Dynamic Mechanical Analysis Studies Research Articles

A Dynamic Mechanical Analysis on the Compatibilization Effect of Two Different Polymer Waste-Based Compatibilizers in the Fifty/Fifty Polypropylene/Polyamide 6 Blend.

This study aims to examine the 50/50 polypropylene/polyamide 6 (iPP/PA6) system molded under confined flow conditions, both in its original state and after being modified by two different interfacial agents. This study provides two main insights. Firstly, it focuses on a polymer blend close to phase inversion. Secondly, it investigates the impact of using two different types of interfacial agents (derived from polymer waste) to enhance the compatibility between iPP and PA6. Dynamic Mechanical Analysis (DMA) has been employed to achieve these objectives. It is important to note that the investigation of the 50/50 iPP/PA6 system is a crucial focus predicted in previous studies, where a series of mechanical properties were evaluated using Box-Wilson design of experiments (DOEs) over the whole compositional range on the iPP/PA6 binary system. Thus, two interfacial modifiers, namely succinic anhydride (SA)-grafted atactic polypropylene with terminal, side, and bridge SA grafts (aPP-SASA) and succinyl-fluoresceine (SF) with bridge succinic anhydride grafting atactic polypropylene (aPP-SFSA), were employed. The authors obtained and characterized these agents. The quantity of these agents used in the blend was identified as a critical coordinate in prior studies conducted by the authors. The processing method used, compression molding under confined conditions, was chosen to minimize any orientation effect on the emerging morphology. All characterization procedures were performed on samples processed by contour machining to retain the blend morphologies as they emerged from the processing stage. Results from WAXS and SAXS synchrotron tests concluded there were no changes in the crystal morphology of the iPP or the PA6 in the blends nor any co-crystallization process throughout the compositional range. These findings, and the long period fits on the PP crystalline phase for the fifty/fifty blends we are discussing, will support the present DMA study. Finally, the efficiency of these interfacial modifiers has been concluded, even in this unfavorable scenario.

Nanofiller‐and basalt fiber‐reinforced recycled polyamide 6 hybrid composites

AbstractThe influence of nanofillers (cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)), and basalt fibers (BF) on the morphology, mechanical and thermal of recycled polyamide 6 (PA6) composites were investigated through scanning electron microscopy (SEM), mechanical testing, rotational rheometry, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). CNF, HNTs and BF were relatively well‐dispersed in the PA6 matrix and the incorporation of these nanofillers and BF increased the strength of the matrix, which indicates a good dispersion of the nanofillers and BF. CNF and HNTs‐filled PA6 nanocomposites increased the tnsile strength by 14% and 6% compared to the neat PA6, respectively. The composites elongation at break decreased with nanofiller, BF and combined nanofillers and BF. The shear storage modulus values of PA6/20B5C, PA6/20B5H, and PA6/25B are significantly elevated compared to neat PA6, with increases of 3.7, 2.8, and 2.5 times, respectively, at an angular frequency of 100 rad/s. PA6/20B5H composites with 20 wt.% BF and 5 wt.% HNTs exhibited the highest storage modulus (9.5 GPa) from the DMA study. Thermal stability and ash content at 800°C increased with the incorporation of HNTs and BF. The DSC findings showed that the glass transition (Tg) and melting temperature (Tm) of the composites did not exhibit any notable changes when nanofillers and BF were added to the resin. The nucleation ability of PA6 was enhanced attributable to BF and hybridization of BF and nanofillers since the crystallization temperatures of PA6 in BF filled and hybrid composites were around 5°C greater than neat PA6. The results suggest hybrid composites with potential environmental characteristics and higher mechanical properties can be utilized in semi‐structural applications in automotive and construction as a sustainable and lightweight alternative to steel and other materials.Highlights The addition of HNTs, CNF, BF and hybridization of nanofillers with BF reduced the brittleness of PA6. Nanoreinforced and hybrid PA6 composites achieved higher storage modulus than neat PA6. Thermal stability and ash content increased with the incorporation of HNTs and BF. The hybrid composites have a higher complex viscosity compared to PA6. The sustainable hybrid composites can be utilized in automotive and construction industries.

