ABSTRACT
With the rapid development of electronic information technology, higher requirements have been put forward for the dielectric properties and load-bearing capacity of materials. In continuous glass fiber-reinforced thermoplastic composites, polypropylene matrix is a non-polar polymer with a very low dielectric constant and dielectric loss, but polypropylene is extremely flammable which greatly limits its application. Aiming at the better application of flame retardant-modified continuous glass fiber-reinforced polypropylene composites (FR/GF/PP) in the field of electronic communication, the effects of four different kinds of flame retardants (Decabromodiphenyl ethane (DBDPE), halogen-free one-component flame retardant (MONO), halogen-free compound flame retardant (MULTI), and intumescent flame retardant (IFR)) on the properties of FR/GF/PP were compared, including the mechanical properties, dielectric properties and flame-retardant properties. The results showed that among the FR/GF/PP, IFR has the highest performance in mechanical properties, MULTI has better performance in LOI, DBDPE and IFR have better performance in flame retardant rating, and DBDPE and IFR have lower dielectric properties. Finally, gray relational analysis is applied to propose an approach for selecting the optimal combination (flame retardant type and flame-retardant content) of comprehensive performance. In the application exemplified in this paper, the performance of IFR-3-modified GF/PP is optimized.
ABSTRACT
The application of continuous glass fiber-reinforced polypropylene thermoplastic composites (GF/PP) is limited due to the inadequate flame retardancy of the polypropylene (PP) matrix. Apart from altering the composition of the flame retardants, the distribution modes of flame retardants also impact material performance. In this study, an alternative approach involving non-uniform distribution is proposed, namely, dispersed distribution, in which non-flame-retardant-content layers (NFRLs) and/or low-flame-retardant-content layers (LFRLs) are dispersed among high-flame-retardant-content layers (HFRLs). The mechanical, flame retardant and dielectric properties of GF/PP with intumescent flame retardant (IFR/GF/PP) are investigated comparatively under uniform, gradient, and dispersed distributions of the flame retardants. The results demonstrate that non-uniform distribution exhibits superior flame retardant performance compared to uniform distribution. Dispersed distribution enables IFR/GF/PP to attain enhanced mechanical properties and reduced dielectric constants while maintaining excellent flame-retardant properties.
ABSTRACT
In this study, in order to expand the engineering application range of thermoplastic corrugated sheets, flame-retardant thermoplastic corrugated sheets were prepared by the thermoplastic molding method. Based on our previous research results, we prepared flame-retardant prepreg tapes with the flame retardant addition accounting for 15%, 20%, and 25% of the resin matrix. Then, we prepared flame-retardant thermoplastic corrugated sandwich panels with corresponding flame retardant addition amounts. The limiting oxygen index test, vertical combustion test, cone calorimetry test, and mechanical property test were carried out on each group of samples and control group samples. The results showed that when the flame retardant was added at 25%, the flame retardant level could reach the V0 level. Compared with the control group, the flexural strength and flexural modulus decreased by 2.6%, 14.1%, and 19.9% and 7.3%, 16.1%, and 21.9%, respectively. When the amount of flame retardant was 15%, 20%, and 25%, respectively, the total heat release decreased by 16.3%, 23.5%, and 34.1%, and the maximum heat release rate decreased by 12.5%, 32.4%, and 37.4%, respectively.
ABSTRACT
Metal-organic frameworks (MOFs) with multifunctional and tunable optical properties have unique advantages in the field of sensing, and the structure and properties of MOFs are significantly influenced by the ligands. In this study, a Y-type tricarboxylic acid ligand containing amide bonds was synthesized through functional guidance, and three isomorphic and heterogeneous three-dimensional MOFs (Eu-MOF, Tb-MOF, and Gd-MOF) were obtained by solvothermal reaction. Further studies revealed that both the Tb-MOF and Eu-MOF could selectively detect picric acid (PA). The luminescence quenching of the two MOFs by PA was attributed to competing absorption and photoelectron energy transfer mechanisms. In addition, due to the energy transfer between Tb and Rhodamine B, Rhodamine B was encapsulated into Tb-MOF. The obtained material exhibited a linear relationship between the temperature parameters I544/I584 and temperature within the range of 280-400 K, the correlation coefficient (R2) reached an impressive value of 0.999, and the absolute sensitivity of the sample used for temperature sensing was 1.534% K-1. What is more, the material exhibited a good response to trifluoroacetic acid vapor, which suggests the potential of the material for temperature sensing and detection of trifluoroacetic acid vapor. The designed and investigated strategy can also serve as a reference for further research on excellent multifunctional sensors.
