Composites of poly(vinyl acetate) filled with calcium carbonate: Microscopy,diffractometry and thermophysical properties

Calcium carbonate (CaCO₃) is used as filler in poly(vinyl acetate)(PVAc) composites to enhance the mechanical properties. The filler is often commercially surface treated with stearic acid to optimize the interfacial bonding and wetting. The effects of the interface on properties were studied using scanning electron microscopy (SEM) of films with initial and deformed morphologies. Plasticizing additives cause a significant change in the appearance of the films and a reduction in the glass transition temperature of the matrix from 40°C to ≈ 18°C, which was not altered by further addition of the filler. A PVAc composite fracture surface shows the particles adhering well to the matrix, suggesting good adhesion and reinforcement. The SEM study is complemented by WAXD, SEM/X-SEM, XPS, and thermal analysis.     

Effect of clinoptilolite filler on the physical and mechanical properties of polypropylene

This study aims to investigate the mechanical and physical properties of polypropylene (PP) filled by natural zeolite. For this purpose, a natural zeolite (at 1–6 wt% filler loadings) with two different particle sizes was used. Two different kinds of silane coupling agents (3‐aminopropyltriethoxysilane, GAPTES and 3‐glycidoxypropyltrimethoxysilane, GPTMS) at three different volume ratios were used to improve the zeolite compatibility with PP and to improve the mechanical properties of composites. Fillers and PP were compounded with a twin screw extruder, and the composites were moulded with injection moulding press. The samples were subjected to mechanical tests (i.e., impact and tensile tests) and physical tests (i.e., hardness, density, and melt flow index, MFI). The physical test results showed that the levels of hardness and density of both unmodified and modified zeolite‐filled PP composites were higher compared with neat PP. The MFI values of composites were decreased by increasing zeolite loading level. Composites including GAPTES modified zeolite showed improved yield strength, impact strength and stiffness compared with composites filled with unmodified zeolite particles. POLYM. COMPOS. 34:1396–1403, 2013. © 2013 Society of Plastics Engineers     

Enhanced mechanical properties of acrylate based shape memory polymer using grafted hydroxyapatite

In the present study, the effect of grafted and ungrafted hydroxyapatite (HAp) filler on the mechanical properties of acrylate based shape memory polymer (SMP) composite is reported. HAp is grafted with polyethylene glycol methacrylate (PEGMA) monomer to avoid agglomeration and the same is embedded as reinforcement in tBA – PEGDMA matrix (70 wt% tBA: tert-butyl acrylate +30 wt% PEGDMA: polyethylene glycol dimethacrylate). The grafting process improved the interfacial interactions of the particles, dispersed in the polymer system and subsequently enhanced the mechanical properties of the shape memory polymer composites. The morphology of HAp particles is investigated by field emission scanning electron microscopy. The mechanical properties of SMP composites are evaluated at room temperature and above glass transition temperature (Tg) with grafted and ungrafted HAp particles. The addition of grafted HAp significantly improved the tensile strength (40%) and shape recovery rate (25%) of the SMP composite when compared to the SMP composite containing ungrafted HAp. SMP composite containing grafted HAp exhibited higher cell viability compared to the neat SMP and the SMP composite containing ungrafted HAp.     

Viscoelastic,mechanical, and thermal characterization of fly ash‐filled ABS composites and comparison of fly ash surface treatments

In the present investigation, viscoelastic, mechanical, thermal properties, and microstructural analysis of ABS reinforced with various surface treated fly ash (FA) has been studied. FA particles were surface treated with various chemical reagents, i.e., Ca(OH)₂, NaOH, and Bis(3‐triethoxysilylpropyl)tetrasulfane (Si69) to improve the interfacial adhesion between ABS and FA. DMA tests confirmed an increase in the stiffness in the surface treated composites. Hybrid ABS/FA composites showed optimum storage modulus and T_g as compared with the virgin matrix. TGA analysis also showed higher thermal stability of ABS/FA composites than virgin matrix with the surface treatments of FA. The treated FA composites also show improved mechanical properties compared to untreated FA composite. The morphology of virgin matrix, untreated and treated FA composites was studied employing SEM. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Contribution of surface silanization process on mechanical characteristics of TPU-based composites involving feldspar and quartz minerals

