPa. Mouse fibroblast cells (L-929) showed good adhesion and growth behavior on the polyurethane samples with more hydrophilic surfaces, and the cell viabilities of more than 50% were achieved with commercial tissue culture polystyrene (TCPS) disk as control. The good mechanical property and biocompatibility of the soybean oil-based polyurethanes will make them suitable for wide range of potential biomedical applications. Practical applications: The synthesized soybean oil-based polyurethanes have adjustable tensile strengths from 9.30–27.1 MPa and elongation at break of 74.1–110.7%. Along with their good biocompatibility, the polyurethanes can potentially replace wide range of part of petroleum-based polymeric materials, particularly as biomedical materials.
Article
Epoxidized soybean oil (ESO) and isopropanolamine were used to synthesize a new polyol mixture for preparation of bio‐based polyurethanes. The chemical synthetic route for reaction of ESO with isopropanolamine was analyzed by 1H‐NMR. The results suggested that both ester groups and epoxy groups in ESO had reacted with amino group of isopropanolamine through simultaneous ring‐opening and amidation reactions. Epoxy groups in various situations exhibited different reactivity, and the unreacted epoxy groups were further opened by hydrochloric acid. The synthesized polyol mixture had high hydroxyl number of 317.0 mg KOH/g. A series of polyurethanes were prepared by curing the synthesized polyol mixture with 1,6‐diisocyanatohexance along with different amount of 1,3‐propanediol (PDO) as chain extender. Tensile tests showed that yield strengths of the polyurethanes ranged from 2.74 to 27.76 MPa depending on the content of PDO. Differential scanning calorimetry analysis displayed one glass transition temperature in the range of 24.4–28.7°C for all of the polyurethane samples, and one melt peak at high content of PDO. Thermogravimetric analysis showed that thermal degradations of the polyurethanes started at 240–255°C. In consideration of simple preparation process and renewable property of ESO, the bio‐based polyurethane would have wide range of applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Article
Ester-based polyurethane (PU) with low glass transition temperature was used to develop shape memory nanocomposites with low trigger temperature. Pristine carbon nanotubes (CNTs) and oxidized CNTs (ox-CNTs) were introduced by melt mixing to improve the mechanical and shape memory properties of the PU matrix. The dispersion of CNTs on the mechanical properties and shape memory behaviors of the nanocomposites were also investigated. The results show that better dispersion of ox-CNTs contributes to more stiffness effect below glass transition temperature (Tg) while lower storage modulus (E′) above Tg. The nanocomposites exhibit high shape fixity and recovery ratio above 98%. The ox-CNT/PU nanocomposite shows higher shape recovery ratio for the first cycle, faster recovery due to better dispersion of CNTs and have potential applications for controlling tags or proof marks in the area of frozen food. The trigger temperature can be tailored by controlling the Tg of the PU matrix or the content of the nanofillers.
Article
Shape-memory bionanocomposites based on a naturally sourced segmented thermoplastic polyurethane and chitin nanocrystals were synthesized and their mechanical properties and thermally-activated shape-memory behavior were studied. The chitin nanocrystals were incorporated during the synthesis of the prepolymer made from a castor oil-based difunctional polyol and hexamethylene diisocyanate. The polymerization was completed by addition of propanediol, as a corn-sugar based chain extender, bringing the weight content of components from renewable resources to >60%. Thermal analysis of the bionanocomposites revealed a phase-separated morphology, which is composed of soft and hard domains, which bestow the material with two melting transitions at 60 and 125 ºC, that are exploitable for a shape memory effect. The soft segment is responsible for temporary shape fixing, while the hard segment crystallites are responsible for the permanent shape. The introduction of small amounts (0.25-2 wt%) of chitin nanocrystals was found to increase the crystallinity of the hard segment by way of nucleation, which in turn improves the shape recovery considerably. The thermally-activated shape-memory behavior of the synthesized bionancomposites is exploitable with a programming and release temperature of 60 ºC. The materials display good in vitro cell response, as shown by short-term cytotoxicity assays, and therefore, the bionanocomposites appear to be potentially useful for biomedical applications.
