Polymer Science, Series A最新文献

Polybutylene terephthalate (PBT) has a strong resistance to abrasion, deformation, and chemical resistance. However, how to further improve the impact toughness of PBT is still an issue that receives the attention of many researchers. This investigation aims to enhance its mechanical properties by mixing it with polypropylene (PP). The tensile strength, impact strength, flexural strength, and microstructure are accorded to ASTM D638, ASTM D256, and ASTM D790. In this analysis, PP was mixed with PBT with different ratios of 95/5, 90/10, 85/15, 80/20, and 75/25. Use injection molding technique to mold specimens for mechanical testing. The results show that the impact strength is 3.7, 6.6, 5.63, 5.2, 5.1, and 4.9 kJ/m², corresponding to 0, 5, 10, 15, 20, and 25% PP. The impact strength of PBT/PP blends is higher than neat PBT. Especially in the 5% PP sample, the impact strength increase can reach the highest level of 80.3% compared to neat PBT. The flexural strength tends to decrease with increasing PP content. After measuring, we get 77.9, 65.6, 62.2, 58.4, 58.2, and 54.0 MPa, corresponding to 0, 5, 10, 15, 20, and 25% PP. The microstructure of the blends showed that spherical PP particles were interwoven into the PBT substrate, but no interphase adhesion was observed. In general, selecting a suitable PBT/PP blend could improve the impact strength while preserving the tensile strength, allowing it to be applied widely.

The study aimed to synthesize ascorbic acid (AA) loaded carboxymethyl guar gum (CMG) hydrogel based film cross linked by citric acid (CA). Bioactive films (CMG-CA and CMG-CA-AA) were synthesized by solvent casting method. The flexibility and mechanical strength of the bioactive film (CMG-CA-AA) were enhanced by the addition of glycerol and optimized by analyzing tensile strength. The structural, morphological and thermal analysis was done by FTIR, XRD, SEM and TGA. Further, the films were evaluated for its anti-oxidant, anti-microbial property and cytotoxicity. Barrier properties, biodegradability and fruit shelf life-enhancer capability were also assessed. The outcomes of the testings demonstrated favorable results and confirms the potential of CMG-CA-AA film in food packaging.

In the present study, an attempt has been made to fabricate kapok fiber-reinforced epoxy composites using the hand lay-up method at 0, 1, 2, 3, 4, 5, 6, and 7 wt % fiber loading. Subsequently, the electrical and mechanical properties of the composites are characterized. It is observed that the mechanical and electrical properties of the composite significantly increase upon the incorporation of kapok fiber with the epoxy matrix. Particularly at 5 wt % loading of the fiber, the optimum properties of the composites were observed. A field emission scanning electron microscope (FESEM) investigation was carried out to observe the fracture behavior of the composites at the interface. 5% kapok fiber reinforced composite has better adhesion and the least fiber pull-out at the interface during mechanical loading. Additionally, it was observed that the dielectric constant of the composite increases with the increase in fiber content and simultaneously, decreases with an increase in frequency.

Ionically conductive hydrogels have attracted increasing interest as skin-like sensors, however, it remains a challenge to fabricate ionically conductive hydrogels with excellent mechanical properties, high electrical conductivity, and high environmental adaptability for high-performance sensors. In this paper, LiCl was introduced into polyacrylamide/linear polyvinyl alcohol (PAM/PVA) composite hydrogels to prepare hydrogels with high ion conductivity. The introduction of LiCl endows the PAM/PVA/LiCl hydrogel with excellent stretchability, high electrical conductivity, good freezing resistance and water retention, and a wide working temperature range. Impressively, this ion-conducting hydrogel can be used for skin-like sensors with high strain sensitivity and excellent durability over 10 consecutive stretches. Therefore, wearable sensors assembled from hydrogels can be used to detect complex human activities with high stability even at –20°C. This work facilitates the development of ionically conductive hydrogels with wide operating temperatures on advanced sensing platforms.

Poly(N-vinyl succinimides) synthesized by classical radical polymerization are studied by the methods of molecular hydrodynamics in dilute solutions in dimethylformamide within a 40-fold MM range. The molecular characteristics and scaling ratios of poly(N-vinyl succinimide) molecules are determined, and their equilibrium rigidity is estimated.

