PPO Content Research Articles

Preparation and Properties of PA10T/PPO Blends Compatibilized with SEBS-g-MAH.

Plant-derived PA10T is regarded as one of the most promising semi-aromatic polyamides; however, shortcomings, including low dimensional accuracy, high moisture absorption, and relatively high dielectric constant and loss, have impeded its extensive utilization. Polymer blending is a versatile and cost-effective method to fabricate new polymeric materials with excellent comprehensive performance. In this study, various ratios of PA10T/PPO blends were fabricated via melt blending with the addition of a SEBS-g-MAH compatibilizer. Molau test and scanning electron microscopy (SEM) were employed to study the influence of SEBS-g-MAH on the compatibility of PA10T and PPO. These studies indicated that SEBS-g-MAH effectively refines the domain size of the dispersed PPO phase and improves the dispersion stability of PPO particles within a hexafluoroisopropanol solvent. This result was attributed to the in situ formation of the SEBS-g-PA10T copolymer, which serves as a compatibilizer. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results showed that the melting-crystallization behavior and thermal stability of blends closely resembled that of pure PA10T. Dynamic mechanical analysis (DMA) revealed that as the PPO content increased, there was a decrease in the glass transition temperature and storage modulus of PA10T. The water absorption rate, injection molding shrinkage, dielectric properties, and mechanical strength of blends were also systematically investigated. As the PPO content increased from 10% to 40%, the dielectric loss at 2.5 GHz decreased significantly from 0.00866 to 0.00572, while the notched Izod impact strength increased from 7.9 kJ/m2 to 13.7 kJ/m2.

Use of an eco‐friendly preservation technology as a strategy to increase the microbiological shelf‐life of a novel ready‐to‐eat salad containing vegetable by‐products

AbstractThe objective of this investigation was to evaluate different UV‐C irradiation doses in a novel ready‐to‐eat vegetable product containing vegetable by‐products (red beet leaves) and determine the microbiological shelf‐life and quality indicators during refrigerated storage (5 ± 1°C). During processing, no chemical disinfection was carried out and after the packaging step, 3 doses of UV‐C irradiation were applied (CTRL: 0 kJ/m2, L: 1 kJ/m2, M: 4 kJ/m2, and H: 7 kJ/m2) on the vegetable product studied (50% Creola purple lettuce, 25% beet leaves, and 25% arugula). It was observed that the intermediate dose (M) was the most suitable treatment since it could increase in six times its microbiological shelf‐life. Additionally, M was the one that showed the lowest loss of total polyphenols and the one that best maintained the antioxidant capacity (DPPH), probably attributed to the decrease in the activity of deterioration enzyme, PPO and higher ascorbic acid content at day 4. When evaluating % CO2/O2 on headspace of bags, UV‐C treatments reached earlier the dynamic equilibrium. Finally, all UV‐C irradiation treatments were successful against the simulated contamination. In that way, significant reductions of L. innocua and E. coli were found, with differences from up to 2 log cycles during storage. Finally, it can be concluded that UV‐C treatment can increase the microbiological shelf‐life of the novel ready‐to‐eat vegetable product, with quality indicators stabilization.Practical applicationsReady‐to‐eat salads present a short shelf‐life, which hinders their commercialization. As preservation technologies are required, UV‐C irradiation is an eco‐friendly alternative for its preservation as it has the potential to replace traditional disinfection treatments by reducing the water footprint of the total process. Therefore, since the UV‐C treatment is applied in the last step of the process (after packaging the product), microbiological contamination occurring in this type of vegetable products during processing is minimized. However, additional investigation is necessary to assess its suitability for a novel ready‐to‐eat salad containing horticultural by‐products.