Article
Elevated environmental consciousness among producers and consumers has resulted in significant interest and research in seed oil derived building blocks for polymer synthesis. While slowly making inroads into selected applications, performance deficits have consistently relegated seed oil derived elastomers to roles having low performance requirements, or where biodegradability is paramount. In this article ester alcohol A-B monomers derived from reductively hydroformylated seed oil fatty acids are polymerized to make polyester soft segments. The seed oil components are separated following functionalization and then polymerized to make soft segments of varying molecular weight, functionality, and with varying polymerization initiators. The soft segments are subsequently polymerized with isocyanates and short chain diols to make thermoplastic polyurethane elastomers of varying compositions. High quality elastomers are obtained that meet tensile requirements for demanding applications. The structure, thermodynamic behavior, and mechanical properties of the elastomers are explained semi-quantitatively by combining theory of block copolymer microphase separation and a two-phase composite model. It is proposed that superior properties of the new elastomers could be understood in light of a relatively large Flory-Huggins parameter between the polyester soft segment and the urethane hard segment.
Article
In this paper, we report on the shape memory behavior of a family of hardblock-free multiblock thermoplastic polyurethanes (TPUs) consisting of poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG). Due to high molecular weight (Mn > 200 kDa), high degrees of entanglement were achieved. Instead of conventional “hard” blocks, entanglements served as the physical crosslinks in this system, slowing stress relaxation (suspending flow) above the melting temperatures of the soft blocks long enough to allow facile elastic deformation for shape fixing. Moreover, highly deformed samples (>800%) imparted by plastic deformation at room temperature completely recovered their as-cast shape within 1 min when heating above the transition temperature. Upon tensile deformation, the constituent chains and domains of both PCL and PEG phases became oriented, while heating-induced recovery reversed this orientation, as evidenced by wide-angle and small-angle X-ray diffraction studies. The observed large recoverable deformation and fast actuation make these materials strong candidates for applications in such medical devices as self-tightening sutures.
Article
A polyurethane (PU) network based on vegetable derived polyol has been characterised and compared to a synthetic based network. Fracture mechanics studies showed the lowest tear strength for the vegetable networks, which decreased as molecular weight of the vegetable based polyol increased. Swelling studies were carried out to determine the molecular weight between crosslinks and polymer networks made from wholly synthetic polyols were shown to have higher molecular weight between crosslinks. Moreover, vegetable networks showed higher solubles' content. Sol-fractions were analysed by several techniques. It was found that vegetable networks based sol-fraction was mainly its correspondent raw polyol while low molecular weight oligomers were detected for the most part in synthetic networks based sol-fraction.
Article
Novel hyperbranched shape-memory polyurethanes based on ε-caprolactone were prepared via A2+B3 approach with different molecular weights (Mw); the molecular weights ranged from 7.2×104 to 32.3×104g/mol. The hard segment content was varied minimally and the B3 monomer was also varied. The polymers were characterized by GPC, DSC, DMA, WAXD and shape-memory test. The crystallinity calculated from DSC and WAXD data indicated that the highly branched architecture does not affect the crystallization of these polymers. More interestingly the storage modulus ratios (E′ ratios) of hyperbranched polymers were found to be significantly high compared to the linear analogue. As a consequence, hyperbranched polymers show 100% more shape-recovery rate compared to their linear counterpart. Antimicrobial susceptibility tests confirmed that these polymers have good antimicrobial activity which is an essential requirement of medical implants.
