Next Article in Journal
Novel Electrodeposited Ni-B/Y2O3 Composite Coatings with Improved Properties
Next Article in Special Issue
A Note on the Dyeing of Wool Fabrics Using Natural Dyes Extracted from Rotten Wood-Inhabiting Fungi
Previous Article in Journal
The Phase Evolution and Property of FeCoCrNiAlTix High-Entropy Alloying Coatings on Q253 via Laser Cladding
Previous Article in Special Issue
Wood-Rotting Fungal Pigments as Colorant Coatings on Oil-Based Textile Dyes
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 7
Issue 10
10.3390/coatings7100159
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Thermoplastic Polyurethanes Stemming from Castor Oil: Green Synthesis and Their Application in Wood Bonding

by
Shaolong Li
*,
Changlian Xu
,
Wenfeng Yang
and
Qingru Tang
Aviation Engineering Institute, Civil Aviation Flight University of China, Guanghan 618307, China
*
Author to whom correspondence should be addressed.
Coatings 2017, 7(10), 159; https://doi.org/10.3390/coatings7100159
Submission received: 27 July 2017 / Revised: 12 September 2017 / Accepted: 21 September 2017 / Published: 29 September 2017
(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)
Browse Figures
Versions Notes

Abstract

:
We report an efficient and green approach to synthesize a linear castor oil-based polyurethane (CPU) without using any solvent or catalyst. Diol monomers were first synthesized by the aminolysis reaction between castor oil and diamines; this was accomplished within 6 h at 130 °C. Polymerization of the diols and isocyanate was further confirmed by Fourier transform infrared (FTIR), 1H-nuclear magnetic resonance (1H-NMR), and gel permeation chromatography analyses. The resultant CPUs showed a good thermal stability with an initial degradation temperature higher than 300 °C, and their mechanical and wood bonding property can be modulated by the structures of diamine. In addition, the CPUs possessed a satisfying water resistance property with the water absorption amount lower than 2%. The green conversion of castor oil to thermoplastic polyurethane affords new opportunities in bio-based industries.

1. Introduction

The prevalence of polyurethane (PU) has become more frequent since Otto Bayer and his colleagues first introduced it. In order to meet the needs of versatile applications such as elastomers, thermoplastics, thermosets, adhesives, coatings, foams, and fibers [1], the structure of PU should be tailored with various polyisocyanates and polyols. Despite some alternative synthetic routes, including carbon dioxide and monoxide, as well as organic carbonates (e.g., carbonyl diimidazole [2,3] carbamoyl-3-nitro-1,2,4-trizole [4], metal-catalyzed oxidative carbonylation of amines and anilines [5]) have been employed to avoid the application of toxic chemicals, these involving strategies that cannot fully displace the employment of polyisocyanates in industry [6]. Therefore, we should also pay greater attention to seeking renewable polyols and green synthesis methods for PU production [7,8].
Among sustainable resources, vegetable oil is one of the most promising options owing to its inherent renewability, easy modifiability, and relative low cost [8,9]. Vegetable oil, no matter from which source, is generally composed of various triglycerides, the presence of unsaturated bonds making it possible to prepare vegetable oil–based polymeric materials [10,11,12,13,14,15,16,17,18,19,20,21]. As for the preparation of sustainable PU, different types of vegetable oils, including soybean oil, rapeseed oil, corn oil, palm oil, and sunflower oil, have been exploited as raw materials. Nevertheless, these vegetable oils contain less than two hydroxyl groups per molecule, and their C=C bonds have to be modified via complicated reactions that introduce more hydroxyl groups for PU production. Since involving polyols originating from the oils contain multiple hydroxyl groups, all the resultant PUs are thermosets [22,23,24,25,26,27,28,29]. Among most commercial vegetable oils, castor oil—a non-edible oil naturally containing approximately 2.7 hydroxyl groups per glyceride—has attracted considerable attention for the synthesis of PUs [30,31,32,33]. However, thermoplastic PU cannot be produced directly from castor oil because of its multifunctional hydroxyl groups. Up to now, there are very few reports dealing with the synthesis of thermoplastic PU from plant oils [34,35,36]. Lligadas and co-workers [37,38,39] utilized the thiol-ene click chemistry method to synthesize a new kind of diol monomer from 10-undecenoic acid, which can be used to prepare linear PUs. Xu et al. [40,41] developed thermoplastic PUs from ricinoleic acid via an approach of transesterification following condensation. Nevertheless, these preparation processes made use of organic solvents and catalysts. The current state of bio-based PU, therefore, encourages us to search for a way to fabricate a bio-based thermoplastic PU without using a catalyst or any organic solvents and that can satisfy the requirements of green manufacturing and engineering.
In the present work, a complete catalyst-free and organic solvent-free method is reported to obtain a linear and double-bond residue castor-based PU. Water resistance and the thermal and mechanical properties of the resultant PUs were investigated using contact angle (CA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile property measurements. Furthermore, the PUs were evaluated as hot melt adhesives for wood-to-wood bonding and showed acceptable adhesive properties.

