Polymer Bulletin最新文献

The effects of concentrated solar radiation on the thermal, chemical, and mechanical properties of post-consumer poly(ethylene terephthalate) (PET) films are studied in the present research work. The films were exposed to solar radiation using a compound parabolic concentrator (CPC), and the results are compared with those obtained from exposing PET films to conditions established in an accelerated weathering chamber (QUV). The CPC and QUV were evaluated on specimens measuring 2 × 13 × 0.5 cm³. Exposure in the CPC was carried out over one year during the periods of February–April, May–July, and October–December. Additionally, in the QUV, the equivalence in hours of exposure to that used in the CPC was sought. The results obtained by differential scanning calorimetry (DSC) indicate a significant increase in crystallinity in the material exposed within CPC, while specimens in QUV exhibited effects related to physical aging. Information obtained from thermogravimetric analysis (TGA) showed a decrease in thermal stability and maximum degradation temperature of the exposed specimens, with a trend consistent with DSC. Intensity decreased in the infrared spectra of films exposed in the CPC, without absorption bands of photo- or thermodegradation. The intrinsic viscosity of specimens exposed to degradation showed a maximum reduction of 17%, attributed to polymeric chain cleavage due to photodegradation. The dynamic mechanical analysis (DMA) evidenced a deterioration in the elastic response of the material, particularly in the one subjected to solar concentration, which is aligned with the surface cracking observed by scanning electron microscopy.

Thermal resistance of expanded polystyrene (EPS) insulation boards are investigated in terms of foam extrusion process equipped with an underwater pelletizer. This method has been used by several companies as an alternative process to obtain EPS beads from suspension polymerization of styrene. In this process either polystyrene granules with no cellular microstructure (general purpose polystyrene) or polystyrene beads with closed cell structure or both together can be used. Therefore, in this study, commercial general purpose polystyrene and expandable polystyrene materials were blended with either carbon black or graphite powder through foam extrusion process to obtain effective thermal resistance values. In order to make a fair comparison, materials were prepared similar to commercial recipes which include flame retardant and nucleating agent. It was observed that the compatibility of graphite powder with general purpose polystyrene was better than expandable polystyrene in terms of glass transition temperatures and thermal insulation values. The density of the prepared materials increased with the addition of carbon black to all samples. The best glass transition temperature was measured as 107.5 °C while the best thermal conductivity value was recorded as 0.2997 W/m.K which is fairly good when compared to commercial polystyrene insulation boards.

The complex dielectric permittivity of Polyvinylpyrrolidone (PVP K-30) [C₆H₉ON]_n in four different alcohols (methanol, ethanol, propanol, and butanol) with no. of carbon atoms ranging from one to four has been determined in the frequency range of 10 MHz to 50 GHz over the temperature range of 278.15–298.15 K at various concentrations of PVP (C) using time-domain reflectometry technique. The dielectric permittivity spectra were described using the Cole-Davidson model. Two modes of relaxation processes were observed, namely low-frequency (secondary) and high-frequency (primary) relaxation. The low-frequency relaxation is due to the interaction between solute–solvent molecules, whereas the reorientation of solvent molecules is responsible for the high-frequency dispersion of relaxation. By using the Harviliak-Negami equation, the frequency-dependent complex dielectric permittivity has been studied. Dielectric parameters such as static dielectric constant (ε_j), relaxation time (τ_j), dipole moment (û), Kirkwood correlation factor (g₁), number of solvent molecules irrotationally bound to solute molecules (Z_ib), and effective volume of rotation (V_eff) were determined. In addition to this, thermodynamic properties such as the free energy of activation (ΔF_j), enthalpy of activation (ΔH_j), and entropy of activation (ΔS_j) were also calculated. It was observed that the low-frequency static dielectric constant (ε_l) increases with the PVP concentration in all cases except in methanol. ε_l values strongly depend on the temperature, and they increase as the temperature of the system decreases, whereas the high-frequency dielectric constant (ε_h) increases towards higher concentrations of solute molecule as well as towards lower temperatures.

To improve the compatibility of ammonium polyphosphate (APP) with thermoplastic polyurethane (TPU), novel phosphorus containing polysilazane was used to microencapsulate APP (APP@SiNP) which was then used for flame retardant TPU. The influence of microencapsulation on the thermal decomposition, mechanical and flame retardant properties of TPU was investigated. The addition of APP@SiNP brought forward the onset thermal decomposition temperature (T5%) of the TPU, but improved the thermal stability of the char layer at high temperatures. The presence of APP@SiNP fillers tended to reduce the tensile strength and elongation at break of TPU, but the tensile strength and elongation at break of TPU/APP@SiNP -10.0 were still higher than those of TPU/APP-10.0, indicating that polysilazane was capable of improving the interfacial interaction between APP and the TPU matrix. Both TPU/APP@SiNP-7.5 and TPU/APP@SiNP-10.0 can achieve UL-94 V-0 level. The PHRR, THR, and TSP values of TPU/APP@SiNP-10.0 were 77%, 58%, and 70% lower than the pristine TPU, which were also better than TPU/APP-10.0. The superior flame retardant efficiency of APP@SiNP was attributed to its catalytic charring capacity and the formation of thermally stable char residues. Keywords: Flame retardance; Polysilazane; Ammonium polyphosphate; Smoke suppression

Graphical abstract

Maleated cassava starch (MCS)/poly (vinyl alcohol) (PVA)/kaolin clay (KC) nanocomposite films with high mechanical and barrier properties were prepared by a simple casting film. Based on the MCS/PVA matrix, the effects of KC content on the MCS/PVA/KC nanocomposite films were investigated. SEM results demonstrated that the MCS/PVA/KC nanocomposite films exhibited KC good dispersion in the polymer matrix. FTIR spectra showed that the molecular interactions in the MCS/PVA/KC films with higher PVA content enhanced. The maximum tensile strength and elongation at break for the MCS/PVA/KC at 6 and 5% KC composite films were 16 MPa and 530%, respectively. The MCS/PVA/KC composite was applied to extend the shelf life of the banana, and results showed that the good shelf life of the banana was accepted. The MCS/PVA/KC composite film is a promising material for high-barrier food packaging.