Effects of tire‐derived pyrolytic carbon black and pyrolytic heavy oil on the curing and mechanical properties of styrene‐butadiene rubber composites

AbstractTo investigate the potential effect of the pyrolytic carbon black (CBp) and pyrolytic heavy oil (HO), we incorporated them into styrene‐butadiene rubber (SBR) as reinforcing filler and plasticizing agent, respectively. Since the industrial N330 CB's specific surface area and other specifications adhere to the CBp standard, it has been selected as a benchmark. To test HO's applicability, conventional (AO) was substituted with it. We experimented with the N330 and CBp in the 1/1 variant. We examined the impacts on the cure behavior, physical characteristics such as density and hardness, mechanical properties, abrasion resistance, dynamic mechanical performance, and thermal properties of the filled SBR composites. According to field emission (FESEM) and transmission electron microscopy (TEM) micrographs, the increased tensile and tear strength is due to N330 black's superior dispersion over CBp in the rubber matrix. Better dispersion in N330 type CB is also justified by lower tan δmax from the dynamic mechanical analysis (DMA) study. Utilizing HO changes the curing conditions since it comprises more sulfur, which accelerates the formation of sulfur–sulfur cross‐links. Increased tensile and tear strengths, as well as improved dispersion in the rubber matrix, have been seen with the combined use of N330 and CBp. Meanwhile, HO could function well in place of commercially available AOs.Highlights The impact of scrap tires on human health and the environment is explored. Recovered carbon black (CB) from waste tire mixed with styrene‐butadiene rubber in various ratios. Pyrolytic oil is also incorporated to check its reusability in tire formulation. Similar cure characteristics and mechanical strength were found in the composites. Replacement of the conventional CB is proposed with recovered black.

Development of Cloisite20A-polyurethane nanocomposite coatings for thermomechanical performance

Cloisite 20A-polyurethane (C20-PU) nanocomposites were prepared using three processing schemes at different reinforcement levels (1, 2 and 3 wt%). The H-bonding chemistry of hard segments (HS) of PU and C20, leads to compartment effect in C20-PU thus varying the mechanical performance, as deduced from nanoindentation studies. Elastic nanocomposites (7.8 % - 60.6 % decrease in the plasticity index) and plastic nanocomposites (4.8 %–25.3 % increase in the plasticity index) are produced by switching the sequence of homogenizer (HSH) and ultrasonic bath (USB), either in tandem or independently. Polymer phase mixing morphology indicated by Fourier transform infrared (FTIR) and plasticity indices derived from nanoindentation, corroborate the active role of compartment effect in governing the properties and performance of PU and C20-PU nanocomposites. Dynamic mechanical analyzer (DMA) studies demonstrate that C20-PU nanocomposites are thermally and mechanically more robust than pure PU, with a >10 °C right shift in the glass transition temperature (Tg) along with a reduction in Tg peak intensities of nanocomposites. These findings articulate the interaction between PU chains and 2D nanofiller with improved thermomechanical properties.

Biobased, Reprocessable Non-isocyanate Polythiourethane Networks with Thionourethane and Disulfide Cross-Links: Comparison with Polyhydroxyurethane Network Analogues

Here, we report the first study of the reprocessability and properties of non-isocyanate polythiourethane (NIPTU) networks in which the cross-links are of two types, thionourethane and disulfide, the latter obtained by auto-oxidation of pendant thiol groups. Our two NIPTU networks are biowaste based because starting materials can be derived from cashew nutshells or rice husks. We use dynamic mechanical analysis, tensile testing, and water sorption studies to compare our NIPTU networks with structurally analogous polyhydroxyurethane (PHU) networks, which are non-isocyanate polyurethanes (PUs). With significant advantages in reactivity, mechanical properties, and cross-link density, NIPTU networks can be favorable alternatives to PHU networks. Our biobased NIPTU networks also exhibit better water resistance, with a factor of ∼3 reductions in water sorption relative to their PHU analogues. Due to their dynamic covalent cross-links, our NIPTUs show excellent reprocessability with complete recovery of cross-link density after multiple reprocessing steps as well as potential as self-healing polymers. Although their creep viscosity activation energies differ by a factor of 2, both NIPTU networks exhibit excellent creep resistance up to 80–100 °C. Thus, with elevated-temperature creep resistance and significant advantages in reactivity, mechanical properties, and water resistance, in many applications, e.g., water-resistant coatings, biobased NIPTU networks are favored as non-isocyanate substitutes for PU networks.

