Search

With the ever-growing demand for 5G networks and the promise of real-time, mission-critical applications, the advanced antennas with high-bandwidth and highly reliable connectivity are urgently needed. 5G networks primarily operate in two areas of spectrum below 6 GHz (known as sub 6) and millimeter wave, which are much higher than the working frequency of 4G cellular networks, thus the previously used materials and integration techniques need to be updated accordingly. In this sense, liquid crystal polyesters (LCP) have been considered as ideal high performance microwave/millimeter wave (mm-wave) substrate and packing materials due to their outstanding properties. More specifically, the LCP normally exhibit good thermal stability, low water absorption, stable dielectric constant and loss tangent in millimeter wave frequency range, which leads to the increasing research interests of LCP for 5G devices application in both academia and industrial fields. However, the review articles focusing on the chemistry and materials aspects of LCP intended for 5G application are unexpectedly limited. In this article, we will summarize the research progress of LCP materials used in 5G networks in the view of polymer science and engineering. More specifically, the polymerization, chemical structure, aggregated state, properties, modification and processing of typical LCP are reviewed, which would be useful for promoting practical application of the LCP in key devices of 5G networks.

[Display omitted] • The synthesis of symmetrical functional monomer flame retardant with benzene ring was reported. • It is found that the amount of flame retardants introduced is not proportional to the flame retardancy. • The influence of flame retardants in a certain range on mechanical properties unchanged. • Synthesis of intrinsic flame retardant PET. In this paper, a kind of symmetric functionalized monomer is presented, and a polyester with flame retardancy and mechanical properties is obtained. Magnesium hydroxide was modified with phenylphosphonic acid to give a novel inorganic–organic monomer (MH-PPOA) with intrinsic flame retardancy. MH-PPOA was incorporated into the main chain of polyethylene terephthalate (PET) in varying amounts (n, wt% relative to terephthalic acid) to give a series of co-polyesters (MH-PPOA n -co-PET), and the effects of the monomer on their flame retardancy and mechanical properties were determined. The structure and morphology of the hybrid monomer was confirmed by Fourier transform infrared spectroscopy, and scanning electron microscopy, and its successful introduction into the polyester chain of PET was verified by proton nuclear magnetic resonance spectroscopy. The thermal characteristics, flame retardancy and burning behavior of the synthesized copolymers were evaluated by differential scanning calorimetry, thermogravimetric analysis, measurement of the limiting oxygen index (LOI), Underwriters Laboratory vertical burning (UL-94) test, and cone calorimetry. The mechanical properties were measured by tensile testing. This study provides a new direction for the introduction of intrinsic flame retardants and demonstrates that the incorporation of a symmetrical phenylphosphonic acid modified magnesium hydroxide monomer can also improve the mechanical properties of the PET copolymer. [ABSTRACT FROM AUTHOR]

In this study, inorganic magnesium hydroxide (MH) was modified by three phosphoric acids respectively to obtain three different novel functionalized monomers. The chemical structure and morphology of (P n -MH) were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Further, functional monomers were introduced into the PET main chain structure. A new type of high-performance co-polyesters was successfully prepared. The specific structure of P 1 -MH-PET was characterized by 1H NMR spectroscopy. Thermal stability of P n -MH-PETs was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The flame retardant properties were evaluated by limiting oxygen index (LOI), vertical combustion test (UL-94) and cone calorimeter. The results show that the thermal stability and flame retardant properties of 5%P n -MH-PETs are greatly improved. Among them, the best performance is 5%P 1 -MH-PET, LOI is 32.5%, UL-94 test reached V-0 grade. Compared with neat PET, the peak heat release rate (PHRR), peak smoke release rate (PSPR), carbon dioxide release rate (CO 2 PR) and carbon monoxide release rate (COPR) decreased by 57.0%, 38.1%, 54.6% and 57.3%, respectively. Fortunately, the mechanical properties of 5%P 3 -MH-PET were also improved. [Display omitted] • Three new functional monomers with small molecular weight, symmetric structure and high phosphorus content were synthesized. • Increases the compatibility of the magnesium hydroxide in the PET matrix, P n -MH-PET has good mechanical properties. • The treated copolyester presented a self-extinguishing behavior. • The CO 2 PR and COPR of 5%P 1 -MH-PET are reduced by 54.6% and 57.3% respectively than pure PET. • Combination of gas phase and condensed phase flame retardant to achieve flame retardant and anti-dripping effects. [ABSTRACT FROM AUTHOR]

