DMTA Analysis Research Articles

Characteristics of Biodegradable Polylactide/Thermoplastic Starch/Nanosilica Composites: Effects of Plasticizer and Nanosilica Functionality

The effect of plasticizer (polydimethylsiloxanol) and neat (SiO2) or modified (having amine functional groups) silica (A‐SiO2) on morphology, thermal, mechanical, and rheological properties of PLA/TPS blends compatibilized by maleated PLA (MPLA) was investigated. Toughened PLA/MPLA/TPS (60/10/30) blend containing 3 wt.% of plasticizer and various contents (1, 3, or 5 wt.%) of silica were prepared in a corotating twin‐screw extruder. From SEM, it is clear that plasticized PLA/MPLA/TPS blend continuous porous structure is highly related to the silica content and its functionality. The results indicate that polydimethylsiloxanol enhances ductility and the initial thermal stability of the plasticized blend. DSC and DMTA analyses show that nucleation ability and reinforcing effect of A‐SiO2 on plasticized blend crystallization are much better than those of SiO2. Silica practically had no effect on the thermo‐oxidative degradation. However, the composites with A‐SiO2 had better thermal stability than those with SiO2. Moreover, silica significantly improved the elongation at break.

Tooth microwear texture in odontocete whales: variation with tooth characteristics and implications for dietary analysis

Abstract Understanding the diets and trophic relationships of toothed whales is central to understanding their roles in marine ecosystems, and associated conservation issues. Yet this is problematic because direct observation of what free ranging marine mammals eat is difficult. Quantitative 3D textural analysis of tooth microwear (DMTA) offers a new way of investigating diet in odontocetes and other marine mammals, but the application of this approach requires that we first understand how non-dietary variables affect the texture of microwear in odontocetes. Here we present the first analysis of microwear texture in odontocetes (beluga, Delphinapterus leucas) testing null hypotheses that microwear texture does not vary with dental surface tissue type (dentine, cementum), and that microwear texture does not vary with tooth characteristics (location in jaw, degree of wear, wear facet slope and facet orientation). Our results reveal that these variables have a significant impact on microwear textures, and thus have the potential to mask variation in texture caused by dietary differences. This does not mean that microwear texture analysis cannot be used as a tool for dietary analysis in toothed whales, but any future studies should adopt sampling protocols that standardize non-dietary variables to mitigate their effects in DMTA analysis.

Unveiling the hybrid interface in polymer nanocomposites enclosing silsesquioxanes with tunable molecular structure: Spectroscopic, thermal and mechanical properties

Organic–inorganic nanobuilding blocks (NBBs) based on silsesquioxanes (SSQs) have potential applications as nanofillers, thermal stabilizers, and rheological modifiers, which can improve thermomechanical properties of polymer hosts. The possibility to tune both siloxane structure and pendant groups can promote compatibilization and peculiar interactions with a plethora of polymers. However, the control on SSQs molecular architecture and functionalities is usually delicate and requires careful synthetic details. Moreover, investigating the influence of NBBs loading and structure on the hybrid interface and, in turn, on the polymer chains mobility and mechanical properties, may be challenging, especially for low-loaded materials.Herein, we describe the preparation and characterization of polybutadiene (PB) nanocomposites using as innovative fillers thiol-functionalized SSQs nanobuilding blocks (SH-NBBs), with both tailorable functionality and structure. Swelling experiments and, more clearly, solid-state NMR, enlightened a remarkable effect of SH-NBBs on the molecular structure and mobility of the polymeric chains, envisaging the occurrence of chemical interactions at the hybrid interface. Finally, thermal and DMTA analyses revealed that nanocomposites, even containing very low filler loadings (i.e. 1, 3 wt%), exhibited enhanced thermomechanical properties, which seem to be connected not only to the loading, but also to the peculiar cage or ladder-like architecture of SH-NBBs.