Fabrication of new proton conducting membrane for fuel cell applications based on porous polyimide Matrimid® and hydrophobic protic ionic liquid

AbstractA new proton conducting membrane has been developed by impregnation of porous polyimide Matrimid® (PI) with hydrophobic protic ionic liquid triethylammonium bis(trifluoromethylsulfonyl)imide (TEA‐TFSI). According to the results of dynamic mechanical analysis (DMA), PI/TEA‐TFSI membrane has satisfactory viscoelastic properties in the temperature range 25–100°C. However, the sharp drop in storage modulus (E') occurs at higher temperatures that is probably caused by the plasticizing effect of ionic liquid. To improve the mechanical properties of PI matrix, it was impregnated with the solution of polyetheramine Jeffamine® D‐400 in the TEA‐TFSI. This approach allowed to obtain a partially cross‐linked PI which is more resistant to deformation at elevated temperatures. Thus, DMA study revealed a storage modulus around 400 MPa for PI/Jeffamine/TEA‐TFSI membrane up to 150°C, like neat porous Matrimid®. Thermogravimetric analysis results indicate high thermal stability of PI/Jeffamine/TEA‐TFSI composite with thermal degradation point of 343°C. The ionic conductivity of the composite membrane is 4·10−3 S/cm at room temperature and reaches the level of 10−2 S/cm above 100°C. Overall, the results of this study indicate that partially cross‐linked porous PI impregnated with hydrophobic protic ionic liquid is a promising polymer electrolyte membrane for fuel cells operating at elevated temperatures in water‐free conditions.

Study of Viscoelastic Behavior and Mechanical Characteristics of Graphene-Filled ABS Composites

Acrylonitrile-Butadiene-Styrene (ABS) thermoplastic composites were reinforced with graphene fillers for three different weight ratios of 0.3%, 0.6%, and 0.9%. The compounding was prepared using a twin-screw extruder, and the specimens were made using an injection molding machine. The thermal gravimetric analysis (TGA)study revealed that the thermal stability of ABS composites was improved (~7%) by adding graphene fillers in pure ABS.The tensile and flexural strength of the ABS/grapheme composites was maximumwith the addition of 0.6 wt% graphene fillers. But the impact strength was reduced (~42%) for the addition of graphene fillers of more than 0.6 wt%. The stiffness of pure ABS was enhanced by more than ~27% with the addition of graphene fillers. It was found from a Dynamic Mechanical Analysis(DMA) study that the storage modulus and Tan Delta values of the composites were improved compared to pure ABS. The storage modulus was increased by more than ~70% over a wide range of temperatures. The addition of graphene fillers in the ABS matrix improved the glass transition temperature (increased from 110 ̊C to 118 ̊C). Scanning Electron Microscope (SEM) images confirmed the homogeneous mixing of the ABS matrix and the graphene fillers, and better dispersion was noticed with 0.6 wt% of graphene fillers.

Development and Characterization of Pigeon Pea Stalk Fiber Reinforced Polylactic Acid Sustainable Composites

ABSTRACT This study focuses on the development and characterization of pigeon pea stalk fiber (PSF) reinforced (10, 20, 30, and 40 wt.%) polylactic acid (PLA) sustainable composites. In particular, the tensile, compression, flexural, impact, shear strength, and hardness characteristics were studied as mechanical properties, while other characterizations included dynamic mechanical analysis, density, water absorption, crystallinity index, and morphology studies were also examined to get a more comprehensive understanding of these green composites. From the results of mechanical properties, the optimal particle loading was up to 30 wt.%, and these properties compare well with other green composites. They could be used as an alternative to natural fiber-based composites for secondary load-bearing applications in various sectors like indoor, packaging, furniture, automobile interiors, etc. The addition of PSFs (30 wt.%) into the PLA matrix increased the storage modulus by 28%. A significant improvement in crystallinity was also found in these green composites. In addition, all composites up to 30 wt.% PSFs exhibited good resistance to water absorption and had a maximum water intake of 5.25%. Morphological studies revealed good adhesion and distribution of PSFs in the PLA matrix.

