Thermal Glass Transition Research Articles

Structure-Property Relationships of CO2 Absorbing Core-Shell Microparticles with Encapsulated Ionic Liquid.

The demand for new ionic liquid (IL)-based systems to selectively sequester carbon dioxide from gas mixtures has prompted the development of individual components involving the tailored design of IL themselves or solid-supported materials that provide excellent gas permeability of the overall material as well as the ability to incorporate large amounts of ionic liquid. In this work, novel IL-encapsulated microparticles comprising a cross-linked copolymer shell of β-myrcene and styrene and a hydrophilic core of the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) are proposed as viable materials for CO2 capture. Water-in-oil (w/o) emulsion polymerization of different mass ratios of β-myrcene to styrene (i.e. 100/0, 70/30, 50/50, 0/100) yielded IL-encapsulated microparticles, where the encapsulation efficiency of [EMIM][DCA] was dependent on the copolymer shell composition. Thermal analysis using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that both thermal stability and glass transition temperatures depend on the mass ratio of β-myrcene to styrene. Images from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microparticle shell morphology as well as measure the particle size perimeter. Particle sizes were found to be between 5 and 44 μm. CO2 sorption experiments were conducted gravimetrically using TGA instrumentation. Interestingly, a trade-off between CO2 absorption capacity and ionic liquid encapsulation was observed. While increasing the β-myrcene content within the microparticle shell increases the amount of encapsulated [EMIM][DCA], the observed CO2 absorption capacity did not increase as expected due to reduced porosity compared to microparticles with higher styrene content in the microparticle shell. [EMIM][DCA] microcapsules with a 50/50 weight ratio of β-myrcene/styrene showed the best synergistic effect between spherical particle diameter (32.2 μm), pore size (0.75 μm), and high CO2 sorption capacity of ∼0.5 mmol CO2/g sample within a short absorption period of 20 min. Therefore, core-shell microcapsules composed of β-myrcene and styrene are envisioned as a promising material for CO2 sequestration applications.

Real-Time Determination of the Glass Transition Temperature during Reversible Network Formation Based on Furan–Maleimide Diels–Alder Cycloadditions Using Dielectric Spectroscopy

The molecular dynamics of the reversible network 4F230-2M230 were studied systematically by dielectric relaxation spectroscopy (DRS) at frequencies between 10–1 and 107 Hz under both isothermal and non-isothermal conditions, focusing on the cooperative segmental dynamics as sensed by the dielectric α-relaxation. This reversible network is based on the furan–maleimide Diels–Alder reaction of a 4-functional furan-functionalized Jeffamine coupled with a 2-functional maleimide. Different strategies for extracting a “dielectric” glass transition temperature (Tg) were employed and compared. First, relaxation times τα were derived by conventional Havriliak–Negami fits of dielectric spectra and then fitted to the Vogel–Fulcher–Tammann (VFT) equation, which yields the dynamic Tg of partially cured samples (approach I). Alternatively, the thermal glass transition temperature was derived from the dielectric spectra ε′(f, T) using a fine structure analysis by bivariate differential sampling. Both the dynamic and thermal Tgs revealed an excellent agreement, confirming the stability of the VFT fits as well as the equivalence of both quantities as usually expected for bulk glass-forming materials. Two attempts were made to find a unique set of VFT parameters based on a global fit considering DRS spectra from partially cured samples during heating from −120 to 100 °C. Via a first procedure (approach II), a unique set of VFT parameters EV and τ∞ was obtained that well describes the relaxation times during non-isothermal cure at temperatures where the effects of ongoing cure kinetics can be neglected. To overcome this restriction, a refined approach III was developed that includes the earlier reported kinetic model for the DA reaction and allows accurate predictions for the relaxation time evolution during both isothermal and non-isothermal cure experiments. Based on this unique description, a new technique for continuous cure monitoring was proposed and tested. This technique allows us to compute in real-time dynamic Tg from the relaxation time τα at any stage of the isothermal or non-isothermal cure process using two unique VFT parameters from the global fit procedure. This approach might stimulate new applications of DRS-based cure monitoring.

