Impact of lignin extraction methods on microstructure and mechanical properties of lignin‐based carbon fibers

In order to optimize the use of residues of enzymatic hydrolysis of corn stalk (REHCS) and explore the low‐cost and sustainable raw material substitute for carbon fibers, three types of lignin samples were extracted from REHCS by various extraction methods, and then they were converted into carbon fibers (CFs) by electrospinning, thermostabilization, and carbonization under the same process conditions. The microstructure and mechanical properties of the three types of carbonized fibers were different. The CFs from the ethanol organosolv lignin were actually smooth and brittle carbon films. The CFs from the formic acid/acetic acid organosolv lignin had microscopic pores, causing poor mechanical properties. Comparatively, the CFs from the alkaline lignin demonstrated preferable microstructure and mechanical properties. The reasons for the differences were analyzed by characterizing the lignin samples, precursor fibers, and resultant CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45580.     

Thermal properties and miscibility of semi‐crystalline and amorphous PLA blends

The focus of this research is the study of the microstructures and miscibility at the interface between semi‐crystalline and amorphous PLAs [poly (l ‐lactic acid)(PLLA) with poly (l ,d ‐lactic acid)(PDLLA), respectively]. The blends are prepared through thermal processing (extrusion and hot‐pressing). To increase the area of interface between PDLLA and PLLA, the fibers from PLLA and PDLLA are used. Thermal and microstructures of the blends were studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), dynamic thermogravimetric analysis(DMA), small‐angle X‐ray diffraction(SAXS) and wide‐angle X‐ray diffraction (WAXD). The two PLAs are miscible in molten state. However, phase separation is detected after various thermal treatments, with PDLLA being excluded from the regions of interlamellar PLLA regions when PDLLA content is low, as determined from X‐ray diffraction studies. The compatibility between the two PLAs is not perfect in the molten state, since enthalpies of the various blends at T_g are lower than any pure PLA material. The semi‐crystalline PLLA fiber can recrystallize alone in the molten amorphous PDLLA, and a higher nuclei density is observed at the interface. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41205.     

Polyester polyols and polyurethanes from ricinoleic acid

Triols of molecular weights (MWs) 1000–4000, suitable for flexible foams, were prepared by transesterification of methyl esters of ricinoleic acid with trimethylol propane. These polyols were noncrystallizing, relatively low‐viscosity liquids. They were reacted with diphenylmethane diisocyanate (MDI) to obtain elastomers having glass transition temperatures below ?60°C. Polymer networks from high‐MW polyols exhibited relatively high sol fractions suggesting that some cyclization occurred during polyol preparation. The low Shore hardness, relatively low strength and modest elongation of the elastomers were attributed to the specific structure of polyricinoleic chains and the presence of dangling chains, serving as plasticizers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Efficient solid‐phase synthesis of acetylated lignin and a comparison of the properties of different modified lignins

The chemical modification of lignin can greatly enhance its functionality and exploit its application areas. To avoid the difficulties of separation and environmental pollution in the traditional liquid‐phase method, we prepared acetylated lignin by a mechanical‐activation‐assisted solid‐phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor and studied its structure and properties. Ultraviolet–visible analysis showed that the degree of esterification (DE) of the acetylated lignin produced by the MASPS technique was 77.59%, whereas the DEs of those produced by traditional liquid‐phase synthesis (LPS) and thermal solid‐phase synthesis (TSPS) were only 42.29 and 27.54%, respectively. Fourier transform infrared spectroscopy and NMR analyses indicated that both phenolic hydroxyls and aliphatic hydroxyls participated in the reaction, and the reactivity of the phenolic hydroxyls was higher than that of the aliphatic hydroxyl groups. The acetylation of aliphatic hydroxyl mainly happened at the γ of arylglycerol‐β‐aryl ether (β‐O‐4). Scanning electron microscopy analysis showed that the acetylated lignins prepared by MASPS and TSPS were irregular blocks with coarse surfaces and loose structures, whereas the lignin prepared by LPS consisted mostly of regular balls with a smooth surface and a compact structure. Differential scanning calorimetry and thermogravimetric analyses indicated that the glass‐transition temperatures and thermal stability of the acetylated lignin increased by orders with the processing techniques of MASPS, TSPS, and LPS. MASPS integrated the activation and reaction in the same equipment without the use of a solvent and showed advantages of a high efficiency, environmental protection, and easy operation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44276.     