Screening of Lentil Germplasm against Stemphylium Blight and Studies on Association between Disease and Biochemical Parameters

Background: Stemphylium blight, an important fungal disease of lentil caused by Stemphylium botryosum Wallr, has been reported to cause an estimated yield loss of 62% in India and Bangladesh. Considering the importance of the crop vis-à-vis the severity of the disease under terai agro-climatic region of West Bengal, the present study was undertaken to evaluate the germplasm of lentil for Stemphylium blight resistance for their utilization in future resistance breeding programme. Methods: The present experiment was carried out during the rabi season of 2019-20 and 2020-21 with forty lentil germplasm including two checks viz; WBL77 and IPL220 in an alpha lattice design under field condition and in completely randomized design under artificial inoculation respectively. Statistical analysis was carried out using R v. 4.1.1 software. Result: ANOVA revealed significant variation among the genotypes for the studied characters. PCV was found to be higher than GCV for all the studied characters. High heritability (broad sense) accompanied with high genetic advance as percent of mean indicated the presence of additive type of gene action. Based on per cent disease index germplasm were categorized as resistant or moderately resistant types for both under field condition and artificial inoculation. AUDPC was significantly but negatively associated with change in phenol and change in OD phenol under field condition same as that was observed between AUDPC and PPO content under artificial inoculation. Above study state that selection based on disease reaction and their associated parameters gives fruitful result to provide disease resistance parent against Stemphylium blight.

Preparation and Property Study of PA56/POE-g-MAH-GMA/PPO Ternary Alloy

Bio-based PA56 is as matrix resin, maleic anhydride (MAH), and glycidyl methacrylate (GMA) dual monomer grafted POE (POE-g-MAH/GMA) polyphenyl ether(PPO) are simultaneous as toughening agents. The PA56/POE-g-MAH-GMA/PPO ternary alloys containing 10 wt% POE-g-MAH-GMA with different PPO content prepared by the melt blending method through twin screw extruder. The structure and property of PA56/POE-g-MAH-GMA/PPO ternary alloys were studied. The results showed that the microscopic morphology of each alloy showed an obvious “sea-island” structure. PA56 is a continuous sea phase, and the island phase assumes the “core–shell structure,” the etched POE-g-MAH-GMA particles are as the nucleus, and PPO are as the shell. When the PPO mass fraction is 30%, the relative crystallinity of the alloy is 11.56%, which is 1.68 times lower compared to the pure PA56, the alloy notch impact strength is 42.1 kJ/m2, and reaches 11.7 times of pure PA56; the water absorption rate of 1.22%, which is 3.22 times lower than pure PA56.

New ultrafast low-cost polyurethane based plastic scintillator

The study of plastic scintillators with polyurethane (PU) matrix based on cycloaliphatic isocyanate 4,4′-methylenebis (cyclohexyl isocyanate) (H12MDI) and 2,5-diphenyloxazole (PPO) as a luminescence activator is presented. A number of samples with different PPO content amounting up to 20 wt% were synthesized and their optical and luminescence characteristics were investigated. Pure H12MDI – PU based polymer exhibits low optical density in the spectral region 350–500 nm characteristic of the PPO emission band. The PU sample loaded with 5 wt% PPO demonstrated a light yield of 1088 photons/MeV and ultrafast rise and decay time of few picoseconds and few nanoseconds, respectively. The estimated coincidence time resolution (CTR) value for a PU sample is 1.4 times smaller than that known for a commercial scintillator BC-422 available for ultrafast timing applications.

Design and synthesis of novel PPO-inhibiting pyrimidinedione derivatives safed towards cotton

Developing innovative and effective herbicides is of utmost importance since weed management has become a worldwide agricultural production concern, resulting in severe economic losses every year. In this study, a series of new pyrimidinedione compounds were developed via combination of pyrimidinediones with N-phenylacetamide moiety. The herbicidal activity test (37.5–150 g of ai/ha) indicated that most of the new derivatives exhibited excellent herbicidal activity against dicotyledonous weeds, but less against grasses. Among them, compound 34 was identified as the best postemergence herbicidal activities against six species of weeds (Amaranthus retrof lexus, AR; Abutilon theophrasti, AT; Veronica polita, VP; Echinochloa crusgalli, EC; Digitaria sanguinalis, DS; Setaria viridis, SV), which were comparable to the commercial control agent saflufenacil (≥90%). The protoporphyrinogen oxidase (PPO; EC. 1.3.3.4) activity experiment suggested that compound 34 could significantly reduce the PPO content in weeds, the relative expression levels of the PPO gene were verified by real-time quantitative polymerase chain reaction (RT-qPCR), and the results were consistent with the trend of the enzyme activity data. Molecular docking showed that compound 34 could occupy the PPO enzyme catalytic substrate pocket, which played an excellent inhibitory effect on the activity of receptor protein. Meanwhile, the tolerance of compound 34 to cotton was better than that of the commercial agent saflufenacil at 150 g of ai/ha. Thus, compound 34 exhibits the potential to be a new PPO herbicide for weed control in cotton fields. This study provided a basis for the subsequent structural modification and mechanism research of pyrimidinedione derivatives.