Gas permeation, thermal, morphology and mechanical properties of polyimide/clay nanocomposites: Effect of organically modified montmorillonite

Novel polyimide/clay nanocomposites were fabricated by incorporating organically modified clay at different loading percentage of 1–5 wt% within the polyimide (PI) matrix. A novel PI was synthesized through a direct polycondensation reaction between novel 5,5′-((4-methoxyphenyl)azanediyl)bis(isobenzofuran-1,3-dione)and 4,4′-(1,4-phenylenebis(oxy))bis(3-(trifluoromethyl)aniline). The organoclay was prepared from Sodium montmorillonite (Na-clay) and protonated form of diamine (modifier) via ion-exchange reaction. The structural characterization of nanocomposites were made using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the mechanical properties were obtained by tension tests. The results of XRD, TEM, and FE-SEM indicated that clay could well disperse in the PI matrix and were intercalated by diamine and PI macromolecules. The thermal stability and glass transition temperature of nanocomposite at lower clay loadings are similar to PI but gradually decrease with increase in clay content. The tensile properties of PI/Clay nanocomposites showed the highest values at the optimum clay content of 3 wt%. The gas permeation of PI/clay nanocomposites was increased with the increase in loading percentage of organoclay, whereas the gas selectivity was maintained at par to that of neat PI film until it diminished at 5 wt% percentage of organoclay causing mineral agglomeration. PI/clay 3 wt% MMMs exhibited 245% and 240% increase in CO2 and O2 gas permeability respectively, while showing minimal variation in the selectivity of O2/N2 and CO2/N2 compared to that of neat PI matrix.

Fabrication and characterization of hexagonal boron nitride/polyester composites to study the effect of filler loading and surface modification for microelectronic applications

AbstractThis work investigates a composite prepared with polyester and hexagonal boron nitride (hBN) in terms of the properties required in the material for microelectronics applications. The influence of filler loading and the surface treatment of hBN with a silane coupling agent (γ‐aminopropyl triethoxy silane) is studied. It has been observed that the silane‐modified hBN improves the compatibility and adhesion with the matrix as verified by SEM images. The experimental investigation reveals that the addition of hBN in polyester unwillingly rises the density, voids content, and water absorption rate. Though, the increment is limited with surface‐modified hBN. The material's mechanical properties improve with filler loading over a particular range of filler loading. The material's thermal conductivity and glass transition temperature increase with hBN content, whereas the coefficient of thermal expansion reduces. Polyester when filled with 40 wt% of the silane‐hBN, the thermal conductivity improves around six times that of unfilled polyester. The dielectric properties are marginally augmented with filler loading whereas, the increase in frequency results in the reduction of dielectric properties. It can be observed from the overall experimental analysis that the developed material can be used in different microelectronic applications.Highlights A new class of composite is developed with polyester and raw/modified hBN. Composite with modified hBN shows improved physical/mechanical properties. Thermal properties of polyester improved appreciably with treated hBN. The dielectric properties of composites remain well within the range. The fabricated composites are recommended for microelectronics applications.

Synthesis of a novel boron‐containing hyperbranched benzoxazine and its flame‐retardant properties in copolymer with epoxy resin

AbstractA novel boron‐containing hyperbranched benzoxazine (HB‐B) was synthesized from the reaction of triethanolamine borate (BAE), bisphenol‐A, and paraformaldehyde via Mannich condensation. The chemical structures of BAE and HB‐B were characterized by Fourier transform infrared (FT‐IR) and hydrogen nuclear magnetic resonance (1H NMR). Afterward, the boron‐containing hyperbranched benzoxazine/epoxy resin copolymers (E51/HB‐B) were prepared. The curing behavior of ‐B and E51/HB‐B was studied by FT‐IR and differential scanning calorimeter (DSC). The thermal stability and flame retardancy properties of the cured HB‐B and E51/HB‐B were evaluated by thermogravimetric analyzer (TGA), limited oxygen index (LOI), UL94 rating test, and microscale combustibility calorimeter experiments (MCC). The initial thermal decomposition temperature and glass transition temperature steadily dropped with increasing HB‐B content, while the char yield kept rising. The LOI value of the E51/HB‐B‐12 wt% was 31.8%, meeting the UL94 V‐0 specification. The result of heat release capacity (HRC) decreased by 20.4%. Moreover, the mechanical properties were also improved, and the tensile strength of E51/HB‐B copolymer was increased by 88.5%. Finally, the fracture morphology of E51/HB‐B was characterized by SEM.