Flexible polyurethane foams modified with biobased polyols: Synthesis and physical‐chemical characterization

A series of flexible polyurethane foams with different polyol compositions were synthesized through the replacement of a portion of the petroleum‐based polyether polyol with biobased polyols, namely, glycerol (GLY) and hydroxylated methyl esters (HMETO). HMETO was synthesized by the alkaline transesterification of tung oil (TO; obtaining GLY as a byproduct) and the subsequent hydroxylation of the obtained methyl esters with performic acid generated in situ. FTIR spectroscopy, ¹H‐NMR, and different analytical procedures indicated that the hydroxyl content increased significantly and the molecular weight decreased with respect to those of the TO after the two reaction steps. The characterization of the obtained foams, achieved through the measurement of the characteristic reaction times, thermal and dynamic mechanical analysis, scanning electronic microscopy, and density measurements, is reported and discussed. The most important changes in the modified foams were found with the addition of GLY to the formulation; this led to an increased foam density and storage rubbery modulus, which were associated with a higher crosslinking density because of the decrease in the chain length between crosslinking points. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43831.     

Mechanical and thermal properties of thermoplastic random copolyesters made from lipid‐derived Medium and long chain poly(ω‐hydroxyfatty acid)s

The physical properties of novel thermoplastic random copolyesters [‐(CH₂)_n‐COO‐/‐(CH₂)_n‐COO‐]_x made of long (n = 12) and medium (n = 8) chain length ω‐hydroxyfatty esters [HO‐(CH₂)_n‐COOCH₃] derived from bio‐based vegetable oil feedstock are described. Poly(ω‐hydroxy tridecanoate/ω‐hydroxy nonanoate) P(?Me13?/?Me9?) random copolyesters (M_n = 11,000–18,500 g/mol) with varying molar ratios were examined by TGA, DSC, DMA and tensile analysis, and WAXD. For the whole range of P(?Me13?/?Me9?) compositions, the WAXD data indicated an orthorhombic polyethylene‐like crystal packing. Their melting characteristics, determined by DSC, varied with composition suggesting an isomorphic cocrystallization behavior. TGA of the P(?Me13?/?Me9?)s indicated improved thermal stability determined by their molar compositions. The glass transition temperature, investigated by DMA, was also found to vary with composition. The crystallinities of P(?Me13?/?Me9?)s however, were unaffected by the composition. The stiffness (Young's modulus) of these materials was found to be related to their degrees of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40492.     

Carbohydrate‐based polyurethanes: A comparative study of polymers made from isosorbide and 1,4‐butanediol

A set of linear polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4‐butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is₂HDI and Is₂MDI) as diols. The thermal transitions, thermal stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those displayed by their polyurethane analogues entirely made of BD. It was found that incorporation of Is units in the polyurethane chain produced significant changes in T_g, T_m, and T_d but no significant differences were noticed between copolymers made from Is or Is₂ monomers. Degradation assays revealed that the presence of Is units increased slightly the hydrolysis rate of polyurethanes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of vegetable‐based polyols in unimodal glass‐transition polyurethane slabstock viscoelastic foams and some guidance for the control of their structure–property behavior. I

We investigated the synthesis and structure–property behaviors of two types of vegetable‐oil polyols (soy oil and castor oil) and their use in viscoelastic (VE) polyurethane foams (PUFs). This article is the first in a two‐part series. In this initial part, we principally address the dynamic mechanical analysis (DMA) behavior of these foams in conjunction with information on the cellular morphology, sol fraction, and rise and reaction temperature profile behavior (the latter two parameters were determined during the foaming process). Particular emphasis is placed on the DMA damping characteristics, which represent one of the most critical parameters in the application of VE PUFs. It is also shown that the damping characteristics could be modified in such foams by the variation of the isocyanate/hydroxyl (×100) index, the addition of plasticizer, and in the case of soy polyols, the soy content. The frequency dependence of the VE PUFs is also briefly addressed. In the second article in this series, which directly follows this article, we further address the details of other relevant physical properties of these same foams in view of their applied nature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of vegetable‐based polyols in unimodal glass‐transition polyurethane slabstock viscoelastic foams and some guidance for the control of their structure–property behavior. II