In this study, nanocomposite films consisting of potato starch (PS), layered double hydroxide (LDH), and microcrystalline cellulose (MCC) were synthesized using the solution casting method. The MCC particles were used to stabilize the dispersion of LDH during film preparation. The study investigated the effect of LDH particles on the optical, electrical, dielectric, mechanical, and barrier properties of PS/MCC films. The X-ray diffraction and scanning electron microscopy analysis confirmed that the PS/MCC/LDH ternary films had a partially intercalated and partially exfoliated structure. FTIR and Raman spectroscopy analysis revealed the formation of new hydrogen bonds between PS hydroxyl groups and nanoparticles. The direct optical band gap decreased from 5.80 to 5.44 eV with increasing LDH content. The refractive index, optical conductivity and optical dielectric constant all improved with increasing LDH content. The presence of MCC and LDH had little effect on the optical clarity of the starch-based films. The improving of dielectric properties was demonstrated by decreasing the dielectric loss tangent with increasing LDH content. The addition of 1%, 3%, and 5% by weight of LDH to the pure starch PS film resulted in significant improvements in tensile strength and tensile modulus of the ternary nanocomposites. In addition, the water solubility of the nanocomposites decreased with the addition of LDH. The principal component analysis results confirmed the positive effect of higher biopolymer content on these properties. The results of the study confirm that PS/MCC/LDH nanocomposites films can be used in optical and electronic applications.

Carbon fiber (CF) is highly valued for its exceptional strength-to-weight relation, making it best for energy-efficient applications in aerospace, automotive, and construction sectors. Recent advancements in CF technology have reduced production costs, enhancing market growth. Carbon fiber-reinforced polymer (CFRP) composites offer benefits such as fatigue resistance, weight reduction, stiffness, and corrosion resistance. The choice of matrix material, particularly thermoplastics, impacts CFRP properties, with thermoplastics favored for recyclability and mass production. Fabrication techniques like filament winding and resin transfer molding ensure precise CF alignment but have complexities. Additive manufacturing (AM) methods, such as FDM, DLP, and SLA, provide design flexibility and efficiency. Recycling approaches, including thermal, mechanical, and chemical methods, address CFRP waste. This review offers an overview of AM technologies in CFRP manufacturing, focusing on advancements in continuous, short, and nano carbon fiber composites, their properties, manufacturing methods, and recycling techniques, as well as their applications and topological optimization.

This research mainly focused on studying the influence of various curing media on the properties of lightweight geopolymer composites. Here, Ground Granulated Blast furnace Slag (GGBS), Paddy straws, and the combination of sodium silicate and sodium hydroxide at the ratio of 2.5:1 were used to produce geopolymer composites. For this experiment, two different parameters, i.e., variation of paddy straw (0, 5, 10, 15, and 20%) and variation of curing media (Intermittent, Heat, and Saline water), were chosen. The compressive strength of a 20% addition of paddy straw is dramatically reduced by 88.6%, while the density is reduced to 40.42%. Maximum flexure and tensile strength were noted as 65.11 and 45.5%, respectively, for the 15% addition of paddy straw. An interesting fact found from the samples cured under Saline water enhanced the overall compressive strength, tensile and flexural strength by 12.85, 45.5, and 21.2%, respectively, compared to the other two curing media.

The performance of incompatible blends is strongly depended on their morphology and interfacial properties that can be controlled by proper compatibilizers. This research systematically investigates the interfacial properties of the binary and the ternary blends based on low-density polyethylene (LDPE), poly(lactic acid) (PLA) and maleic anhydride-grafted polyethylene (PE-g-MAH) through the melt linear viscoelastic rheological behavior of the blends and neat components analyzed by proper rheological models. Moreover, the relationship between rheology, phase morphology and mechanical properties of LDPE/PLA ternary blends with different amounts of PE-g-MAH was studied. In the rheological analyses via the additive rule indicated in the molten state, no consistent interfacial interaction between LDPE and PLA phases is made due to the presence of PE-g-MAH at the interface of the blend. However, the analyses based on the Palierne’s model implied that the interfacial tension of compatibilized blends decreases. This not only resulted in improving PLA dispersed phase morphology in the compatibilized blends, but also forming in situ fibrillar composites where the compatibilizer amount was relatively high (5 and 7.5 wt.%). Unlike the molten state, because of the strong interactions between PE and PLA phases of compatibilized blends in the solid state, the tensile mechanical properties, including Young’s modulus, strength and elongation-at break, could be reinforced up to 24%, 25% and 90%, respectively. Overall, findings make a profound realization of the amount depended performance of PE-g-MAH as the most common compatibilizer for PE/PLA blends, very helpful not only from scientific viewpoints but also in terms of the blend industry applications.