Grafting of hyperbranched poly(amidoamine) onto waste tire rubber powder and its potential application as the curing agent for epoxy resin

To realize the high‐valued application of waste tire rubber (WTR), hyperbranched poly(amidoamine) (PAMAM) were synthesized from the surface of WTR powders to endow its chemical reactivity. The hyperbranched PAMAM‐grafted WTR powders containing a large amount of amine groups on their surface were obtained through “divergent procedure.” First, methyl methacrylate‐grafted WTR powders (MMA‐g‐WTR) were prepared by ozone‐induced grafting polymerization. Afterwards, Michael reaction and subsequent amidation reactions were carried out repetitively to obtain hyperbranched PAMAM chains grafted from the surface of the MMA‐g‐WTR powders. The resulting hyperbranched PAMAM‐grafted WTR powders exhibit good dispersibility in water. Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis demonstrate the successful grafting of hyperbranched PAMAM on WTR surface. The hyperbranched PAMAM‐grafted WTR powder could be utilize as curing agent and potential toughener for epoxy resin due to abundant amine groups and elastomeric feature of WTR. Differential scanning calorimetry shows that the hyperbranched PAMAM‐grafted WTR powders can be used as effective curing agent for epoxy resin. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal study of phenol–formaldehyde resin modified with cashew nut shell liquid

In this study, an experimental phenol–formaldehyde resin with 20% phenol replacement by cashew nut shell liquid (CNSL) was studied and compared with a conventional phenol–formaldehyde resin synthesized totally from petrochemical raw materials. The resins were characterized with standard lab analysis for their physicochemical specifications, while their thermal properties were studied with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). For comparison reasons pure CNSL and wood were also included in the TGA study. A DSC study conducted both for the neat resins and the system wood–resin as to examine the effect of wood on the curing performance of the resins in the real time conditions of their usage at the wood-based panels industry.The adhesion strength of these resins was investigated by their application in plywood production. The plywood panels were tested for their shear strength and wood failure performance while their free formaldehyde emissions were determined with the desiccator method. It was proved that although the neat CNSL modified PF resin (PCF) cures at longer time and higher temperature than a conventional PF resin, wood affects it more significantly, resulting in the evening of their curing performance. This is a novel finding that manifests the possibility of replacing a convention PF resin by a CNSL modified one in the plywood production, without changing any of their production conditions and with improvement to their overall properties.     

Properties of Aqueous Polyurethane Dispersion Modified by Epoxide Resin and Their Use as Adhesive

The aqueous polyurethane hybrid dispersion modified by the epoxy resin were synthesized using 1,4-butanediol ( BDO ) and dimethylolpropionic(DMPA) as chain extenders. A kind of automobile interior decoration adhesive was made by the modified hybrid dispersions. Effects of the content and the kinds of epoxide resin on the properties of dispersions and dispersion-cast films such as appearance, pot life, viscosity, particle size, molecular mass, hardness, swelling in water, contact angle, strength of stress, elongation at break, and other mechanical properties were studied. At the same time the effect of the E20 content on the peel strength of the adhesive for several automobile interior decoration substrates such as rubber/wood, poly(vinyl chloride)/wood; leather/wood, sponge/wood was investigated. The experimental results show that when the epoxy resin E20 content was 8%, the modified polyurethane hybrid dispersions possess better properties and the adhesive made by the modified dispersions posses better adhesion for automobile interior decoration substrates. The stress-strain curve of the modified aqueous polyurethane hybrid dispersions films shows the modified aqueous cast films possess better rigidity and toughness.     

Physico-chemical and anatomical characterization of residual lignocellulosic fibers

Anatomical and physico-chemical properties of residual natural fibers (sugarcane bagasse, coconut fibers and peanut hulls) were characterized in order to evaluate their potential for use in the production of particleboard. The bulk density was determined by helium pycnometer and the chemical characteristics by using an electronic pH meter (for pH determination) on fibers dissolved in acidic and neutral detergents (to determine the levels of cellulose, hemicellulose and lignin). The anatomical characteristics were established using scanning electron microscopy coupled with an X-ray detector system, as well as energy dispersive X-ray spectroscopy. Results indicated similarities and differences between physico-chemical and anatomical characteristics of the residual lignocellulosic fibers when compared with the Pinus sp. wood commercially employed in particleboard production. Bulk density and pH for residual lignocellulosic fibers and Pinus sp. wood presented analogous values. Similar amounts of cellulose and lignin were identified between waste fibers and Pinus sp. wood. The presence of silica was identified in coconut fiber, peanut hull and sugarcane bagasse waste fibers, and may affect the mechanical characteristics of panels. Coconut and sugarcane bagasse fibers show surface pores with diameters ranging from 1.2 to 2.1 μm, below the 5 μm identified for Pinus sp. wood. Both fibers present pores distributed over their entire surface, whereas peanut hull fibers have no pores on their surface. This characteristic contributes to resin dispersion among particles, reflecting positively on the physical–mechanical properties of the panels. Particleboards produced with residual lignocellulosic fibers present similar physical–mechanical properties to those of Pinus sp. wood panels.     