Preparation of nanocomposite based on chitosan-PDCOEMA containing biosynthesized ZnO: Biological and thermal characterization

In this study, poly(2-(3,5-dichloroanilino)-2-oxoethyl 2-methylprop-2-enoate) (PDCOEMA), a new synthetic polymer based on methacrylate, was synthesized and characterized. The blend of PDCOEMA with chitosan (CS) was prepared by the hydrothermal method and the DSC technique confirmed its formation. It was observed that PDCOEMA increased the thermal stability and glass transition temperature (Tg) of CS. The Tg value of the PDCOEMA-CS blend was increased at about 7 °C with the highest ZnO NPs contribution rate. PDCOEMA-CS/ZnO nanocomposites were prepared by adding ZnO NPs produced by biosynthesis at different weight ratios to the PDCOEMA-CS blend by hydrothermal method. When the thermal stability of nanocomposites determined by TGA was examined, it was observed that it increased significantly compared to CS. While the initial decomposition temperature of CS was 270 °C, this value increased to 293 °C after blending with DCOEMA, and to 317 °C with the addition of 7 % ZnO NPs. Antimicrobial, anticancer, cytotoxic, antioxidant, and wound healing properties of PDCOEMA, CS, PDCOEMA-CS blend, and nanocomposites were determined. According to the obtained results, it was observed that nanocomposites containing 5 % and 7 % ZnO NPs showed good anticancer activity against A549 cells at a dose of 10 μg/mL. The results show that the produced nanocomposites can contribute to developing CS-based materials.

Colorless polyimide copolymers derived from isomeric biphenyltetracarboxylic dianhydrides and 2,2′-bis(trifluoromethyl)benzidine

Colorless polyimide (CPI) copolymers were synthesized by one-step or two-step methods, using 2,2′-bis(trifluoromethyl)benzidine (TFMB), 2,2′,3,3′-biphenyltetracarboxylic dianhydride (3,3′-BPDA), and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (4,4′-BPDA) as the monomers. These polymers exhibited a d-spacing value of 5.7–6.7 Å, and their d-spacing values increased while the intensity of π-π stacking interactions decreased with the increase of 3,3′-BPDA/TFMB contents. The solubility of the copolymers were gradually enhanced as the increase of 3,3′-BPDA/TFMB contents. Their coefficients of thermal expansion and glass transition temperatures increased with 3,3′-BPDA/TFMB contents, ranging from 15 to 68 ppm K−1 and 300 to 359 °C, respectively. These polymers exhibited excellent optical transparency (λ0 < 390 nm, T450 > 83.2%, and b* < 4). CPI-4 and CPI-5 with 40 mol% and 20 mol% of 3,3′-BPDA/TFMB contents exhibited well-balanced solution processability and physical properties. The CPI copolymers can be potentially used in optical and optoelectronic fields owing to their desirable overall properties.

Molecular‐level fabrication strategies for the POSS cross‐linked polybenzoxazines

AbstractIn order to study the dispersion and compatibility of polysilsesquioxane (POSS) with different functional groups in benzoxazine resin, four different polysilsesquioxane/polybenzoxazine (POSS/PBZ) composites are prepared based on 3‐phenyl‐3,4‐dihydro‐2H‐benzoxazine (PHa), unreactive Octaphenylsilsesquioxane (OPS), Mercaptopropyl‐isobutyl silsesquioxane (SPOSS) containing one reactive sulfhydryl group, Aminopropyl‐isobutylsilsesquioxane (NPOSS) containing one reactive amino group and Octa (aminophenyl) silsesquioxane (OAPS) containing eight reactive amino groups, respectively. Scanning electron microscope (SEM), transmission electron microscope (TEM), and transmission electron microscope with probe corrector (AC‐TEM) are used to investigate compatibility. The results indicate that OAPS have very good compatibility and interaction with benzoxazine in the molecular level based on the microstructure. Besides, molecular and mesoscopic dynamic simulations (MesoDyn) also confirms OAPS and PHa have the best compatibility based on the micro and mesoscopic aspects. Then their properties of thermal stability and glass transition temperature (Tg) are identified by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. While OAPS is beneficial to increase the initial decomposition temperature (T5%) of PBZ by 26 °C and the Tg by 16 °C, comparing with pure PHa. However, NPOSS and SPOSS aggregate into micron‐sized silicon spheres, and OPS precipitates and deposits on the bottom of the resin, which could weaken the property of their thermal stability.