The big challenge today is the upgrading of sustainable materials to replace miscellaneous ones from petroleum resources. Thus, a generic bio-based building block lays the foundation of the huge bio-market to green economy. 2,5-Furandicarboxylic acid (FDCA), a rigid diacid derived from lignocellulose or fructose, represents a great potential as a contender to terephthalic acid (TPA). Recently, studies on the synthesis, modification, and functionalization of bio-based polyesters based on FDCA have attracted widespread attention. To apply furanic polyesters on engineering plastics, packaging materials, electronics, etc., researchers have extended the properties of basic FDCA-based homo-polyesters by directional copolymerization and composite preparation. This review covers the synthesis and performance of polyesters and composites based on FDCA with emphasis bedded on the thermomechanical, crystallization, barrier properties, and biodegradability. Finally, a summary of what has been achieved and the issues waiting to be addressed of FDCA-based polyester materials are suggested. [ABSTRACT FROM AUTHOR]

Sustainability and recyclability are among the main driving forces in the plastics industry, since the pressure on crude oil resources and the environment is increasing. The aim of this research is to develop a sustainable thermoformable multilayer food packaging, based on co-polyesters, which is suitable for hot-fill applications and allows for recycling in a conventional waste stream. As a polymer material for the outer layer, we selected a modified polyethylene terephthalate (PETM), which is an amorphous co-polyester with a high glass transition temperature (±105 °C) and thus high thermal stability and transparency. The inner layer consists of 1,4-cyclohexylene dimethanol-modified polyethylene terephthalate (PETg), which is allowed to be recycled in a PET stream. Multilayers with a total thickness of 1 mm and a layer thickness distribution of 10/80/10 have been produced. To test the recyclability, sheets which contained 20% and 50% regrind of the initial multilayer in their middle PETg layer have been produced as well. The sheet produced from virgin pellets and the one containing 20% regrind in the middle layer showed no visible haze. This was not the case for the one containing 50% regrind in the middle layer, which was confirmed by haze measurements. The hot-fill test results showed no shrinkage or warpage for the multilayer trays for all temperatures applied, namely 95, 85, 75 and 65 °C. This is a remarkable improvement compared to pure PETg trays, which show a visible deformation after exposure to hot-fill conditions of 95 °C and 85 °C. [ABSTRACT FROM AUTHOR]

To obtain a biodegradable polymer material with satisfactory thermal properties, higher elongation and modulus of elasticity, a series of biodegradable aliphatic/aromatic co-polyesters, poly(hexylene terephthalate-co-lactide) (PHTL), was synthesized via melt polycondensation from dimethyl terephthalate (DMT), 1,6-hexanediol (HDO) and oligo(lactic acid) (OLA) in the presence of titanium (IV) butoxide. The resulting co-polyesters were characterized by proton nuclear magnetic resonance (1H-NMR), differential scanning calorimetry, thermogravimetry and wide-angle X-ray scattering, and their melting temperature, melting heat of fusion, glass-transition temperature (Tg) and thermal decomposition temperature (Tm) (1.5 wt%) were obtained. Only one Tg and two Tm values were observed for all samples, and were found to decrease gradually with increase of lactide moieties. By using the relative integral areas of the dyad peaks in the 1H-NMR spectrum of co-polyesters PHTL, the sequence lengths of the hexylene terephthalate (nHT) units in the resultant co-polyesters are 3.5. The PHTL co-polyesters exhibited a pronounced hydrolytic degradability, which increase with the content in lactide units. 1H-NMR analysis of the residue left by evaporation of the mother solution after hydrolytic degradation revealed that the degradation products consisted mostly of lactide and hexylene terephthalate blocks. [ABSTRACT FROM AUTHOR]

• Co-polyesters were synthesized by polycondensation and transesterification. • Intermolecular interaction improve both specific heat capacity and thermal diffusivity. • Intermolecular interaction helps enhancing thermal conduction and heat absorption. • Young modulus grew with the augment of offset π-π stacking structure. It has been known that phonon mean free path along polymer chains is much larger than in transverse directions because weak interaction between polymer chains leads to chain distortion and entanglement. In order to improve intensity of intermolecular interaction, a series of co-polyesters (CPE) containing different content of offset π-π stacking structure in side chains were synthesized by means of polycondensation and transesterification in this work. WAXD patterns unfolded diffraction peak at 2θ of 27.6°, standing for structure of offset π-π stacking. On enlarging intensity of offset π-π stacking interaction, specific heat capacity of CPE increased from 1.140 Jg−1K−1 to 1.410 Jg−1K−1 and thermal diffusivity rose from 0.194mm2s−1 to 0.245mm2s−1. As a result, CPE sample exhibited excellent thermal conductivity (TC) of 0.381 Wm−1K−1, which is around twice that of traditional thermoplastics. Hence offset π-π stacking interaction could strengthen capacity of heat absorption and thermal conduction at the same time, which might be a good candidate for enhancing thermal conductivity of intrinsic polymers. Furthermore, strong π-π interaction in side chains could maintain modulus when temperature is over glass temperature. And the Young modulus grew from 0.14 GPa to 0.44 GPa with the augment of offset π-π stacking structure. [ABSTRACT FROM AUTHOR]