Modification of epoxy resin using reactive liquid (ATBN) rubber

Epoxy resins are widely utilised as high performance thermosetting resins for many industrial applications but unfortunately some are characterised by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins by the introduction of rigid particles, reactive rubbers, interpenetrating polymer networks and engineering thermoplastics within the matrix.In the present work liquid amine-terminated butadiene acrylonitrile (ATBN) copolymers containing 16% acrylonitrile is added at different contents to improve the toughness of diglycidyl ether of bisphenol A epoxy resin using polyaminoimidazoline as a curing agent. The chemical reactions suspected to take place during the modification of the epoxy resin were monitored and evidenced using a Fourier transform infrared. The glass transition temperature (T_g) was measured using a differential scanning calorimeter. The mechanical behaviour of the modified epoxy resin was evaluated in terms of Izod impact strength (IS), critical stress intensity factor, and tensile properties at different modifier contents. A scanning electron microscope (SEM) was used to elucidate the mechanisms of deformation and toughening in addition to other morphological features. Finally, the adhesive properties of the modified epoxy resin were measured in terms of tensile shear strength (TSS).When modifying epoxy resin with liquid rubber (ATBN), all reactivity characteristics (gel time and temperature, cure time and exotherm peak) decreased. The infrared analysis evidenced the occurrence of a chemical reaction between the two components. Addition of ATBN led to a decrease in either the glass transition temperature and stress at break accompanied with an increase in elongation at break and the appearance of some yielding. As expected, the tensile modulus decreased slightly from 1.85 to about 1.34 GPa with increasing ATBN content; whereas a 3-fold increase in Izod IS was obtained by just adding 12.5 phr ATBN compared to the unfilled resin. It is obvious that upon addition of ATBN, the Izod IS increased drastically from 0.85 to 2.86 kJ/m² and from 4.19 to 14.26 kJ/m² for notched and unnotched specimens respectively while K_IC varies from 0.91 to 1.49 MPa m^1/2 (1.5-fold increase). Concerning the adhesive properties, the TSS increased from 9.14 to 15.96 MPa just by adding 5 phr ATBN. Finally SEM analysis results suggest rubber particles cavitation and localised plastic shear yielding induced by the presence of the dispersed rubber particles within the epoxy matrix as the prevailing toughening mechanism.     

Preparation and properties of graded styrene‐butadiene rubber vulcanizates

Styrene‐butadiene rubber (SBR) vulcanizates with graded network‐chain densities in the thickness direction were prepared by layering and heat pressing the compounding sheets. The effect of the gradient of network‐chain density on the mechanical properties of the graded rubber vulcanizates was investigated in comparison with those of SBR vulcanizates that were prepared from the homogeneous compounding sheets. The matrix with a high network‐chain density exclusively affected the mechanical properties of the graded rubber vulcanizates when the gradient was given in the thickness direction. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 358–364, 2002; DOI 10.1002/polb.10096     

Synthesis and characterization of novel fluorosilicone rubber using imide modified vinyl‐containing fluorosilicone resin as cross‐linker

A novel imide modified vinyl‐containing fluorosilicone resin (MP‐VFS) was firstly prepared from maleopimaric acid (MPA), and characterized by ¹H NMR and ¹³C NMR. Containing MPA based imide heterocycle (MPABI), MP‐VFS was further used as a novel cross‐linker to prepare MPA modified fluorosilicone rubber (MP‐FSR). Morphology, mechanical and oil‐resistance properties, thermal properties, and low temperature resistance of MP‐FSR had been studied. Microphase separation was observed in MP‐FSR. Although the tensile strength of fluorosilicone rubber was not significantly enhanced, the tearing strength, breaking elongation, rebound resilience and hardness were effectively improved. When the MP‐VFS content was 2.0 wt %, the tearing strength of MP‐FSR was increased by 23.5%, breaking elongation by 18.6% and rebound resilience by 9.7%. The thermal stability was enhanced due to the incorporation of MPABI. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1769–1776     

