Blends of natural rubber and polyurethane latices studied by 1H wideline and 13C MAS solid‐state NMR

¹H wideline and ¹³C magic‐angle spinning NMR have been used to study the morphology and dynamics of latex‐cast and solution‐cast film blends of natural rubber (NR) and a polyurethane (PU) based on poly(?‐caprolactone) diol and isophorone di‐isocyanate. ¹H T₁ and T_1ρ relaxation times have been measured, and the extent of interpenetration of the NR and PU constituents has been monitored using the Goldman–Shen technique. The NMR spectra and relaxation properties indicated that the NR and PI constituents largely occupy separated domains on a distance scale of >10 nm. The Goldman–Shen experiments indicated that there was slightly greater contact between NR and PU in the solution‐cast samples than in the latex‐cast. The tensile properties of the films have been measured. The tensile strength and initial Young's modulus pass through a maximum at a PU content of about 50 wt%. © 2002 Society of Chemical Industry     

Study of poly(vinyl chloride) blends with solid‐state chlorinated polyethylene

The influence of solid‐state chlorinated polyethylene of various chlorine content and residual crystallinity on the mechanical properties of rigid poly(vinyl chloride) has been studied. The impact strength of poly(vinyl chloride) was found to increase significantly as 10–20 mass% chlorinated polyethylene, containing from 10.2 to 27.3% chlorine content (preferably 21.8% Cl) were added. This dependence corresponded to the higher elasticity and impact strength of the solid‐state chlorinated polyethylene with chlorine content below 30% as well as the microstructure of its chlorinated block fragments. Multicomponent system of high impact strength and good flowability, consisting of poly(vinyl chloride), chlorinated polyethylene, hydroxyl‐terminated polybutadiene, and ethylene–propylene–ethylidenenorbornene terpolymer was also obtained. Regardless of the incompatibility between the polymer components of this blend, the similarity in the chemical nature of poly(vinyl chloride) and chlorinated polyethylene blocks on one hand, and the methylene sequences in the chlorinated polyethylene and elastomers on the other, resulted in the formation of an efficient interfacial layer. The changes in the structure of the blends were established by both calorimetric and microscopic studies. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2602–2613, 2006     

Reactivity,chemical structure,and molecular mobility of urea–formaldehyde adhesives synthesized under different conditions using FTIR and solid‐state 13C CP/MAS NMR spectroscopy

This study was conducted to investigate the effects of reaction pH condition and hardener type on the reactivity, chemical structure, and molecular mobility of urea–formaldehyde (UF) resins. Three different reaction pH conditions, such as alkaline (7.5), weak acid (4.5), and strong acid (1.0), were used to synthesize UF resins, which were cured by adding four different hardeners (ammonium chloride, ammonium sulfate, ammonium citrate, and zinc nitrate) to measure gel time as the reactivity. FTIR and ¹³C‐NMR spectroscopies were used to study the chemical structure of the resin prepared under three different reaction pH conditions. The gel time of UF resins decreased with an increase in the amount of ammonium chloride, ammonium sulfate, and ammonium citrate added in the resins, whereas the gel time increased when zinc nitrate was added. Both FTIR and ¹³C‐NMR spectroscopies showed that the strong reaction pH condition produced uronic structures in UF resin, whereas both alkaline and weak‐acid conditions produced quite similar chemical species in the resins. The proton rotating‐frame spin–lattice relaxation time (T_1ρH) decreased with a decrease in the reaction pH of UF resin. This result indicates that the molecular mobility of UF resin increases with a decrease in the reaction pH used during its synthesis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2677–2687, 2003     

The curing of UF resins studied by low‐resolution 1H‐NMR

A series of UF resins and one MUF resin were studied by low‐resolution ¹H‐NMR. The mobility of the resin during curing could be followed by measuring the spin‐spin relaxation time (T₂) with curing time. The relative curing behavior was similar to that found by traditional gel time measurements. In addition, extra features in the T₂ plots with curing time showed at what point the bulk of the condensation reactions took place. The speed of cure was also related to the chemical groups in the liquid resin, and it was found that the linear methylol groups were mainly responsible for the curing speed of the resins. By studying the curing with different hardener levels and glue concentrations it was found that a UF resin is more sensitive to the glue mix concentration than an MUF resin. A cured resin was also studied after curing to investigate postcuring effects. Water seemed to play the biggest role in the postcure, with substantial amounts present immediately after cure, which decreased with curing time and aging. For the low mol ratio resins studied here further curing reactions did not seem to play a major role in the post curing phenomenon. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 754–765, 2000     

Structural analysis of oriented poly(ε‐caprolactone) including CaCO3 particles with 13C solid‐state NMR

