Pure PF Research Articles

Development and Characterisation of Phenolic Foams with Phenol-Formaldehyde-Chestnut Tannins Resin

With the depletion of fossil resources, tannin extracts can be a natural alternative to some synthetic products. Hydrolysable chestnut tannin extracts have been used to partially replace phenol in PF resins for phenolic rigid foams. Phenol-formaldehyde-chestnut tannin (PFT) phenolic foams were initially made from copolymerized PFT resins of different molar ratio. The PFT foams so prepared were tested for thermal conductivity, these being slightly worse than that of pure PF foams; and for mechanical and water absorption, these two properties being better than those of pure PF foams. Indeed, PF resins represent an important part of synthetic resins. They are used in different fields of application such as in phenolic foams or for the preparation of particleboard. So it is important to work on the possibility of going green with these resins.

Highly efficient de-polymerization of organosolv lignin using a catalytic hydrothermal process and production of phenolic resins/adhesives with the depolymerized lignin as a substitute for phenol at a high substitution ratio

The objective of this study was to produce green phenolic resins and adhesives using bio-phenolic compounds produced from lignin/forestry residuals. To produce bio-phenolic compounds, an organosolv lignin (OL) was catalytically degraded in 50/50 (v/v) water–ethanol and pure ethanol media under sub/supercritical condition in hydrogen atmosphere. Effects of lignin degradation process conditions (catalyst, temperature, type of reactor, etc.) on the yields and properties (molecular weights) of the degraded lignin (DL) products were examined in this study. The DL products were used to substitute for phenol in the synthesis of bio-phenol formaldehyde resins, denoted as degraded lignin phenol-formaldehyde (DLPF) resins, whose properties (such as viscosity, non-volatile contents, storage time, free formaldehyde contents, curing behavior, and thermal stability) were compared with pure PF resin and organosolv lignin phenol-formaldehyde (OLPF) resins. Plywood samples glued with the OLPF and DLPF adhesives with a phenol replacement ratio up to 75wt% showed higher dry and wet tensile strengths than those of PF adhesives. Although the OLPF adhesives have better bond strengths and thermal stability than DLPF adhesives, the DLPF resins have a lower free formaldehyde content and can be cured at a lower temperature.

Curing of phenol-formaldehyde resin mixed with wood preservatives

The effects of preservatives used for glue-line treatment on the curing of phenol-formaldehyde resin (PF) were studied by dynamic mechanical analysis and differential scanning calorimetry. Storage modulus, G′, loss modulus, G″, and loss tangent, tan δ, of PF with and without preservatives were recorded as a function of time under isothermal heating. The time required for G′, G″, and tan δ to reach steady values increased with addition of preservative. The G′, G″, and tan δ curves of PF containing benzyl alcohol (used in the preservative as a diluent) were almost identical to those of PF containing preservative. However, the addition of antitermite and anti-fungal compounds alone had no effect on the curing process. There were no differences in total reaction enthalpy or dependence of activation energy on degree of conversion between pure PF and mixtures. Our results indicate that benzyl alcohol in preservatives plasticizes the curing system for PF. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and thermal properties of mesoporous silica/phenolic resin nanocomposites via in situ polymerization

In order to enhance the adhesion between inorganic particles and polymer matrix, in this paper, the mesoporous silica SBA-15 material was synthesized by the sol-gel method. The surface of SBA-15 was modified using !-glycidy- loxypropyltrimethoxysilane (GOTMS) as a coupling agent, and then mesoporous silica/phenolic resin (SBA-15/PF) nanocomposites were prepared via in situ polymerization. The structural parameters and physical properties of SBA-15, SBA-15-GOTMS (SBA-15 surface treated using GOTMS as coupling agents) and E-SBA-15/PF (SBA-15/PF nanocom- posites extracted using ethanol as solvent) were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The thermal properties of the nanocomposites were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results demonstrated that the GOTMS were suc- cessfully grafted onto the surface of SBA-15, and chemical bonds between PF and SBA-15-GOTMS were formed after in situ polymerization. In addition, it is found that the in situ polymerization method has great effects on the textural parame- ters of SBA-15. The results also showed that the glass transition temperatures and thermal stability of the PF nanocompos- ites were obviously enhanced as compared with the pure PF at silica contents between 1-3 wt%, due to the uniform dispersion of the modified SBA-15 in the matrix.

Effect of Surface-Treated Carbon Nanotubes on the Mechanical and Tribological Performances of Phenolic Resin

Reinforced phenolic resin (PF) was prepared by in situ polymerization of different fractions of carbon nanotubes (CNTs) that had undergone oxidation. The compressive strength and hardness of the material, according to mechanical property testing, was improved by the modified CNTs. The tribological properties of PF composites were investigated by a block-on-ring friction and wear tester. The results indicated that CNTs reinforced PF showed lower friction coefficient and higher wear resistance, compared with pure PF. The morphologies of the worn surfaces, debris, and transfer films were observed by scanning electron microscopy (SEM) and optical microscopy (OM). A continuous and thinner transfer film formed during the friction test of the composites led to the significant improvement of the tribological properties.