2. Materials and Methods

2.1. Materials

Castor oil (CO), hexamethanylenediamine (HDA), and ethyldiamine (EDA) with AR grade were obtained from Kelong Chemical Corporation (Chengdu, China) and were used without any further purification. Butanediamine (BDA) was purchased from Aladdin Corporation (Shanghai, China), and hexamethylene diisocyanate (HDI, AR grade) was purchased from Sigma-Aldrich Corporation (St. Louis, MO, USA) and used as received.

2.2. Synthesis of Precursor Diols from Castor Oil

Aminolysis of castor oil was performed in the presence of EDA, BDA, and HDA, and the resultant amide diols were named as EDRA, BDRA, and HDRA, respectively. Typically, castor oil and diamines with a molar ratio of 2:3 were mixed in the reactor under a nitrogen atmosphere with magnetic stirring at 70–130 °C. After reacting for different periods, the reaction mixture was poured into pure water to remove unreacted diamines, castor oil, and the byproduct (glycerol). The solid-liquid mixture was filtered and washed by deionized water three to five times. Finally, the obtained white or buff solid products were toasted by an infrared lamp for 6 h and then dried in vacuum at 50 °C for two days. The sample yields were 85, 88, and 79% for EDA, BDA, and HAD, respectively.

2.3. Preparation of Castor Oil-Based Thermoplastic PUs

Castor oil-based thermoplastic polyurethanes were synthesized via a solvent-free and catalyst-free method at with equal molar ratio of diols to HDI. HDRA (0.03 mol, 24.4 g) was selected as a represent resultant amide diols to react with HDI (0.03 mol, 4.8 mL) as a chain-extender. Typically, HDRA was added into a two-necked flask, which was evacuated and then purged with nitrogen three times. The flask was immersed in a 100 °C silicon oil bath, and the reactant was mechanically stirred after being completely melted. Then, a predetermined amount of HDI was added into the flask. The chain-extension was carried out under continuous stirring for 2 h.

2.4. Characterization Methods

The 1H-nuclear magnetic resonance (1H-NMR) spectra of precursor diols and resultant PUs were recorded on a spectrometer (Bruker AC-P 400 MHz, Rheinstetten, Germany) using CDCl3 as the solvent. Gel permeation chromatography (GPC) was performed on a GPC instrument (Waters Co., Victoria, Australia) with a refractive index detector. The samples with a concentration of 2.5 mg/mL were analyzed at 35 °C with tetrahydrofuran as an eluent at a flow rate of 1.0 mL/min. Fourier transform infrared (FTIR) spectra of materials and products were recorded on a Nicolet 6700 spectrometer (Nicolet Instrument Co., Madison, WI, USA). Thermal behaviors were analyzed by a TA Instruments DSC-Q200 (TA Instruments, New Castle, DE, USA). Samples were first heated at 130 °C for 5 min to eliminate their thermal histories and then quenched at −50 °C. After this, the quenched samples were reheated to 130 °C at a heating rate of 10 °C/min. Thermomechanical properties of PU films were measured by a dynamic mechanical analyzer (DMA Q800, TA Instrument, New Castle, DE, USA) in tensile resonant mode with a heating rate of 3 °C/min within −60 to 50 °C. The frequency was fixed at 1 Hz. In order to provide identical samples and to ensure consistency in DMA and tensile test measurements, the synthesized polymers were compression molded by a vulcanizer with a pressure of 10 MPa at 130 °C, and then the obtained films were quenched at room temperature. The PU specimens for DMA analysis were cut into 6 × 8 mm2 (width × length) pieces. Tensile properties of the PU films were evaluated by a SANA CMT4104 testing machine (SANS Group, Shenzhen, China) at a crosshead speed of 10 mm/min. The dumbbell shaped specimens with thickness and width of 0.5 and 0.4 mm were used for the measurements, which were carried out at least five times for each sample.