In this study, quartz and feldspar powders were surface treated using a silane coupling agent to achieve a more compatible mineral surface with the polymer matrix. Details of surface characteristics of minerals were examined by energy-dissipative X-ray spectroscopy, contact angle measurements, and infrared spectroscopy. Thermoplastic polyurethane-TPU was compounded with minerals using the melt-blending technique. Mechanical, thermo-mechanical, melt-flow, and morphological characterizations of TPU and relevant composites were performed by utilizing tensile and Shore hardness tests, dynamic mechanical analysis (DMA), melt flow index (MFI) measurements, and scanning electron microscopy (SEM), respectively. Water repellency of TPU and composites were also evaluated experimentally. Effects of surface treatments were discussed by comparing the results of composites filled with pristine and modified minerals. Results revealed that enrichment of quartz and feldspar surfaces confer mechanical and thermo-mechanical performance of composites. Mineral inclusions caused no drastic changes to the MFI parameter of TPU. The silane layer on the mineral surface displayed a barrier effect to water uptake of composites. Homogeneous dispersion and improved interfacial adhesion of mineral particles to the TPU phase were confirmed with help of SEM observations. Quartz exhibited slightly higher performance thanks to its silica-rich composition. The findings of this research exhibited the considerable influence of the silane layer on the mineral surface on the mechanical performance of TPU-based composites.     

Synthesis of hydroxyapatite/poly(vinyl alcohol phosphate) nanocomposite and its characterization

Hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared using a solution‐based method varying HAp from 10 to 60% (w/w). X‐ray diffraction, Fourier transform infrared absorption spectra (FTIR), and thermal analysis have indicated the presence of bonding between HAp particles and PVAP matrix. Transmission electron microscope analysis shows the needle‐like crystals of HAp powder having a diameter of 6–10 nm and a length of 26–38 nm. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. Particle size distribution analysis shows the narrow distribution of hydrodynamic particles in the polymer matrix. The tensile stress–strain curves show the improvement in mechanical properties of the composites with increase in amount of HAp particles loading. The composites along with polymer are highly hemocompatible. The use of PVAP promotes the homogeneous distribution of particles on the polymer matrix along with strong particle–polymer interfacial bonding, which has supported the improvement in mechanical properties of the composites. The prepared HAp/PVAP composite with uniform microstructure would be effective to act as a potential biomaterial. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

PTC effect in HDPE filled with carbon blacks modified by Ni and Au metallic particles

Several types of positive temperature coefficient (PTC) composites are prepared by using Ni and Au modified carbon black. The major aim of this work was the lowering of the room temperature resistivity of the composites by enhancement of electrical conduction of the CB particles by incorporating metallic particles. Investigations showed that the metal particles fill the cavities and surface defects of the CB and thus surface free area reduces after modification. Metallic particles also change the nature of the CB particles after modification. Several types of PTC composites were prepared by using modified and unmodified CB by several loading level of filler. Measuring electrical properties of the PTC samples showed that the Ni modified CB reduce room temperature resistivity to lower than that of PTC composites prepared by unmodified CB. PTC composites prepared by Au modified CBs showed very different properties compared to PTC composites prepared by Ni modified CB. Their resistivities were quite higher than the others showing a poor compatibility between the matrix and Au modified CB. The effect of thermal annealing also investigated on the electrical properties of the prepared composites. Room temperature resistivities reduced for most of the samples while PTC intensities increased after annealing. Theoretical bases are employed to discuss the room temperature resistivity and PTC behavior of the composites before and after annealing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Surface modification of ultra‐high‐molecular‐weight polyethylene. II. Effect on the physicomechanical and tribological properties of ultra‐high‐molecular‐weight polyethylene/poly(ethylene terephthalate) composites

We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching, with the aim of improving the performance of its composites with poly(ethylene terephthalate) (PET) fibers. In this article, we report on the morphology and physicomechanical and tribological properties of modified UHMWPE/PET composites. Composites containing chemically modified UHMWPE had higher impact properties than those based on unmodified UHMWPE because of improved interfacial bonding between the polymer matrix and the fibers and better dispersion of the fibers within the modified UHMWPE matrix. Chemical modification of UHMWPE before the introduction of PET fibers resulted in composites exhibiting improved wear resistance compared to the base material and compared to unmodified UHMWPE/PET composites. On the basis of the morphological studies of worn samples, microploughing and fatigue failure associated with microcracking were identified as the principle wear mechanisms. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