Preparation of three new Mn based nanocluster photoinitiators and their application in copolymerization of carbon dioxide and propylene oxide

Carbon dioxide derived copolymers are becoming useful materials in the fields of packaging, construction, household products and auto parts. In which, the polycarbonate and cyclic carbonate can be obtained by ring opening copolymerization with epoxy compounds. Here, three manganese based nanoclusters were prepared and their catalytic copolymerization with CO2 and propylene oxide (PO) was studied. The results show that the catalytic efficiency of nano clusters catalyst G1 is higher than that of K1 and J1. When Mn and Cd atoms are in a certain proportion and R1 or R2 combined action with clusterss, the catalytic efficiency is promoted. Due to the synergistic effect of G1 and R2, the catalytic efficiency is greatly improved. When the external light source with wavelength of 493 nm and 100 W is introduced, the copolymerization efficiency is the highest. For G3, TON increased by nearly two-thirds to 232.3, CPC content was 6.34%, and PPO content reaches 88.47%.

Exogenous application of melatonin to mitigate drought stress-induced oxidative damage in Phoebe sheareri seedlings.

Drought stress is a major prevalent environmental factor impairing growth. Melatonin mitigates the impacts of drought stress on plants. However, melatonin's role in Phoebe sheareri (Hemsl.) Gamble (P. sheareri) is unknown. We aimed to reveal the protective effects of melatonin on P. sheareri seedlings under drought conditions. Melatonin was sprayed under drought or normal water conditions. The parameters, including growth, physiological factors, and phytohormones of P. sheareri, were examined. Compared to the normal control group, drought stress inhibited the growth of seedlings and significantly reduced the content of carotenoids, SOD, POD, APX, PPO, CAT, GR, and soluble sugars, and increased the contents of MDA, O2 •-, proline, soluble proteins, ABA, and JA-Me in P. sheareri seedlings. However, melatonin treatment significantly reversed the adverse drought-induced responses and promoted the P. sheareri seedling's growth. Moreover, the heatmap and principal component analysis suggested a high similarity in the behavior patterns of the six measured antioxidant enzymes in P. sheareri seedlings. Our study reported for the first time that melatonin has a protective role in P. sheareri seedlings under drought-stress conditions. This role is related to ROS scavenging, activation of antioxidant enzymes, and crosstalk of phytohormones. This study provided a theoretical basis for improving the ability of P. sheareri adapted to arid environments.

Development and characterization of gamma ray and EMS induced mutants for powdery mildew resistance in blackgram

