Properties of Colloidal Silica‐Fixed and Propionylated Wood Composites (I): Preparation and Dimensional Stability of the Composites

Abstract

Colloidal silica‐fixed and propionylated dual‐treated wood (CSPW) composites were prepared and their dimensional stability evaluated. The results indicated that: (1) colloidal silica only–treated wood composites had minimal dimensional stability improvement, and they could be propionylated similarly to untreated wood specimens and (2) CSPW composites had a high antiswelling efficiency (ASE) during liquid water or moisture vapor absorption relative to propionylated only–treated wood, and a lower moisture excluding efficiency (MEE) during the moisture vapor absorption than propionylated wood.     

Mechanism of fiber/matrix bond and properties of wood polymer composites produced from alkaline‐treated Daniella oliveri wood flour

The effects of sodium hydroxide (NaOH) concentration and time of treatment on the mechanism of fiber/matrix bond and functional properties of Daniella oliveri reinforced wood polymer composites (WPCs) were investigated. The WPCs were evaluated using Fourier transform infrared spectroscopy, mechanical testing, scanning electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry. The fiber/matrix adhesion mechanism could be attributed to the disruption of hydrogen bonding in the D. oliveri wood fiber network structure and the removal of lignin, wax and oils covering the external surface of the fiber cell wall. This leads to an increase in desirable functional properties as alkaline concentrations reached 4 wt%, but subsequently reduced at higher concentrations, while they increased with treatment time. Analysis of the fractographs of the WPCs suggests optimization of interfacial fiber–matrix adhesion and functional properties when D. oliveri wood fiber was treated with a 4 wt% solution of NaOH for 150 min. POLYM. COMPOS., 37:2657–2672, 2016. © 2015 Society of Plastics Engineers     

Correlation between physical bonding and mechanical properties of wood–plastic composites: part 2: effect of thermodynamic factors on interfacial bonding at wood–polymer interface

Abstract

The main objective of this study was to find out if there is any significant correlation between physical properties and interfacial bonding of interphases in wood–plastic composites. To this end, high-density polyethylene (HDPE), mixture of 3% maleic anhydride grafted polyethylene (MAPE) and HDPE (coded as MHDPE) and polylactic acid (PLA) were separately interacted with veneers to identify factors underlying interfaces. Plastics were first melted at 180?°C and dispensed on wood surfaces so that the contact angle (CA) could be directly measured. Wood sanding moderately decreased the CAs of plastics in order of PLA, MHDPE, and HDPE. The treatment of veneers with MAPE comprehensively improved wetting, as the CA of HDPE was significantly reduced on the wood surface after the treatment. Thereafter, the interfacial shear strengths (IFSS) of the wood–polymer interface were determined using the automated bonding evaluation system. PLA had the highest IFSS both for unsanded and sanded veneers. Comparing both parts of this research finally revealed that applying sanding or/and MAPE treatments resulted in lower surface free energy and higher IFSS at the wood–polymer interface. However, our observations support the idea that, at higher temperatures, wetting of composites is mainly influenced by polymer properties rather than interfacial tension at the wood–polymer interface.     

Mechanical,flammability, and thermal properties of polyvinyl chloride‐wood composites with carbide slag

Carbide slag, an industrial waste produced by calcium carbide hydrolysis to prepare C₂H₂ gas, was successfully used as inorganic filler in the production of polyvinyl chloride (PVC)‐wood composites. carbide slag had an average diameter of 8.1 μm which thermally decomposed at about 450°C, and its main component was Ca(OH)₂. Incorporating carbide slag into PVC‐wood composites substantially decreased the flexural, tensile, and impact strength of the composites as a result of the poor interfacial adhesion between carbide slag and PVC matrix, which could be evidently observed from the scanning electron microscopy (SEM) study. To give carbide slag better use, silane coupling agent KH570 were chose to modify carbide slag. The results indicated that adding carbide slag modified by KH570 (MCS) into PVC‐wood composites could significantly improve its notched impact strength and flexural modulus. The thermogravimetric analysis (TGA) data showed that with the addition of MCS, composite had better thermal stability. It also turned out that with the addition of MCS, its smoke suppression property and flammability were enhanced effectively. To ensure sufficient properties of PVC‐wood composites, the optimal adding content of MCS was 20 phr and it leaded to remarkable performance (its flexural modulus was 3.4 GPa, notched impact strength was 3.87 KJ/m², limiting oxygen index value was 41.5% and smoke density ranting was 55.1%), all of which endowed PVC‐wood composites better utilization. All the results indicated that the preparation of PVC‐wood composites with carbide slag could resolve environmental pollution, reuse carbide slag in different fields, and provide a new method for resource utilization of carbide slag. POLYM. COMPOS., 38:2898–2906, 2017. © 2015 Society of Plastics Engineers     

