In-Line Chemical Composition Monitoring for the Injection Molding Process of Biodegradable Polymer Blends Using Simultaneous Measurement of Near-Infrared Diffuse Reflectance and Transmission Spectra.

In the processing of polymer blends and composites, in-line near-infrared (NIR) spectroscopy enables monitoring of the composition and its composite uniformity and contributes to rapid process development and quality control. However, in the injection molding process, the study of the composition of polymer materials has been delayed due to high-pressure conditions. Our research group developed NIR probes for transmission and diffuse reflectance measurements that can withstand high-pressure and temperature conditions up to 130 MPa and 200 °C. In this research, transmission and diffuse reflectance spectra were measured inline during the injection molding process of polymer blends of poly(lactic acid) and polybutylene succinate adipate. The intensity of each polymer band in the second-derivative spectra exhibited a monotonic increase or decrease in response to changes in the blend ratio. Using transmission and diffuse reflectance spectra as explanatory variables of the partial least squares regression model simultaneously, the model showed high estimation accuracy for the entire region of the blend ratio. Finally, this model was applied to monitor the polymer changeover operation, and the change in the blend ratio in the molded product was successfully estimated in line.

Dynamic Molecular Simulation of Polyethylene/Organoclay Nanocomposites for Their Physical Properties and Foam Morphology.

Polyethylene materials are of great interest to be used in many applications due to their many advantageous characteristics. It is light, highly chemical resistant, easy to process, low in cost and has good mechanical properties. Polyethylene is widely used as a cable-insulating material. However, research is still needed to further improve its insulation quality and properties. In this study, an experimental and alternative approach through a dynamic modeling method was conducted. The main objective was to investigate the effect of modified organoclay concentration on the properties of polyethylene/organoclay nanocomposites by observing their characterization and optical and mechanical properties. The thermogram curve reveals that 2 wt% organoclay used has the highest crystallinity (46.7%) while the highest amount of organoclay used produced the lowest crystallinity (31.2%). The presence of cracks was also observed mostly in the nanocomposite with higher content of organoclay, usually where 2.0 wt% and above of organoclay was used. Morphological observation from simulation results supports the experimental work. Only small pores were observed to form in lower concentrations, and as the concentration was increased to 2.0 wt% and above, the pores present became larger in size. Increasing the concentration of organoclay up to 2.0 wt% reduced the interfacial tension while increasing the concentration above 2.0 wt% did not bring any changes to the interfacial tension value. Different formulations produced different behavior of nanocomposite. Hence the control of the formulation was important to control the final result of the products for appropriate application in different sectors of industry.

Improved thermal insulation and compressive property of bimodal poly (lactic acid)/cellulose nanocomposite foams.

In this work, an innovative PLA/CNF nanocomposite foam with a bimodal cell structure is prepared by a simple one-step depressurization foaming process using only supercritical carbon dioxide (ScCO2) as the foaming agent. Only at a specific foaming temperature, PLA/CNF nanocomposites foam with a bimodal cell structure could be obtained. According to the different crystallization kinetics and nucleation efficiency of samples, it was inferred that the crystallization rate and phase interface would affect the cell structure. The prepared PLA/CNF nanocomposite foam with a bimodal cell structure had an expansion ratio as high as 20 times and thermal conductivity of 0.041 w m-1 k-1, which exhibited low density and excellent thermal-insulation property. Meanwhile, the PLA/CNF nanocomposite foam exhibited excellent compression performance due to the presence of CNFs, which showed promising application in packaging and construction materials.

Cellulose nanofiber reinforced poly (lactic acid) with enhanced rheology, crystallization and foaming ability.

The incorporation of micro-/nano-particles is one of the most efficient approaches to reinforce poly (lactic acid) (PLA). However, introducing the inorganic particles which can compromise the green nature of PLA. Herein, we proposed a green strategy to add biodegradable cellulose nanofibers (CNFs) into the PLA matrix for eliminating its low melt strength and slow crystallization rate. Well-dispersed hydrophobic-modified CNFs in the PLA matrix were obtained through the combination of acetylation surface modification and the melt-compounding technology. The PLA/CNF composites notably improved crystallization properties and melt elasticity, compared with the neat PLA. Additionally, the foaming behavior of PLA was dramatically enhanced by introducing 2 wt% modified CNFs. At an ultralow pressure of 1.5 MPa, the prepared PLA/CNF nanocomposite foams exhibited the highest expansion ratio approximately 20.4. These results demonstrated that CNFs were extraordinarily helpful in enhancing the foamability of PLA, which are expected to be applied as a sustainable packaging material.