2.5. Wood Bonding and Water-Resistant Testing

Lap shear strength of wood joints were characterized by the SANA CMT4104 testing machine according to the standard GB/T 7124-2008/ISO 4587:2003 [42] Prior to the tests, the teak wood pieces were cut into strips with a thickness of 1.6 mm and 25 × 300 mm2 area. PUs were first heated to 100 °C for 5 min and then applied to both pieces of teak wood strips with a thickness of 0.2 mm and a lap joint giving and area of overlap of 25 × 12.5 mm2. A load (2.5 kg) was placed over the contact points of wood samples at 25 °C for 48 h. After bonding, each sample was placed at room temperature (25 °C) and 50 ± 5% relative humidity (RH) at least seven times before mechanical testing. The water contact angle was measured by a CA system (Zhongchen Corporation, Beijing, China). Three microliters of deionized water were dropped onto the samples. The PU films were dried in a vacuum oven at 40 °C for 24 h before the swelling experiment. Then, samples were immersed in pure water for more than 24 h to record the weight increments at different predetermined times at room temperature (25 °C). The water adsorption was calculated as the following equation:
Water   adsorption   ( % )   =   W 2 − W 1 W 1   ×   100 %
where W1 and W2 represent the initial and final weights of PU.

3. Results and Discussion

3.1. Synthetisis Procedures

As is well known, castor oil contains approximately three hydroxyl groups and is rarely used to synthesize linear PUs. Therefore, precursor diols are typically obtained prior to the condensation with polyisocyanates. To remove the necessity for a catalyst, in this work, we selected three primary amines (EDA, BDA, and HDA) with high reaction activities to induce the aminolysis of castor oil (Scheme 1). To enhance the “green characteristics” of this approach, water was then applied to remove the unreacted diamine, as well as the product, glycerol. Generally, the reaction temperature and period are two important factors for synthesis of new compounds. HDA, therefore, was selected as a representative diamine to react with castor oil at 70, 100, and 130 °C.

3.2. Structural Characterization

At predetermined reaction time points, the resulting reaction mixtures were characterized by 1H-NMR measurement (Figure 1). The characteristic signals of the castor oil were observed at 3.63 ppm (Ha, –CH), 5.4–5.6 ppm (Hb and Hc, CH=CH), 4.16 ppm, 4.30 ppm, and 5.25 ppm (included in frame I, attributed to glyceride). When HDA was mixed with castor oil, a peak at 3.27 ppm (Hd, –CH2) was clearly observed. The presence of the signal at 2.70 ppm, from HDA binding to the amine group (the arrow marking in frame II), indicated that the aminolysis reaction was not accomplished within a short time period at a comparably low temperature. With the increase in reaction time at a fixed temperature, the intensity of the peak at 2.70 ppm became weaker and weaker. It should be noted that the peak was not completely absent at reaction temperatures of 70 and 100 °C within 8 h. However, increasing the temperature to 130 °C could remarkably reduce the reaction time: only about 6 h were needed to complete the reaction. Therefore, the aminolysis reactions between castor oil and the other two diamines were also performed at 130 °C, and the 1H-NMR spectra of resultant EDRA and BDRA are shown in Figure 2. As a further investigation of the reaction between CO and diamines, FTIR analysis was conducted to compare the differences in spectra of CO and the resultant amide diols (Supplementary Materials Figure S1). After reacting with different diamines, the absorbance peak of –COOR belonging to castor oil at 1740 cm−1 was not detected, and a new peak appeared at 1693 cm−1, which indicated that castor oil could react entirely with the diamines. The results met our expectations and showed that the chain-extension products would be linear thermoplastic polyurethanes.
The secondary OH groups of ricinoleic acid possess a comparably low reaction activity with NCO. Therefore, the reaction temperature was set at 100 °C, which guarantees successful reaction between them. In addition, to prevent a reaction between the secondary NH groups of amide fragment with NCO [43,44], no catalyst was introduced, and the feeding molar ratio of NCO/OH and reaction period were fixed at 1:1 and 2 h, respectively. The resultant PUs based on HDRA, BDRA, and EDRA were named as CPU1, CPU2, and CPU3, and their chemical structures were confirmed by 1H-NMR measurement (shown in Figure 2). The disappearance of the peak at 3.63 (Ha) as well as the appearance of two peaks at 4.75 and 3.16 ppm (Ha’ and He) mean that the polycondensation occurred between HDI and the OH groups of diols. As seen in Supplementary Materials Figure S2, moreover, no absorbance peak was determined between the wavenumbers 2250 to 2270 cm−1. This suggests that there was no NCO group left in the resultant PUs, which is a desirable characteristic for eco-friendly materials. Even though the polymerization was performed in a solvent-free manner, the PDI of resultant CPUs was well controlled at a comparably low level with a Mn of 9.53–11.0 KDa (Table 1). The results indicated that appropriate molecular weights of CPUs were achieved, meeting our expectations.