Mechanical and acoustical properties of particleboards made with date palm branches and vermiculite

The main goal of this study was to determine the performance of particleboards made from date palm branches (DPB, Phoenix dactylifera), as a low-value raw material and expanded vermiculite (VER), as a natural inorganic filler. DPB is underutilized abundant byproduct in southern parts of Iran. For the purpose of evaluation, compositions of DPB and VER at different mixture rates were compared for some properties. Variable parameters were: number of particleboard layers (single- and three-layer), VER size (micro and nano meter), and VER content (0, 10 and 20 wt%). Other parameters such as resin content (10%), hardener content (2%), pressing time (6 min), board density (0.75 g/cm³), press pressure (35 kg/m²) and press temperature (175 °C) were held constant. Physical properties (thickness swelling (TS), water absorption (WA), and sound absorption coefficient (SAC)), and mechanical properties (modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB)) of the boards were determined. Based on the findings of this study, all mechanical properties of the boards slightly decreased when the VER content was increased from 0 to 20 wt%. Analysis of data revealed that the mechanical properties were significantly different among the board types. In general, WA and TS increased with the increase of WER content. The presence of nano VER in the particleboards resulted in higher WA and TS. The SACs of composite boards filled with VER increased as the frequency increased. Nano VER and single-layer boards showed higher SACs in frequency range of 800–1250 Hz. Finally, it can be stated that DPB has potential as replacement fibrous material for particleboard manufacturing and indoor applications.     

The use of furan oligomers for modifying phenol-formaldehyde resin in plywood industry

The modification of phenol-formaldehyde resins by furan oligomers to increase the service characteristics of plywood and plywood products has been suggested. The strength properties, water resistance, fire resistance of plywood based on phenol resin SFZh-3013 modified by furfural-acetone FA monomer at the stage of the mixing of the adhesive composition components have been estimated.     

The effect of chemical composition on microfibrillar cellulose films from wood pulps: water interactions and physical properties for packaging applications

The interactions with water and the physical properties of microfibrillated celluloses (MFCs) and associated films generated from wood pulps of different yields (containing extractives, lignin, and hemicelluloses) have been investigated. MFCs were produced by combining mechanical refining and a high pressure treatment using a homogenizer. The produced MFCs were characterized by morphology analysis, water retention, hard-to-remove water content, and specific surface area. Regardless of chemical composition, processing to convert macrofibrils to microfibrils resulted in a decrease in water adsorption and water vapor transmission rate, both important properties for food packaging applications. After homogenization, MFCs with high lignin content had a higher water vapor transmission rate, even with a higher initial contact angle, hypothesized to be due to large hydrophobic pores in the film. A small amount of paraffin wax, less than 10%, reduced the WVTR to a similar value as low density polyethylene. Hard-to-remove water content correlated with specific surface area up to approximately 50 m²/g, but not with water retention value. The drying rate of the MFCs increased with the specific surface area. Hornified fibers from recycled paper also have the potential to be used as starting materials for MFC production as the physical and optical properties of the films were similar to the films from virgin fibers. In summary, the utilization of lignin containing MFCs resulted in unique properties and should reduce MFC production costs by reducing wood, chemical, and energy requirements.     

Sustainable,fire‐resistant phthalonitrile‐based glass fiber composites

The sustainable resveratrol‐based phthalonitrile was used in the preparation of E‐glass fiber‐reinforced phthalonitrile composite panels fabricated by hot pressed prepreg consolidation with bis[4‐(3‐aminophenoxy)phenyl]sulfone (m‐BAPS) as the curing additive. This amorphous monomer exhibited excellent viscosities at temperatures below 200 °C, which is applicable to standard processing conditions. Rheometric measurements were used to evaluate the cure of the composite as a function of the postcure conditions. The composite retains >95% of its room temperature storage modulus up to 450 °C based on these postcuring parameters. More importantly, flammability performance of the composite—which was determined in terms of ignitability, heat release, and mass loss rate—excels over other state‐of‐the‐art polymer/glass composites. Even under the most extreme heat fluxes (e.g., 100 kW⋅m⁻²), the composite performs exceptionally well suggesting that resveratrol‐based phthalonitrile composites can be used in fire‐resistant applications. Published 2018.^† J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1128–1132     

One‐Step Grafting of Al2O3 onto Acid‐Made Mesoporous Silica

We report a one‐step convenient chemical coating method of high alumina content onto mesoporous silicas. Aluminia‐coated mesoporous silica with high surface area (?900 m²/g), tuneable pore size (2.0–3.0 nm) and high hydrothermal stability (> 60 h) is obtained. The method may also be generalized for grafting other metal oxides onto mesoporous silica in future work.     