Article
A diol-based refined, bleached, and deodorized (RBD) palm kernel oil polyol was prepared. It was found that the polyurethane foam produced only gives a good compressive strength property at a 45 kg/m3 molded density. The combination of sorbitol into the polyol system resulted in a better dimensional stability and improved thermal conductivity as well as enhanced compressive strength. These were obtained by increasing the functionality of the polyol (functionality of 4.5) through introduction of a high molecular weight and branching polyhidric compound. Direct polycondensation and transesterification methods were used for the syntheses. The hydroxyl value, TLC, and FTIR were used to study the completion of the reaction. A comparative study of the mechanical properties and morphological behavior was carried out with a diol-based polyol. From the water-blown molded foam (zero ODP) with a density of about 44.2 kg/m3 and a closed-cell content of 93%, a compressive strength of 222 kPa and a dimensional stability of 0.09, 0.10, and 0.12% at the length, width, and thickness of the foam, respectively, conditioned at −15°C for 24 h, were obtained. The thermal conductivity improved to an initial value of 0.00198 W/mK, tested at 0°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 384–389, 2001
Article
The effects of the dextrin cross-linking and hard-segment content on the shape-memory property of a polyurethane (PU) block copolymer were investigated. Although dextrin was selected due to its large number of free hydroxyl groups and ubiquitous availability, it is unfortunately insoluble in most organic solvents. The insolubility of dextrin was resolved by attaching a phenyl group onto the dextrin to reduce its hydrophilicity. The phase separations of hard and soft segments were not dependent on the dextrin cross-linking and hard-segment content, as per the results obtained from FTIR, DSC, and XRD analysis. An increased content of chemically cross-linked dextrin increased the maximum stress, but did not decrease the strain for most cases. The cross-linking density increased with increasing dextrin content, as expected. After dextrin cross-linking, the shape recovery rate was generally over 90%, and remained the same after four cyclical tests, while a low shape retention rate was observed for most cases. The best shape-memory effect, considering both the shape recovery and retention rate, was found for a PU consisting of 35 wt.% hard segment and 2 wt.% dextrin. Finally, dextrin was compared to other cross-linking compounds, such as glycerol and pentaerythritol, in this investigation.
Article
Effect of glucose cross-linking on the shape memory and mechanical properties of polyurethane (PU) block copolymer was investigated. Glucose was selected due to its large number of free hydroxyl groups, easy availability, miscibility with other reactants, and cyclic structure. The glycerol cross-linking did not affect the molecular interaction and phase separation of hard and soft segments in polyurethane structure as judged from IR and DSC analysis. Viscosity of glucose cross-linked PU increased after cross-linking due to the cross-linked structure. Maximum stress drastically improved with the adoption of glucose as a cross-linker together with a slight increase in strain at break. Shape recovery also increased with the adoption of glucose as a cross-linker, and shape recovery was not diminished after four cyclic shape recovery tests. In contrast, shape retention significantly decreased if glucose was included for two different hard segment contents. Finally, glucose cross-linking was compared with other cross-linkers used in shape memory polymer and the advantage of glucose cross-linking was discussed.
Article
Effect of cross-linking agent on the shape memory and mechanical property of polyurethane (PU) block copolymer is comprehensively investigated. The selected chemical cross-linking agents are glycerol, 1,2,6-trihydroxyhexane, and 2,4,6-trihydroxybenzaldehyde that are differentiated from each other in having remote hydroxyl group and aromatic ring. Significant increase in maximum stress was observed for all of the cross-linked PUs, although the cross-linker structure was different. Structural change of PU after cross-linking as evidenced by differential scanning calorimetry and infrared spectra was not detected, suggesting that interaction between PU chains remained intact. Shape recovery went to as high as 95 % after cross-linking for all of the cross-linking agents, and shape retention did not improve even if cross-linker was used. The remarkable increase in shape recovery and maximum stress definitely originated from the employment of a cross-linking agent, and the effect of different cross-linker structure on shape memory and mechanical property is discussed.
Article
A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (T m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and T m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).
Article
Celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, was used as a cross-linker of polyurethane (PU) copolymer chains to improve its shape memory and mechanical properties. PU copolymers with different Celite contents were prepared and characterized by IR, DSC, and universal testing machine. The glass transition temperature of PU copolymers was maintained around 20°C independent of Celite content. The shape memory and mechanical properties were dependent on when Celite was added during the polymerization reaction. The reaction in which Celite was added at the middle stage of polymerization showed the best shape memory and mechanical properties. The best shape recovery of PU was found at 0.3 wt % Celite and increased to 97% even after the third cycle. Likewise, the shape retention also maintained a remarkable 86% after three cycles. The reasons underlining the high shape recovery and shape retention by adopting Celite as a cross-linker are discussed in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Article