Development of hydrophobic polyurethane film from structurally modified castor oil and its anticorrosive performance

AbstractHydrophobic polyurethane (PU) films are widely used for various commercial and industrial applications due to their excellent water repelling and self‐cleaning property. Nevertheless, achieving appreciable hydrophobicity in PU film is quite a challenge. Herein, we report on the development of a novel hydrophobic PU (fluorinated polyurethane [FCO‐PU]) film and comprehensively evaluate its anticorrosive property. The FCO‐PU was prepared by structural modification of castor oil (CO) through attachment of long fluorocarbon chains as pendant groups onto the backbone of CO. A model PU film (CO‐PU) was also prepared from unmodified CO to compare the properties of FCO‐PU film. All intermediate compounds, FCO‐PU and CO‐PU films were characterized by various spectroscopic techniques. Morphological, thermal and mechanical properties of the PU films were analyzed by field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) studies. Successful introduction of long fluorocarbon chains into the FCO‐PU film is reflected by its high hydrophobicity with a water contact angle of 119.1°, compared to the model CO‐PU film with a water contact angle of 84.4°. Anticorrosive properties of the PU films were evaluated by polarization technique and electrochemical impedance spectroscopy under corrosive environment and the obtained results reveal a significant corrosion resistance (corrosion rate: 6.72 × 10−6 mm/year) behavior by the FCO‐PU film. This work represents an effective strategy for the backbone modification of CO to develop novel functional PU materials.

Physical aging of PC:PS blends: Dynamic mechanical analysis and nuclear magnetic resonance studies

AbstractThe effect of physical aging of the partially miscible blend of polycarbonate:polystyrene (PC:PS) at temperatures near the glass transition temperature (Tg) of the PS was studied as a function of time. For this purpose, blends of PC and PS with different ratios were elaborated and characterized using SEM, FTIR, DSC, and DMA techniques. The results indicated the presence of weak interaction upon blending with a maximum of interaction for the 50:50 blend. The effect of physical aging on the latter was then investigated via DMA, DSC, and NMR analyses. The DMA results showed that both phases were sensitive to aging. The effect was found to be strongly dependent on both the temperature and time. The aging of PC:PS blend was also found to trap stress during the process which induced an instability in the viscoelastic behavior. The latter was found to be associated with a phase‐separation morphology of the blend and influenced by its composition. The NMR analysis also showed a pronounced distortion of the conformation combined with increasing molecular motion. These effects were found to be important for aging below the PS's Tg.

Complementarity of mDSC, DMA, and DRS Techniques in the Study of Tg and Sub-Tg Transitions in Amorphous Solids: PVPVA, Indomethacin, and Amorphous Solid Dispersions Based on Indomethacin/PVPVA.