Purpose During post-rainy and rice fallow cropping seasons, popular blackgram varieties are severely affected by powdery mildew leading to severe yield loss. The lack of natural genetic variability for powdery mildew resistance in blackgram germplasm warrants mutation breeding. Hence, in this study, blackgram cultivar CO6 was mutagenized with gamma ray and ethyl methanesulphonate (EMS) to create variability for powdery mildew resistance. Materials and methods Seeds of blackgram CO6 were irradiated with three doses of gamma ray (200 Gy, 300 Gy and 400 Gy) followed by two doses of ethyl methanesulphonate (EMS; 20 and 30 mM) to achieve six combination treatments. Selected resistant mutants of M2 generation were characterized for agronomic, histological, enzyme and biochemical traits along with powdery mildew resistant LBG 17 and susceptible CO6 checks. Molecular variability was studied using 72 simple sequence repeat (SSR) markers. Results In the M2 generation, 60 powdery mildew resistant mutants were identified and a total of 25 high yielding mutants were evaluated further to confirm powdery mildew resistance and yield. Nine resistant mutants (PM 13, PM 20, PM 21, PM 42, PM 53, PM 54, PM 56, PM 57 and PM 60) and the resistant check (LBG17) showed significantly higher values for leaf density, trichome density, SOD, CAT, POX, PPO, total phenols, phytic acid and silica content. SSR markers viz., CEDG154, CEDG290, CEDG139, CEDG259, CEDG191, CEDG024, CEDG 282, CEDG 166, CEDG 232 and CEDG 088 were found polymorphic between resistant mutants and the parent CO6. Conclusion The study has demonstrated that sufficient variability was induced in the blackgram for powdery mildew resistance. The elevated levels of SOD, CAT, POX, PPO, total phenols, phytic acid, and silica content observed in selected mutants may be attributed to powdery mildew resistance. The superior mutants identified in this study may be used as donors for the development of powdery mildew resistant lines or released as a new variety.

Anion exchange membranes based on poly (styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) grafted poly (2,6‐dimethyl‐1,4‐phenylene oxide)

AbstractPoly (styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) has been widely studied in the field of anion exchange membranes (AEMs) due to its superior flexibility and chemical stability, but the poor dimensional stability of functionalized SEBS restricts its further application. Thus, we adopt an effective strategy to reinforce AEMs based on SEBS via grafting poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) using Williamson ether synthesis reaction. With the addition of PPO, grafted membranes exhibit outstanding comprehensive properties, such as mechanical strength, chemical stability, especially dimensional stability. SEBS‐PPO‐QA‐1 grafted membrane with the highest content of PPO showed the best tensile strength (20.54 MPa), and restrained swelling behavior (swelling ratio of 4.81% at 25°C). Moreover, the conductivity retention of SEBS‐PPO‐QA‐1 grafted membrane is up to 92.71% at 80°C after 10 days alkaline treatment. The ion exchange capacity of SEBS‐PPO‐QA‐3 grafted membrane is 1.719 mmol/g, and the ionic conductivity of SEBS‐PPO‐QA‐3 grafted membrane reach 58.27 mS/cm at 80°C and 25.53 mS/cm at 20°C. Therefore, the SEBS‐PPO‐QA‐X grafted membranes, which combine the advantages of PPO and SEBS, are promising in AEM application.

Impacts of carboxymethyl cellulose-based coatings with calcium oxide and GABA on storage life and quality maintenance of fresh pistachio fruit

ABSTRACT The fresh in-hull pistachio fruit was sprayed with 1% calcium oxide (CaO), 10 mM w/v γ-aminobutyric acid (GABA), 1% carboxymethyl cellulose (CMC), and their combination (CMC+GABA+CaO) for 30 sec at room temperature. Spraying with distilled water was considered as a control. Following drying of fruits at room temperature, they were packed in perforated polyethylene terephthalate containers and kept under cold storage (at 2 ± 1 °C with 85 ± 2% RH) for 75d. Pistachios treated showed the lower weight loss, and the highest hull safety, taste, aroma, and overall acceptance than control. Total chlorophyll and anthocyanin of fresh pistachio kernel were preserved by combined treatment. Combined treatment reduced the PPO, POD, PAL activity and MDA content of the hull and maintained kernel phenolic compounds compared to other treatments. Besides these, the best effects were obtained with combined treatment, which maintained the physical, biochemical and visual characteristics of the fresh fruit for 50 days.