3.3. Thermal Behavior of CPUs

Supplementary Materials Figure S3 shows DSC curves of the CPUs. It shows that CPU1 exhibited no endothermic melting peak, while CPU2 and CPU3 display low-intensity peaks around 60 °C. For HDRA in CPU1, the strong interactions (H-bonds) with the residual urethane groups changed the original conformation and crystallization, resulting in amorphous soft segments in CPU1 and no endothermic melting peak. However, the rest chains of BDRA and EDRA in CPU2 and CPU3 made it difficult to form H-bonds, so the soft segments kept their original conformation and crystal structure. Therefore, small peaks can be observed on the curves for samples CPU2 and CPU3 around 60 °C. Although glassy transition temperatures (Tg) of PUs were observed, it was hard to compute the thermal transition differences from DSC results. To better clarify these differences between the CPUs, DMA measurements were carried out. As shown in Figure 3, all PUs presented similar changes of storage modulus with the increase in temperature. The storage moduli of CPUs were dependent on their structures, that is that CPU1 possessed a higher modulus than the other two CPUs. In addition, only one tan delta peak was found for each PU, and the corresponding Tg increased with a longer length of diamine molecule. The weight ratio of hard segments (the rest of the urethane groups) of CPU1, CPU2, and CPU3 were 17.0%, 17.5%, and 18.1%, respectively. All samples showed similar composition of hard and soft regions. However, urethane groups and amide groups easily form strong interactions (H-bonds). In these cases, longer chain amines might, in fact, lead to greater molecular mobility. It is possible that the more flexible chains of HDA enable the macromolecules to change their conformation in a way that facilitates the formation of strong interactions (H-bonds) with the residual urethane groups. We assumed that all the amide groups in contact with urethane groups form new hard segments. The weight ratio of hard segments was 37.6%, 35.5%, and 33.2% for each CPU, respectively. CPU1 showed a higher hard segment content. In fact, only a part of the amide groups formed H-bonds with urethane groups and thus created a different flexibility of the target molecular. The contents and molecular mobility of diamine chains were the main factors determining flexibility. When the weight ratio of the diamine chain is comparable, longer chains (HDA) more easily move to bond with urethane groups and form H-bonds, which increased the content of hard segments. Thus, a higher content of hard segment of CPU1 resulted in a comparable high mechanical property, as well as a difficult thermal transition [45,46].
Thermal stability of the CPUs is an important factor in application and evaluation by TGA measurement. As shown in Figure 4, 5% of the initial degradation temperatures of all CPUs were higher than 300 °C, which is comparable to some commercialized PUs [47,48], indicating that there were nearly no residues of small molecules in the resultant materials. In addition, a similar one-step degradation method was observed for all CPU samples, indicating that the CPUs possessed a high thermal stability independent of the structure of diamine.

3.4. Wood Bonding and Water-Resistant Properties

Polyurethane is a class of polymer used as a hot melt adhesive for wood-to-wood bonding. The bonding strength and water-resistance are two very important aspects of adhesive performance of PU. Hence, wood bonding and water-resistant properties of CPUs were studied to find their potential application as bio-based adhesive. Tensile strength (TS), elongation at break (ε), and Young’s modulus of the CPUs are summarized in Table 1. CPU1 possessed comparably high TS and Young’s modulus, which were attributed to the higher content of hard segment introduced by strong interactions (H-bonds) between the residual amine groups and urethane groups when using diamine with a longer chain as the aminolysis agent. To further investigate whether the CPUs have the potential to be used as wood adhesives, their wood-to-wood bonding properties were evaluated. As shown in Table 1, lap shear strength of the CPUs was found to be between 12.0 and 18.9 N/m2, which is comparable to previous reports [49,50,51]. The lap shear strength increased with the decrease of the chain length in CPUs. This is because higher soft content and lower glass transition temperature (Tg) improve the adhesive properties. This meant that the CPUs synthesized in this work might fulfill the needs of adhesives for wood. Furthermore, the water resistance of adhesive is quite important for practical applications. Water contact angle measurement was utilized to evaluate the surface property of CPU films. As illustrated in Figure 5, the water contact angles of CPU1, CPU2, and CPU3 films were 106 ± 1°, 104 ± 1°, and 97 ± 1°, respectively, showing good anti-wetting properties. In addition, the water uptake amount of the CPU films was suppressed lower than 2%, even after 24-h of immersion, and there were no obvious differences between the samples, which implied a good water resistance of the prepared bio-based PU films.