ABSTRACT
NaH2SIP was selected as an organic ligand (NaH2SIP = 5-sulfoisophthalic acid monosodium salt). We successfully constructed a new class of lanthanide coordination polymers Ln-HS ([Ln(SIP)(DMF)(H2O)4]DMF·H2O; Ln = Eu, Tb, Sm, and Dy) by a simple solvothermal synthesis method. They exhibited excellent photoluminescence properties for Ln3+ ions, where Eu-HS and Tb-HS exhibited high quantum yields of 13.70 and 42.38%, respectively. The codoped lanthanide coordination polymers obtained by doping with different ratios of Eu3+/Tb3+ serve as excellent ratiometric thermometers with high sensitivities in the physiological temperature range, with values of 16.8, 7.0, and 14.5%·K-1, respectively. The luminescent colors of Tb0.95Eu0.05-HS and Tb0.94Eu0.06-HS exhibit variations from green to yellow to orange, achieving visualized luminescence in a narrow temperature range. The composite film material Tb0.94Eu0.06-HS@PMMA demonstrates this color variation. Next, Tb0.5Sm0.5-HS obtained by Tb3+/Sm3+ codoping was investigated. The difference in the luminescence colors visible to the naked eye at different excitation wavelengths and the change in luminescence colors occur in a very narrow temperature range. All of them show the great value of the visualized luminescence in practical anticounterfeiting, with double anticounterfeiting function and high security.
ABSTRACT
Lanthanide luminescent MOF materials show excellent luminescent properties. However, obtaining lanthanide luminescent MOFs with high quantum yield is a challenging research. A novel bismuth-based metal-organic framework [Bi(SIP)(DMF)2] was constructed by solvothermal method, utilizing 5-sulfoisophthalic acid monosodium salt (NaH2SIP) and Bi(NO3)3·5H2O. Thereafter, doped MOFs (Ln-Bi-SIP, Ln = Eu, Tb, Sm, Dy, Yb, Nd, Er) with different luminescent properties have been obtained by in situ doping with different lanthanide metal ions, among which Eu-Bi-SIP, Tb-Bi-SIP, Sm-Bi-SIP, and Dy-Bi-SIP have high quantum yield. What is special is that the doping amount of Ln3+ ions is very low, and the doped MOF can achieve high luminescence quantum yields. EuTb-Bi-SIP obtained by Eu3+/Tb3+ codoping and Dy-Bi-SIP exhibit good temperature sensing performance over a wide temperature range with the maximum sensitivity Sr of 1.6%·K-1 (433 K) and 2.6%·K-1, respectively (133 K), while the cycling experiments also show good repeatability in the assay temperature range. Finally, considering the practical application value, EuTb-Bi-SIP was blended with an organic polymer poly(methyl methacrylate) (PMMA) to produce a thin film, which shows different color changes at different temperatures.
ABSTRACT
Structural characterizations of marsupial milk oligosaccharides have been performed in four species to date: the tammar wallaby (Macropus eugenii), the red kangaroo (Macropus rufus), the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula). To clarify the homology and heterogeneity of milk oligosaccharides among marsupials, the oligosaccharides in the carbohydrate fraction of eastern quoll milk were characterized in this study. Neutral and acidic oligosaccharides were separated and characterized by (1)H-nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The structures of the neutral oligosaccharides were Gal(ß1-3)Gal(ß1-4)Glc (3'-galactosyllactose), Gal(ß1-3)Gal(ß1-3)Gal(ß1-4)Glc (3",3'-digalactosyllactose), Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (lacto-N-novopentaose I), Gal(ß1-3)Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (galactosyl lacto-N-novopentaose I), Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-3)Gal(ß1-4)Glc (galactosyl lacto-N-novopentaose II), Gal(ß1-3)[Gal(ß1-3)Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (galactosyl lacto-N-novopentaose III) and Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (lacto-N-novooctaose). The structures of the acidic oligosaccharides detected are Neu5Ac(α2-3)Gal(ß1-4)Glc (3'-sialyllactose), Gal(ß1-3)(O-3-sulfate)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (lacto-N-novopentaose I sulfate a), Gal(ß1-3)[Gal(ß1-4)(O-3-sulfate)GlcNAc(ß1-6)]Gal(ß1-4)Glc (lacto-N-novopentaose I sulfate b), Neu5Ac(α2-3)Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (sialyl lacto-N-novopentaose a), Gal(ß1-3)[Neu5Ac(α2-3)Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc (sialyl lacto-N-novopentaose c), Neu5Ac(α2-3) Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc, and Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-3)[Gal(ß1-4)GlcNAc(ß1-6)]Gal(ß1-4)Glc with an α(2-3) Neu5Ac linked to ß(1-4)Gal residue of either branch of Gal(ß1-4)GlcNAc(ß1-6) units. The most predominant oligosaccharides in the carbohydrate fraction of mid-lactation milk were found to be lacto-N-novopentaose I and lacto-N-novooctaose, i.e., branched oligosaccharides that contain N-acetylglucosamine. The predominance of these branched oligosaccharides, rather than of a series of linear ß(1-3) linked galacto oligosaccharides, appears to be the main feature of the eastern quoll milk oligosaccharides that differentiates them from those of the tammar wallaby and the brushtail possum.