Highly Reliable BaTiO3‐Polyphenylene Oxide Nanocomposite Dielectrics via Cold Sintering

AbstractIn the design of the ceramic capacitor, high capacitance, temperature stability, and high operating voltage must be balanced against the failure mechanisms of degradation. Cold sintering is used to develop dense BaTiO3 – poly (p‐phenylene oxide) (PPO) nanocomposites with PPO throughout the grain boundary microstructure. To obtain the desired PPO distribution, a process is introduced that distributes the polymers on the BaTiO3 powders prior to the cold sintering process. With the cold sintering enabled by a Ba(OH)2·8H2O transient phase, theoretical densities ≈95% could be obtained at a sintering temperature ≈225 °C with up to 15 vol% PPO content. The rationale is to influence the local electric field distribution within the dielectric, to maximize resistivity (1013–1014 Ω cm) and degradation resistance, minimize temperature dependence of permittivity, and minimize the field dependent permittivity. All these properties are investigated as a function of the volume fraction of PPO. The magnitude of the permittivity follows a logarithmic mixing law: 1460 to 680 for the nanocomposite with 5 to 15 vol% PPO content, respectively, at room temperature. The BaTiO3‐PPO composite dielectrics are contrasted under accelerated lifetime testing conditions, noting superior resistance toward degradation kinetics, indicating an important breakthrough opportunity towards the development of high reliability dielectrics.

The use of modified silica to control the morphology of polyamide 11 and poly(phenylene oxide) blends

Silica having amine functional groups (A-SiO2) obtained by the sol-gel process was used to improve compatibility of polyamide 11 and poly(phenylene oxide) (PA11/PPO 80/20) blend via reactive extrusion in a co-rotating twin screw extruder. Amine functional groups of A-SiO2 can react with the carboxyl groups of PA11 to form graft copolymer with PA11 which can efficiently control the phase morphology of the blend. Silica, thanks to the reinforcing effect, significantly increased stiffness of PA11/PPO blend. On the other hand, it greatly improved impact strength and reduced the crystallinity without affecting the crystallization temperature of PA11due to excellent compatibilizing effect. SEM results showed that despite the lower content of PPO, it formed a continuous phase and PA11 - a dispersed. The addition of A-SiO2 changed the morphology from the droplet-matrix to co-continuous with interpenetrating phases. The greatest size-reduction of both phases, reflecting the highest impact toughness, was observed for the content of 3 wt % A-SiO2. With a higher silica loading, phase inversion was observed with the reappearance of the droplet structure, resulting in a slight decrease in impact strength and significant in elongation at break. TGA showed that the composites exhibited better thermal properties as evidenced by the higher initial degradation temperature (Tonset) and the maximum weight loss rate temperature (Tmax).

Transcriptional and physiological analyses of reduced density in apple provide insight into the regulation involved in photosynthesis.

Different densities have a great influence on the physiological process and growth of orchard plants. Exploring the molecular basis and revealing key candidate genes for different densities management of orchard has great significance for production capacity improvement. In this study, transcriptome sequencing of apple trees was carried out at three different sampling heights to determine gene expression patterns under high density(HD) and low density(LD) and the physiological indices were measured to determine the effect of density change on plants. As a result, physiological indexes showed that the content of Chlorophyll, ACC, RUBP and PEP in the LD was apparently higher than that in control group(high density, HD). While the content of PPO and AO in the LD was noticeably lower than that in the HD. There were 3808 differentially expressed genes (DEGs) were detected between HD and LD, of which 1935, 2390 and 1108 DEGs were found in the three comparisons(middle-upper, lower-outer and lower-inner), respectively. 274 common differentially expressed genes (co-DEGs) were contained in all three comparisons. Functional enrichment and KEGG pathway analysis found these genes were involved in Carbon fixation in photosynthetic organisms, Circadian rhythm, Photosynthesis − antenna proteins, Photosynthesis, chlorophyll metabolism, Porphyrin, sugar metabolism and so on. Among these genes, LHCB family participated in photosynthesis as parts of photosystem II. In addition, SPA1, rbcL, SNRK2, MYC2, BSK, SAUR and PP2C are involved in Circadian rhythm, the expression of genes related to glycometabolism and hormone signaling pathway is also changed. The results revealed that the decrease of plant density changed the photosynthetic efficiency of leaves and the expression of photosynthesis-related genes, which provide a theoretical basis for the actual production regulation of apples.

Influence of Cholesterol and Bilayer Curvature on the Interaction of PPO-PEO Block Copolymers with Liposomes.