Building on the dynamic mechanical analysis (DMA) characterization of the viscoelastic (VE) foam materials discussed in part I of this two‐part sequential series of articles, in this second part, we provide further information on the general physical properties of many of the same soy polyol and castor‐oil VE foams. In particular, the tensile, tear, elongation, indentation force deflection, support factor, compression set, hysteresis and ball‐rebound (resilience), and density properties are addressed in this article. The air flow and force buildup after compression deformation are also considered. Particular attention is also given to noting the degree of correlation of ball‐rebound behavior to that of the DMA damping data provided in part I. We concluded that when all of the properties of these vegetable‐based VE foams were taken as a whole, they had acceptable structure–property behaviors for VE applications, although certainly, the formulations could undoubtedly be further fine‐tuned for additional optimization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Production of polyols and waterborne polyurethane dispersions from biodiesel‐derived crude glycerol

This study investigated the preparation of polyols and waterborne polyurethane dispersions (CG‐WPUDs) from biodiesel‐derived crude glycerol. The polyols were produced from biodiesel‐derived crude glycerol via a thermochemical conversion process, which converted crude glycerol components such as glycerol, free fatty acids, and methyl esters of fatty acids (FAMEs) into polyols under optimized reaction conditions. CG‐WPUDs with different hard segments (41.0% to 63.2 wt %) were prepared from the crude glycerol‐based polyols produced. PU coating films cast from CG‐WPUDs showed increasing glass transition temperatures (T_g) from 63°C to 81°C when hard segment content increased from 41.0% to 63.2% and had good thermal stability up to 240°C. CG‐WPUD‐based coatings showed excellent adhesion to steel panel surfaces, pencil hardness as high as F, but relatively low flexibility. This study demonstrated the potential of biodiesel‐derived crude glycerol for the production of bio‐based polyols and WPUDs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41425.     

Structure and properties of poly(lactic acid)/poly(ε‐caprolactone) nanocomposites with kinetically induced nanoclay location

Poly(lactic acid)/poly(ε‐caprolactone)/organically modified montmorillonite (PLA/PCL/OMMT) nanocomposites were melt‐processed in a twin‐screw extruder under high shear conditions. As a result of the processing conditions employed, the OMMT layers located in the less compatible PCL phase in all the ternary nanocomposites. The morphology of the PLA/PCL blend evolved from “sea‐island” to co‐continuous upon the addition of OMMT. Both the X‐ray diffraction (XRD) and viscoelastic characterization suggested similar OMMT dispersion in the reference PLA binary and in the PLA/PCL ternary nanocomposites, regardless of its location in the PLA and PCL phase, respectively. The reinforcing effect of the organoclay was also similar. The addition of OMMT to the PLA/PCL blend fully compensated the loss in stiffness and oxygen barrier performance produced by PCL in PLA; the nanocomposite with 3% OMMT showed the same modulus and permeability values as those of pure PLA. Moreover, the ductile behavior (elongation at break > 80%) of the PLA/PCL blend remained constant even in the nanocomposite containing 5% OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43815.     

The preparation and crystallization of long chain branching polylactide made by melt radicals reaction

Long chain branching (LCB) of polylactic acid (PLA) was successfully prepared by melt radicals reaction with pentaerythritol triacrylate (PETA) and bis (1‐methyl‐1‐phenylethyl) peroxide (DCP). The topological structure of the LCB was investigated by rheology and branch‐on‐branch (BOB) model was used to estimate the exact chain structures of the products, where comb‐like LCB structures were generated due to the complex coupling between different macro‐radicals. LCB structure was found to affect the crystallization of PLA products. In the temperature range of 110–130°C, the crystallization rate parameter (k) was improved sharply and the half crystallization time was decreased significantly after the grafting of PETA, which was ascribed to the enhanced hydrogen bonding in PETA‐grafted long chain branching PLA. By comparing with the LCB PLA made from chain extension using multifunctional monomer, it shows that the crystallization becomes slower in a highly branched material with extremely long relaxation time if the effect of hydrogen bonding is similar. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reinforcement of soy polyol‐based rigid polyurethane foams by cellulose microfibers and nanoclays