The results of a study of the relation between the oriented structure and drawn Poly(ε‐caprolactone) specimens including CaCO₃ particles and their dynamic mechanical properties are presented. The loss elasticity, E″, showed almost the same curve for both undrawn sheets and drawn sheets as a function of CaCO₃ content. On the other hand, the storage modulus, E′, of drawn sheets increased nonlinearly with increasing CaCO₃ content, and their curve showed lower E′ values than those of undrawn sheets. By simulation of ¹³C CP NMR spectra of drawn PCL/CaCO₃ sheets, both oriented and unoriented components were observed. The distribution parameter, p, of drawn PCL/CaCO₃ sheets was 13°, which was larger than those (8°) of drawn PCL. Further, the fraction of the unoriented component increased with increasing CaCO₃ content. Thus, adding CaCO₃ particles into the PCL, the arrangement of the oriented component was disturbed and decreased. In addition, from the line shape analyses of ¹³C CP MAS NMR spectra, four peaks were obtained in not only undrawn sheets but also in drawn sheets of both PCL and PCL/CaCO₃ compounds. Besides, structural change occurred at only drawn PCL/CaCO₃ sheets. Therefore, the change in dynamic mechanical properties observed only for drawn PCL/CaCO₃ sheets were strongly dependent on the orientational structure, which was formed under shear stress of the stretching drawn process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2376–2382, 2001     

Value‐added bioconversion of biomass by solid‐state fermentation

The value‐added bioconversion of biomass is necessary due to the depletion of fossil fuels and deterioration of the global environment situation. Based on the analysis of characteristics of solid materials and the applicability of solid agro‐industrial residues used as feedstock for solid‐state fermentation (SSF), the authors established a value‐added bioconversion system for biomass using the key technology SSF. This article gives an overview of biomass bioconversion by SSF and the corresponding advances achieved in recent years. Copyright © 2012 Society of Chemical Industry     

Detection of lead ion binding on bifunctional chelating/ion‐exchange resins by cross‐polarization/magic‐angle spinning solid‐state nuclear magnetic resonance

Solid‐state nuclear magnetic resonance (S‐NMR) can reveal much useful information, including conformations, stereoregularity, defect structures, and comonomer sequence. S‐NMR is especially useful for revealing microstructural differences that can alter local polymer chains. A series of bifunctional chelating/ion‐exchange resins, containing differing ratios of iminodiacetic acid to acetic acid, were synthesized. Cross‐polarization magic‐angle spinning (CP/MAS) ¹³C‐NMR was employed to measure conformation changes both before and after the bonding of ligands and lead ion adsorbed on bifunctional chelated/ion‐exchange resins in this investigation. From the ¹³C‐NMR spectra, as the lead ion was adsorbed by the iminodiacetic acid chelating group, the motion of molecular chain would be inhibited and the resonance peaks of the carboxylate anion at 170 ppm would shift downfield. Compared to the FTIR results, the downfield shift of the resonance peaks indicated that the bonding of carboxylate anion and lead ion adsorbed displayed an ionic trend. Furthermore, the bonding of the carboxylic group and lead ion adsorbed changed from ionic to covalent as the chelating group in bifunctional/ion‐exchange resins decreased. The linear relationship between the areas of those resonance peaks and the amount of lead ion adsorbed was obtained from the spectra fitting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 919–928, 2002     

Natural abundance 15n solid‐state nmr study of nylon‐6 in blends

Natural abundance solid‐state nuclear magnetic resonance spectroscopy (NMR) of nitrogen‐15 (¹⁵N) was applied to investigate the films of nylon‐6 and their blends with poly(propylene oxide) (PPO). The NMR ¹⁵N results allowed us to identify the crystalline forms present in these blends and also confirmed the previous NMR results obtained by ¹³C‐NMR study. From all NMR data the antiplasticization phenomena and plasticization effects caused by PPO content, in the blends were characterized. The polyoxide action is a function of its proportion. However, because the samples were prepared by solution casting, the residual solvent action cannot be ignored. The ¹⁵N chemical shift changes were influenced by both PPO and residual solvent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3872–3875, 2003     

Solid‐state 13C‐NMR and study of the subproducts obtained from corn industry

The two types of commercial corn flour subproducts from the Brazilian corn industry containing starch with low fat and with fat were investigated by solid‐state NMR techniques to improve their uses. From the NMR techniques used, it was characterized that after a treatment the quantity of fibers decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1680–1685, 2002; DOI 10.1002/app.10547     

Formation Kinetics and Structural Features of Beta‐Amyloid Aggregates by Sedimented Solute NMR

The accumulation of soluble toxic beta‐amyloid (Aβ) aggregates is an attractive hypothesis for the role of this peptide in the pathology of Alzheimer's disease. We have introduced sedimentation through ultracentrifugation, either by magic angle spinning (in situ) or preparative ultracentrifuge (ex situ), to immobilize biomolecules and make them amenable for solid‐state NMR studies (SedNMR). In situ SedNMR is used here to address the kinetics of formation of soluble Aβ assemblies by monitoring the disappearance of the monomer and the appearance of the oligomers simultaneously. Ex situ SedNMR allows us to select different oligomeric species and to reveal atomic‐level structural features of soluble Aβ assemblies.     