4. Conclusions

A new thermoplastic polyurethane was synthesized from castor oil via a totally catalyst-free and solvent-free procedure under mild conditions. The aminolysis of castor oil with diamines was accomplished completely at 130 °C for 4 h. The CPU synthesized from the diamine with a longer chain length exhibited comparably high tensile strength and Young’s modulus. As a wood adhesive, the CPUs met the needs of wood-to-wood bonding and showed outstanding water-resistance, with water adsorption of less than 2%. This means the unique bio-based CPU system reported here shows promise in bio-based adhesive applications. More research needs to be made in our future work to further improve the properties and the range of applications.

Supplementary Materials

The following are available online at www.mdpi.com/2079-6412/7/10/159/s1. Figure S1: FTIR spectra of castor oil and amide diols; Figure S2: FTIR spectra of CPUs; Figure S3: DSC curves of CPUs.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. U1233202) and the Science Research Foundation of Civil Aviation Flight University of China (Grant No. BJ2016-02).

Author Contributions

Shaolong Li and Changlian Xu conceived and designed the experiments; Changlian Xu performed the experiments; Wenfeng Yang measured and analyzed the 1H-NMR spectra; Qingru Tang measured and analyzed the DMA data; and Shaolong Li wrote the paper. Wenfang Yang and Qingru Tang approved the final version of the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Escouvois, M. From vegetable oils to polyurethanes: Synthetic routes to polyols and main industrial products. Polym. Rev. 2012, 52, 38–79. [Google Scholar]
  2. Rannard, S.P.; Davis, N.J. The selective reaction of primary amines with carbonyl imidazole containing compounds: Selective amide and carbamate synthesis. Org. Lett. 2000, 2, 2117–2120. [Google Scholar] [CrossRef] [PubMed]
  3. Grzyb, J.A.; Batey, R.A. Achieving functional group diversity in parallel synthesis: Solution-phase synthesis of a library of ureas, carbamates, thiocarbamates, and amides using carbamoylimidazolium salts. Tetrahedron Lett. 2008, 49, 5279–5282. [Google Scholar] [CrossRef]
  4. Shimizu, M.; Sodeoka, M. Convenient method for the preparation of carbamates, carbonates, and thiocarbonates. Org. Lett. 2007, 9, 5231–5234. [Google Scholar] [CrossRef] [PubMed]
  5. Chaturvedi, D. Cheminform abstract: Perspectives on the synthesis of organic carbamates. Cheminform 2012, 43, 15–45. [Google Scholar] [CrossRef]
  6. Kreye, O.; Mutlu, H.; Meier, M.A.R. Sustainable routes to polyurethane precursors. Green Chem. 2013, 15, 1431–1455. [Google Scholar] [CrossRef]
  7. Pfister, D.P.; Xia, Y.; Larock, R.C. Recent advances in vegetable oil-based polyurethanes. Chemsuschem 2011, 4, 703–717. [Google Scholar] [CrossRef] [PubMed]
  8. Zhang, C.; Xia, Y.; Chen, R.; Huh, S.; Johnston, P.A.; Kessler, M.R. Soy-castor oil based polyols prepared using a solvent-free and catalyst-free method and polyurethanes therefrom. Green Chem. 2013, 15, 1477–1484. [Google Scholar] [CrossRef]
  9. Xia, Y.; Larock, R.C. Vegetable oil-based polymeric materials: Synthesis, properties, and applications. Green Chem. 2010, 12, 1893–1909. [Google Scholar] [CrossRef]
  10. Ahn, B.K.; Kraft, S.; Wang, D.; Sun, X.S. Thermally stable, transparent, pressure-sensitive adhesives from epoxidized and dihydroxyl soybean oil. Biomacromolecules 2011, 12, 1839–1843. [Google Scholar] [CrossRef] [PubMed]
  11. Altuna, F.I.; Pettarin, V.; Williams, R.J.J. Self-healable polymer networks based on the cross-linking of epoxidised soybean oil by an aqueous citric acid solution. Green Chem. 2013, 15, 3360–3366. [Google Scholar] [CrossRef]