Interactions of nonionic poly(ethylene oxide)- b-poly(propylene oxide) (PEO-PPO) block copolymers, known as Pluronics or poloxamers, with cell membranes have been widely studied for a host of biomedical applications. Herein, we report how cholesterol within phosphatidylcholine (POPC) lipid bilayer liposomes and bilayer curvature affects the binding of several PPO-PEO-PPO triblocks with varying PPO content and a tPPO-PEO diblock, where t refers to a tert-butyl end group. Pulsed-field-gradient NMR was employed to quantify the extent of copolymer associated with liposomes prepared with cholesterol concentrations ranging from 0 to 30 mol % relative to the total content of POPC and cholesterol and vesicle extrusion radii of 25, 50, or 100 nm. The fraction of polymer bound to the liposomes was extracted from NMR data on the basis of the very different mobilities of the bound and free polymers in aqueous solution. Cholesterol concentration was manipulated by varying the molar percentage of this sterol in the POPC bilayer preparation. The membrane curvature was varied by adjusting the liposome size through a conventional pore extrusion technique. Although the PPO content significantly influences the overall amount of block copolymer adsorbed to the liposome, we found that polymer binding decreases with increasing cholesterol concentration in a universal fashion, with the fraction of bound polymer dropping 10-fold between 0 and 30 mol % cholesterol relative to the total content of POPC and cholesterol. Increasing the bilayer curvature (decreasing the radius of the liposome) in the absence of cholesterol increases polymer binding between 2- and 4-fold over the range of liposome sizes studied. These results demonstrate that cholesterol plays a dominant role, and bilayer curvature has a less significant impact as the curvature decreases, on polymer-membrane association.

Comparison between 'Fuyan' and 'Dongbi' longans in aril breakdown and respiration metabolism

This study aimed to investigate the difference between ‘Fuyan’ longan (Dimocarpus longan Lour. cv. Fuyan) fruit and ‘Dongbi’ longan (Dimocarpus longan Lour. cv. Dongbi) fruit in term of their aril breakdown and respiratory metabolism. As compared to ‘Fuyan’ longans, the ‘Dongbi’ longans exhibited lower fruit respiration rate, lower aril breakdown index, higher NADK activity, higher total activities of G-6-PDH and 6-PGDH, higher contents of NADP and NADPH, lower activities of AAO, CCO, PPO, PGI, and SDH, and lower contents of NAD and NADH in aril. These findings suggest that better storability and lower aril breakdown index in ‘Dongbi’ longans than ‘Fuyan’ longans might be due to lower activities of respiratory terminal oxidases, and lower respiratory metabolic pathways of EMP-TCA cycle related-enzymes in ‘Dongbi’ longan aril, which decreased respiratory rate and reduced the consumption of substrates, and subsequently maintained the integrity of the aril of ‘Dongbi’ longans during storage.

Effect of Blend Composition on Scratch Behavior of Polystyrene/Poly(2,6‐dimethyl‐1,4‐phenyleneoxide) Blends

AbstractThe relationship between the scratch behavior and molecular aggregation states of polystyrene (PS), poly(2,6‐dimethyl‐1,4‐phenyleneoxide) (PPO), and their blends, is investigated based on differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), polarized optical microscopy (POM), and indentation and scratch tests. DSC reveals that all the PS/PPO blends show the single glass transition temperature (Tg) and the Tg monotonically increase and Tg breadth exhibits a maximum, with an increase in PPO content. Furthermore, density and intermolecular chain distance obtained by WAXD exhibits maximum and minimum values at near 50 wt% of PPO, respectively. It is evident that densification occurs by blending PS and PPO. The scratch coefficient of friction (SCOF) value of PS is the largest and PS exhibits a fish‐scale pattern after scratch testing, while the SCOF value of PPO is much smaller than PS and PPO exhibits smooth groove formation. The PS50/PPO50 and PS20/PPO80 blends exhibit superior scratch and indentation resistance than PS and PPO. Damage morphology observation by POM and indentation tests reveals that molecular orientation is more restricted, and resistance against indentation increases for blends. This is due mainly to densification of the blend system.