Recently, glasses, a subset of amorphous solids, have gained attention in various fields, such as polymer chemistry, optical fibers, and pharmaceuticals. One of their characteristic features, the glass transition temperature (Tg) which is absent in 100% crystalline materials, influences several material properties, such as free volume, enthalpy, viscosity, thermodynamic transitions, molecular motions, physical stability, mechanical properties, etc. In addition to Tg, there may be several other temperature-dependent transitions known as sub-Tg transitions (or β-, γ-, and δ-relaxations) which are identified by specific analytical techniques. The study of Tg and sub-Tg transitions occurring in amorphous solids has gained much attention because of its importance in understanding molecular kinetics, and it requires the combination of conventional and novel characterization techniques. In the present study, three different analytical techniques [modulated differential scanning calorimetry (mDSC), dynamic mechanical analysis (DMA), and dielectric relaxation spectroscopy (DRS)] were used to perform comprehensive qualitative/quantitative characterization of molecular relaxations, miscibility, and molecular interactions present in an amorphous polymer (PVPVA), a model drug (indomethacin, IND), and IND/PVPVA-based amorphous solid dispersions (ASDs). This is the first ever reported DMA study on PVPVA in its powder form, which avoids the contribution of solvent to the mechanical properties when a self-standing polymer film is used. A good correlation between the techniques in determining the Tg value of PVPVA, IND, and IND/PVPVA-based ASDs is established, and the negligible difference (within 10 °C) is attributed to the different material properties assessed in each technique. However, the overall Tg behavior, the decrease in Tg with increase in drug loading in ASDs, is universally observed in all the above-mentioned techniques, which reveals their complementarity. DMA and DRS techniques are used to study the different sub-Tg transitions present in PVPVA, amorphous IND, and IND/PVPVA-based ASDs because these transitions are normally too weak or too broad for mDSC to detect. For IND/PVPVA-based ASDs, both techniques show a shift of sub-Tg transitions (or secondary relaxation peaks) toward the high-temperature region from -140 to -45 °C. Thus, this paper outlines the usage of different solid-state characterization techniques in understanding the different molecular dynamics present in the polymer, drug, and their interactions in ASDs with the integrated information obtained from individual techniques.

Poly (vinyl alcohol)/chitosan/sodium alginate composite blended membrane: Preparation, characterization, and water‐induced shape memory phenomenon

AbstractIn this study, we successfully prepared poly (vinyl alcohol)/chitosan/sodium alginate blended (PCS/SA) composite membranes by a simple solution casting method and solvent evaporation technique. The physicochemical properties and effect of different wt% of sodium alginate (SA) on poly (vinyl alcohol)/chitosan (PCS) membranes were systematically evaluated and studied along with its shape memory properties and mechanism. With increased wt% of SA, the crystallinity of PCS/SA membranes reduced significantly. PCS/SA membrane has better thermal stability than pure PVA membrane but is slightly lower than PCS membrane and decreased with higher SA contents. Dynamic mechanical analysis (DMA) study revealed that water act as a stimulus for the shape recovery behavior. The mechanical study showed that PCS membranes with a small amount of SA (0.1 and 0.2 wt%) have a much better elongation at break than other membranes. The swelling ratio, gel contents, and contact angle results concurred with the results of shape memory effect (SME) of all membranes, where the PCS with higher contents of SA possess better and faster shape recovery speed. The above results demonstrate that SA is a potential additive that can be used for water‐induced shape memory applications.

Fracture mechanism and scratch behaviour of MWNTs reinforced 70/30 (wt/wt) PC/ABS blends and their nanocomposites

In this work, multiwalled carbon nanotubes (MWNTs) are dispersed in 70/30 (wt/wt) polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) (PC70ABS30) blends and their nanocomposites by the melt-processing method. The morphology observations suggest the development of matrix-droplet morphology. There exists an interaction between MWNTs and the PC phase, which is observed from Raman spectroscopic investigation. Dynamic mechanical analysis (DMA) studies show the increase in storage modulus values depicting the stiffening effect of MWNTs, tanδ value increase depicting the energy dissipation. The flexural and impact properties increase significantly. The mechanism of flexural fracture is craze formation in the skin layer with a shear band and facets formation in the bulk region as observed from the SEM investigation of a flexural fractured surface of MWNTs reinforced PC70ABS30 blends and their nanocomposites. In addition, the deformation at the edge, river-like pattern, striation associated shear bands, craze, cavitation, and facets formation are the impact fracture mechanism as observed from SEM investigation of impact fractured surface of MWNTs reinforced PC70ABS30 blends and its nanocomposites. Scratch studies reveal the improved dispersion of MNNTs at 0.5–1 wt% in PC70ABS30 blends and their nanocomposites with a slightly higher scratch coefficient of friction and scratching force.

Fracture Behavior of Polyrotaxane-Toughened Poly(Methyl Methacrylate).