  12. Fourcade, D.; Ritter, B.S.; Walter, P.; Schönfeld, R.; Mülhaupt, R. Renewable resource-based epoxy resins derived from multifunctional poly(4-hydroxybenzoates). Green Chem. 2013, 15, 910–918. [Google Scholar] [CrossRef]
  13. Tsujimoto, T.; Uyama, H. Full biobased polymeric material from plant oil and poly(lactic acid) with a shape memory property. Acs Sustain. Chem. Eng. 2014, 2, 2057–2062. [Google Scholar] [CrossRef]
  14. Budde, C.F.; Riedel, S.L.; Willis, L.B.; Rha, C.K.; Sinskey, A.J. Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from plant oil by engineered Ralstonia eutropha strains. Appl. Environ. Microbiol. 2011, 77, 2847–2854. [Google Scholar] [CrossRef] [PubMed]
  15. Rao, U.; Sridhar, R.; Sehgal, P.K. Biosynthesis and biocompatibility of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) produced by cupriavidus necator from spent palm oil. Biochem. Eng. J. 2010, 49, 13–20. [Google Scholar] [CrossRef]
  16. Obruca, S.; Marova, I.; Snajdar, O.; Mravcova, L.; Svoboda, Z. Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by cupriavidus necator from waste rapeseed oil using propanol as a precursor of 3-hydroxyvalerate. Biotechnol. Lett. 2010, 32, 1925–1932. [Google Scholar] [CrossRef] [PubMed]
  17. Ma, F.; Hanna, M.A. Biodiesel production: A review. Bioresour. Technol. 1999, 70, 1–15. [Google Scholar] [CrossRef]
  18. Espinosa, L.M.D.; Gevers, A.; Woldt, B.; Graß, M.; Meier, M.A.R. Sulfur-containing fatty acid-based plasticizers via thiol-ene addition and oxidation: Synthesis and evaluation in PVC formulations. Green Chem. 2014, 16, 1883–1896. [Google Scholar] [CrossRef]
  19. Das, G.; Bordoloi, N.K.; Rai, S.K.; Mukherjee, A.K.; Karak, N. Biodegradable and biocompatible epoxidized vegetable oil modified thermostable poly(vinyl chloride): Thermal and performance characteristics post biodegradation with Pseudomonas aeruginosa and Achromobacter sp. J. Hazard. Mater. 2012, 209, 434–442. [Google Scholar] [CrossRef] [PubMed]
  20. Türünç, O.; Firdaus, M.; Klein, G.; Meier, M.A.R. Fatty acid derived renewable polyamides via thiol-ene additions. Green Chem. 2012, 14, 2577–2583. [Google Scholar] [CrossRef]
  21. Luo, Q.; Liu, M.; Xu, Y.; Ionescu, M.; Petrović, Z.S. Thermosetting allyl resins derived from soybean oil. J. Appl. Polym. Sci. 2011, 127, 7149–7157. [Google Scholar] [CrossRef]
  22. Garrison, T.F.; Zhang, Z.; Kim, H.J.; Mitra, D.; Xia, Y.; Pfister, D.P.; Brehm-Stecher, B.F.; Larock, R.C.; Kessler, M.R. Thermo-mechanical and antibacterial properties of soybean oil-based cationic polyurethane coatings: Effects of amine ratio and degree of crosslinking. Macromol. Mater. Eng. 2015, 299, 1042–1051. [Google Scholar] [CrossRef]
  23. Allauddin, S.; Narayan, R.; Raju, K.V.S.N. Synthesis and properties of alkoxysilane castor oil and their polyurethane/urea-silica hybrid coating films. ACS Sustain. Chem. Eng. 2013, 1, 910–918. [Google Scholar] [CrossRef]
  24. Yongshang, L.; Larock, R.C. Aqueous cationic polyurethane dispersions from vegetable oils. Chemsuschem 2010, 3, 329–333. [Google Scholar]
  25. Xia, Y.; Larock, P.R.C. Soybean oil-isosorbide-based waterborne polyurethane-urea dispersions. Chemsuschem 2011, 4, 386–391. [Google Scholar] [CrossRef] [PubMed]
  26. Zhang, C.; Ding, R.; Kessler, M.R. Reduction of epoxidized vegetable oils: A novel method to prepare bio-based polyols for polyurethanes. Macromol. Rapid Commun. 2014, 35, 1068. [Google Scholar] [CrossRef] [PubMed]
  27. Pan, X.; Webster, D.C. New biobased high functionality polyols and their use in polyurethane coatings. Chemsuschem 2012, 5, 419–429. [Google Scholar] [CrossRef] [PubMed]
