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Syntactic foam made from hollow glass microspheres (HGM) in an epoxy matrix has proven to be a good material with a strong structural strength. Understanding filler particle size variation is important in composite material formation, especially in syntactic foam, because of its numerous applications such as aerospace, marine, and structural purposes. In this present work, the effects of particle variation in different sizes (20–24 µm, 25–44 µm, 45–49 µm, and 50–60 µm) on the mechanical properties of the syntactic foam composites with a focus on flexural strength, modulus, and fracture surfaces are investigated. The particle sizes are varied into five volume fractions (5, 10, 15, 20, and 25 vol%). The results show that the highest flexural strength is 89 MPa at a 5 vol% fraction of 50–60 µm particle size variation with a 69% increase over the neat epoxy. This implies that the incorporation of HGM filler volume fraction and size variation has a strong effect on the flexural strength and bending modulus of syntactic foam. The highest particle size distribution is 31.02 at 25–44 µm. The storage modulus E’ increased at 30 °C, 50 °C, and 60 °C by 3.2%, 47%, and 96%, respectively. The effects of wall thickness and aspect ratio on the size of the microstructure, the fracture surfaces, and the viscoelastic properties are determined and reported accordingly.

Focus on biofibre-reinforced biopolymer composites as sustainable alternatives to non-biodegradable composites in high-performance applications is increasing. This work focused on characterising the performance of kenaf non-woven mat/PLA biocomposites under medium velocity impact loads. Biocomposite laminates of different fibre contents were fabricated and then analysed for their resistance to medium velocity impact on a high speed gas gun. The perforation threshold limit was determined and impact-induced damages analysed using non-destructive techniques. Results showed that kenaf non-woven mat/PLA biocomposites have a perforation threshold limit of 26 m/s and doubling of fibre content improved the perforation threshold limit by 42.3 %. The impact damage resistance of kenaf non-woven mat/PLA biocomposites increased by 27.6 % when fibre content was doubled. The failure modes resembled that of some conventional fibre-reinforced composites. It was concluded that kenaf non-woven mat/PLA biocomposites have a potential to cushion against medium velocity impacts and hence could be good replacements for the non-biodegradable composites used for cushioning against secondary debris in the medium velocity range.

Density measurements (i.e., physical magnitude) are quick, efficient, and crucial in determining the structure and quality of solid materials. For polymer composites, properties tend to increase, decrease, or both with density. In this work, poly(lactic acid) composites (PLAC) filled with carbon black (CB), multiwalled carbon nanotubes (MWCNTs), and cellulose nanofibers (CNFs) were prepared using the dissolution–dispersion method (DD) and oligomeric–dispersion method (OD). To study the hybrid effect, PLAC with 2.5 weight percent (wt%) CB + MWCNTs (0.2, 0.4, 0.6, 0.8, 1.0, 1.5 and 2.0wt%) and 2.5wt% CB + CNFs (0.2, 0.4, 0.6, 0.8, 1.0, 1.5 and 2.0wt%) were prepared using DD and OD. Density measurements were performed on PLAC to determine the extent of dispersion and interphase characteristics. PLAC prepared by OD showed an increase in density values in comparison to DD, irrespective of the filler.

The objective of this work is to study the effect of nanoclay fillers on the biodegradation and barrier properties of corn starch polymer-based biofilm. Starch derived from corn plant source was used to prepare a biofilm by plasticization method. The barrier properties, namely, water absorption, moisture permeation, oxygen permeation and swelling of unfilled and nanoclay-filled corn starch biofilms were examined. The results indicate: ∼22% reduced water absorption, 40% reduced moisture uptake, 30% reduced oxygen permeation and 31% reduced swelling for 2–3 wt.% nanoclay-filled biofilm, when compared with unfilled biopolymer. The biodegradation result of unfilled and nanoclay-filled film series indicates that the nanoclay addition delays the biodegradation and is a function of nanoclay content in the film. The tensile, dynamic mechanical analysis and biodegradable studies were conducted on the biopolymers before and after water absorption, and the result shows that the nanoclay-filled biopolymer increased these properties when compared with unfilled biopolymer even after water absorption and is dependent on the nanocomposite structure and morphology as examined by X-ray diffraction and transmission electron microscopy analysis.