Effect of nanosize CaCO3 and nanoclay on morphology and properties of linear PP/branched PP blend foams

Branched polypropylene (PP) polymer (BPP), two nanoparticles with different aspect ratios, nano CaCO3, and nanoclay (Cloisite 20A), were used for improving the melt strength of linear PP (LPP) and producing microcellular foam via a solid‐state foaming process using supercritical N2 as a physical foaming agent. The effects of BPP and nanoparticles were investigated on the rheological and mechanical properties of the nanocomposite and morphological properties of the foamed samples. The effect of temperature, saturation pressure, and foaming time were studied on the morphological properties of the foams, too. The results showed that the BPP increased the elongation at break of nanocomposite samples, and nano CaCO3 increased tensile strength, elongation at break, and tensile modulus, except at its highest content (15 wt%) and improving the dispersion of nanoclay. The nanoclay improved tensile strength and tensile modulus of nanocomposites, except at its highest content (6 wt%). The nanoclay increased the cell density and reduced the cell size and improved melt strength and cell stability during the foaming process. The nano CaCO3 improved foamability, cell size, and cell density. The simultaneous presence of nanoclay and nano CaCO3 synergistically improved the cell density and decreased the cell size of the foams. The best process conditions were found as 140°C temperature, 80 bar pressure, and 2 h time. The results of the DSC analysis showed that the crystallinity of foamed samples was higher than the nanocomposites and DMTA analysis showed that the tan δ of foamed samples was higher than unfoamed samples. POLYM. COMPOS., 40:E227–E241, 2019. © 2017 Society of Plastics Engineers

Characterization of poly(lactic acid) biocomposites filled with chestnut shell waste

The aim of this study was to determine thermal and mechanical properties and applicability of ground chestnut shell waste as a filler for poly(lactic acid) composites. The used amount of filler was ranging from 2.5 to 30 wt%. Spectroscopic analysis of composites and its ingredients was conducted by means of FT-IR method. The mechanical and thermal properties of the composites were determined in the course of static tensile test, Dynstat impact strength test, DMTA analysis, and DSC method. The fractured surface morphology of biocomposites was evaluated by SEM analysis. Incorporation of the filler influenced the overall mechanical properties of the composites characterized by high stiffness and lowered impact resistance. Fabricated composites with different amounts of non-reactive natural waste filler exhibited acceptable mechanical and thermal properties. Therefore, these composites can be used as eco-friendly, biodegradable materials for low-demanding applications.

Improved thermal and mechanical properties of polynorbornene upon covalent attachment with graphene sheets

Graphene carboxylic acid based polynorbornene nanocomposites were fabricated following simple synthetic protocol with different graphene loading. Polynorbornene (PNDA) was functionalized with hexamethylene diamine modified graphene carboxylic acid (HXNG) to form new hybrids: PNDHXNG1-3. Formation of monomer (NDA) and PNDA were confirmed by standard analytical techniques. Covalent attachment between PNDA and HXNG was confirmed by IR, Raman and PXRD. Hybrids exhibited excellent solubility in DCM:MeOH (2:1). Increased thermal stability and enhanced value of Tg of the hybrids, as compared to PNDA was evidenced from TGA, DTG, DTA and DMTA analysis. 69% increment in storage modulus was achieved in case of PNDHXNG3. Almost 97%, 73% and 181% increment were observed in yield stress, stress at break and Young's modulus respectively in case of PNDHXNG3. Improved thermal and mechanical properties were observed with increasing HXNG loading in PNDHXNG1-3. Morphological studies revealed excellent miscibility between HXNG and PNDA in PNDHXNGs owing to improved thermal and mechanical properties.