Synthesis and Characterization of Pyrimidine‐Based Novel Phthalonitrile Resins with Excellent Processing Performance and High Glass Transition Temperature

AbstractThree phthalonitrile monomers containing pyrimidine ring and benzene ring side group were successfully synthesized with 4, 6‐dichloro‐2‐phenylpyrimidine, three kinds of phenols (resorcinol, bisphenol A and bisphenol AF) and 4‐nitrophthalonitrile via nucleophilic substitution reaction. All the phthalonitrile monomers exhibited excellent processing performance due to low melting points (Tm) (below 100 °C) and wide processing windows (difference between melting temperature and curing temperature) above 140 °C. By introducing pyrimidine ring and benzene ring side group, the lower melting point of monomers did not affect the thermal stability and thermal mechanical properties of the phthalonitrile resins based on different bisphenols. In particular, 5 % thermal decomposition temperature (T5%) and glass transition temperature (Tg) of phthalonitrile resin based on resorcinol surpassed 455 and 400 °C while storage modulus (E′) was 3209 MPa. Therefore, phthalonitrile resin containing pyrimidine ring and benzene ring side group have potential applications in the field of high temperature resistant polymers and composites.

Impact of electrical percolation on mechanical, thermal and flame properties of carbon filler‐epoxy composites

AbstractHybrid combination of carbon fillers is utilized in an epoxy matrix to enhance DC/AC conductivity and dielectric constant. Influence at electrical percolation on mechanical strength, thermal stability, co‐efficient of thermal expansion (CTE), and flame properties have been investigated since proper balance of the properties is critical. Multiwalled carbon nanotube and graphene nanoplatelets of different weight proportions are incorporated in epoxy matrix to understand their impact of electrical, mechanical and thermal properties. It is observed that weight fraction of the carbon fillers at electrical percolation tends to deteriorate the mechanical and flame properties, minimally influences thermal stability while decreasing the CTE. The weight fractions below the electrical percolation are observed to enhance mechanical and flame properties as compared to percolation level. Though the formation of network of carbon fillers is responsible for enhancement of electrical conduction and CTE, the synergy of carbon fillers is not evident in mechanical and flame properties due to dominating influence of aspect ratio, orientation, and alignment. DC conductivity of 3 × 10−6 S/m, AC conductivity of 4 × 10−2 S/m at 8 MHz is observed at electrical percolation. However, composite reveals 5% to 10% reduction in mechanical strength, while the thermal stability and glass transition (126°C) are minimally affected at percolation. Co‐efficient of thermal expansion improves to 2 × 10−6/°C and heat deflection temperature increases to 140°C. Flame properties reveal divergent trends. The need for proper balance of electrical, thermal and mechanical properties at electrical percolation is emphasized.

Elucidation of temperature dependent hydration behaviour of chickpea seeds: Prerequisite for germination

Soaking to a desirable extent of moisture is an unavoidable prerequisite in the utilization of chickpea seeds. Partially hydration of chickpea before germination, roasting or puffing of chickpea is a common practice for its propagation and preparation of ready-to-eat confectionary products. Almost completely soaked chickpeas are preferred in making soaked chickpea, sprouts, baked chickpea, and various cooked delicacies. The present research was carried out to study the hydration characteristics of chickpea seeds. Water absorption characteristics in terms of weight gain were investigated, and the process was segregated into three different phases comprising of rapid water absorption phase (Phase I), slow water absorption phase (Phase II) and termination phase (Phase III). Three empirical models, namely the Newton model, Henderson and Pabis model, and Weibull model, were used to assess their adequacy to describe temperature (10–60 °C) dependent water absorption phenomenon. Weibull model was found to describe the water uptake phenomenon better than the Newton and Henderson and Pabis models. The Arrhenius plot for Fick's law of diffusion was used to calculate the activation energy. It was observed that breakpoint occurs at 41.67 °C, correlated with the thermal glass transition of seed coat during soaking. Germination potential of chickpea seeds at different soaking temperatures was also investigated. Effect of soaking and germination of chickpea seeds on thermal properties and x-ray diffraction pattern were also studied.