Plasma‐induced,solid‐state polymerization of N‐isopropylacrylamide

The radio‐frequency plasma‐initiated polymerization of N‐isopropylacrylamide (NIPAM) in the solid state was performed. The isolated linear polymer was characterized by ¹³C‐NMR, ¹H‐NMR, and Fourier transform infrared spectroscopy, and the effects of selected operational plasma parameters (discharge power and time) on the conversion rates were studied. Reversible transitions at the volume‐phase‐transition temperatures of the swelled poly(N‐isopropylacrylamide) hydrogels were investigated by differential scanning calorimetry. The surface morphologies before and after plasma treatment were followed by scanning electron microscopy. With the obtained X‐ray diffraction results, we propose a solid‐state plasma polymerization mechanism for the NIPAM. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optimization of inulinase production by solid‐state fermentation in a packed‐bed bioreactor

BACKGROUND: This work is focused on inulinase production by solid‐sate fermentation (SSF) using sugarcane bagasse, corn steep liquor (CSL), pre‐treated cane molasses, and soybean bran as substrates in a 3‐kg (dry basis) packed‐bed bioreactor. SSF was carried out by the yeast Kluyveromyces marxianus NRRL Y‐7571 and response surface methodology was used to optimize the temperature, air flow rate and initial mass of cells. RESULTS: The optimum inulinase activity (436.7 ± 36.3 U g^?1 dry substrate) was obtained at 24 h at an inlet air temperature of 30 °C, air flow rate 2.2 m³ h^?1 and 22 g of cells for fermentation. Inulinase productivity at these conditions was 18.2 U gds^?1 h^?1. Kinetic evaluation at the optimized conditions showed that the maximum inulinase production was verified at 24 h of fermentation. The carbon dioxide and the metabolic heat generation are directly associated with the consumption of total reducing sugars present in the medium. CONCLUSION: The high productivity achieved in this work shows the technical viability of inulinase production by SSF in a packed‐bed bioreactor. Copyright © 2009 Society of Chemical Industry     

The rate acceleration in solid‐state polycondensation of PET by nanomaterials

The effect of nanomaterials on the solid‐state polycondensation (SSP) of PET was investigated using intrinsic viscosity measurement, wide‐angle X‐ray diffraction, differential scanning calorimetry, and polarizing microscope. The results showed that the montmorillonite nanomaterials could greatly increase the rate of solid‐state polycondensation of PET, probably due to the nucleation of montmorillonite nanomaterials for PET crystallization, which resulted in lower crystallinity, more small crystals, and more surfaces of the crystals. The surfaces of microcrystal and richer amorphous regions benefitted the polycondensation reaction of PET and diffusion of volatile by‐products, which led to the higher rate of SSP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 971–976, 2004     

Unambiguous Assignment of Short‐ and Long‐Range Structural Restraints by Solid‐State NMR Spectroscopy with Segmental Isotope Labeling

We present an efficient method for the reduction of spectral complexity in the solid‐state NMR spectra of insoluble protein assemblies, without loss of signal intensity. The approach is based on segmental isotope labeling by using the split intein DnaE from Nostoc punctiforme. We show that the segmentally ¹³C,¹⁵N‐labeled prion domain of HET‐s exhibits significantly reduced spectral overlap while retaining the wild‐type structure and spectral quality. A large number of unambiguous distance restraints were thus collected from a single two‐dimensional ¹³C,¹³C cross‐correlation spectrum. The observed resonances could be unambiguously identified as intramolecular without the need for preparing a dilute, less sensitive sample.     

Kinetics of the solid‐state polymerization of nylon‐6

The kinetics of the thermally induced solid‐state polymerization (SSP) of nylon‐6 were examined in both a fixed‐bed reactor and a rotary reactor. Factors such as the regulator content, the reaction temperature and time, the particle size, the type and geometry of the nylon‐6 prepolymer, the nitrogen gas flow rate, the water content of the nitrogen gas flow, and the polymerization process were studied. The results showed that the regulator content, the reaction temperature and time, and the particle size were the primary factors, and that the others were negligible. Moreover, the SSP rate and number‐average molecular weight (M_n) increased with increasing reaction temperature and time and decreasing particle size. The SSP rate and M_n had maximum values with increasing regulator content in an experimental range of 0.03–0.07 wt %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 616–621, 2002; DOI 10.1002/app.10341     