Latex‐state NMR spectroscopy for quantitative analysis of epoxidized deproteinized natural rubber

Method of quantitative analysis through latex‐state ¹³C NMR spectroscopy was established for in situ determination of epoxy group content of epoxidized natural rubber in latex stage. The epoxidized natural rubber latex was prepared by epoxidation of deproteinized natural rubber with freshly prepared peracetic acid in latex stage. The resulting epoxidized deproteinized natural rubber (EDPNR) latex was characterized through latex‐state ¹³C NMR spectroscopy. Chemical shift values of signals of latex‐state ¹³C NMR spectrum for EDPNR were similar to those of solution‐state ¹³C NMR spectrum for EDPNR. Resolution of latex‐state ¹³C NMR spectrum was gradually improved as temperature for the nuclear magnetic resonance (NMR) measurement increased to 70°C. Signal‐to‐noise ratio of latex‐state ¹³C NMR measurement was similar to that of solution‐state ¹³C NMR measurement at temperature above 50°C. The epoxy group content determined through latex‐state NMR spectroscopy was proved to be the same as that determined through solution‐state NMR spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd.     

Influence of carboxyl‐terminated (butadiene‐co‐acrylonitrile) loading on the mechanical and thermal properties of cured epoxy blends

A mixture of epoxy with liquid nitrile rubber, carboxyl‐terminated (butadiene‐co‐acrylonitrile) (CTBN) was cured under various temperatures. The cured resin was a two‐phase system, where spherical rubber domains were dispersed in the matrix of epoxy. The morphology development during cure was investigated by scanning electron microscope (SEM). There was slight reduction in the glass transition temperature of the epoxy matrix (T_g) on the addition of CTBN. It was observed that, for a particular CTBN content, T_g was found to be unaffected by the cure temperature. Bimodal distribution of particles was noted by SEM analysis. The increase in the size of rubber domains with CTBN content is due probably to the coalescence of the rubber particles. The mechanical properties of the cured resin were thoroughly investigated. Although there was a slight reduction in tensile strength and young's modulus, appreciable improvements in impact strength, fracture energy, and fracture toughness were observed. Addition of nitrile rubber above 20 parts per hundred parts of resin (phr) made the epoxy network more flexible. The volume fraction of dispersed rubbery phase and interfacial area were increased with the addition of more CTBN. A two‐phase morphology was further established by dynamic mechanical analysis (DMA). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2531–2544, 2004     

Activation of Spruce Wood Surfaces by Plasma Treatment After Long Terms of Natural Surface Inactivation

Surface inactivation is a phenomenon that causes poor adhesion. A wood surface exposed to contaminants such as dust or atmospheric grime can experience surface inactivation. Inactivation mechanisms can reduce the attractive forces on the wood surface and lead to a decrease in wettability. Plasma treatment has been applied to recover inactivated wood surfaces for better adhesion and bonding. Plasma treatment technology is very simple and the cost is rather low. In addition, this treatment produces no environmental pollution. In this study, low pressure plasma treatment was applied to reactivate the surfaces of spruce wood for glue bonding and to increase wettability after a 9-year period of natural surface inactivation. Changes in contact angles, surface energy, surface colour and bonding strength of inactivated and oxygen plasma treated wood surfaces were studied. Wettability, bonding and other mechanical strength properties of plywood panels increased with the oxygen plasma treatment.     

The role of thiophosphoryl disulfide on the co‐cure of CR‐EPDM blends: effect of white fillers

Bis(diisopropyl) thiophosphoryl disulfide (DIPDIS) being a rubber accelerator has a definite role as a coupling agent in the silica filled polychloroprene rubber with ethylene propylene diene rubber (CR‐EPDM) blends. Diethylene glycol can further improve the beneficial effect of DIPDIS in silica filled CR‐EPDM blends. Two‐stage vulcanization technique further improves the physical properties of silica filled CR‐EPDM blends. The results have been compared with non‐reinforcing calcium carbonate filled systems. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled CR‐EPDM blend vulcanizates obtained from this two‐stage process. Copyright © 2004 John Wiley & Sons, Ltd.     