ZnO-containing nanocomposites produced from Mentha pulegium L. of a new HEMA-based methacrylate copolymer: improvement the thermal and antimicrobial effect

In this study, firstly, (2-oxo-2-(3,4,5-trifluoroanilino)-ethyl-2-methylprop-2-enoate) FAOEME, a methacrylate monomer with arylamide side group containing three fluorine atoms in the side branch, was synthesized. Poly(HEMA-co-FAOEME) was obtained due to radical copolymerization of FAOEME with 2-hydroxyethyl methacrylate (HEMA). Structural characterization of its copolymer with FAOEME and HEMA was performed by spectroscopy methods such as FTIR, 1H, and 13C-NMR. Biosynthesis of ZnO nanoparticles was carried out using Mentha Plegium L. extract. Three nanocomposites of poly(HEMA-co-FAOEME) containing biosynthesized ZnO nanoparticles were produced by hydrothermal technique, which is an environmentally friendly method. The formation of Poly(HEMA-co-FAOEME)/ZnO nanocomposites and the structural changes of the components was elucidated by SEM, XRD, and FTIR techniques. The effect of ZnO nanoparticles on the thermal properties of Poly(HEMA-co-FAOEME) was investigated by TGA and DSC techniques. The results showed that ZnO nanoparticles significantly increased the thermal stability and glass transition temperature (Tg) of the matrix (poly(HEMA-co-FAOEME). The antimicrobial properties of the materials were determined by the disk diffusion method using five different bacteria and one yeast cell. It was observed that the nanocomposites showed activity against all pathogens except one bacterial species, and the source of the activity was ZnO nanoparticles.

Experimental investigation on mechanical and thermal characteristics of waste sheep wool fiber-filled epoxy composites

With the escalating trends of environmental contamination, the necessity of exploring environment friendly composites has increased. Foreseeing a sustainable future, this study investigates mechanical and thermal characteristics of woven (W), and non– woven waste sheep wool fiber (N, C, F) reinforced epoxy composites. The composites are fabricated using the in-house Vacuum Assisted Resin Transfer Molding (VARTM) technique in a controlled environment. Using animal fiber-filled epoxy composites were created. The density, void content, hardness, and tensile strength of differentially ordered waste sheep wool fiber have been examined. Also, thermal characteristics such as effective thermal conductivity (Keff) and glass transition temperature (Tg) of the said composites have been evaluated. The results of the experimental investigation reveal that non-woven needle punched (N) animal fiber polymer composites exhibit good interfacial adhesion between fiber and matrix with lower void content and higher tensile strength. Also, waste animal fiber-woven (W) and felt (F) polymer composites exhibit better hardness and low thermal conductivity. Thus, it can be said that the fabricated waste sheep wool fiber-filled epoxy composites exhibit better mechanical and thermal characteristics for insulating building components.

Ultraviolet-curable optically clear resins using novel fluorinated imide-modified urethane acrylates