Protease production by Aspergillus oryzae in solid‐state fermentation using agroindustrial substrates

BACKGROUND: An inexpensive and readily available agroindustrial substrate such as rice bran can be used to produce cheap commercial enzymes by solid‐state fermentation. This work investigates the production of food‐grade proteases by solid‐state fermentation using readily available Thai rice bran. RESULTS: A local strain of Aspergillus oryzae (Ozykat‐1) was used to produce proteases. Rice bran used alone proved to have poor substrate morphology (insufficient porosity) for satisfactory solid‐state fermentation. A certain amount of wheat bran was necessary to improve the morphology of the substrate. The following variables affected protease production: substrate composition, initial moisture content and initial pH. A high protease activity (∼1200 U g⁻¹ dry solids) was obtained on a substrate that had a wheat bran to rice bran ratio of 0.33 by dry weight, a moisture content of 50%, initial pH of 7.5, and incubation temperature of 30 °C. CONCLUSION: Nutritionally, rice bran used alone was as good a substrate as mixed bran for producing protease, but rice bran had poor morphological characteristics for consistent fermentation. A substrate that had a wheat bran to rice bran ratio of 0.33 by dry weight was best for producing protease. Copyright © 2008 Society of Chemical Industry     

Post‐extrusion solid‐state polymerization of fully drawn polyester yarns

Post‐extrusion solid‐state polymerization (SSP) of a commercial fully drawn filament yarn (FDY) of poly(ethylene terephthalate) was carried out at 220°C, 230°C, and 240°C for a duration of 30 min to 2 h under inert atmosphere. Molecular weight of the solid‐state polymerized polyester filaments was increased from 1.67 × 10⁴ gm/mol to a maximum of 2.61 × 10⁴ gm/mole for the sample subjected to 240°C for 2 h. The kinetics of the SSP in the highly oriented crystalline FDY polyester filaments was investigated using an empirical relation between initial molecular weight and time of SSP and was found to be greatly enhanced, compared to amorphous unoriented polyester chips. Though the free annealing (i.e., under no tension) of samples at high temperature during solid‐state polymerization had a detrimental effect on the orientation of the FDY yarn, the simultaneous increase in the molecular weight compensated the loss in mechanical properties to a great extent. Application of tension during SSP was found to improve the mechanical properties of the SSP yarn by a small value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5113–5122, 2006     

13C solid‐state NMR analysis of the DGEBA/TETA epoxy system

Mechanical properties measurements, like Charpy impact tests, provided evidence that the macromolecular network of the epoxy system formed by the hexafunctional triethylene tetramine hardener, TETA, with the diglycidyl ether of bisphenol A monomer, DGEBA, can be modified by changing the hardener content. The previously analyzed monomer‐to‐hardener ratios were here studied by ¹³C‐NMR solid state techniques. The results from crosspolarization/magic angle spinning (CPMAS) ¹³C‐NMR spectra, together with the evaluation of proton spin‐lattice relaxation time in the rotating frame (Tρ), display the behavior of these epoxy/hardener mixtures considering the mobility and interaction of molecular segments present at the macromolecular structure. The results also show that the epoxy‐rich mixtures form tight, and therefore brittle, structures as previously observed by mechanical tests. The stoichiometric monomer‐to‐hardener ratio is a transition point where an increase in the mobility was found. For the amine‐rich mixtures the obtained results suggest the presence of domains with different segmental mobilities. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2358–2362, 2000     

Polypropylene‐dispersed domain as potential nucleating agent in PS and PMMA solid‐state foaming

The potential of using dispersive domains in a polymer blend as a bubble nucleating agent was investigated by exploiting its high dispersibility in a matrix polymer in the molten state and its immiscibility in the solid state. In this experiments, polypropylene (PP) was used as the nucleating agent in polystyrene (PS) and poly(methyl methacrylate) (PMMA) foams at the weight fraction of 10, 20, and 30 wt %. PP creates highly dispersed domains in PS and PMMA matrices during the extrusion processing. The high diffusivity of the physical foaming agent, i.e., CO₂ in PP, and the high interfacial tension of PP with PS and PMMA could be beneficial for providing preferential bubble nucleation sites. The experimental results of the pressure quench solid‐state foaming of PS/PP and PMMA/PP blends verified that the dispersed PP could successfully increase the cell density over 10⁶ cells/cm³ for PS/PP and 10⁷ cells/cm³ for PMMA/PP blend and reduce the cell size to 24 μm for PS/PP and 9 μm for PMMA/PP blends foams. The higher interfacial tension between PP and the matrix polymer created a unique cell morphology where dispersed PP particles were trapped inside cells in the foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011