Synthesis and properties of nano carboxylic acrylonitrile butadiene rubber latex toughened phenolic resin

AbstractNano carboxylic acrylonitrile butadiene rubber latex‐toughened‐phenolic resins (XNBRL‐PF) were prepared by in situ polymerization in this work. The influence of nano XNBRL on the microstructure and physical properties of modified PF resin was investigated. Impact test testified that the impact strength of XNBRL‐PF was remarkably improved compared to pure PF and as the content of XNBRL increased to 10 wt %, the impact strength of the XNBRL‐PF kept increasing. Scanning electron microscope analysis of the fracture surface of the XNBRL‐PF indicated that the XNBRL were uniformly dispersed in the PF matrix, with diameters ranging from 200 to 400 nm. The results of Fourier transform infrared spectroscopy proved that chemical reaction occurred between XNBRL and PF matrix, which can greatly improve the interface interaction between rubber particles and PF matrix. Thermogravimetric analysis test showed that the incorporation of XNBRL can improve the thermostability of PF at low temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of grafted polytetrafluoroethylene nanoparticles on the mechanical and tribological performances of phenol resin

Reinforced phenol resin (PF) was prepared by in situ polymerization of different fractions of nano polytetrafluoroethylene particles (nano-PTFE) undergone grafting acrylic acid irradiation. The bending strength and hardness of the material, according to mechanical property testing, were improved by the grafted nano-PTFE. The tribological properties of PF composites were investigated by a block-on-ring friction and wear tester. The results indicated that nano-PTFE reinforced PF showed lower friction coefficient and higher wear resistance, compared with pure PF. The morphologies of the worn surfaces, debris and transfer films were observed by a scanning electron microscopy (SEM) and an optical microscopy (OM). A continuous and thinner transfer film formed during the friction test led to the significant improvement on the tribological properties.

Preparation and Characterization of Lignin-Phenolic Foam

In this paper, lignin could partly replaced phenol to prepare lignin-phenolic(LPF) foam.The effects of amount of lignin on mechanical properties, thermal stability, fire-retardant and micro-structure of LPF foam. The results indicated that the addition of lignin decreased the brittleness and flexibility of foam, and the foam hole became larger in diameter and distributed more unevenly. When the lignin replacement amount was lower, the foam had regular foam hole structure and even distribution of foam hole, the size of foam hole increased with an increase of lignin content, SEM observations were in accordance with the early research of the mechanical properties of foams. And the addition of lignin slightly affected the fire-retardant and thermal stability of foam. When lignin replacement amount was 30% and 40%, the critical oxygen index of foam was even slightly higher than the pure PF foam.

Mechanical and physical properties of wheat straw boards bonded with a tannin modified phenol–formaldehyde adhesive

The objective of this work is to evaluate the mechanical and physical properties of three-layer boards made with wheat straw and bonded with a tannin-based adhesive. The mechanical properties of panels were evaluated by the static bending (modulus of rupture – MOR and modulus of elasticity – MOE) and the internal bond (IB) tests. Physical properties such as water absorption (WA) and thickness swelling (TS) in water were determined. In general, all types of straw panels made produced in this work met the MOR, MOE, IB and TS requirements for general uses according to European standards. Although, wheat straw boards made with tannin-modified PF resins had slightly poorer mechanical properties compared to the boards made with pure PF, the T10% PF resin showed higher bond ability than other modified PF resins. The highest MOR, MOE, IB and the lowest WA and TS were achieved at a 12min press time and by using T10% PF resin. An increase in the press time positively affected the physical and mechanical properties of the panels produced. With respect to the findings of this study, it may be stated that wheat straw can be used as a promising raw material for panel production with the use of a tannin-modified PF adhesive.

Synthesis and characterization of phenolic resol resin blended with silica sol and PVA

The phenolic resol resin (PF) has a wide application in industry, but its poor tensile ductility and insufficient mechanical strength have severely limited its application. To overcome these limitations, in this study, the mixtures of silica sol and poly(vinyl acohol) (PVA) were used to modify the PF. The structure, morphology, mechanical properties, and thermal stability of these hybrid materials were investigated by FTIR, SEM, tensile shear test (TSS), and TG. FTIR spectra indicated that the multiple reactive functional silanol group SiOH on the surface of SiO2 particles reacted with PVA and PF. Compared with pure PF, the composite 50-50-3% exhibited the maximum shear strength which increased by 158%, whereas the elongation at break increased by 63%. Morphological results agreed well with the mechanical properties. The TG results suggested that the composite material 50-50-3% and pure PF had almost the same thermal stability because silica sol and PVA had opposite effects on the heat resistance of the hybrid materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Hatchery broodstock conditioning of the blue mussel Mytilus edulis (Linnaeus, 1758). Part II. New formulated feeds offer new perspectives to commercial hatcheries