Homologs of novel fluorinated aromatic imide-modified urethane acrylate oligomers (FI-UAs) with different flexible methylene chain lengths were successfully synthesized using 4,4-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA)-based diimide diols (FI-OHs), isophorone diisocyanate (IPDI), and 2-hydroxyethyl methacrylate (HEMA). Ultraviolet (UV)-curable resins (FI-UARs) were prepared using these oligomers, and the UV-curing behavior of these resins was studied by monitoring the C=C bond conversion and gel fraction while varying the UV dose. The thermal (glass transition temperature and thermal stability), optical (transmittance, yellowness, and haze), and adhesion properties of the cured films were investigated. The cured films of the resins exhibited improved thermal and optical properties, except for haze, which could be primarily due to the presence of fluorinated aromatic imide moieties in the oligomer. Furthermore, higher adhesion and improved haze were observed with increasing methylene chain length of FI-UA oligomers. • A series of new fluorinated imide-modified urethane acrylates (FI-UAs) were synthesized by reacting 6FDA-based diimide-diol and diisocyanate, followed by capping with a hydroxyl functional acrylate. • Ultraviolet-curable fluorinated imide-modified urethane acrylates resins (FI-UARs) were prepared by combining novel FI-UAs, isobonyl acrylate (IBOA), and Irgacure 1173, which were used as oligomers, the monomer, and photoinitiator, respectively. • The cured FI-UAR films exhibited enhanced glass transition temperature, thermal stability, transmittance, and yellowness, which could be primarily due to the presence of fluorinated aromatic imide moieties in the oligomer. • In addition, the adhesion and haze of cured films were improved as the methylene chain length of the FI-UA oligomers increased.

Improving mechanical and thermal properties of short carbon fiber/polyamide 6 composites through a polydopamine/nano‐silica interface layer

AbstractCarbon fiber (CF) reinforced matrix composites have been applied widely, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To solve this problem, A polydopamine/nano‐silica (PDA‐SiO2) interfacial layer on carbon fiber surface was constructed via polydopamine and nano‐ SiO2 (CF‐PDA‐SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of PDA‐SiO2 interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. Furthermore, interfacial reinforcement mechanism of composites has been discussed. This interfacial layer greatly increased the number of active groups of CF surface and its wettability obviously. The tensile strength of CF‐PDA‐SiO2/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated‐CF/PA6, CF‐PDA/PA6, and CF‐SiO2/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, and glass transition temperature (Tg) of CF‐PDA‐SiO2/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano‐SiO2 in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. This work provides a novel strategy for the construction of interfaces suitable for advanced CF composites with different structures.

Synthesis and Fabrication of a Betulin-Containing Polyolefin Electrospun Fibrous Mat for Antibacterial Applications.

Biocompounds play a significant role in the area of renewable polymers in terms of sustainability, as they can be employed or converted into monomers for polymerization in a manner similar to many petroleum-derived monomers. In this work, betulin, a plant-derived triterpene with antibacterial and antiviral properties, was converted to two kinds of α,ω-diene derivatives with different methylene spacer lengths between the olefin and the ester group via an esterification reaction. Polyolefins were subsequently made by acyclic diene metathesis (ADMET) polymerization of betulin-based α,ω-diene. The polymer consists of rigid betulin and flexible unsaturated aliphatic segments, which was confirmed by NMR spectroscopy and gel permeation chromatography (GPC). The influence of different parameters including temperature, catalysts, and catalyst loading on ADMET polymerization was investigated. These polyolefins with high molar mass (up to 20.0 kg/mol) were obtained in an elevated yield (≥95%). Thermal analysis of these (co)polymers showed excellent thermal stability (up to 360 °C) and tunable glass transition temperatures depending on the nature of betulin and alkene segments. To evaluate the antimicrobial potential of betulin-containing polymers, the fabrication of polyolefin fibrous mats (ca. 400 nm diameter) via the electrospinning technique was successfully achieved. Their morphology and hydrophobicity were studied by scanning electron microscopy (SEM) and water contact angle analyses. The fibrous mats possessed broad-spectrum antibacterial property, providing a feasible strategy to design betulin-based polymeric fibers for many applications in the biomedical field.

One pot synthesis of bio-based porous isocyanate-free polyurethane materials

In the current study, synthesis of porous isocyanate-free polyurethane materials derived from xylose is reported through a one-pot process, and the impact of varying amounts of crosslinker is studied. The synthesized materials were characterized using various techniques. The formation of the urethane bridge was confirmed using Fourier Transform Infra-Red (FTIR) spectra that exhibited characteristic bands around 1700 cm−1, 1600 cm−1, and 3400 cm−1. The characteristic peak observed at 21◦ (2θvalue) in Powder X-ray (PXRD) diffractogram further confirms the synthesis of segmented polyurethane porous materials. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) thermograms indicate that thermal stability and glass transition temperature (Tg) of synthesized non-isocyanate polyurethane (NIPU) materials increase with increase in the amount of crosslinker. The increase in Limiting Oxygen Index (LOI) values with an increment in the amount of crosslinker suggests improvement in flame retardant behavior of NIPU material due to formation of highly crosslinked network in the polyurethane matrix. These porous NIPU materials align well with the principles of sustainable development.