The vegetable oil based biodegradable advanced materials with hyperbranched architecture drawn tremendous attraction in recent years. In the present study, sunflower (Helianthus annuus L.) oil mod- ified hyperbranched polyurethane (HBPU) and linear polyurethane (LPU) were synthesized using toluene diissocyanate, poly(�-caprolactone), butanediol and monoglyceride of oil, with and without pentaerythritol as a multifunctional unit, respectively. The structures of polyurethanes by Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopic and X-ray diffraction (XRD) studies. 1 H NMR study confirmed the hyperbranched structure with degree 0.76 for HBPU. Physico-mechanical properties like impact resistance (90 cm vs. 100 cm), scratch hardness (4.3 kg vs. 4.7 kg), tensile strength (18.9 MPa vs. 23.18 MPa) and elongation at break (750% vs. 700%); biodegradability as tested by broth culture technique using Pseudomonas aeruginosa and Bacillus subtilis strains, and thermal stability (239 ◦ C vs. 250 C) were found to be higher for HBPU than LPU. Therefore, the bio-based synthesized HBPU with the desired properties in terms of physico-mechanical, thermal, and biodegradability has the potential to be used as a thin film material for advanced multifaceted applications. ◦ were of has by confirmed branching
Article
Biobased thermoplastic polyurethanes (TPUs) obtained from dimer acid-based polyols, 4,40-diphenyl- methane diisocyanate and 1,4-butanediol were synthesised by using a two-step prepolymer process. The effect of dimer acid-based polyols on the processing parameters was investigated. A full thermal, mechanical and thermo-mechanical characterisation of TPUs synthesised with different hard segment (HS) contents was also carried out. Thermogravimetric analysis showed the presence of three degra- dation steps which varied between the different TPU structures depending on the HS content. Colour tests showed substantial differences between TPU samples which were related to degradation param- eters. Initial degradation temperatures were lower than the polyol’s one and decreased with increasing HS contents. Tensile tests showed high deformation at break for these elastomeric TPU samples, except for the sample with 40 wt% of HS. Finally, rheology studies revealed that the melting temperature generally decreased with higher HS contents.
Article
Two types of shape memory polyurethanes (PUs) with various hard segment contents (hsc) were designed and synthesized based on the position of crosslinks, either in the soft segment or in the hard segment, and were tested for tensile cyclic loading behavior as well as mechanical and dynamic mechanical properties. It was found that hard segment crosslinks gave much smaller shape fixability and much higher shape recoverability as compared with soft segment crosslinks at the same hsc. For soft segment crosslinks, shape recovery increased as the hsc decreased, and these results could possibly be interpreted in terms of dynamic mechanical properties of the PUs, which possibly were interpreted in terms of microphase separation and crosslink density.
Article
Various polyurethane-based SMPUs were synthesized using five types of polyols as soft segments and two different diisocyanates as hard segments. The effects of diisocyanate concentration on material properties such as crystallinity, transition temperature, shapememory effect and tensile strength were investigated. SMPUs with a maximum strain near 1 000%, recovery rate up to�98%, fixity up to�90% and Tgs of 35–45 8C were obtained. A high MDI content results in SMPUs with better shape-memory effect, whereas increasing IPDI content leads to a weaker shape-memory effect. High IPDI concentration seems to prevent or restrict chemical reactions and crosslinks between the polyols and the hard segments, leading to large phase separation and coexistence of soft and hard segments in the macrophases.
Article
In this article, thermoplastic polyurethane (PU) with a shape memory property was synthesized. First, the PU prepolymer was prepared by reacting poly(tetramethylene glycol) with 4,4′-diphenylmethane diisocyanate, then extended with various extenders such as linear aliphatic 1,4-butanediol, benzoyl-type 4,4-bis(4-hydroxyhexoxy)-isopropylane and naphthalate-type bis(2-phenoxyethanol)-sulfone or naphthoxy diethanol. The experimental results showed that the tensile strength, elongation at break, and initial modulus at 300% of these copolymer films were in the range of 31–64 Mpa, 42%–614%, and 8.26–11.5 MPa, respectively. Thermal analysis showed that the glass-transition temperature of these copolymers was in the range of −73°C to −50°C for the soft segment (Tgs) and 70°C–106°C for the hard segment (Tgh) and that the melting point was in the range of 14.6°C–24.2°C for the soft segment and 198°C–206°C for the hard segment. The extender with a benzoyl or naphthalate group was better able to promote its shape memory property than was the regular polyurethane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 607–615, 2006
Article