Five diets were compared for their efficiency at maturing the gonads of the blue mussel, Mytilus edulis. The diets consisted of a 1:1:1 mixture of Isochrysis galbana (T-Iso), Pavlova lutheri, and Chaetoceros calcitrans given at concentrations of 2.4 × 1011 cells day−1 for the positive control treatment (PF) and 3.0 × 1010 cells day−1 (=1/8) for the negative control treatment (NF). The other three treatments, MB10+, MyStock+, and Frippak+, consisted of the NF diet supplemented with one of the micro-encapsulated diets MB10 (mixture of dried algae), MyStock (formulated diet), and FRiPPAK® Fresh #1 CAR (larval shrimp diet) at a level of 0.2% of the live weight (LW). Treatments PF, MB10+, and MyStock+ led to high percentages of spawning animals (80, 78, and 85%, respectively) and large numbers of eggs (on average 3.0 × 106 eggs female−1). Females given the NF and Frippak+ treatments produced only half the number of eggs per female, and only 17 and 6%, respectively, of the animals spawned. A high hatching rate was observed for all treatments, 71% for the pure algae diets PF and NF and more than 80% for the micro-encapsulated diets. The larvae resulting from the NF treatment were smaller, with 41% of D-larvae measuring less than 90 μm, whereas with the other treatments only 5–11% belonged to that size category. The four most important fatty acids found in mussel eggs were 16:0, 16:1(n−7), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA); these represented at least 50% of the fatty acids in all treatments. The high DHA content of MB10 and MyStock was not reflected in the fatty acid composition of the eggs whereas the high concentration of linoleic acid in MyStock was. To our knowledge, this is the first time that mussels are successfully conditioned with formulated feeds.

Improvements in Essential Electrical and Physical Properties of Phenol Formaldehyde Resin by Incorporation of Modified Coal Tar Pitch

AbstractPhenol-formaldehyde (PF) resin is used here for making thermosetting composites along with environmentally friendly coal tar pitch(CTP). These PF-CTP composites are made with dual objectives of using environment-friendly CTP to improve the electrical and physical properties of PF resin and to reduce cost of PF resin for final applications. The composites are prepared by a two-step method using standard compression molding technique. Comparing the properties of the samples containing varying amount of CTP with pure PF resin as the reference sample, significant improvements in electrical properties like surface resistivity, volume resistivity and dielectric strength are observed with the increase in amount of CTP. The waterproofing tendency also improved as the amount of CTP is increased. The best properties are observed for the thermosetting composition with 40 phr of CTP.

Restraining the aggregation of poly(9,9-dihexylfluorene) by crosslinked poly(methyl methacrylate) networks

A crosslinked network was used to restrain undesired interchain aggregation of fluorescent polymers in this study. Primarily, solutions of poly(9,9-dihexylfluorene) (PF) in toluene and in curable liquid monomer mixtures of methyl methacrylate (MMA) and ditrimethylolproane tetracrylate (DTTPT) were compared to study the effect of concentration on absorption and emission behaviors. Results from ultraviolet–visible absorption, photoluminescence (PL) emission, and PL excitation reveal that the degree of aggregation depended strongly on the concentration and was correlated to the size of the polymer coil as determined from light scattering. Solutions of known PF content in MMA/DTTPT were then photoirradiated to yield PF/crosslinked poly(methyl methacrylate) (X-PMMA) composite films. Comparison among the pure PF, PF/MMA/DTTPT mother liquid, and PF/X-PMMA solid composites were then conducted to evaluate the effect of crosslinking on the degree of aggregation. With small amounts of imbedded PF (0.0015 wt %), the PF/X-PMMA composite had a PL quantum yield (0.70) higher than the pure PF (0.65) itself. Most notably, the PF/X-PMMA composites after annealing at 120 and 200°C for 5 h still retained a reasonable emission efficiency (with related PL quantum yields of 0.61 and 0.43), in contrast to the large PL quantum yield reductions to 0.32 and 0.19 for the annealed PFs after the same treatment. Suggestively, interchain aggregation during a high-temperature annealing process can be largely inhibited by the surrounding crosslinked network matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Voltammetry of ferrocene in supercritical carbon dioxide containing water and tetrahexylammonium hexafluorophosphate

The voltammetric oxidation of ferrocene has been examined with microdisk electrodes in supercritical CO{sub 2} containing small-amounts of added water. Voltammograms obtained under these conditions indicate a high rate of diffusion for ferrocene but exhibit considerable ohmic drop. The ohmic distortion of the voltammograms is reduced by the addition of tetrahexylammonium hexafluorophosphate ((THA)PF{sub 6}) to the cell. However, when large amounts of (THA)PF{sub 6} are added to the cell, visual inspection indicates a two-phase system under the conditions used. Near-infrared spectra show that the upper phase is supercritical CO{sub 2} and the lower phase is liquid (THA)PF{sub 6}. This result is obtained at a temperature that is 64{degree}C below the melting point of pure (THA)PF{sub 6} at atmospheric pressure. Ferrocene is found to have a much lower diffusion coefficient in the molten salt. However, the limiting current recorded in the molten salt is not attenuated relative to that in the upper phase, because ferrocene preferentially dissolves in the molten salt. It is shown that the molten salt, when added in small amounts to the cell, acts as an electrode-surface modifier that promotes ionic conductivity and allows the oxidation of ferrocene extracted from the supercritical CO{sub 2}. This occurs even whenmore » the electrode is placed in the upper CO{sub 2} phase.« less