Erratum

Abstract

Abstract

The physical, physicochemical and antimicrobial properties of novel cement type calcium hydroxide/nanohydroxyapatite composites were evaluated by measuring setting time, compressive strength, phase analysis, pH, water solubility and bacterial inhibition zone. Different cement pastes were obtained by mixing biphasic powders (comprising mixtures of calcium hydroxide and nanohydroxyapatite in various weight ratios) and ester of salicylic acid as liquid. Cements with different amounts of nanohydroxyapatite set at approximately 4-14?min and had a compressive strength of 8-16?MPa. The crystalline phases of the set cements were hydroxyapatite and calcium hydroxide. Finally, all composite samples showed antibacterial activity, and the larger zone of bacterial inhibition was observed in composites with higher amount of Ca(OH)₂.     

Modification of poly(vinyl alcohol) with lactose and calcium lactate: potential filler from dairy industry

Abstract

Characteristics of a newly developed environmentally friendly biocomposite material, poly(vinyl alcohol) (PVA) modified with lactose and calcium lactate, potential fillers, byproduct of dairy industry, are reported in the present paper. Sample films containing 0, 10, 20, 33 and 42 wt-% of filler were prepared by conventional solvent casting into acrylic plates. Morphological, mechanical and thermal properties of PVA, PVA–lactose and PVA–calcium lactate composites were studied by optical microscopy, stress–strain analysis, Fourier transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR), differential scanning calorimetry, thermogravimetric analysis (TGA), and also the biodegradability was tested. The films were thin and transparent, and became gradually white with increasing concentration of the filler. Optical microscopy and FTIR–ATR analysis of PVA–lactose and PVA–calcium lactate confirmed that they are composite materials. Their mechanical properties increased up to 33 wt-% filler. The glass transition temperature also decreased with rising content of filler, which indicates the influence of moisture absorbed by the composites (confirmed by TGA measurements). Poly(vinyl alcohol) modification with lactose showed that the biodegradability is improved in aqueous environment.     

Stability of Basalt Fibers in a Medium of Hydrating Cement

The stability of basalt and aluminoborosilicate fibers of different diameters under the effect of an alkaline medium of hydrating cement (concrete) is investigated. Kinetic dependences of CaO absorption by fibers from a saturated solution of Ca(OH)₂ are determined. General regularities of the variation in the breaking strength of fibers after exposure in the specified solution for 3, 6, or 12 months are specified. The obtained data can be used for analysis and deducing estimated dependences of long-time strength of basalt-fiber composites based on cement matrixes.     

Chemistry and Pulping Feasibility of Compression Wood in Black Spruce

Abstract

This research was conducted to study the organic and inorganic constituents and pulping behaviour of compression wood (CW), in comparison to normal wood (NW) and opposite wood (OW). It was found that differences in the chemical properties of OW and NW were not significant, except in alpha-cellulose and hemicellulose content; whereas both differed significantly from CW which contained more lignin and calcium and less alpha-cellulose. These chemical characteristics of CW resulted in high residual lignin and poor pulp yields, in comparison with normal and opposite woods, when different cooking times and temperatures were applied. Bleachable grade pulp could be obtained from normal wood with H-factor 2300. Using CW, however, this was not practical even under severe cooking conditions.     

Adhesion of Polypropylene Fiber to Cement Matrix

Abstract

In this research, the adhesion of polypropylene (PP) fibers to cementitious matrix has been investigated and the chemical bonding and mechanical interlocking between PP fiber and hardened cement paste has been studied. Furthermore, thermodynamic work of adhesion and loss-function (dissipation energy) has been calculated in the PP-cement matrix model system. To investigate the work of adhesion, the pull-out test has been used. Also, the surface free energy and contact angle of the PP monofilaments and cement matrix have been measured using a tensiometer and the fiber–cement interfacial interactions and thermodynamic work of adhesion and loss-function were calculated. Scanning electron microscopy (SEM) analysis was used to study the fiber–cement matrix interfacial transition zone (ITZ). The results showed that the application of theories of polymer–polymer adhesion in fiber–cement matrix systems was feasible. To verify the accuracy of the method, the adhesion of two other fibers (nylon 6,6 and acrylic polymer) was studied.     

Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes

Multi-walled carbon nanotubes after modified by using a H₂SO₄ and HNO₃ mixture solution were added to cement matrix composites. The mechanical properties of the newly formulated composites were analyzed, and the results show that the treated nanotubes can improve the flexural strength, compressive strength, and failure strain of cement matrix composites. The porosity and pore size distribution of the composites were determined by using Mercury intrusion porosimetry, and it is observed that the addition of carbon nanotubes can fine the pore size distribution and decrease porosity. The phase composition was characterized with Fourier transform infrared spectroscopy. It is found that there are interfacial interactions between carbon nanotubes and the hydrations (such as C-S-H and calcium hydroxide) of cement, which will produce a high bonding strength between the reinforcement and cement matrix. The mineralogy and microstructure were analyzed by using scanning electron microscope. It is shown that carbon nanotubes act as bridges across cracks and voids, which guarantees the load-transfer in case of tension.     

Mechanical properties and microstructure of oil-well cement stone enhanced with submicron SiC whiskers

In order to improve the intrinsically brittle nature of the oil-well cement stone, a new type of submicron-fibrous whisker, referred to as the silicon carbide whisker (SiC whisker) was added into cement paste. The cement-based composites were prepared with the various amounts of submicron SiC whiskers. The composites were analyzed via scanning electron microscopy (SEM), mechanical testing, X-ray diffraction (XRD), infrared spectrum analysis (FTIR), and thermal stability analysis in order to understand the enhanced effect that the submicron SiC whiskers had on the applied properties and mechanisms of oil-well cement stone. The compressive strength, the tensile strength, and the flexural strength of the sample with 1% of additional submicron SiC whiskers increased by 9%, 104%, and 26%. The ultimate strain was more than 5%, which increased 194%. The elasticity modulus was 4648.4MPa, which decreased 31.1% after 28 curing days. These improved the mechanical properties of the cement-based composites primarily because of the microscopic mechanism of reinforcement via the submicron SiC whisker, including the bridging effect, the crack deflection, and the pull-out effect.

• HIGHLIGHTS

• A submicron SiC whisker was used to enhance the oil-well cement

• The submicron SiC whisker could significantly increase the mechanical behaviors of the oil-well cement

• The reinforcing mechanism that the submicron SiC whisker had on the oil-well cement was discussed in detail.

• The influence that the submicron SiC whisker had on the integrity of the cement sheaths were evaluated

     

Influence of potassium titanate whisker on the mechanical properties and microstructure of calcium aluminate cement for in situ combustion

This study investigated potassium titanate whisker-reinforced calcium aluminate cement (CAC)-based composites, and evaluated the influence of the quantity (0–5% of the weight of the binder) of potassium titanate whiskers on the mechanical properties of hardened cement mortar. X-ray diffraction analysis and Scanning electron microscopy (SEM) were employed to determine the phase compositions and micro-morphology of the cement composites, respectively. Experimental results indicated that the addition of potassium titanate whisker exhibits significant potential to improve the tensile strength and toughness of cement mortars. The compressive and tensile strengths of samples cured at 50 °C were increased by 46.90 and 74.10%, and the tensile strength samples under high-temperature treatment increased by 113.67%, with the addition of 4% potassium titanate whisker. Typical cement slurry properties, such as basic rheology, free water, and fluid loss could maintain stability when added with 0–5% dosages of potassium titanate whiskers. SEM analysis indicated that the whisker could increase the toughness of oil cement, which contributed to whisker pullout and whisker-cement coalition pullout in the cement matrix.     

Structural characteristics of poly(vinyl alcohol)–calcium carbonate composites prepared by sequential method

Abstract

Composites of poly(vinyl alcohol) (PVA) and calcium carbonate (CaCO₃) were prepared by a sequential method involving first in situ synthesis of CaCO₃ in PVA solution, then physical crosslinking of synthetic suspension and subsequently washing of resultant elastic gel followed by consolidation. The phase and composition, mechanical properties and microstructure of the composites and possible molecular interactions between both components were evaluated. X-ray diffraction analysis revealed that calcium carbonate was mainly composed of aragonite and calcite. Compression tests confirmed the composites prepared by this sequential method had good mechanical properties and that the compressive strength of the composites increased with higher content of calcium carbonate. PVA formed an interconnected network and needle-like CaCO₃ crystals together with some fine grains were well compatible with PVA. In situ synthesis induced a spectral shift of hydroxyl groups and C–O bonds of PVA and the suppression of the characteristic adsorption of calcite was also observed, according to Fourier transform infrared spectroscopy measurements.     

Dynamic mechanical properties of extruded nylon–wood composites

Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon–wood composite in under‐the‐hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon–wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (T_g), physical aging effects, long‐term performance prediction, and comparisons to similar products. The storage modulus of the nylon–wood composite was found to be more temperature stable than pure nylon 66. The T_g range of the nylon–wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon–wood composites have good temperature‐dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon–wood composite with other similar products shows that nylon–wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Adsorption Studies on Modified Magnesia Cement

Abstract

Adsorption removal of actinide and lanthanide ions from aqueous solutions using modified synthetic humic acid magnesia cement was investigated. Experiments were carried out as a function of solute concentration and temperature (25–50°C). Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated. The study showed that the pore diffusion is the rate limiting for the metal ions studied. The results indicated that modified synthetic humic acid magnesia cement (MF‐2) can be used as an efficient adsorbent for removal of actinide and lanthanide ions from radioactive wastewaters.     

Preparation and characterisation of calcium phosphate cement made by poly(acrylic/itaconic) acid

Abstract

In this study, the compressive strength and bioactivity of strong polymeric calcium phosphate cement (PCPC), made by mixing a calcium phosphate powder (a mixture of tetracalcium phosphate and dicalcium phosphate dihydrate) and an aqueous solution of poly(acrylic/itaconic) acid, were investigated. The characteristics of the cement such as phase composition, setting reaction products and microstructure were analysed and compared to those of a control sample made by the same solid phase and water as a liquid. The hard tissue healing capability of PCPC was tested in a rabbit model by radiographical observations of the healing process as well as the cement condition. The results showed that the compressive strength of the set PCPC was ~35 MPa before soaking in a simulated body fluid (SBF), which was much higher than that of the control specimen. However, it sharply decreased when the cement was immersed in the SBF. X-ray diffraction analysis revealed that tricalcium phosphate was formed in the set PCPC and only a small amount of hydroxyapatite was produced after seven days soaking. In contrast, hydroxyapatite was almost the only phase of the control specimen after the soaking period. Radiography tests showed a cement (PCPC) with an irregular macrostructure after three months implantation, with a decreased radiopacity, and without any periosteal or intercortical callus formation.     

The effect of chemical treatment of wood and polymer characteristics on the properties of wood–polymer composites

The physical-mechanical properties and the microscopic structure of caixeta (Chrysophyllum viride) and slash pine (Pinus elliottii) impregnated with polystyrene (PS) were investigated. The influences of a pretreatment with hydrogen peroxide (H₂O₂) solutions utilized in the production of the wood–polymer composites (WPC) and the characteristics of polystyrene formed in situ on the properties of WPC were analyzed. The incorporation of polystyrene improved the compression and static bending properties of slash pine and caixeta. The micrographies confirmed that there were distinct but continuous phases of polymer and wood cell wall which granted the composites a better physical-mechanical behavior. The sensibilizing treatment with dilute hydrogen peroxide solution led to an increase in the viscosity average molecular weight (M _v) of polystyrene, and to the graft polymerization of the monomer, which, in turn, enhanced the stress properties of caixeta–polystyrene composites. Concentrated H₂O₂ solutions degraded caixeta wood, decreasing its tensile properties. Lower initiator concentration favoured higher molecular weight of polystyrene formed in pine wood. A fivefold increase in M _v of PS, however, had little effect on the compression properties of pine–polystyrene composites.     

纳米粒子和PVA纤维增强水泥基复合材料抗裂性能研究

采用两种纳米粒子(纳米SiO2和纳米CaCO3),通过水泥基复合材料抗裂性能试验,探讨了PVA纤维和纳米粒子单掺和复掺两种情况下PVA纤维用量、纳米材料种类和用量对水泥基复合材料抗裂性能的影响.研究结果表明,在PVA纤维增强水泥基复合材料中掺入纳米SiO2,可以显著提高水泥基复合材料抗裂性能,而且在本文试验纳米粒子掺量范围内,水泥基复合材料抗裂性能随着纳米SiO2掺量的增加不断增强;在纳米SiO2水泥基复合材料中掺入PVA纤维,可以提高水泥基复合材料的抗裂性能,当纤维体积掺量不大于1.2%时,PVA纤维体积掺量较大的纳米水泥基复合材料具有较高的抗裂性能;纳米CaCO3与纳米SiO2均能增强水泥基复合材料的抗裂性能,纳米SiO2的增强效果略优于纳米CaCO3.     

Nanoparticles and Apparent Activation Energy of Portland Cement

Although chemically inert nanosize mineral fillers have been shown to modify early cement hydration kinetics, with the effects dependent upon usage rate, particle size, and dispersibility, the effects of such fillers on the “apparent activation energy” (E_a) of cement has not been previously examined. Here, cement E_a was calculated from isothermal calorimetry performed at different temperatures with two different types of fillers (i.e., titanium dioxide and limestone) using a linear method as well as a modified ASTM C1074 method. The use of both types of nanoparticles increased the rate of cement hydration as well as accelerated the reaction rate, due to heterogeneous nucleation effect, as previously demonstrated. E_a increased in the presence of nanosized fillers, demonstrating an increased temperature sensitivity of the filler‐cement composites relative to ordinary cement. These results show that chemically inert nanoparticles behave fundamentally differently compared with supplementary cementitious materials such as fly ash and silica fume which instead decrease temperature sensitivity. The increased temperature sensitivity could thus be used to modify and optimize the reaction mechanism and kinetics of cement hydration, especially to increase the rate of cement hydration, to decrease setting time, and to achieve faster strength gain accounting for higher or lower temperatures during curing.     

Effects of acrylic‐based processing aids on processibility,rheology, thermal and structural stability,and mechanical properties of PVC/wood–sawdust composites

Methyl methacrylate and ethylacrylate (MMA‐co‐EA) and methyl methacrylate and butylacrylate (MMA‐co‐BA) copolymeric processing aids were introduced into poly(vinyl chloride) (PVC)/33.3 wt % wood–sawdust composites containing 0.6 and 2.4 phr of calcium stearate lubricant. The properties of the composites were monitored in terms of processibility, rheology, thermal and structural stability, and mechanical properties. It was found that the mixing torque, wall shear stress, and extrudate swell ratio increased with increasing processing aid content because of increased PVC entanglement. MMA‐co‐BA (PA20) was found to be more effective than MMA‐co‐EA (K120 and K130), this being associated with the flexibility of the processing aids, and the dipole–dipole interactions between sawdust particles and polymeric processing aids. The sharkskin characteristic of the composite extrudate at high extrusion rate was moderated by the presence of processing aids. Adding the acrylic‐based processing aids and lubricant into PVC/sawdust composites improved the thermal and structural stability of the composites, which were evidenced by an increase in glass transition and decomposition temperatures and a decrease in polyene sequences, respectively. The changes in the mechanical properties of the composites involved a composite homogeneity, which was varied by degree of entanglement and the presence of wood sawdust, and un‐reacted processing aids left in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 782–790, 2004