Sepiolite as a promising nanoclay for nano-biocomposites based on starch and biodegradable polyester

The effects of sepiolite addition (0, 1, 3 and 5wt%) were evaluated on dynamic-mechanical behaviour, water uptake, thermal and optical properties of thermoplastic starch (TPS)/poly (butylene adipate-co-terephthalate) (PBAT) nano-biocomposites, with different TPS/PBAT (w/w) ratios and nanofiller contents. The results highlighted the improvement of the dynamic-mechanical behaviour with the addition of sepiolite, producing high performance materials. An increase of 25°C in the Tg of TPS was recorded by DMTA analysis at sepiolite content of 5wt%. The sepiolite influenced the crystallisation of nano-biocomposites, without causing interference in the crystal organisation, evidenced by DSC analysis. The addition of sepiolite nanoclay decreased the water adsorption rate and water adsorption capacity of the corresponding nano-biocomposites. For such multiphase systems, the successful use of natural sepiolite brought a clear benefit, without the need of any modifications or additional processes to produce advanced nano-biocomposites.

Effect of compatibilization in situ on PA/SEBS blends

This paper presents the mechanical, thermal and rheological properties of polymer blends of polyamide 6 (PA) and styrene-butylene-styrene (SEBS) using SEBS-g-MA as a coupling agent. The increase in the interfacial interaction of PA/SEBS blends with the addition of SEBS-g-MA was observed to enhance the mechanical properties studied (excellent elongation at break revealed by a 500% increase). Higher hardness values and a higher degree of crystallinity were obtained for compatibilized blends. In the presence of the SEBS-MA compatibilizer, the heat sweep thermograms obtained by DSC showed only one melting peak, which confirms the effect of the compatibilizer. The best rheological properties were observed for the ternary blends. The lowest concentration of SEBS-g-MA promoted the toughening of PA, and 7.5 phr of compatibilizer increased the modulus E' of the ternary blends compared to that of the binary blends. DMTA analysis allowed for the system to be characterized as partially miscible.

Ultrathin wood laminae—polyvinyl alcohol biodegradable composites

Novel polyvinyl alcohol (PVOH) based biodegradable composites were prepared by a hand lay‐up process using ultrathin beech laminae cut by a specialized planer machine, and the resulting materials were thermo‐mechanically characterized. Density measured showed how the adopted procedure led to laminates having a high porosity degree (about 50% by volume) and an elevated wood concentration (about 80% by weight). In fact, because the wood fibers were perfectly cut (not pressed and abraded), wood porosity was partially filled by the PVOH resin, as documented by field emission scanning electron microscope (FESEM) micrographs. The occlusion of wood porosity by the PVOH matrix resulted to be beneficial for the tensile mechanical properties of the composites. In fact, quasi‐static tensile tests and DMTA analysis revealed how the stiffness (E, E′) and strength (σb) values of the composites both along longitudinal and transversal directions were considerably higher than those of the constituents. On the other hand, the values of the specific energy adsorbed under impact conditions by the composites samples were rather low, if compared to the neat matrix. POLYM. COMPOS., 39:1116–1124, 2018. © 2016 Society of Plastics Engineers

Fabrication of polyhydroxybutyrate (PHB)/γ-Fe2O3 nanocomposite film and its properties study

Magnetic separation has numerous advantages in isolating cancerous and normal cells used in the diagnosis and treatment sectors. Here, we produced magnetic nanocomposite films made of polyhydroxybutyrate (PHB)/magnetite nanoparticles (γ-Fe2O3), and the properties of the films by SEM, TEM, FTIR, DMTA, contact angle, and cellular analyses were investigated. The microscopic images showed uniform distribution of γ-Fe2O3 magnetic nanoparticles in polymeric matrix. The chemical bounds between magnetic nanoparticles and polymeric matrix demonstrated using the FTIR spectrophotometer. The DMTA and contact angle results indicated an increase in the glass transition temperature and hydrophilic properties of nanocomposites is achieved by increasing the magnetic nanoparticles amount in polymer matrix. The cellular results were showed that adhesion of cancer cells compared to normal cells was significantly enhanced by the induction of a magnetic field. These nanocomposite films can be used as a substrate for cellular adhesion and separation processes.