Water‐blown rigid polyurethane foams from soy‐based polyol were prepared and their structure–property correlations investigated. Cellulose microfibers and nanoclays were added to the formulations to investigate their effect on morphology, mechanical, and thermal properties of polyurethane foams. Physical properties of foams, including density and compressive strength, were determined. The cellular morphologies of foams were analyzed by SEM and X‐ray micro‐CT and revealed that incorporation of microfibers and nanoclays into foam altered the cellular structure of the foams. Average cell size decreased, cell size distribution narrowed and number fractions of small cells increased with the incorporation of microfibers and nanoclays into the foam, thereby altering the foam mechanical properties. The morphology and properties of nanoclay reinforced polyurethane foams were also found to be dependent on the functional groups of the organic modifiers. Results showed that the compressive strengths of rigid foams were increased by addition of cellulose microfibers or nanoclays into the foams. Thermogravimetric analysis (TGA) was used to characterize the thermal decomposition properties of the foams. The thermal decomposition behavior of all soy‐based polyurethane foams was a three‐step process and while the addition of cellulose microfibers delayed the onset of degradation, incorporation of nanoclays seemed to have no significant influence on the thermal degradation properties of the foams as compared to the foams without reinforcements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of vegetable‐oil‐based polymers

The utilization of renewable resources for the preparation of new materials is an alternative option for reducing the high demand of fossil feedstocks. Vegetable oils are potential bioresources that are renewable and abundantly available. Triglyceride‐based vegetable oils, such as soybean, jatropha, linseed, sunflower, palm, castor, nahar seed, and canola oil, are being considered as precursors in the production of polymers. In this article, we attempt to summarize advancements in processes and technologies for the synthesis of polymers from various kinds of vegetable oils. The advantages and disadvantages of these biobased polymers with respect to traditional monomer‐based ones are also highlighted. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40787.     

Solvent‐free synthesis of polyols from 1‐butene metathesized palm oil for use in polyurethane foams

Green Polyols were synthesized from a 1‐butene cross metathesized palm oil (PMTAG) using a green, solvent free epoxidation and hydroxylation pathway. The synthetic strategy was adapted to control the degree of double bond epoxidation and ultimately the hydroxyl value of the polyols. The polyols comprised diol and tetrol monomers with terminal hydroxyl groups content as high as ～18 mol %, and achieved hydroxyl values between 83 and 119 mg KOH g^?1. Functional Rigid and highly flexible foams were prepared from two designer Green Polyols. The foams presented a high thermal stability (T_on of degradation of ～270 °C), suitable glass transition temperatures (～?12 °C and ～50 °C) and compressive strength (0.21 MPa at 10% strain and ～1 MPa at 10% strain for the flexible and rigid foams, respectively) which are superior to existing lipid‐based counterparts. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43509.     

Biodegradable polyester‐based heat management materials of interest in refrigeration and smart packaging coatings

In this study, two biodegradable matrices, polycaprolactone (PCL) and polylactide (PLA) were used to encapsulate for the first time a phase changing material (PCM), specifically dodecane (a paraffin which has a transition temperature at ?10°C), through the use of the electrospinning technique with the aim of developing coating materials with energy storage capacity for thermal insulation applications. The encapsulation efficiency obtained using both matrices has been studied and the different morphology, thermal properties, and molecular structure of the materials developed were characterized. Results showed that dodecane can be properly encapsulated inside both biopolymers with a submicron drop size, albeit PCL provides better encapsulation performance. A temperature mismatch between melting and crystallization phenomena (the so‐called supercooling effect) was observed in the encapsulated paraffin, mainly ascribed to the reduced PCM drop size inside the fibers. Addition of dodecanol was seen to best act as a nucleating agent for the PCL/PCM and PLA/PCM structures, allowing a significant amount of heat storage capacity for these systems without supercooling. These innovative ultrathin structured biomaterials are of interest as energy storage systems to advantageously coat or wrap temperature sensitive products in refrigeration equipment and constitute smart food or medical/pharmaceutical packaging. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3251–3262, 2013     

Effect of the diisocyanate structure and the molecular weight of diols on bio‐based polyurethanes