Comparative Fungicidal Activity of some Pure and Nanoemulsion Monoterpenes Effects on Soil Borne Plant Pathogenic Fungi

Comparative study between pure and nanoemulsions (NEs) monoterpenes, cinnamaldehyde, citral, geraniol pulegone, and (R)-carvone for their fungicidal activity against three of soil borne pathogenic fungi namely, Pythium digitatum, Rhizoctonia solani and Fusarium solani by using poisoned food technique were evaluated. Results indicated that all examined monoterpenes have displayed antifungal activity under different tested concentrations. Further more. NEs- monoterpenes reduced significantly the linear growth of all tested pathogens than pure monoterpenes. NEs citral and geraniol ranked the first for their effective antifungal compounds on the tested fungi with EC50 values of 31.31 and 49.41 μg/ml on R. solani, 48.21 and 54.16 μg/ml on P. digitatum and 83.61 and 100.75 μg/ml on F. solani, respectively. Carbendazim fungicide was the reference in this study. NEs citral and geraniol were induced effective defense responses in vivo in tomato plants against R. solani at a rate of 1000 mg/L. Determination in the leaves after 0, 1, 3, 7 and 15 days of inoculation for polyphenoloxidase (PPO), peroxidase (POD) as well as total phenolic content activities as defense-related enzymes were measured. A significant increase in PPO, POD activities and total phenol content were detected. Results, also, showed that to reflect the resistance and susceptibility nature of tomato cultivars against the pathogenic fungi, R. solani., POD and PPO activities can be considered as biochemical markers. The obtained results indicated that the elicitor's NEs-citral and geraniol have brought about defense reaction in tomato plants towards the pathogenic fungi. These effective NEs monoterpenes could be effective potentially and environmentally safe to control tomato damping- off disease.

Toughening poly(lactic acid) with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers

This study describes the toughening of poly(lactic acid) (PLA) through blending it with poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymers (EPE, Pluronic®) at loadings less than 10 wt%. The miscibility of EPE copolymers in PLA was examined by thermal, morphological, and rheological analysis. Copolymers with low molecular weight and low poly(propylene oxide) (PPO) content were more miscible with PLA but less efficient as a toughening agent. In contrast, copolymers with high PPO content and high molecular weight formed droplets in the PLA and significantly increased the ductility of PLA at 5 wt% loading. More importantly, it was found that the toughening mechanism in those toughened PLA/EPE blends is similar to “rubber toughening of brittle plastics” rather than plasticization. Since the refractive indices of PLA and EPE are nearly matched, the blends were transparent. For the first time, the rheological properties of PLA/EPE blends are studied. Both the miscible and immiscible blends exhibited lower viscosity than neat PLA on account of different mechanisms. The low viscosity of the miscible blends resulted from the plasticization effect of the molecularly dissolved EPEs while the low viscosity of the immiscible blends resulted from the lubrication effect of the phase-separated EPE liquids. This lubrication effect also led to low adhesion on metal surfaces.

Characterization of polypropylene/poly(2,6-dimethyl-1,4-phenylene oxide) blends with improved thermal stability

In this article, the morphological, mechanical and thermal properties of melt blended of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and polypropylene (PP) have been studied. The solubility parameters for the molecular structure of the PP and PPO polymers were calculated using the Hoftyzer-Van k. and Hoy methods. The theoretical calculations reveal that the blend of PP and PPO polymers is immiscible. The miscibility of the PP/PPO blends containing different weight content of PPO (ranging from 5 to 20 wt%) was also evaluated by the scanning electron microscopy. The matrix-dispersed particle structure of the PP/PPO blends confirms the immiscibility of the blends. The flexural stress–strain curves were plotted for the PP and PP/PPO blends. A further improvement has appeared in the values of the bending modulus and strength of the blends comparing with that of the neat PP. The crystallization and melting temperatures of the PP/PPO blend have been evaluated using differential scanning calorimetry. The crystallization temperatures of the PP/PPO blend were shifted toward higher values with the addition of the PPO. One can see that the PPO affected the crystallinity behavior of the PP. Moreover, a significant reduction in thermal degradation rate of the PP/PPO blend was observed with the addition of PPO polymer into the host PP matrix.