Thermal stability and glass transition kinetics in GeTeSb glasses by using non-isothermal measurement

In this paper we have analysed the thermal properties of three different compositions of chalcogenide glasses Ge15Te85-xSbx (x=0.5, 1, 1.5). The samples have been prepared using the melt quenching technique and the characterisation is done using X-ray diffraction. The compositional dependence on properties were studied using Differential Scanning Calorimetry (DSC) analysis using non-isothermal measurement. The glassy sample crystallized by two transition temperatures Tg1 and Tg2.The dependence of glass transition temperature on heating rate has been studied by Lasocka empirical relation and the Kissinger equation. As a result, the apparent activation energy for glass transition has been determined. Thermal stability has also been determined from the temperature difference between the onset crystallization and glass transition temperature.

Overview of the mechanical, thermal and barrier properties of biobased and/or biodegradable thermoplastic materials

This study gives an overview of the most relevant processing and performance properties of a wide selection of biobased and biodegradable plastic materials that are currently commercially available. It provides the most extensive and up-to-date scientific overview of critical properties of biobased and biodegradable plastics. Materials that are tested include fully biobased polymers (polylactic acid, polyethylene, polyamide 10,10 and a range of polyhydroxy alkanoates), partially biobased polymers (polybutylene succinate, polybutylene succinate adipate, cellulose acetate, cellulose acetate propionate, polyethylene terephthalate, polytrimethylene terephthalate, an isosorbide based polycarbonate, a thermoplastic urethane and a starch based blend) and a number of fossil-based materials (polycaprolactone, polybutylene adipate terephthalate, polyglycolic acid and polypropylene). The mechanical (tensile, flexural, impact resistance and hardness), thermal (glass transition temperature, melting temperature, melt-flow index and haul-off force) and barrier (oxygen transmission rate, water vapour transmission rate) properties of all these materials were measured and are presented in a comprehensive overview. This overview shows that the majority of functionalities that are currently being offered by fossil based polymers can be met by biobased alternatives and by biodegradable materials if this is considered to be favourable at end-of-life.

Whey protein isolate/jujube polysaccharide-based edible nanocomposite films reinforced with starch nanocrystals for the shelf-life extension of banana: Optimization and characterization

The formulation of new bionanocomposite (BNC) films using whey protein isolates (WPI, 3.3–11.7 %)-jujube polysaccharide (JPS, 1.59–18.41 %)/starch nanocrystals (SNCs, 0.32–3.68 %) blends was optimized. The ultrasound-assisted acid hydrolysis produced ~63.1 nm SNCs from native starch with −24.3 mV ζ-potential. The extracted JPS purification led to a single symmetrical peak for galactoarabinan-rich fraction (1.35 × 105 Da). The optimal levels of barrier (oxygen (11.85 cm3 m−2 d−1 atm−1) and water vapor (3.22 × 10−10 g m−1 s−1 Pa−1) permeability rate), optical (opacity index (2.7 AU μm−1), total color difference (18.69), and whiteness index (77.40)), and thermal (glass transition temperature (−8.29 °C) and melting point (110.38 °C)) properties were obtained at 5.0 % WPI, 15.0 % JPS, and 3.0 % SNCs. The film-forming solution of optimal BNCs had a significant antibacterial effect against Staphylococcus aureus and Escherichia coli. The improved crystallinity of BNCs at an optimal SNC level was confirmed by the X-ray diffraction (XRD). The field emission-scanning electron (FE-SEM) and atomic force (AFM) microscopy images confirmed a continuous and uniform network for the optimal BNCs without any pores or cracks accompanied by low surface roughness. The FTIR spectroscopy proved covalent interaction and hydrogen bonding among chemical functional groups of WPI and JPS reinforced with SNCs. The optimal BNC could preserve banana fruits with favorable physicochemical and microbial quality during storage.