Promoted formation of stereocomplex in enantiomeric poly(lactic acid)s induced by cellulose nanofibers.

Stereocomplex (SC) crystallization between enantiomeric poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) is believed to yield poly(lactic acid) (PLA) with superior physiochemical properties. However, homocrystallization (HC) crystallites are inevitably generated in the PLLA/PDLA blends. Herein, we report a simple approach to fabricate PLLA/PDLA racemic blends with high contents of SC crystallites by introducing cellulose nanofibers (CNFs). The isothermal crystallization results revealed that the half-crystallization time of the PLLA/PDLA blend was significantly decreased by adding CNFs. Additionally, with the incorporation of 3 wt% modified CNFs, the PLLA/PDLA blend was overwhelmingly crystallized into SC crystallites with no HC crystallite formation. Based on Fourier transform infrared spectroscopy findings, it was speculated that the preferred SC crystallization of PLLA/PDLA/CNF was caused by enhanced interchain molecular interactions between CNFs and PLA. This work presents a feasible and efficient method to fabricate PLA with exclusively SC crystallites, which possesses great potential for producing high-performance PLA materials.

Novel Approaches to In-Situ ATR-FTIR Spectroscopy and Spectroscopic Imaging for Real-Time Simultaneous Monitoring Curing Reaction and Diffusion of the Curing Agent at Rubber Nanocomposite Surface.

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Highly Ordered Nanocellular Polymeric Foams Generated by UV-Induced Chemical Foaming.

Nanocellular polymer foams have shown significant potential for industrial applications because of their superior thermal, mechanical, and optical properties. Some of these properties may be further improved by enhancing the ordering of cell structures. However, it is challenging for conventional foaming methods to control both the cell size and ordering at the nanoscale. Here, we show an innovative method to produce highly ordered nanocellular polymer foams by incorporating the self-assembly of an asymmetric diblock copolymer with the UV-induced chemical foaming technique. The minor domains are designed to generate a gaseous compound from the partial cleavage of the functional group. It is demonstrated that the gas-producing reaction can be accelerated at a temperature low enough to prevent melting of the whole self-assembled template, by mixing a small amount of photoacid generator into the copolymer, followed by UV irradiation. The result is the production of polymer foams with the nanoscale cells highly aligned to the self-assembled domains.

A rice gene that confers broad-spectrum resistance to ß-triketone herbicides.

The genetic variation of rice cultivars provides a resource for further varietal improvement through breeding. Some rice varieties are sensitive to benzobicyclon (BBC), a ß-triketone herbicide that inhibits 4-hydroxyphenylpyruvate dioxygenase (HPPD). Here we identify a rice gene, HIS1 (HPPD INHIBITOR SENSITIVE 1), that confers resistance to BBC and other ß-triketone herbicides. We show that HIS1 encodes an Fe(II)/2-oxoglutarate-dependent oxygenase that detoxifies ß-triketone herbicides by catalyzing their hydroxylation. Genealogy analysis revealed that BBC-sensitive rice variants inherited a dysfunctional his1 allele from an indica rice variety. Forced expression of HIS1 in Arabidopsis conferred resistance not only to BBC but also to four additional ß-triketone herbicides. HIS1 may prove useful for breeding herbicide-resistant crops.

Effect of Cellulose Nanofiber (CNF) Surface Treatment on Cellular Structures and Mechanical Properties of Polypropylene/CNF Nanocomposite Foams via Core-Back Foam Injection Molding.