The correlation between cure properties and structure of nanoclay filled composite laminate has not been studied extensively. Most of the cure studies were preferably done using small samples through a calorimetric method. In this study, the effect of varying weight ratio of nanoclay (1–5 wt%) on bulk cure properties of epoxy glass fiber reinforced composite (GFRC) laminates was studied. Bulk cure of unfilled and clay filled GFRC laminates was determined using the dynamic mechanical analysis-reheat method (DMA-RM). DMA-RM cure properties gave a better coordinate method, with better cure efficiency achieved in clay filled GFRC laminates when compared to unfilled GFRC laminates. The correlation between nanoclay and DMA-RM degree of cure was coordinated with compressive and in-plane shear strength properties. The degree of cure value of 78% by DMA-RM at 1 wt% clay filled GFRC corresponds with the compressive modulus and in-plane shear strength highest values, which are 20% and 14% increase, respectively, also at 1 wt% clay filled GFRC. The structures of the unfilled and clay filled epoxy were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Clay filled epoxy up to 3 wt% showed no distinct diffraction peak, which suggested that nanoclay is randomly dispersed in the matrix.

Copyright: 2015. Taylor & Francis Online. Due to copyright restrictions, only the abstract is available. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in Polymer-Plastics Technology and Engineering. Vol 54(16) : 1715-1722. http://dx.doi.org/10.1080/03602559.2015.1036440

Copyright: 2015. Wiley Online Library. Due to copyright restrictions, only the abstract is available. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in Composites http://onlinelibrary.wiley.com/wol1/doi/10.1002/pc.23718/full

This study focuses on the thermoformability of biopolymer films derived from corn starch and filled with montmorillonite-based nanoclay fillers. Biopolymer films with nanoclay concentrations from 0 to 5 wt% were prepared by solution casting and followed by thermoforming. The result shows that nanoclay addition improves the formability (dimensional stability and plugging property) of thermoformed specimen and also depends on the nanocomposite structure and clay concentration. Improved product stability with optimized properties was observed at 2–3 wt% nanoclay concentration due to exfoliated structure and better nanoclay particle dispersion in the polymeric matrix. Thermogravimetric analysis and dynamic mechanical analysis show maximum of 27℃ increased decomposition temperature, 12% increased storage modulus and 4℃ increased Tg at 5 wt% nanoclay-filled biopolymer film. Tensile result shows 13% increased strength, two-fold increased modulus and 29% reduced elongation for 3 wt% nanoclay-filled biopolymer series.

The objective of this work was to find a possible engineering application for polypropylene (PP) by preparing fibers filled with nanoclay particles. Unfilled and nanoclay filled (0–5 wt%) PP fibers were continuously drawn and examined. The surface morphology and topographic studies of fibers were carried out using a scanning electron microscope (SEM). It was observed that unfilled PP fibers possess poor density distribution with the nonuniform diameter across the fiber length affecting structural integrity. However, PP fibers filled with ≥2 wt% nanoclay had shown improvement in structural integrity. The structure and morphology of fibers were examined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis, and the result indicated good dispersion of nanolayers of clay in PP matrix with exfoliated nanocomposite structure up to 2 wt% nanoclay and above 2 wt% showing intercalated nanocomposite structure. Improved tensile, thermal and water barrier properties of nanoclay filled PP were also observed.

Properties of polymer composites depend to a large extent on the characteristics of dispersion and interphase layers. In this work, poly (lactic acid) composites (PLAC) were prepared via the dissolution–dispersion method (DD) and oligomeric–dispersion method (OD). Ultraviolet–Visible spectroscopy (UV–VIS) was used to determine the dispersion and interphase characteristics within the PLAC. An increase in absorbance at a higher wavelength within the absorbance spectra was observed for PLAC prepared by DD and OD, which can be attributed to the formation of strong adlayers as well as “near to homogenous dispersion” for carbon-based particulate filled composites. An increase in absorbance was observed for PLAC prepared by OD in comparison to DD and can be attributed to modifications occurring at interphase regions. PLAC using carbon black, multiwalled carbon nanotubes in poly (lactic acid) were prepared via DD and OD and further characterized by UV–VIS. To study the “hybrid effect,” composites with 2.5 weight percent of carbon black with varied concentration of multiwalled carbon nanotubes and nanocellulose fibers were prepared via DD and OD, further characterized for UV–VIS. This manuscript portrays the role of UV–VIS to determine dispersion as well as the interphase characteristics for poly (lactic acid) filled carbon composites.