Graft copolymerization of acrylic acid on to styrene butadiene rubber (SBR) to improve morphology and mechanical properties of SBR/polyurethane blend

ABSTRACTGraft copolymerization of acrylic acid (AA) on to styrene butadiene rubber (SBR) is carried out via free radical polymerization using benzoyl peroxide (BPO) as initiator. Graft yield (GY) and graft efficiency (GE) measurements reveal that the optimum grafting is achieved when 100 wt % of AA and 3 wt % of BPO are used for a reaction time of 6 h at 60 °C. The execution of the grafting process is confirmed through ATR‐IR spectroscopy and DMTA analysis. Tan δ thermograms indicate that the graft copolymerization occurs in the styrene segments of the SBR backbone. An in situ polymerized, semicrystalline polyurethane (PU) is then used to prepare a series of SBR‐g‐PAA/PU blends. It is found that the SBR‐g‐PAA with the highest GY exhibits the best compatibility with PU matrix. One‐phase morphology (SEM), as well as the appearance of only one glass transition (DMTA) verify the homogeneous miscibility of the modified blend compositions. Moreover, the integration of PUs crystalline structure into blends gives rise to elongation‐induced crystallinity as the prominent phenomenon in tensile testing, which proves to synchronously enhance tensile strength, modulus, elongation at break, and toughness. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43699.

Effect of Carbon Fillers in Ultrahigh Molecular Weight Polyethylene Matrix Prepared by Twin-Screw Extrusion

Oxidized (GO) and expanded (G-Exp) graphite were employed to prepare composites with ultrahigh molecular weight polyethylene (UHMWPE) matrix using masterbatches of polyethylene with different compositions. The materials and a blend of UHMWPE/HDPE were prepared by extrusion and their properties were evaluated. The effect of carbon fillers on the crystalline structure, thermo dynamic-mechanical (DMTA) and thermal properties (melting and crystallization temperatures) of the composites were discussed. The thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) measurements showed that the addition of masterbatch with GO and G-Exp significantly increased the crystallite size of composites, increasing the temperatures of melting, degradation, glass transition and the degree of crystallinity of polyethylene. DMTA analysis indicated the storage and loss moduli of composites in relation to neat UHMWPE, the blend and UHMWPE/composites. SEM micrographs showed a flatter, continuous and uniform surface meaning a compact lamellar structure. The present work resulted in interesting findings on the effects of GO on the crystalline structures, mechanical and thermal properties of UHMWPE, which can lead to generalizations useful for future work.

Synthesis and characterization of polyhedral oligomeric titanized silsesquioxane: A new biocompatible cage like molecule for biomedical application

Organic–inorganic hybrid materials have shown improved properties to be used as biocompatible coating in biomedical applications. Polyhedral oligomeric silsesquioxane (POSS) containing coatings are among hybrid materials showing promising properties for these applications. In this work an open cage POSS has been reacted with a titanium alkoxide to end cap the POSS molecule with titanium atom to obtain a so called polyhedral oligomeric metalized silsesquioxane (POMS). The synthesized POMS was characterized by FTIR, RAMAN and UV–visible spectroscopy as well as 29Si NMR and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) techniques. Appearance of peaks at 920cm−1 in FTIR and 491cm−1 and 1083cm−1 in Raman spectra confirmed Si–O–Ti linkage formation. It was also demonstrated that POMS was in a monomeric form. To evaluate the biocompatibility of hybrids films, pristine POSS and synthesized POMS were used in synthesis of a polycarbonate urethane polymer. Results revealed that POMS containing hybrid, not only had notable thermal and mechanical stability compared to POSS containing one, as demonstrated by DSC and DMTA analysis, they also showed controlled surface properties in such a manner that hydrophobicity and biocompatibility were both reachable to give rise to improved cell viability in presence of human umbilical vein endothelial cells (HUVEC) and MRC-5 cells.

Preparation of stimuli-responsive functionalized latex nanoparticles: the effect of spiropyran concentration on size and photochromic properties.