The fracture behavior of polyrotaxane (PR)-modified poly(methyl methacrylate) (PMMA) was investigated. PR is a supramolecule with rings threaded onto a linear backbone chain, which is capped by bulky end groups to prevent the rings from de-threading. The ring structure is α-cyclodextrin (CD), and it can be functionalized to enhance its affinity with the hosting polymer matrix. Adding only 1 wt % of PR containing methacrylate functional groups (mPR) at the terminal of some of the polycaprolactone-grafted chains on CD promotes massive crazing, resulting in a significant improvement in fracture toughness while maintaining the modulus and transparency of the PMMA matrix. Dynamic mechanical analysis and atomic force microscopy studies reveal that mPR strongly interact with PMMA, leading to higher molecular mobility and enhanced molecular cooperativity during deformation. This molecular cooperativity may be responsible for the formation of massive crazing in a PMMA matrix, which leads to greatly improved fracture toughness.

Closed-Loop Controlled Photopolymerization of Hydrogels.

Here, we present a closed-loop controlled photopolymerization process for fabrication of hydrogels with controlled storage moduli. Hydrogel crosslinking was associated with a significant change in the phase angle of a piezoelectric cantilever sensor and established the timescale of the photopolymerization process. The composition, structure, and mechanical properties of the fabricated hydrogels were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). We found that the storage moduli of photocured poly(ethylene glycol) dimethacrylate (PEGDMA) and poly(N-isopropylacrylamide) (PNIPAm) hydrogels could be controlled using bang-bang and fuzzy logic controllers. Bang-bang controlled photopolymerization resulted in constant overshoot of the storage modulus setpoint for PEGDMA hydrogels, which was mitigated by setpoint correction and fuzzy logic control. SEM and DMA studies showed that the network structure and storage modulus of PEGDMA hydrogels were dependent on the cure time and temporal profile of UV exposure during photopolymerization. This work provides an advance in pulsed and continuous photopolymerization processes for hydrogel engineering based on closed-loop control that enables reproducible fabrication of hydrogels with controlled mechanical properties.

Mechanical and thermal properties of cellulose nanocrystals from jute fibers reinforced epoxy composites

This study investigated the effects of loadings of cellulose nanocrystals (CNC) extracted from jute fibers on the chemical, mechanical and thermal properties of the Epoxy matrix. The CNC/Epoxy composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry, tensile tests, dynamic mechanical analysis, and thermogravimetric analysis. Experimental results showed that the tensile strength, modulus, and work of fracture showed a statistically significant increase from 1 to 5 wt.% CNC loading. In addition, TG measurements revealed that the onset temperature (Tonset) and temperature at maximum decomposition rate (Tmax) for composites decreased compared to neat epoxy with increasing CNC concentration. Dynamic mechanical analysis studies showed that the storage modulus values at 35 °C and 120 °C decreased for lower 1 wt% CNC content sample compared to neat epoxy, then increased for samples loaded with 3 and 5 wt% of CNC.

Nano‐metal oxide fillers in thermo‐responsive polycaprolactone‐based polymer nanocomposites smart materials: Impact on thermo‐mechanical, and shape memory properties

AbstractThe present study introduces the properties of three thermo‐responsive shape memory polymer nanocomposites (SMPCs), viz. SMPC–NiO (SMP with nickel oxide), SMPC‐Fe2O3 (SMP with iron oxide), and SMPC‐Fe2NiO4 (SMP with iron nickel oxide) along with the neat SMP blend. Styrene‐Butadiene rubber and poly ε‐caprolactone (PCL) polymer are the vital part, which forms the backbone of polymer‐elastomer blend matrix. This study helps to understand the effect and influence of these metal oxide nanofillers' integrated blend on their different inbuilt properties. The tensile test and dynamic mechanical analysis studies confirmed that SMPC‐Fe2NiO4 holds a large elastic modulus value and very rigid compared to other SMPCs. Thermal decomposition studies using differential scanning calorimetry, thermogravimetric (TG) analysis, and TG‐gas chromatography and mass spectrometry results show that the nanocomposites undergoes a two‐stage decomposition process. The shape memory test reveals that the time taken for temporary shape recovery is high for SMPC‐Fe2NiO4 because of its rigid nature and low for SMPC‐Fe2O3. The results revealed that, from this exploratory study, the integration of metal oxide nanopowder fillers, especially Fe2O3 with neat SMP, showed better properties.