This paper examines the influence of nanoclay on the structure, thermal and mechanical and gas barrier properties of a polyethylene terephthalate (PET)-based copolyester using a new modified formula. The copolyester considered in this work consists of partially replaced acid and diol monomers in main chain PET polymers, namely, polyethylene glycol (PEG) and isophthalic acid monomers, i.e., PET-IP. Nanoclays were filled from 0–3 wt% in PET-IP using the melt mixing method. The structural examination of composites tested by X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the distribution of nanolayers of clay particles in polymeric matrix. Up to 1 wt% nanoclay in PET-IP, an exfoliated structure resulted and above 1 wt% nanoclay an intercalated structure resulted. It was observed that 0.5 wt% nanoclay filled PET-IP resulted in improved nucleation characteristics and above 0.5 wt% nanoclay dramatically increased the gas transport (CO2, O2, N2 and water vapor), thermal and mechanical properties. The results also showed that the distribution of nanoclays affected the gas barrier properties of the polymer and can be controlled by processing parameters.

This article discusses the reuse of a thermoset-based epoxy polymer. In this method, cured epoxy polymer is ground to powder of particle size ranging from 1 to 30 μm. The ground epoxy is then filled in an epoxy polymer to form an epoxy–epoxy composite system using both room and high temperature processing. The amount of filler material was varied from 1 to 10 wt% in the epoxy matrix. Rheology and tensile properties test were then performed. The result shows that the room temperature-processed epoxy composites (above 5 wt% of powders) resulted in the formation of voids, agglomeration of particles, and reduced degree of cure leading to a decrease in tensile properties. These drawbacks (voids, agglomeration, and low degree of cure) were correspondingly absent in composites processed at high temperature. Results from this work suggest that the thermoset polymer can be reused effectively with minimal changes to the unfilled resin properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

The objective of this article is to study the combined effect of isophthalic acid (IPA) and polyethylene glycol (PEG-400) in PET polymer and film on thermal, mechanical, and gas transport properties. The purpose of developing this material is to reduce the melting point, improve mechanical, thermal, and gas barrier properties. The chosen raw materials, namely, IPA and PEG for copolyester synthesis will replace partially the acid and diol monomers of PET. The molar concentration of comonomers (IPA and PEG-400) were varied from 2 to 50% and the result shows that the gas barrier properties (namely O2, CO2, N2, and water vapor transmission rate), mechanical, and thermal properties were lesser than that of PET polymer. On improving the crystallinity of PET-isophthalate-PEG (PET-IP) copolymer, barrier properties are improved than that of PET polymer. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Infrared spectroscopy helps in investigating the relationship existing between the structure of polymer composites and their structure-sensitive properties by determining molecular interactions. Neat polylactic acid and carbon black (0.5, 1.0, 1.5, 2.0, and 2.5 wt.%) filled polylactic acid composites were fabricated via dissolution dispersion solution casting. Composites filled with 2.5 wt.% of carbon black showed increased mechanical properties in tensile mode, in comparison to its neat and filled polylactic acid. Hence, an interest in analyzing the structure and property dependence via attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy for neat polylactic acid and carbon black filled composites was felt. Analyzing ATR-FTIR spectrographs for neat polylactic acid and filled polylactic acid composites confirms strong interactions with the addition of carbon black; these interactions are at a maximum for 2.5 wt.% of carbon black. Displacement (i.e., shift), percent transmittance, and area of absorption peak in infrared spectra, confirm the strength of molecular interaction in polylactic acid composites, and are corroborated with the numerical values of the mechanical properties in tensile mode.