Bio‐based polyurethanes (PU) containing poly(ε‐caprolactone) diol (PCL) and hydroxyl telechelic natural rubber (HTNR) were synthesized. The effect of the diisocyanate structure and the molecular weights of diols on the mechanical properties of PU were investigated. Three different molecular structures of diisocyanate were employed: an aliphatic diisocyanate (hexamethylene diisocyanate, HDI), an aromatic diisocyanate (toluene‐2,4‐diisocyanate, TDI) and a cycloalkane diisocyanate (isophorone diisocyanate, IPDI). Two molecular weights of each diol were selected. When HDI was employed, a crystalline PU was generated while asymmetrical structures of TDI and IPDI provided an amorphous PU. The presence of crystalline domains was responsible of a change in tensile behavior and physical properties. PU containing TDI and IPDI showed a rubber‐like behavior: low Young's modulus and high elongation at break. The crystalline domains in PU containing HDI acted as physical crosslinks, enhancing the Young's modulus and reducing the elongation at break, and they are responsible of the plastic yielding. The crystallinity increased the tear strength, the hardness and the thermal stability of PU. There was no significant difference between the TDI and IPDI on the mechanical properties and the physical characteristics. Higher molecular weight of PCL diol changed tensile behavior from the rubber‐like materials to the plastic yielding. Thermal and dynamic mechanical properties were determined by using DSC, TGA and DMTA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cross‐linked chitosan beads for phosphate removal from aqueous solution

Chitosan beads were cross‐linked with glutaraldehyde (GA) and epichlorohydrin (EP), respectively, at variable composition. The general features of the adsorptive and textural properties of the bead systems were characterized using p‐nitrophenolate (PNP) at pH 8.5. As well, a systematic adsorption study of phosphate dianion (phosphate ( ) species was carried out in aqueous solution at pH 8.5 and 295 K. The Sips isotherm model yielded adsorption parameters for the chitosan bead systems: (i) monolayer adsorption capacity (Q_m) for PNP ranged from 0.30 to 0.52 mmol g^?1 and (ii) Q_m values for the bead systems with ranged from 22.4–52.1 mg g^?1 for these conditions. GA cross‐linked beads reveal greater Q_m values for PNP while EP cross‐linked beads showed greater Q_m values for , in accordance with the surface chemistry and the materials design described herein. The EP cross‐linked beads show favorable adsorption–desorption properties and represents a promising tunable adsorbent system for the effective removal of phosphate dianion species in aqueous solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42949.     

Strong and ductile poly(butylene adipate‐co‐terephthalate) biocomposites fabricated by oscillation shear injection molding

Poor interfacial properties and uncontrollable phase morphology encountered during the fabrication of poly(butylene adipate‐co‐terephthalate) (PBAT)/thermal plastic starch (TPS) biocomposites, result unfortunately in low mechanical performances and thus limit its applications. Here an approach in terms of phase morphology controlling, i.e., extrusion compounding followed by oscillation shear injection molding (OSIM), is proposed to construct in situ TPS fiber and skin‐core structure consisting of TPS fiber and droplet in skin layer, and spherical TPS in core layer, which tremendously benefits the mechanical properties. Specifically, the tensile strength, modulus and ductility for the biocomposites with various loadings of TPS, even when TPS loading as high as 55 wt %, outperform pure PBAT sample fabricated by conventional injection molding (CIM) with the increment of 51%, 308% in strength and modulus, respectively. Meanwhile, the elongation at breakage can maintain at 196%. The unprecedented establishment of high‐performance PBAT/TPS biocomposites is in great need for potential applications, such as green packaging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43312.     

Polyurethane foams made from liquefied bark‐based polyols

Liquefaction is known to be an effective method for converting biomass into a polyol. However, the relationships between bark liquefaction conditions and properties of the resulting foams are unclear. In this study, polyurethane foams (PUF) were made using bark‐based polyols obtained through liquefaction reactions of bark at two different temperatures (90 and 130°C). Through systematic characterization of the PUFs the influence of the liquefied bark and liquefaction conditions on foam properties could be observed. The bark‐based foams had similar foaming kinetics, thermal stability, and glass transition temperatures compared with the PEG‐based control foam. The bark‐based PUF from the polyol obtained at the higher liquefaction temperature showed comparable specific compressive strength to the PEG‐based control foam. Lastly, both bark foams exhibited a high amount of open‐cell content, with the foam made from the lower temperature liquefied polyol having poor cell morphology. This deviation from the controls in the open‐cell content may explain the lower modulus values observed in the bark PUFs due to the lack of cell membrane elastic stretching as a strengthening mechanism. These results demonstrated the influence of the bark liquefaction conditions on foam properties, thereby providing a better fundamental understanding for the practical application of bark‐based PUFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40599.