DMA Study of the Molecular Structure of Porcine Fat in-Water Emulsions Stabilised by Potato Starch.

The aim of the study was to determine how the molecular structure of porcine fat-in-water type emulsions stabilised with potato starch affected their rheomechanical properties. Dynamic mechanical analysis (DMA) and instrumental analysis of the texture were the method used in experiments. Starch gels with concentrations corresponding to the water starch concentration of the examined emulsions were used as control systems. The analysis of the starch and starch–fat systems showed that the values characterising their rheomechanical and textural properties reflected the spatial reaction of the amylose matrix to dynamic mechanical interactions. Changes in their values resulted from conformational changes in the structure of segments and nodes of the lattice, conditioned by the concentration of starch and the presence of fat. As a result of these changes, starch–fat emulsions are distinguished by greater densities of network segments and nearly two times greater functionalities of nodes than starch gels. The instrumental analysis of the texture showed that the values of the texture parameters in the starch gels were greater than in the starch–fat emulsions. The high values of the correlation coefficients (R~0.9) between the texture determinants and the rheological parameters proved that there was a strong correlation between the textural properties of the tested systems and their rheomechanical properties.

Novel epoxy resin adhesives toughened by functionalized poly (ether ether ketone) s

Epoxy resins are inherently brittle due to their high crosslink density. Hybridization of epoxies with a thermoplastic phase is an effective solution for reducing the brittleness and improving the toughness without impairing the thermal and mechanical properties. The present study focuses on the development of a novel room temperature curable epoxy resin by blending with different proportions of hydroxyl terminated poly (etheretherketone)s (PEEKTOH) as thermoplastic toughening agent. The systems were cured using triethylenetetramine (TETA). Isothermal rheological studies showed that, incorporation of PEEKTOH phases reduced the gelation time of the blend from 175 min to 30 min. The glass transition temperature of the blends were improved marginally (from 74 to 80 °C) as evidenced by dynamic mechanical thermal analysis studies. The toughened and the unmodified systems were examined for their adhesive properties on aluminium substrates. It was noted that, about 19% improvement in lap shear strength (LSS) was achieved for the toughened adhesive. Higher proportions of PEEKTOH in the epoxy matrix led to increased viscosity which consequently reduced the wetting characteristics, as proven by contact angle measurements. The fracture toughness of the cured blends improved up to 86%. Fracture morphology evaluation by scanning electron microscopy (SEM) showed a brittle fracture for the unmodified epoxy and a phase separated morphology for the toughened blends. Transparency was reduced in the toughened formulations due to phase separation of PEEKTOH.

Development of barite-filled acrylonitrile butadiene styrene composites: Mechanical, thermal, melt-flow and morphological characterizations

Barite mineral (BRT) was compounded with acrylonitrile butadiene styrene terpolymer (ABS) with four varied filling ratio of 5%, 10%, 15% and 20% by weight. ABS/BRT composites and unfilled ABS were fabricated by twin screw micro-extruder and test samples were shaped using injection molding process. Tensile tests, shore hardness measurements and impact tests, dynamic mechanical analysis (DMA), melt-flow index (MFI) study and scanning electron microscopy (SEM) characterization techniques were performed in order to investigate mechanical, thermo-mechanical, melt-flow and morphological performance of composites, respectively. Mechanical tests results showed that tensile strength and hardness of unfilled ABS were enhanced as BRT content increased. DMA study revealed that in addition to glass transition temperature, storage modulus of ABS raised by BRT inclusions. However, impact energy of ABS exhibited decreasing trend with the loading level of BRT. According to MFI measurements, BRT additions caused no significant change for MFI parameter of ABS regardless of concentration. It was confirmed by SEM microphotographs that the dispersion of BRT particles was found to be more homogeneous into ABS phase for their lower contents. The filling ratio of 10% BRT yield the highest performance among fabricated ABS based composites according to test results.