Incorporation of photochromic compounds to polymer matrix through chemical bonding results in an enhancement of photoactivity and stabilization of optical properties. Here, spiropyran ethyl acrylate monomer (SPEA) was synthesized, and then photochromic particles bearing epoxy functional groups were prepared through semicontinuous emulsion copolymerization. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) results depicted an increase in particle size and particle size distribution with the increase in SPEA monomer-surfactants ratio. Studies on photochromic properties by UV-vis analysis demonstrated a decrease in the absorption intensity despite the increase in SPEA content due to the enhancement in particle size. The prepared acrylic copolymer particles showed reasonable photostability, photoreversibility, and fast photoresponsivness according to the convenient test methods under UV/vis irradiation. DSC and DMTA analyses indicate an increase in Tg of the obtained copolymers with the increase in SPEA content. Finally, stimuli-responsive cellulosic papers were prepared by impregnation, and their photochromic behavior was investigated in dry and wet forms in various media under UV radiation. Morphology studies, due to stabilization of the photochromic copolymer on cellulose fibers, were conducted by SEM micrographs and showed good adhesion and compatibility between the two phases.

Poly 2-ethyl-2-oxazoline/microcrystalline cellulose composites for cultural heritage conservation: Mechanical characterization in dry and wet state and application as lining adhesives of canvas

The aim of this work is the investigation of the stabilizing effect of microcrystalline cellulose powder (MCC) on the mechanical performance of two commercial thermoplastic resins (Aquazol® 200 and Aquazol® 500) used as adhesives in the conservation of artworks. The two polymers, having different molecular weights, were melt-compounded and compression molded with various amounts of MCC (5–30wt%). The mechanical response of the microcomposites under dry and wet (equilibrium at 23°C and a R.H. 55%) conditions, was investigated. DMTA analysis showed an increase of the dynamic moduli and the glass transition temperature with the microfiller content more pronounced for conditioned samples over the dried ones, and a concurrent decrease of the thermal expansion coefficient. Creep tests showed that MCC caused an improvement of the creep stability (i.e. a reduction of the creep compliance) for both dried and conditioned samples. For wet samples, the simultaneous enhancement of the elastic modulus and the stress at break limited the embrittling effect detected for dried composites. These materials were applied as lining adhesive for oil paintings between two kinds of canvas an English linen and a woven polyester under environmental conditions at temperature of 23°C and a relative humidity of 55%. Single-lap shear tests both in quasi-static and creep conditions confirmed the improvement of the dimensional stability provided by MCC with a reduction of the joint displacement and an increase of the adhesive strength as the filler content increases. Additionally, post-fracture optical microscope observations of the cross-sections of the adhesive area proved how MCC introduction did not change the fracture behavior of the neat adhesives.

Renewable thermoplastic polyurethanes containing rigid spiroacetal moieties

Unprecedented polyurethanes with rigid spiroacetal linkages in the backbone were synthesized from renewable resource compounds. First, the large-scale synthesis of a rigid diol monomer containing acetal bonds was established. Subsequently, this diol monomer was combined with seven different diisocyanates to vary the backbone of thermoplastic polyurethanes, leading to a spectrum of chemical and physical properties. The molar masses of the polymers ranged from 8 to 45kDa and the corresponding polymers were obtained in high yields. DSC and DMTA analysis demonstrated glass transition temperatures up to 85°C. Acid-mediated degradation of the materials was not noticed during hydrolytic stability tests.

Structure and properties of biodegradable wheat gluten bionanocomposites containing lignin nanoparticles