Herein, lightweight nanocomposite foams with expansion ratios ranging from 2⁻10-fold were fabricated using an isotactic polypropylene (iPP) matrix and cellulose nanofiber (CNF) as the reinforcing agent via core-back foam injection molding (FIM). Both the native and modified CNFs, including the different degrees of substitution (DS) of 0.2 and 0.4, were melt-prepared and used for producing the polypropylene (PP)/CNF composites. Foaming results revealed that the addition of CNF greatly improved the foamability of PP, reaching 2⁻3 orders of magnitude increases in cell density, in comparison to those of the neat iPP foams. Moreover, tensile test results showed that the incorporation of CNF increased the tensile modulus and yield stress of both solid and 2-fold foamed PP, and a greater reinforcing effect was achieved in composites containing modified CNF. In the compression test, PP/CNF composite foams prepared with a DS of 0.4 exhibited dramatic improvements in mechanical performance for 10-fold foams, in comparison to iPP, with increases in the elastic modulus and collapse stress of PP foams of 486% and 468%, respectively. These results demonstrate that CNF is extraordinarily helpful in enhancing the foamability of PP and reinforcing PP foams, which has importance for the development of lightweight polymer composite foams containing a natural nanofiber.

Near-Infrared Hyperspectral Absorption/Scattering Imaging Method Using Multiple Ground Plates for Evaluating Polymer Composites.

This paper proposes a nondestructive method of evaluating polymer composites using near-infrared (NIR) diffuse reflection spectroscopy with multiple ground plates. Wavelength-dependent absorption and reduced scattering coefficients were acquired to evaluate the chemical structure and the concentration of the substances from absorption and to determine the size and the dispersity of filler in the polymer domain from scattering. NIR spectra of the sample were measured on multiple ground plates, namely, "ground-plate-dependent" diffuse reflection spectra. The effects of the external reflection on the ground-plate-dependent diffuse reflection spectra were subsequently removed. The internal reflection coefficient was calculated based on the difference between the diffuse reflectances of the neat resin and ground plates without prior information on the incident angle of light and the refractive index of sample. The external reflection coefficient was evaluated by the gap of diffuse reflectances between the sample and a white ground plate. After the corrections of reflections, the spectra were fitted by a physical model of light propagation based on the two-flux theory to acquire the absorption and the reduced scattering coefficients. The calculated absorption coefficients indicated a good linear relationship with particle concentration. The calculated reduced scattering coefficients agreed with the theoretical values by Mie scattering theory. It was demonstrated that the proposed method achieved the simultaneous evaluation of particulate-filler concentrations and sizes in polymer composites.

Evolution of cellular morphologies and crystalline structures in high-expansion isotactic polypropylene/cellulose nanofiber nanocomposite foams.

Herein, the development of cell morphology and crystalline microstructure of injection-molded isotactic polypropylene/cellulose nanofiber (PP/CNF) composite foams with 2-10-fold expansion ratios was investigated through scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). Compared with isotactic polypropylene (iPP) foams, the added CNF improved the cell morphology and resulted in a great reduction in cell size. Additionally, the PP lamella orientation and crystal type were notably altered during the core-back FIM process. As the expansion ratio increased, the original isotropic lamellae in the iPP foams were transformed into an oriented lamellar structure and then further transformed into a typical shish-kebab structure, while hybrid shish-kebab structures were simultaneously generated in the high-expansion PP/CNF nanocomposite foams. Accordingly, the highest content of ß-crystals was observed in the low-expansion iPP foams. In contrast, the ß-crystal content in PP/CNF composites decreased monotonously as the expansion ratio increased, which resulted from the combined effects of CNF's nucleating ability for α-crystals and the more dominant extensional flow effect assisted by the added CNF.

Unprecedented Development of Ultrahigh Expansion Injection-Molded Polypropylene Foams by Introducing Hydrophobic-Modified Cellulose Nanofibers.

Herein, an ultrahigh 18-fold expansion of isotactic polypropylene (iPP)/cellulose nanofiber (CNF) nanocomposite foams was achieved for the first time using a core-back foam injection molding technique. It was found that CNFs were well dispersed and aligned along the cell wall in the core-back direction. Interestingly, the formations of a hybrid shish-kebab of CNFs and classic shish-kebab of PP were simultaneously achieved in the PP/CNF composites. Finally, we proposed that the combination of local strong melt strength, probably resulting from the strong alignment of CNFs and subsequent formation of hybrid shish-kebab structures, and weak melt strength in the unreinforced PP melt might be the driving force for remarkably enhancing the PP foamability.

Near-Infrared Spectroscopic Evaluation of the Water Content of Molded Polylactide under the Effect of Crystallization.