A flame‐retardant phosphate and cyclotriphosphazene‐containing epoxy resin: Synthesis and properties

A novel flame‐retardant epoxy resin, (4‐diethoxyphosphoryloxyphenoxy)(4‐glycidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4‐diethoxyphosphoryloxyphenoxy)(4‐hydroxyphenoxy)cyclotriphosphazene and was characterized by Fourier transform infrared, ³¹P NMR, and ¹H NMR analyses. The epoxy resin was further cured with diamine curing agents, 4,4′‐diaminodiphenylmethane (DDM), 4,4′‐diaminodiphenylsulfone (DDS), dicyanodiamide (DICY), and 3,4′‐oxydianiline (ODA), to obtain the corresponding epoxy polymers. The curing reactions of the PPCTP resin with the diamines were studied by differential scanning calorimetry. The reactivities of the four curing agents toward PPCTP were in the following order: DDM > ODA > DICY > DDS. In addition, the thermal properties of the cured epoxy polymers were studied by thermogravimetric analysis, and the flame retardancies were estimated by measurement of the limiting oxygen index (LOI). Compared to a corresponding Epon 828‐based epoxy polymer, the PPCTP‐based epoxy polymers showed lower weight‐loss temperatures, higher char yields, and higher LOI values, indicating that the epoxy resin prepared could be useful as a flame retardant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 972–981, 2000     

Magnetic composites based on natural rubber prepared by using peroxide and sulfur curing system

In this work, rubber magnetic composites were prepared by incorporation of strontium ferrite into elastomeric matrix based on natural rubber. Cross‐linking of the rubber matrix was performed by using sulfur and peroxide curing system. The study was aimed at the investigation of the type of curing system and magnetic filler content on curing process and cross‐link density of prepared materials. Then, the influence of both factors on physical–mechanical and magnetic properties was observed. The obtained results demonstrate that sulfur‐cured composites show better physical–mechanical properties, especially at lower content of strontium ferrite. With increasing amount of ferrite, the differences between the characteristics of both types of composites became less visible, while peroxide‐cured sample with maximum ferrite content showed superior tensile strength in comparison with tensile strength of maximally filled sample cured with sulfur system. The obtained results demonstrate better compatibility between the rubber and the filler when peroxide system was introduced for cross‐linking of the rubber matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Toughening of cyanate ester resin by carboxyl terminated nitrile rubber

The carboxyl terminated butadiene‐acrylonitrile (CTBN) rubber was used to improve the toughness of the cyanate ester (CE) resin. The toughness of the modified blends depended on the CTBN content. The addition of 10 phr (g/100gCE) CTBN in CE resin led to a 200% increase in the impact strength with a loss of storage modulus. The transmission electron microscopy result showed the existence of rubber particles, inferring that phase separation had occured after curing. The thermogravimetric analysis curve of CTBN indicated the presence of cavities which also can be observed on the fractured surface in the scanning electron microscopy pictures using high magnification. Thus, phase‐separation and cavities toughening mechanisms function together to improve the toughness. Copyright © 2004 John Wiley & Sons, Ltd.     

Introducing flexibility in urea–formaldehyde resins: Copolymerization with polyetheramines

Adhesives obtained by copolymerizing urea, formaldehyde, and difunctional polyetheramine with different molecular weights (230, 600, 900, and 2000 g mol⁻¹) are presented as a more resilient alternative to conventional urea–formaldehyde resins. Urea and polyetheramine contents were varied and the resulting resins characterized by FTIR, ¹³C‐NMR, and TGA. These resins were used for production of agglomerated cork panels, an application that demands that the binder system is flexible. Polyetheramine with molecular weight 900 g mol⁻¹ yielded the most promising agglomerated cork panel, with remarkable flexibility, good tensile strength, and with the E1 formaldehyde content specification for wood‐based panels used in construction, according to European Standard EN 12460‐5. These new thermoset adhesives have demonstrated to be capable of being used in systems where conventional formaldehyde‐based resins do not perform well due to inherent high rigidity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1834–1843