表面改性对聚丙烯/微米氢氧化镁复合材料性能的影响

研究了表面处理剂（钛酸酯和硅烷偶联剂）和原位聚合方法对聚丙烯/微米氢氧化镁（MH）复合材料的力学性能及流变性能的影响。采用DSC、SEM和毛细管流变仪对PP/MH（80/20）复合材料的性能进行了研究。结果表明：原位聚合改性后的微米MH与PP基体间的界面黏结力得到了加强,复合材料的冲击强度较填充未改性MH的复合材料提高了26.4 ％。在PP基体中添加聚合物包覆改性微米MH粒子的复合材料熔体流动速率较纯PP上升了64 ％。在相同剪切速率下,填充聚合物包覆改性MH的复合材料熔体表观黏度明显低于填充未改性微米MH的复合材料,表明聚合物包覆改性后的MH降低了其对PP熔体流动的阻碍作用,改善了PP/MH复合材料的流动性能。     

Preparation and characterization of UV-curable epoxy/silica nanocomposite coatings

To enhance the interfacial interaction in silica nanoparticles filled polymer composites, the silica surface was firstly treated with glycidoxypropyl trimethoxysilane (GPTMS), and its structure was analyzed by ¹³C NMR and FTIR spectrophotometry. Then a series of GPTMS-modified silica/cycloaliphatic epoxy nanocomposite coatings with 0–6 wt% silica content were prepared by UV-induced cationic polymerization in the presence of a diaryliodonium photoinitiator and thioxanthone photosensitizer. The physical and mechanical properties such as hardness, adhesion, gloss, impact as well as tensile strength were examined. As a result, these composites demonstrated superior tensile strength and tensile modulus with increasing proportion of modified silica up to a certain level. An increase in abrasion resistance of nanocomposites with the addition of modified silica was observed. The thermal stability of nanocomposites was not enhanced with the addition of silica particles. SEM studies indicate that silica particles were dispersed homogenously through the polymer matrix.     

Morphology and failure in nanocomposites. Part I: Structural and mechanical properties

Nanocomposites are expected to exhibit new and improved properties when compared to their microcomposite counterparts. By lowering the particle size to nanodimensions (<100 nm), the special effects in polymer composites appear. In this study we compared the properties of composites filled with micro- and nano-sized calcium carbonate (CaCO₃) filler particles in poly (vinyl acetate) (PVAc) matrix. The morphology of the composite was found to be responsible for the composite properties. The filler nanoparticles are dispersed in the matrix in the form of a 'net-like' structure, contrary to microparticles, which are dispersed as 'islands' in the matrix. The other systems investigated in this study were based on polyacrylate (PA) copolymer matrices filled with layered kaolin filler, which is well suited for creating nanocomposites. Mathematical models were used to quantify the interfacial interactions in the composites under investigation. Improved mechanical properties are obtained where there is a strong interfacial bond between the matrix and the filler. It seems that a key characteristic of the nanocomposites is the formation of a three-dimensional interphase with a significant amount of matrix with restricted chain mobility. The restricted molecular mobility in PVAc/CaCO₃ nanocomposites resulted in changes of relaxation behavior, i.e. in the appearance of a second transition above the T_g but only at large enough loading.     

Morphology and properties tuning of PLA/cellulose nanocrystals bio-nanocomposites by means of reactive functionalization and blending with PVAc

A novel method for the preparation of PLA bio-nanocomposites containing cellulose nanocrystals (CNCs) is reported. In order to enhance interfacial adhesion and dispersion of nanocrystals into PLA matrix, functionalization of PLA and CNCs by radical grafting of glycidyl methacrylate (GMA) and pre-dispersion of CNCs in poly (vinyl acetate) (PVAc) emulsion were applied. Morphologies, thermal and mechanical properties of nanocomposites for CNCs content of 1–6 wt.% were examined. Addition of functionalized components (PLA-GMA, CNC-GMA) and/or PVAc dispersed CNCs both improved the phase distribution of nanofiller and tensile properties, compared to the binary PLA/CNC nanocomposites. Thermal analyses demonstrated that glass transition, melting temperature and crystallinity of PLA were affected by the PVAc amount. Nanocomposites with PVAc dispersed CNCs exhibited higher thermal resistance than other composites. The filler effectiveness (CFE) was evaluated for all samples on the basis of storage modulus values: CNC-GMA and PVAc dispersed CNCs (3 wt. %) resulted the most effective fillers.     