During melt processing, the moisture inside polylactide (PLA) easily induces hydrolysis, which deteriorates the mechanical and thermal properties of the product. The state of dryness of resin pellets must be monitored to prevent PLA hydrolysis. In this study, near-infrared (NIR) spectroscopy was applied to measure water content in PLA. In addition, the shape of the NIR spectrum is also affected by crystallization, which could lead to a reduction in the accuracy of evaluating the water content. The objective of this research is to construct a robust model for estimating the water content with varying dispersive extents of crystallization. Two methods for estimating water content measured during a drying process were conducted: the integration of absorbance and partial least squares (PLS) regression were conducted to estimate the water contents in PLA considering the effect of crystallization. The slope of the calibration line of the water content obtained from integrating absorbance varied between PLA with different crystallinities. This is due to the overlap between the NIR band of water and that of PLA crystal in the range of 5100-5400 cm-1. We found that the shape of the NIR spectrum was changed by crystallization, and the crystallinity, compared to the thickness of lamellae, was the dominant factor determining such a change of NIR spectra. The PLS model of water content constructed from only amorphous PLA showed large error of estimation in crystallized PLA. In contrast, the PLS model constructed from both amorphous and crystallized PLA estimated the water contents with lower errors. This was because latent variables obtained from both amorphous and crystallized PLA cancelled the effect of crystallization on NIR spectra.

Selecting genetic transformants of indica and indica-derived rice cultivars using bispyribac sodium and a mutated ALS gene.

Bispyribac sodium (BS), a pyrimidinyl carboxy herbicide, is a well-known inhibitor of acetolactate synthase (ALS) activity. ALS is an enzyme in the biosynthetic pathway for branched-chain amino acids. A mutant form of rice ALS (OsmALS [W548L/S627I]) that confers resistance to BS can be used as an in vitro selection marker gene for plant transformation. Since indica and indica-derived cultivars are thought to have lower BS sensitivity than japonica rice, the application of BS as a selectable reagent for genetic transformation in indica and indica-derived cultivars is more challenging than for japonica cultivars. In this study, callus and seedlings of eight different rice cultivars (five indica-derived cultivars, two indica cultivars and one japonica cultivar) were tested for BS sensitivity. Our study indicates for the first time that callus shows a higher sensitivity to BS than seedlings in indica and indica-derived cultivars. We used BS with OsmALS [W548L/S627I] to select transformed calli, and transgenic rice plants from indica and indica-derived cultivars were successfully obtained.

High temperatures cause male sterility in rice plants with transcriptional alterations during pollen development.

Plant male reproductive development is highly organized and sensitive to various environmental stressors, including high temperature. We have established an experimental procedure to evaluate high temperature injury in japonica rice plants. High temperature treatment (39 degrees C/30 degrees C) starting at the microspore stage repeatedly reduced spikelet fertility in our system. Morphological observations revealed that pollen viability in plants exposed to high temperatures was lower than that in control plants. Most pollen grains in high temperature-treated plants displayed a normal round shape and stained reddish purple with Alexander's reagent; however, the pollen grains were very poorly attached and displayed limited germination on the stigma. To investigate gene regulatory mechanisms in the anther in high temperature environments, DNA microarray analysis was performed by comparing non-treated samples with samples treated with 2-4 d of high heat. Genes responsive to high temperatures were identified from clustering of microarray data. Among these, at least 13 were designated as high temperature-repressed genes in the anther. Expression analyses revealed that these genes were expressed specifically in the immature anther mainly in the tapetum at the microspore stage and down-regulated after 1 d of high temperature. The expression levels of Osc6, OsRAFTIN and TDR, which are tapetum-specific genes, were unaffected by high temperatures. These results suggest that not all tapetal genes are inhibited by increased temperatures and the tapetum itself is not degraded in such an environment. However, high temperatures may disrupt some of the tapetum functions required for pollen adhesion and germination on the stigma.

Time-lapse observation of cell alignment on nanogrooved patterns.