Lignin nanoparticles (LNPs), prepared through precipitation from an ethylene glycol solution by using diluteacidic aqueous solutions, were obtained. Fourier transform infrared spectroscopy confirmed the removal of hemicelluloses from pristine lignin by acidolysis, while the TGA analysis revealed a retained thermal stability of the nanoparticles with respect of pristine lignin. The lignin nanoparticles presented a uniform size distribution and good stability at various aqueous pH mediums. Wheat gluten (WG) bionanocomposites filled with 0, 1 and 3% wt. of LNPs were produced and thermally and mechanically characterized by means of TGA, modulated DSC and DMTA analysis. UV–Vis spectroscopy and water sensitivity measurements were also performed, in order to fully characterize the produced materials. The results indicated that LNPs could also effectively absorb ultraviolet spectrum and improve the water sensitivity of WG bionanocomposites. Moreover, even if the addition of LNPs reduced the transparency at the two different weight contents, it enhanced the mechanical behavior and thermal stability of resulted bionanocomposites. A strong interaction between LNPs and WG matrix, as well as homogeneous distribution of LNPs within the WG matrix, was confirmed by FESEM investigation and mechanical characterization. The reduction of absorbed water as well as the increase in glass transition suggested that LNPs can be beneficial to enlarge the potential applications for WG based materials and confirmed the great potential of using these novel nanofiller in bio-based matrices.

Chemical Modification of Glycidyl Methacrylate Copolymers with Alcoholes Containing Pyridine Groups

Abstract. In this work the homopolymer and copolymers of glycidyl methacrylate (GMA) with ethylmethacrylate (EMA), methylacrylate(MA) and ethylacrylate (EA) were synthesized by free radical polymerization using azobis(isobutyronitrile) (AIBN) as initiator at 70 ±10C. Then, copolymers of glycidyl methacrylate have been modified by incorporation of 2-(2-pyridile)ethanol by the ring opening reaction of the epoxy groups. The polymers were characterized by 1H-NMR and FT-IR. Presence of bulk the 2-(2-pyridile)ethanol groups in polymer side chains leads to an increase in the rigidity and glass transition temperature of polymer as shown by DMTA analysis. The research demonstrated that the synthesized modified polymer could successfully remove heavy metals from solution. With the incorporation of the 2-(2-pyridile)ethanol groups in the polymer side chains, a series of novel modified polymer containing new properties are obtained, that can find some applications in polymer industry.

Fracture Toughness of Hydrothermally Aged Epoxy Systems with Different Crosslink Density

The present work investigates the fracture toughness behaviour of Single Edge Notched Bending (SENB) samples of epoxy systems subject to water uptake aging. Two epoxy systems with a significantly different Glass Transition Temperature, Tg, are in particular considered: a typical commercial non-aeronautical grade resin matrix for composite applications, reaching aTgof 90°C, and a DGEBA+DDS epoxy system achieving a Tg of 230°C.The materials have been conditioned by hydrothermal aging in a thermal bath at the temperature of 50°C. TransmissionPhotoelastic Stress Analysisis carried outon SENB samples during water aging, monitoring the presence and evolution of swelling stresses. The KIC Fracture toughness is measured and correlated with the internal stress field, with the water diffusion kinetics evaluated by gravimetric tests, and with the data from DMTA analyses. Results have highlighted significant differences in the fracture behaviour ofthe two epoxy systems.

Effects of coconut oil concentration as a plasticizer and Yucca schidigera extract as a surfactant in the preparation of extruded corn starch films

In this study, extruded films of corn starch (CS) plasticized with coconut oil (CO) (as an alternative plasticizer to glycerol) in the presence of Yucca schidigera extract (YSE) as a surfactant were investigated. It was observed that corn starch films (CSF) plasticized with a lower concentration (15 wt%) of CO showed a better equilibrium of mechanical properties, a higher WVP (5.8 ± 0.2 × 10−9 g m−1 s−1 Pa−1) and percentage of elongation (8 ± 0.5), and a lower Young modulus (99 ± 8 MPa) than those with a higher amount of plasticizer. However, films with Yucca schidigera extract (YSE) as a surfactant showed a decrease in WVP (4.9 ± 0.2 × 10−9 g m−1 s−1 Pa−1), a lower Young modulus (61 ± 2 MPa) and an increase in the percentage of elongation (13 ± 0.4). In order to describe the viscoelastic properties before the extrusion processes in materials in water suspensions and after extrusion process in CSF, rheological and DMTA analysis were performed, showing consistent behaviors for both samples.