Fabrication and characterization of HCl‐treated clinoptilolite filled ethylene vinyl acetate composite films

As received and HCl treated Clinoptilolite (C)‐ethylene vinyl acetate (EVA) composites were prepared via the melt‐mixing technique, and extruded through a single‐screw extruder to obtain composite strips with an average thickness of 0.5 mm. The films were then characterized for their morphological, structural, thermal, and mechanical properties. Optical micrographs show that at higher C loading, the particles form large agglomerates, resulting in the formation of voids on the surface of the films. With increasing zeolite loading, the films become brittle, resulting in reduced Young's modulus. Acid treatment of the C tends to affect the crystal structure of the zeolite, resulting in poor tensile properties of the HCl‐treated zeolite‐filled EVA films. Addition of the zeolite also increased the crystallinity of the structure, acting as a nucleating agent in the EVA crystallization. Modeling of the tensile yield data with Pukanszky model indicate that there is poor interfacial adhesion between the polymer matrix and the filler particles. Thermal characterization studies showed that addition of the zeolites retarded the onset degradation temperature of EVA. However, degradation temperatures including T_max and the final decomposed temperature were increased, suggesting improved thermal stability due to reduced inter‐chain mobility in the composite materials as a result of increased zeolite loading. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of thermoplastic olefin/nanosilica composites using a silane-grafted polypropylene matrix

This work reports the morphology and physical properties of silane-grafted polypropylene (PP-g-VTEOS) reinforced with silica nanoparticles and toughened with an elastomeric ethylene-octene copolymer (POE). Vinyltriethoxysilane (VTEOS) was grafted to polypropylene (PP) to form (PP-g-VTEOS), using a peroxide-initiated melt compounding technique. TEM observations of composites containing up to 7 wt% of the nanosilica revealed good dispersion of the silica nanoparticles, which partitioned selectively within the PP-g-VTEOS matrix. Rheological characterization in the linear viscoelasticity region showed significant increases in the low-frequency complex viscosity, storage and loss moduli, which stem from the polymer/filler and filler/filler interactions. The effects of surface treatment of the nanosilica on the morphology, thermal and mechanical properties of the composites were also investigated. The mechanical properties of the composites were greatly enhanced in terms of tensile and flexural strength, while impact strength was preserved when the silane-treated nanosilica was used.     

Fiber–Matrix Interfacial Characteristics in a Fiber-Reinforced Ceramic-Matrix Composite

Fiber—matrix interfacial shear stress and mechanical properties in zirconmatrix composites uniaxially re-inforced with either uncoated or BN-coated silicon carbide filaments were measured in the as-fabricated state and after a thermal treatment at 1300°C for 100 h. All the tested composites showed higher fiber—matrix interfacial debond stress than frictional stress and toughened-composite behavior. Mechanical properties of composites reinforced with uncoated filaments were unaffected by an annealing treatment at 1300°C for 100 h. In contrast, an identical annealing treatment given to a composite reinforced with BN-coated filaments led to a decrease in first matrix cracking stress and ultimate strength. These observations were related to the changes in the measured interfacial shear stress values as a result of the annealing treatment.     

Novel copolymer for SiO2 nanoparticles dispersion

High performance polymers exhibiting multifunctional characteristics can be achieved by the introduction of inorganic nanoparticles like SiO₂ into the functional polymers. In the present work a copolymer epoxy poly(dimethylacrylamide) was synthesized to disperse the SiO₂ nanoparticles. The aim of the work is to develop a new method/process/material for the dispersion of nanoparticles and evaluating the performance of these composites. FT‐IR studies of the polymer adsorbed SiO₂ nanoparticles confirmed that the polymer molecules chain was anchored on the surface of the SiO₂ nanoparticles. The improved interfacial interaction between the particles and polymer enhanced the thermal properties of the composites. The results also show the newly synthesized polymer disperse the nanoparticles well as evidenced by SEM analysis, the uniformly dispersed SiO₂ nanoparticles in the polymer matrix and the particles almost remained in their original shape and size even after incorporation in to the polymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication of thermally conductive composite with surface modified boron nitride by epoxy wetting method