Cells elongate on a surface with nanogrooved (NG) patterns and align along that pattern. Although various models have been proposed for how this occurs, much remains to be clarified. Studies with fixed cells do not lend themselves to answering some of these open questions. In this study, the dynamic behaviours of living mesenchymal stem cells on an NG substrate with a 200 nm groove depth, an 870 nm ridge width and a 670 nm groove width were observed using time-lapse microscopes. We found that filopodia moved as if they were probing the surroundings of the cell protrusion, and then some cell protrusions invaded the probed areas. Cell protrusions that extended perpendicular to the NG direction tended to retract more rapidly than those parallel to the grooves. From these facts, we think that the retracting phase of cell protrusions play a rule in cell alignment along the NG patterns.

Preparation of porous poly(L-lactic acid) honeycomb monolith structure by phase separation and unidirectional freezing.

A honeycomb monolith structure with micro/nanoscale porous walls was successfully fabricated in poly(l-lactic acid) (PLLA) by integrating polymer-solvent and polymer-polymer phase separations induced during a pseudosteady-state unidirectional freezing process. Poly(ethylene glycol) (PEG) and PLLA were dissolved in 1,4-dioxane to prepare a single phase polymer solution. The direction of freezing created a honeycomb monolith structure of PLLA/PEG polymers. Crystallization of the solvent reduced the solvent concentration and induced liquid-liquid phase separation during the unidirectional freezing. A sea-and-island morphology, where PEG domains were dispersed in the PLLA matrix, was developed, and pores were created in the channel walls of the honeycomb monolith structure by leaching out the PEG domain. The effects of the PEG molecular weight and the PLLA/PEG weight ratio on the aligned honeycomb structure and the pores in the channel walls were investigated. A ternary phase diagram for PLLA, PEG, and 1,4-dioxane was created from cloud point temperature measurements. Based on this phase diagram, hypotheses for the mechanism of the cellular-dendritic transition and the formation mechanism of the pores in the channel walls are proposed.

Supercritical CO2-assisted embossing for studying cell behaviour on microtextured surfaces.

Recently, cell responses to micro- and nanoscale structures have attracted much attention. Although interesting phenomena have been observed, we have encountered some difficulties in elucidating purely topographical effects on cell behaviour. These problems are partially attributable to the introduction of functional groups and the persistence of chemicals during surface processing. In this study, we introduced supercritical CO(2)-assisted embossing, which plasticizes a polycarbonate plate by dissolving supercritical CO(2) and thus can emboss wide-scale patterns onto the plate at a lower temperature than the polycarbonate glass transition temperature. Uniform micro- and nanopatterned surfaces were observed across the whole area of the polycarbonate plate surfaces. Nickel, fluorine, and nitrogen were not detected on the fabricated surfaces, and the surface carbon-to-oxygen ratios were equivalent to the theoretical ratio (C:O=84.2:15.8) calculated from the polycarbonate molecular structure. Human mesenchymal stem cells were cultured on the fabricated microlens and nanogroove substrata. Cell-adhered areas became smaller on the microlens than on non-treated polycarbonate. Meanwhile, cells aligned along the ridges of nanogrooves with valleys deeper than 90 nm. This supercritical CO(2)-assisted embossing can produce fine substrates for studying the effects of surface topography of synthetic materials on cell behaviours.

Periodic porous stripe patterning in a polymer blend film induced by phase separation during spin-casting.

A periodic striping pattern with microscale pore size is observed on the surface of thin films prepared by spin-casting from a polystyrene (PS) and polyethylene glycol (PEG) blend solution. The pattern is created by the convection generated by thermal gradients in the solution between the substrate and film solution during solvent evaporation, the radial flow of the spin-coated solution, and the primary and secondary phase separation of the PS and PEG solutions. The formation mechanism of the periodic porous stripe pattern is discussed, wherein the effects of the polymer blend weight ratio, polymer concentration, and drying rate on the formation of the periodic porous striping pattern are investigated using scanning electron and atomic force microscopy.

Alpha-amylase production is induced by sulfuric acid in rice aleurone cells.

The hydrolytic enzyme alpha-amylase (EC 3.2.1.1) is produced mainly in aleurone cells of germinating cereals, and the phytohormone gibberellin (GA) is essential for its induction. However, in rice (Oryza sativa L.), sulfuric acid (H(2)SO(4)) induces alpha-amylase production in aleurone tissue even in the absence of GA. Here, the pre-treatment of rice aleurone cells with H(2)SO(4) and incubation in water induced alpha-amylase activity, as if the cells had been incubated in GA solution.