  28. Garrison, T.F.; Kessler, M.R.; Larock, R.C. Effects of unsaturation and different ring-opening methods on the properties of vegetable oil-based polyurethane coatings. Polymer 2014, 55, 1004–1011. [Google Scholar] [CrossRef]
  29. Clark, A.J.; Seng, S.H. Copolymers of tetrahydrofuran and epoxidized vegetable oils: Application to elastomeric polyurethanes. Polym. Chem. 2014, 5, 3238–3244. [Google Scholar] [CrossRef]
  30. Thakur, S.; Karak, N. Castor oil-based hyperbranched polyurethanes as advanced surface coating materials. Prog. Org. Coat. 2013, 76, 157–164. [Google Scholar] [CrossRef]
  31. Xu, C.L.; Zeng, J.B.; Wang, Y.Z. Sustainable waterborne polyurethane ionomer reinforced poly(vinyl alcohol) composite films. Compos. Sci. Technol. 2014, 96, 109–115. [Google Scholar] [CrossRef]
  32. Madbouly, S.A.; Xia, Y.; Kessler, M.R. Rheological behavior of environmentally friendly castor oil-based waterborne polyurethane dispersions. Macromolecules 2013, 46, 4606–4616. [Google Scholar] [CrossRef]
  33. Wang, H.J.; Rong, M.Z.; Zhang, M.Q.; Hu, J.; Chen, H.W.; Czigány, T. Biodegradable foam plastics based on castor oil. Biomacromolecules 2008, 9, 615–623. [Google Scholar] [CrossRef] [PubMed]
  34. Rao, J.L.; Balakrishna, R.S.; Shirsalkar, M.M. Cathodically electrodepositable novel coating system from castor oil. J. Appl. Polym. Sci. 2010, 44, 1873–1881. [Google Scholar] [CrossRef]
  35. Roy, T.; Mannari, V.; Raval, D. Two-package polyurethane coatings based on castor oil-modified polyesteramides for industrial maintenance coatings. J. Sci. Ind. Res. 1996, 55, 971–976. [Google Scholar]
  36. Yadav, S.; Zafar, F.; Hasnat, A.; Ahmad, S. Poly (urethane fatty amide) resin from linseed oil—A renewable resource. Prog. Org. Coat. 2009, 64, 27–32. [Google Scholar] [CrossRef]
  37. Lluch, C.; Ronda, J.C.; Galià, M.; Lligadas, G.; Cádiz, V. Rapid approach to biobased telechelics through two one-pot thiol-ene click reactions. Biomacromolecules 2010, 11, 1646–1653. [Google Scholar] [CrossRef] [PubMed]
  38. Lluch, C.; Lligadas, G.; Ronda, J.C.; Galià, M.; Cádiz, V. Thermoplastic polyurethanes from undecylenic acid-based soft segments: Structural features and release properties. Macromol. Biosci. 2013, 13, 614–622. [Google Scholar] [CrossRef] [PubMed]
  39. Lligadas, G.; Ronda, J.C.; Galià, M.; Cádiz, V. Plant oils as platform chemicals for polyurethane synthesis: Current state-of-the-art. Biomacromolecules 2010, 11, 2825–2835. [Google Scholar] [CrossRef] [PubMed]
  40. Xu, Y.; Petrovic, Z.; Das, S.; Wilkes, G.L. Morphology and properties of thermoplastic polyurethanes with dangling chains in ricinoleate-based soft segments. Polymer 2008, 49, 4248–4258. [Google Scholar] [CrossRef]
  41. Petrovic, Z.S.; Cvetkovic, I.; Hong, D.P.; Wan, X.; Zhang, W.; Abraham, T.; Malsam, J. Polyester polyols and polyurethanes from ricinoleic acid. J. Appl. Polym. Sci. 2008, 108, 1184–1190. [Google Scholar] [CrossRef]
  42. GB/T 7124-2008 ISO 4587:2003 Adhesive Test of Tensile Shear Strength; China National Standardization Management Committee: Beijing, China, 2003.
  43. Hesp, K.D.; Bergman, R.G.; Ellman, J.A. Expedient Synthesis of N-Acyl Anthranilamides and β-Enamine Amides by the Rh(III)-Catalyzed Amidation of Aryl and Vinyl C–H Bonds with Isocyanates. J. Am. Chem. Soc. 2011, 133, 11430–11433. [Google Scholar] [CrossRef] [PubMed]
  44. Saunders, J.H. The reactions of isocyanates and isocyanate derivatives at elevated temperatures. Rubber Chem. Technol. 1959, 32, 337–345. [Google Scholar] [CrossRef]
  45. Momtaz, M.; Razavi-Nouri, M.; Barikani, M. Effect of block ratio and strain amplitude on thermal, structural, and shape memory properties of segmented polycaprolactone-based polyurethanes. J. Mater. Sci. 2014, 49, 7575–7584. [Google Scholar] [CrossRef]