Boron nitride (BN) particles fabricated with different surface treatments were used to prepare thermally conductive polymer composites by epoxy wetting. The polar functionality present on the BN particles allowed the permeation of the epoxy resin because of a secondary interaction, which allowed the fabrication of a composite containing high filler concentration. The different cohesive energy densities of the synthesized material due to a functional-group-induced surface treatment effect on surface free energy and wettability determined the thermal and mechanical properties of the polymer. The results indicate that surface-curing agents interrupt the interaction between the filler and matrix, and do not always enhance thermal conductivity. Moreover, the composites showed maximum thermal conductivity at 30 wt% epoxy loading when the fixed-pore volume fraction reached in the filtrated BN film. The measured storage modulus was also enhanced by surface treatment because of the sufficient interface produced and interaction between the large amount of the filler and epoxy.     

SrTiO3 as a new solar reflective pigment on the cooling property of PMMA-ceramic composites

Polymer-ceramic hybridization is an important method for preparing functional materials. Strontium titanate (SrTiO₃, ST), a typical perovskite ceramic, has been widely applied in the electronics industry and photocatalytic fields. However, ST was barely reported to be utilized in cool materials. Herein, ST ceramic, as a solar reflective pigment, was introduced into a polymer matrix to prepare cool material. Specifically, the influences of both weight contents and surface grafting modification about ST on the properties of poly(methyl methacrylate) (PMMA)/ST composites were investigated, which include cooling performance, surface roughness, thermal emissivity, dispersion of particles and mechanical strength. The obtained composites containing 20 wt% unmodified ST possess excellent cooling property due to high thermal emissivity (86.8%, in 8–13 μm) and high solar reflectance (70.7%, in the whole solar band) which increased by 142% than that of pure PMMA resin. Temperature test highlighted that the composites containing 20 wt% unmodified ST was only 26.6 °C, 11.4 °C lower than that of PMMA resin and only 2 °C higher than initial temperature. Moreover, the surface grafting modification of ST by the silane coupling agent was proved to improve the dispersibility of ST in PMMA resin. Both the cooling and mechanical properties of composites containing modified ST particles were further improved. Though the solar reflectance of PMMA/ST composites was lower than that of PMMA/TiO₂ composites, temperature tests showed that the PMMA/ST composites had a similar cooling performance with the PMMA/TiO₂ composites when the content of the ceramic particles were 5.8 v%. This work not only prepared the polymer-ceramic hybrid materials with excellent cooling performance but also expanded the application of ST ceramic in the field of composites.     

Synthesis and modification of silica-based epoxy nanocomposites with different sol–gel process enhanced thermal and mechanical properties

This research article describes the results of nano-silica composites filled with different epoxy contents containing nano-SiO₂ particles from (5–25 wt%). Reinforcing hybrid composites enhance thermal and mechanical properties to achieve vital and sustainable products. Silica-based nanocomposites with high purity were prepared and used for the surface modification of nanosized silica particles. The surface structure's composition and physical properties of modified nano-SiO₂ particles were characterized through Fourier transferred infrared spectrometer, X-ray photoelectron spectroscopy, thermogravimetric analyzer, and scanning electron microscopic. Silica-based nanocomposites were prepared by incorporating of modified nano-SiO₂ as an enhancing filler. The morphology of fracture surface and dynamic mechanical properties were investigated. Results showed that the silica-based epoxy nanocomposites are bearing a long chain structure that could improve the compatibility of silica nanocomposites with epoxy resin and contribute to a better dispersion state in the matrix, which enhanced the overall performance of epoxy-cured products.     

Poly(lactic acid) and zeolite composites prepared by melt processing: Morphological and physical–mechanical properties

Poly(lactic acid), PLA, composites containing 0, 1, 3, and 5 wt % zeolite type 4A were prepared using extrusion/injection compounding techniques. Morphological characterizations were carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Physical properties were evaluated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) and mechanical properties by standard tensile testing. The morphological studies showed a homogenous dispersion of zeolite particles within the PLA matrix. As the fracture stress propagated, zeolite particles remained embedded into the matrix, indicating the existence of good interfacial adhesion between zeolite particles and the PLA matrix. The improvement in the interfacial adhesion was also confirmed by applying Nicolais‐Narkis and Pukanszky models. The percent crystallinity of the PLA and the temperature‐ dependant elastic and viscous modulus of the composite increased with the proportion of zeolites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010