The effect of nanoclays (0—5 wt%) on short glass fiber (GF)-reinforced polypropylene (PP) composites is examined in this study with special emphasis on the processing, structure, tensile, and wear properties. Addition of nanoclay reduces the melt flow rate of PP and PP—GF composites; however, it improves the crystallization characteristics due to their nucleating effect. This nucleating effect of nanoclay is due to the nanolevel dispersion in polymer matrix and this phenomenon is not observed in the unmodified microclay-filled PP composites. Improved tensile properties are observed in nanoclay-filled PP—GF composites due the intercalated/exfoliated nanocomposite structure. Furthermore, the addition of nanoclay in PP—GF composites improves the wear properties.

Diglycidyl ether of bisphenol — A (DGEBA) epoxy resin — clay nanocomposites was synthesized with diamino-diphenyl methane (DDM) curing agent. Nanocmposites were synthesized at different curing temperatures (60°C, 80°C, 100°C and 120°C), at various level of clay content in matrix (1–3% and 5%). The aim of this work is to study the effect of curing temperature on nanocomposite structure and properties. It is observed that property and structure of nanocomposites is governed by curing temperature and clay content in the matrix. Higher curing temperature shows increased mechanical properties over low temperature curing. Maximum increase in tensile properties is observed for 2 wt% nanoclay concentration irrespective of curing condition.

The compressive response of cross-linked and linear PVC foam core materials, namely, H130 and HD130 having identical densities were evaluated. Both cores were subjected to compressive loading at various strain rates ranging from quasi-static to 1560 s1. At quasi-static loading, the compressive strength of the H grade was approximately 30% higher than the HD grade. On the other hand, at HSR loading the HD grade was 20% higher. HSR tests were also conducted at various temperatures ranging from 25 to 12°C. It was observed that degradation of strength was more severe for the HD grade as temperatures increased. A recovery of the cores original volume was also noticed during high strain rate and elevated temperature tests. Accordingly, residual properties were determined. Results show that only the residual properties of the HD grade were affected by temperature.

When a sandwich structure is subjected to transverse loads, the face sheets carry bending moments as tensile and compressive stresses and the core carries transverse forces as shear stresses. The core is typically the weakest component of the structure and is the first to fail in shear. In this study the shear fatigue behavior of two closed-cell cellular PVC foams, Divinycell HD130 (linear) and H130 (cross linked), with the same nominal density of 130 kg/m3, were investigated. Static shear tests reveal that HD130 foams are more ductile, have almost twice the energy absorption capability, and an extraordinary crack propagation resistance when compared to the H130 foams. Shear fatigue tests were conducted at room temperature, at a frequency of 3 Hz and at a stress ratio, R = 0.1 on the HD130 and H130 foams. S–N curves were generated and shear fatigue characteristics were determined. The number of cycles to failure for the linear foams was substantially higher than that of the cross-linked PVC foams. HD foams have smaller cells with thicker faces and edges. This microstructure supports absorption of larger amounts of liquid resin forming a resin rich sub interface zone just below the actual core skin interface. The high intrinsic toughness of the sub interface delays the initiation of fatigue cracks and thereby increases the fatigue life of the HD foams. For both foams, shear deformation occurs without volume change and the materials fail by shearing in the vicinity of the centerline of the specimen along the longitudinal axis. In both cases numerous 45° shear cracks form across the width of the specimen and are equidistantly spaced along the length of the specimen. The occurrence of these through the thickness shear cracks signals the final failure event during fatigue. Details of the experimental investigation and the evaluation of the fatigue performance are presented.

This work deals with processing of nanocomposite gel coat system using unsaturated polyester resin, aerosil powder and dodecylamine treated nanoclays. Further, the work focuses on the influence of nanoclay addition on mechanical and water barrier properties of a polyester gel coat system with different weight fractions (1, 2, 3, 4 & 5 wt.%) of nanoclay. The nanocomposite gel coat system exhibits 94% improvement in tensile modulus for 5wt.% nanoclay and 24% improvement in tensile strength for 2wt.% nanoclay. Nanocomposite gel coat system exhibit a maximum of 68% improvement in barrier resistance for 3 wt.% nanoclay compared to the conventional gel coat system. At higher clay concentration (>3%) the mechanical and barrier properties decrease due to the limitation in the processing as well as the high viscosity of resin/clay/aerosol system.