A series of shape-memorized crosslinked ester-type polyurethanes (PUs), based on different compositions of 4,4′-diphenyl methane diisocyanate (MDI), poly(butylene adipate) glycol (PBAG) with different molecular weight (MW) and trimethylol propane (TMP), were synthesized. The morphology of samples was investigated by using DSC, WAXD, and dynamic mechanical analysis (DMA). It was found that the morphology of the soft segment, which was PBAG with a different MW, was in an amorphous state and no crystalline domain was found. By increasing the crosslinked density (varying the content of TMP) or decreasing the length of the soft segment (MW of PBAG), the glass transition temperature of studied samples increased. But the range of transition broadened and the modulus ratio E′−20°C)/E′+20°C) also decreased. The shape-memory behavior was studied by the bending test method adopted from the shape-memory alloy. The sample with high Tg showed not only a high recovered temperature (Tr) but also a high recovered rate (Vr) with a high modulus ratio. By introducing the chemical crosslinked structure, the deformed samples completely recovered their original shape and rendered shape-memory behavior under the complex deformation. The shape-memorized crosslinked ester-type PUs can be applied at different operating temperatures. A mechanical viscoelastic model is discussed for the shape-memory behavior of PUs, and the modified Bonart's viscoelastic model properly describes the mechanism of the shape memory of PUs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1305–1319, 1999
Article
A series of biodegradable polylactide-based polyurethanes (PLAUs) were synthesized using PLA diol (Mn = 3200) as soft segment, 4,4′-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI) as hard segment, and 1,4-butanediol as chain extender. The structures and properties of these PLAUs were studied using infrared spectroscopy, differential scanning calorimetry, tensile testing, and thermomechanical analysis. Among them, the MDI-based PLAU has the highest Tg, maximum tensile strength, and restoration force, the TDI-based PLAU has the lowest Tg, and the IPDI-based PLAU has the highest tensile modulus and elongation at break. They are all amorphous. The shape recovery of the three PLAUs is almost complete in a tensile elongation of 150% or a twofold compression. They can keep their temporary shape easily at room temperature (20 °C). More importantly, they can deform and recover at a temperature below their Tg values. Therefore, by selecting the appropriate hard segment and adjusting the ratio of hard to soft segments, they can meet different practical demands for shape memory medical devices. Copyright © 2007 Society of Chemical Industry
Article
The crystallization kinetics and degree of crystallinity of polycaprolactone (PCL) were studied using the technique of differential scanning calorimetry (DSC). The crystallization exotherms measured using DSC were analyzed using a modified Avrami equation. The modification limited the analysis of the data to the primary crystallization process, where the Avrami equation is applicable. Both the degree of crystallinity and primary composite rate constant were found to decrease with increasing molecular weight. The observations have been explained in terms of the unified reptation-nucleation theory. Copyright © 2006 John Wiley & Sons, Ltd.
Article
A series of new shape memory polymers are synthesized by the cationic copolymerization of regular soybean oil, low saturation soybean oil (LoSatSoy oil), and/or conjugated LoSatSoy oil with styrene and divinylbenzene, norbornadiene, or dicyclopentadiene initiated by boron trifluoride diethyl etherate or related modified initiators. The shape memory properties of the soybean oil polymers are characterized by the deformability (D) of the materials at temperatures higher than their glass-transition temperatures (Tg), the degree to which the deformation is subsequently fixed at ambient temperature (FD), and the final shape recovery (R) upon being reheated. It is found that a Tg well above ambient temperature and a stable crosslinked network are two prerequisites for these soybean oil polymers to exhibit shape memory effects. Good shape memory materials with high D, FD, and R values are prepared by controlling the crosslink densities and the rigidity of the polymer backbones. The advantage of the soybean oil polymers lies in the high degree of chemical control over the shape memory characteristics. This makes these materials particularly promising in applications where shape memory properties are desirable. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1533–1543, 2002; DOI 10.1002/app.10493
Article
In this study, a series of shape-memory polyurethanes were prepared from polycarbonate diol (PCDL) with a molecular weight of 2000, trimethylol propane, and isophorone diisocyanate (IPDI). The properties of crosslinked poly(carbonate urethane) (PCU) networks with various compositions were investigated. The chemical structures and thermal properties were determined with Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. FTIR analysis indicated that PCU had the structures of IPDI and PCDL and the amido formyl ester in polyurethanes. The gel content of PCU showed that PCU could be effectively formed as crosslinked polyurethane networks. The glass-transition temperatures of the PCU networks increased slightly with decreasing soft-segment content in the networks. The values of Young's modulus in the networks at 25°C increased with decreasing soft-segment content, whereas the tensile stress and breaking elongation decreased significantly. PCU showed shape-memory effects with a high strain fixity rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009