  46. Zhang, Z.; Wang, G.; Luo, N.; Huang, M.; Jin, M.; Luo, Y. Thermal decomposition of energetic thermoplastic elastomers of poly(glycidyl nitrate). J. Appl. Polym. Sci. 2014, 131, 8558–8572. [Google Scholar] [CrossRef]
  47. Wei, H.; Ding, D.; Wei, S.; Guo, Z. Anticorrosive conductive polyurethane multiwalled carbon nanotube nanocomposites. J. Mater. Chem. A 2013, 1, 10805–10813. [Google Scholar] [CrossRef]
  48. Ding, D.; Wei, H.; Zhu, J.; He, Q.; Yan, X.; Wei, S.; Guo, Z. Strain sensitive polyurethane nanocomposites reinforced with multiwalled carbon nanotubes. Energy Environ. Focus 2014, 3, 85–93. [Google Scholar] [CrossRef]
  49. Poh, A.K.; Sin, L.C.; Cheng, S.F.; Hock, C.C. Polyurethane wood adhesive from palm oil-based polyester polyol. J. Adhes. Sci. Technol. 2014, 28, 1020–1033. [Google Scholar]
  50. Silva, B.B.R.; Santana, R.M.C.; Forte, M.M.C. A solventless castor oil-based pu adhesive for wood and foam substrates. Int. J. Adhes. Adhes. 2010, 30, 559–565. [Google Scholar] [CrossRef]
  51. Patel, R.M.; Shukla, M.J.; Patel, K.N.; Patel, H.K. Biomaterial based novel polyurethane adhesives for wood to wood and metal to metal bonding. Mater. Res. 2009, 12, 385–393. [Google Scholar] [CrossRef]
Coatings 07 00159 sch001 550
Scheme 1. Synthetic route to linear castor oil-based polyurethane (CPU).
Scheme 1. Synthetic route to linear castor oil-based polyurethane (CPU).
Coatings 07 00159 sch001
Coatings 07 00159 g001 550
Figure 1. 1H-NMR spectra of castor oil and amide diol monomers synthesized from hexamethanylenediamine (HDA).
Figure 1. 1H-NMR spectra of castor oil and amide diol monomers synthesized from hexamethanylenediamine (HDA).
Coatings 07 00159 g001
Coatings 07 00159 g002 550
Figure 2. 1H-NMR spectra of EDRA, BDRA, HDRA, as well as their corresponding CPU products.
Figure 2. 1H-NMR spectra of EDRA, BDRA, HDRA, as well as their corresponding CPU products.
Coatings 07 00159 g002
Coatings 07 00159 g003 550
Figure 3. Dependences of storage modulus (a) and tan delta (b) on temperature for CPUs.
Figure 3. Dependences of storage modulus (a) and tan delta (b) on temperature for CPUs.
Coatings 07 00159 g003
Coatings 07 00159 g004 550
Figure 4. TGA curves of different CPUs.
Figure 4. TGA curves of different CPUs.
Coatings 07 00159 g004
Coatings 07 00159 g005 550
Figure 5. Water adsorption behaviors of CPUs (inserted photos are the illustrations of their water contact angles).
Figure 5. Water adsorption behaviors of CPUs (inserted photos are the illustrations of their water contact angles).
Coatings 07 00159 g005
Table
Table 1. Structure characteristics and mechanical properties of CPUs.
Table 1. Structure characteristics and mechanical properties of CPUs.
SampleMn (kDa)Mw (kDa)Mw/MnTensile strength (TS) (MPa)Young‘s Modulus (MPa)ε (%)Lap Shear Strength (×105 N/m2)
CPU19.5315.71.76.2 ± 0.246.6 ± 3.452.0 ± 1.112.0 ± 0.2
CPU210.918.11.75.0 ± 0.243.7 ± 1.948.7 ± 1.817.2 ± 0.1
CPU311.020.01.83.6 ± 0.133.2 ± 0.669.1 ± 2.518.9 ± 0.2

Share and Cite

MDPI and ACS Style

Li, S.; Xu, C.; Yang, W.; Tang, Q. Thermoplastic Polyurethanes Stemming from Castor Oil: Green Synthesis and Their Application in Wood Bonding. Coatings 2017, 7, 159. https://doi.org/10.3390/coatings7100159

AMA Style

Li S, Xu C, Yang W, Tang Q. Thermoplastic Polyurethanes Stemming from Castor Oil: Green Synthesis and Their Application in Wood Bonding. Coatings. 2017; 7(10):159. https://doi.org/10.3390/coatings7100159

Chicago/Turabian Style

Li, Shaolong, Changlian Xu, Wenfeng Yang, and Qingru Tang. 2017. "Thermoplastic Polyurethanes Stemming from Castor Oil: Green Synthesis and Their Application in Wood Bonding" Coatings 7, no. 10: 159. https://doi.org/10.3390/coatings7100159

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop