Influence of potassium permanganate pretreatment on mechanical properties and thermal behavior of moso bamboo particles reinforced PVC composites

To illustrate the mechanism of oxidizer treatment on wood cellulose reinforced plastic composites, moso bamboo particles were modified with potassium permanganate aqueous solutions and then filled in polyvinyl chloride (PVC) matrix. Mechanical properties and thermal behaviors of moso bamboo particles reinforced PVC composites (BPPC) were investigated. Results showed that tensile strength of BPPC achieved its maximum value of 13.79 MPa with 0.5% potassium permanganate treatment while modulus of rupture and modulus of elasticity reached their highest values of 30.36 MPa and 3261.89 MPa, respectively, at 0.2% concentration. Potassium permanganate treatment enhanced elongation at break and flexural deformation of BPPC. The melting temperature reached 190.8°C with 0.5% potassium permanganate treatment and the melting enthalpy of crystallization was reduced to 69.82 J/g with 0.2% potassium permanganate treatment. A uniform dispersion of moso bamboo particles in PVC matrix was obtained after potassium permanganate treatment. Low concentration potassium permanganate would oxidize hydroxyl groups of moso bamboo cellulose while too high concentration would degrade moso bamboo cellulose. POLYM. COMPOS., 35:1460–1465, 2014. © 2013 Society of Plastics Engineers     

Tensile properties,morphology, and thermal behavior of PVC composites containing pine flour and bamboo flour

Composites of unplasticized poly(vinyl chloride) (PVC) blended with bamboo flour and pine flour, respectively, were prepared in a batch mixer followed by compression molding. The effects of wood flour fillers on the morphology, static mechanical properties, and thermal properties of the composites were investigated. Compared with neat PVC resin, the introduction of both bamboo flour and pine flour significantly improved the stiffness of the composites, while decreasing the tensile strength to some extent. Tensile tests showed that pine flour–filled composites exhibited better mechanical properties than those filled with bamboo flour with the same particle size at the same loading level. Scanning electron microscopic examination revealed good dispersion and alignment tendency of short pine fiber within the composites at a lower loading level. Moreover, experimental results indicated that both bamboo flour and pine flour additions showed no obviously adverse effect on the thermal stabilities of these composites. Based on the comprehensive properties, these composites meet the need of woodlike material for use as wood structures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1804–1811, 2004     

改性无机黏土/PVC复合材料的制备及性能

比较了3种无机黏土(超细无机黏土A、偶联剂表面改性无机黏土B、实验室自制大分子表面处理剂DF包覆改性无机黏土C)对PVC材料力学性能、微观形貌的影响,重点研究了无机黏土C对PVC材料动态力学性能、耐热性能的影响。结果表明:①适量添加无机黏土可以提高PVC材料的拉伸性能和冲击性能;②无机黏土C/PVC复合材料具有很好的耐热性能;③无机黏土C的填充效果较好。     

Effects of chicken eggshell filler size on the processing,mechanical and thermal properties of PVC matrix composite

The effects of filler particle size of poly(vinyl chloride)/chicken eggshell powder (PVC/ESP) composites on the processing, tensile properties, morphology and thermal degradation were investigated. The mixing of composites was done using Rheomix internal mixer. The processing torque of PVC/ESP composite at a particle of 0.2 μm exhibits lower processing torque compared to that at a particle size of 7 μm due to the dispersive resistance from larger ESP filler particles. Good interfacial adhesion exists between the filler and matrix in composites prepared via a filler particle size of 0.2 μm, which has improved the tensile strength and modulus of PVC/ESP composite compared to a filler particle size of 7 μm as justified from FESEM images on the tensile fracture surface of the composites. Thermogravimetric analysis results show that the filler particle size of 0.2 μm composite exhibits higher thermal stability compared to the filler particle size of 7 μm composite.     

Experimental and computational study on the bubble behavior in a 3-D fluidized bed

The results from a two-fluid Eulerian–Eulerian three-dimensional (3-D) simulation of a cylindrical bed, filled with Geldart-B particles and fluidized with air in the bubbling regime, are compared with experimental data obtained from pressure and optical probe measurements in a real bed of similar dimensions and operative conditions. The main objectives of this comparison are to test the validity of the simulation results and to characterize the bubble behavior and bed dynamics. The fluidized bed is 0.193 m internal diameter and 0.8 m height, and it is filled with silica sand particles, reaching a settle height of 0.22 m. A frequency domain analysis of absolute and differential pressure signals in both the measured and the simulated cases shows that the same principal phenomena are reproduced with similar distributions of peak frequencies in the power spectral density (PSD) and width of the spectrum. The local dynamic behavior is also studied in the present work by means of the PSD of the simulated particle fraction and the PSD of the measured optical signal, which reveals as well good agreement between both the spectra. This work also presents, for the first time, comparative results of the measured and the simulated bubble size and velocity in a fully 3-D bed configuration. The values of bubble pierced length and velocity retrieved from the experimental optical signals and from the simulated particle fraction compare fairly well in different radial and axial positions. Very similar values are obtained when these bubble parameters are deduced from either simulated pressure signals or simulated particle volume fraction. In addition, applying the maximum entropy method technique, bubble size probability density functions are also calculated. All these results indicate that the two-fluid model is able to reproduce the essential dynamics and interaction between bubbles and dense phase in the 3-D bed studied.     

Influence of tacticity on the thermal degradation of PVC. VI. New advances in the degradation process through the behavior of modified PVC samples

Three PVC samples having different tacticities, as well as the products resulting from their reaction with sodium thiophenate, which was previously found to occur selectively by some definite isotactic conformations, were degraded at 180°C in solid state up to 0.3%. In agreement with prior works, the stability of the substituted polymers was shown to be higher as the substitution extent increased up to a definite value, which depends on the overall isotactic content of the starting materials. On the other hand, the found changes in polyene distribution for the degraded samples with the substitution extent, as followed by UV-visible spectroscopy, demonstrate that the specific bands at 393, 416, and 437 nm, which are known to be characteristic for the most unstable PVCs, arise from the lability of some chlorine atoms located at GTTG′ (or TTTG) conformations, as prior results suggested. On the basis of the so-obtained correlation between the content of some isotactic triads (especially the GTTG′) and both the thermal instability and the formation of the above-indicated specific polyenes, new advances in the degradation mechanism are proposed.     

聚氯乙烯结晶行为的研究进展

聚氯乙烯结晶结构对聚氯乙烯性能有很大的影响。文中综述了聚合温度、增塑剂、热处理等因素对聚氯乙烯结晶行为的影响，分析了聚氯乙烯结晶的特点，并总结了聚氯乙烯结晶与制品性能的关系。     

Experimental study of PLA thermal behavior during fused filament fabrication

Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts.     

An investigation into the thermal stability of PVC/montmorillonite composites

An effective stabilizing system for poly (vinyl chloride) (PVC)/clay composites was established. Different types of stabilizers, i.e., organotin, calcium/zinc, barium/zinc, and an epoxy costabilizer, were investigated. The combination of the organotin stabilizer and the epoxy costabilizer was the most effective stabilizing system. Different grades of Cloisite nanoclays were investigated. Cloisite Na did not cause premature degradation of PVC. Cloisite 10A strongly accelerated the degradation of PVC because of the presence of excess surfactant, while a PVC/Cloisite 30B system showed much better thermal stability because there was less organic impurity in the Cloisite 30B. Phosphonium‐modified clays were also prepared. They showed better thermal stability than ammonium‐modified clays, but the drying conditions still need to be optimized in order to produce a dispersible clay powder. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

A new proposed model for dielectric behavior of PVC/rice husk composites

Ecofriendly materials are becoming a need of the day. We have severe setback when there is lot of use of agro wastes in plastics. To reduce pure plastic use in agriculture, this study has been made to find some remedial measure. In the process, we sought the effect of addition of rice husk (RH) in polyvinylchloride (PVC) on the dielectric properties at different frequency and temperature has been studied. Measurements have been performed in the frequency range from 1 to 10 kHz and temperature range of 32–80°C. The experimental results show that dielectric constant (ε′) increases with the addition of RH in PVC. Dielectric constant (ε′) decreases with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. Dielectric constant (ε′) increases with increasing temperature due to greater freedom of movement of dipoles within PVC at higher temperatures. A theoretical model for dielectric constant with temperature and frequency dependent is proposed. Experimental results are in good agreement with the proposed theoretical model. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PEW-g-MAH改性竹粉对PVC材料加工性能的影响

采用自制的聚乙烯蜡接枝马来酸酐(PEW-g-MAH)对竹粉进行包覆改性,研究了竹粉用量对竹粉/PVC复合材料加工性能的影响,并通过SEM对其界面进行了观察。结果表明:①竹粉/PVC复合材料的平衡转矩、平衡温度、塑化时间均随竹粉用量的增加而增大;②与未改性竹粉相比,经过PEW-g-MAH处理的竹粉可降低竹粉/PVC复合材料的平衡转矩、平衡温度,稍微缩短塑化时间;③SEM照片表明,PEW-g-MAH不仅改善了竹粉在PVC基体中的分散性,而且提高了两者的相容性。     

硫酸铝铵相变蓄热材料实验研究

通过对硫酸铝铵[NH4Al(SO4)2.12H2O]的实验研究,寻找减小其过冷度,改善其储热性能的方法。按照溶液配制法,在熔融的硫酸铝铵中依次加入适量的有效添加剂及去离子水,记录蓄热体系放热时的温度变化,反复调节添加剂的质量比,达到最佳配置。结果表明,硫酸铝铵中添加质量分数为1.8%的氟化钙、0.4%的碳、6%的去离子水能够较好地抑制过冷,保证放热速率。重复性实验验证,该材料是低温范围内具有较高相变温度、相变潜热大、放热性能稳定、重复性良好的蓄热材料,可以应用于电蓄热、回收城市废热等领域。     

Experimental and computational study of thaumasite structure

The structure of thaumasite has been studied experimentally by means of a single crystal X-ray diffraction and FTIR methods, and theoretically using density functional theory (DFT) method. Very good agreement was achieved between calculated and experimental structural parameters. In addition, calculations offered the refinement of the positions of the hydrogen atoms. The detailed analysis of the hydrogen bonds existing in the thaumasite structure has been performed. Several types of hydrogen bonds have been classified. The water molecules coordinating Ca^2 +cation act as proton donors in moderate OH⋯O hydrogen bonds formed with CO₃^2 −and SO₄^2 −anions. The multiple OH⋯O hydrogen bonds exist among water molecules themselves. Finally, relatively weak hydrogen bonds form water molecules with the OH groups from the coordination sphere of the Si(OH)₆^2 − anion. Further, calculated vibrational spectrum allowed complete assignment of all vibrational modes which are not available from the experimental spectrum that has a complex structure with overlapped bands, especially below 1500 cm^− 1.     

Design of green zinc‐based thermal stabilizers derived from tung oil fatty acid and study of thermal stabilization for PVC

In this study, a new type of mixed calcium (Ca) and zinc (Zn) thermal stabilizers was prepared and evaluated for poly(vinyl chloride) (PVC) thermal stabilization. The mixed stabilizers were based on the Ca and Zn salts of polycarboxylic acid derived from eleostearic acid—the dominant fatty acid of tung oil fatty acids. Eleostearic acid was converted to a 21‐carbon diacid (C21DA) and a 22‐carbon triacid (C22TA), respectively, which were subsequently turned into calcium (Ca) and zinc (Zn) salts. Thermal stability of PVC compounds was examined by thermogravimetric analysis (TGA), discoloration test, Congo red test, and thermal decomposition kinetics. In comparison, commercial mixed Ca/Zn thermal stabilizers composed of stearate salts (CaSt₂/ZnSt₂), were employed as controls. Because the salts of C21DA, C22TA and stearate have different metal contents, thermal stabilization effects were compared on the basis of both equal salt weight and equal metal ion content. It was noted that under both cases the long‐term thermal stability of the PVC samples followed the order of C21DA‐Ca/C21DA‐Zn > C22TA‐Ca/C22TA‐Zn > CaSt₂/ZnSt₂. The results suggest that the mixed Ca/Zn salts based on tung oil‐derived polycarboxylic acids have higher metal ion contents and cycloaliphatic structures and can effectively improve the thermal stability of PVC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44679.     

Experimental investigation of mechanical,thermal, and ablation performance of ZrO2/SiC modified C-Ph composites

In this study, an effort has been made to improve the mechanical, thermal, and ablation performance of carbon-phenolic (C-Ph) composites. The ZrO₂, SiC, and ZrO₂/SiC hybrid fillers were synthesized using sol-gel method followed by individual incorporation into C-Ph composites. The thermal stability and flexural strength of these C-Ph composites were analyzed using thermogravimetry analysis and three-point bending test, respectively. A significant improvement in the flexural strength and modulus of the reinforced C-Ph composites was observed and also exhibited the higher thermal stability. The oxyacetylene flame test was conducted to measure the ablation behavior of these filler reinforced C-Ph composites under a heat flux of 4.0 MW/m² for 60 seconds. ZrO₂/SiC0.5 reinforcement in the C-Ph composite decreased the linear and mass ablation rates by 46% and 22%, respectively when compared with pure C-Ph composite. The surface morphology analysis revealed that the burnt composite covered with the ZrC ceramic phase and SiO₂ bubble-like structure, which could have improved the ablation resistance of composites. These results were found well within the acceptable range when using the surface energy dispersive spectroscopy and X-ray diffraction analysis.     

Comparative study on the properties of wood polymer composites based on different modified soybean oils

The growing awareness for greener and more sustainable technologies has focused the attention of researchers recently for the development of high performance biopolymer-based composites. Wood polymer composites (WPC) based on functionalized epoxidized soybean oil (ESO) and soft wood, Krishnachura (Delonix regia), were prepared by compression molding technique. ESO was functionalized by acrylic acid (AESO), methacrylic acid (MESO), and methacrylic anhydride (MAESO), which were used as matrices in the composite. Wood flour from soft wood was used as reinforcing agent. The fiber/resin ratio was maintained at 40:60. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Mechanical testing, limiting oxygen index (LOI), and swelling behavior were checked for the prepared composites. WPC based on methacrylic anhydride exhibited maximum improvement in properties.     

Silica-silicon composites for near-infrared reflection: A comprehensive computational and experimental study

Compact layers containing embedded semiconductor particles consolidated using pulsed electric current sintering exhibit intense, broadband near-infrared reflectance. The composites consolidated from nano- or micro-silica powder have a different porous microstructure which causes scattering at the air-matrix interface and larger reflectance primarily in the visible region. The 3 mm thick composite compacts reflect up to 72% of the incident radiation in the near-infrared region with a semiconductor microinclusion volume fraction of 1% which closely matches predictions from multiscale Monte Carlo modeling and Kubelka-Munk theory. Further, the calculated spectra predict a reddish tan compact with improved reflectance can be obtained by decreasing the average particle size or broadening the standard deviation. The high reflectance is achieved with minimal dissipative losses and facile manufacturing, and the composites described herein are well-suited to control the radiative transfer of heat in devices at high temperature and under harsh conditions.     

Mechanical and thermal properties of polypropylene/modified basalt fabric composites

Basalt fabric (BF) was first treated with silane coupling agent KH550, modified basalt fabric (MBF) was obtained. Then MBF were molded with polypropylene (PP) matrix, and polypropylene/modified basalt fabrics (PP/MBF) composites were obtained. The influence of concentration and treating time of KH550 on MBF were characterized by hydrophilicity and lipophilicity. The tensile strength and morphology of basalt fabric were tested by single filament strength tester and scanning electron microscopy. The mechanical properties of composites were measured with electronic universal testing machine and impact testing machine, and the thermal properties were tested by thermogravimetric analysis and dynamic mechanical analysis. The results showed that the lipophilicity of MBF is improved significantly by KH550 while the tensile is nearly damaged. The mechanical properties of composites are larger than that of pure PP, among which the impact property was improved the most, showing 194.12% enhancement. The thermal stability and dynamic viscoelasticity were better than pure PP; furthermore, the concentration of KH550 virtually had no effect on the thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42504.     

UV curing of composites based on modified unsaturated polyester

Synthesis and photocrosslinking of glass fiber-reinforced composites, based on epoxy acrylate-modified unsaturated polyester, have been investigated. The efficiency of the photocrosslinking process for glass fiber laminates of the polyesters that contain different comonomers has been evaluated by measuring mechanical properties. The data show (i) that 2 mm thick laminates, containing 30–40% glass fiber mats, are cured with UV irradiation for 15 sec at room temperature in air; (ii) that multifunctional acrylate or acrylether monomers added to the polyester resin improve the tensile and flexural properties of the photocured product to a greater extent than do added allylic monomers, due to the different photocrosslinking mechanisms; (iii) that the physical properties of the photocrosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. © 1994 John Wiley & Sons, Inc.     

A study on the effect of cenosphere on thermal and ablative behavior of cenosphere loaded ceramic/phenolic composites

Composites of ceramic woven and phenolic resin filled with cenosphere were prepared and their thermal properties and ablative properties were studied by Thermogravimetric Analysis (TGA) and oxyacetylene ablation test. Classical thermal stability parameters, based on initial decomposition temperature and mass loss at various temperatures were calculated before and after subtraction of cenosphere concentration from the TGA curves. Ablation behavior of the filled composites were investigated based on the linear ablation rate, mass ablation rate and back face temperature profiles. Without cenosphere mass subtraction, the thermal stability of the filled composites seems to be improved and reduction of mass loss was achieved with addition of cenosphere. Ablation results showed that the addition of cenosphere content exhibits the favorable ablation resistance. In comparison to neat ceramic/phenolic composites, the introduction of micro sized cenosphere particles embedded in the phenolic matrix significantly improved the ablative properties in terms of mass ablation rate and linear ablation rate.