Bio composites of acrylonitrile butadiene rubber (NBR) reinforced with chitosan were prepared using dicumyl peroxide (DCP) as a curing agent. Composites with two types of chitosan with different degrees of deacetylation (DD) were studied i.e., Chitosan with 85% DD and 75% DD. The cure characteristics of composites were studied. The mechanical properties of NBR were found to be improved by the incorporation of chitosan. The composite containing 20 phr chitosan has the best balance of mechanical properties. The swelling behavior of the composites in non-polar solvents such as petrol, diesel, kerosene, toluene, and hexane were analyzed for the swelling coefficient values which supports the results of mechanical properties. Antimicrobial properties of the composites were studied by inoculating the composites with Aspergillus niger (A. niger) fungus on a potato dextrose agar media and incubated for 60 days at room temperature. It is found that presence of chitosan resist the microbial action on the composite samples compared to the gum sample. It is believed that the outcome obtained from the present study is to develop environment-friendly composites for various applications such as oil seals, hoses, automobile bushes, etc.

The spatial distribution of filler particles and their agglomeration depending on concentration and size was studied. In all cases, silica particles served as filler. The particle size varied over a wide range, from nanoparticles to glass beads, and therefore the filler particles have the same nature. An amorphous polymer (polysulfone) and a crystallizing polymer (polypropylene) were chosen as a matrix for comparison. The filler concentration over the cross-section of the samples was determined visually and by electronic chemical analysis. It was shown that with increasing particle size, the tendency to redistribute the concentration increases in such a way that the near-wall region becomes depleted of filler. This effect is more pronounced for high filler concentrations and for a crystallizing polymer compared to an amorphous one.

Due to wide application of biomaterials in drug delivery systems for wound healing, this research work is focused on the development and characterization of a Gelatin/Glycerol composite film for delivering the antibiotic Erythromycin. The aim was preparing gelatin/glycerol films loaded with erythromycin suitable for a future application as a patch for skin wound healing application. A set of films were prepared with various gelatin to glycerol weight ratio and the impact of glycerol content on the mechanical, physicochemical and thermal behavior of film evaluated. Erythromycin was loaded into the film and the antibacterial activity evaluated versus E.coli and S.aureus. Results demonstrate a correlation between the content of glycerol and the physico-chemical properties of the film. The Ge/GY films containing the drug show good antibacterial effects only against Staphylococcus aureus bacteria. TGA and DSC of Ge/ GY thin films showed thermal stability until 110°C, however, the complete decomposition occurred at 350°C.

Dual-modal fluorescent/magnetic resonance imaging attracts more and more attentions in biomedical applications. Herein, star-shaped poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) amphiphilic copolymer with a tetrakis-(4-amino)-terminated tetraphenylethylene core was synthesized. Then, dual-functional nano micelles were achieved via a facile self-assembly of the star copolymer and in situ encapsulation of iron oxide nanoparticles. The fluorescent characteristic of the tetraphenylethylene moiety and encapsulation of iron oxide endowed the resultant dual-functional micelles with bright fluorescence and superparamagnetic properties, which indicated that the PCL segments coated on magnetic nanoparticles is effective at separating the conjugated core from iron oxide nanoparticles to minimize fluorescence quenching. The obtained micelles were found to have a good colloidal and fluorescent stability in different environment. In vitro studies revealed that these dual-functional micelles could serve as an effective fluorescent probe to achieve imaging of MCF-7 cells without obvious cytotoxicity. Thus, this work provides a facile strategy to fabricate fluorescent-magnetic dual-functional micelles for dual-modal imaging applications.

To study the effects of graphene oxide (GO) dimension on the mechanical and dielectric performance of epoxy resin (EP), two kinds of GO with different dimensions were selected and characterized by Fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results showed that the two kinds of GO had similar chemical structure, but different average particle sizes of 190.1 nm (SGO) and 1510 nm (MGO), respectively. The mechanical properties, dynamic mechanical properties, and dielectric properties of the EP/GO composites are analyzed using electronic universal testing machine, Rockwell hardness tester, dynamic mechanical analysis (DMA) and broadband dielectric impedance relaxation spectrometer. Results revealed that the GO dimension plays important role in determining the dispersion of the filler in EP matrix, and further determines the mechanical properties and dielectric performance of the composites. EP/SGO with better dispersion of GO in the EP matrix exhibits better mechanical properties, higher glass transition temperature, higher dielectric constant. Related mechanism has been proposed.