Rheology, Non-Isothermal Crystallization Behavior, Mechanical and Thermal Properties of PMMA-Modified Carbon Fiber-Reinforced Poly(Ethylene Terephthalate) Composites

In Situ Growth of Highly Compatible Cu2O-GO Hybrids Via Amino-Modification for Melt-Spun Efficient Antibacterial Polyamide 6 Fibers

Polyamide 6 (PA6) fiber has the advantages of high strength and good wear resistance. However, it is still challenging to effectively load inorganic antibacterial agents into polymer substrates without antimicrobial activity. In this work, graphene oxide is used as a carrier, which is modified with an aminosilane coupling agent (AEAPTMS) to enhance the compatibility and antimicrobial properties of the inorganic material, as well as to improve its thermal stability in a high-temperature melting environment. Cuprous oxide-loaded aminated grapheme (Cu2O-GO-NH2) is constructed by in situ growth method, and further PA6/Cu2O-GO-NH2 fibers are prepared by in situ polymerization. The composite fiber has excellent washing resistance. After 50 times of washing, its bactericidal rates against Bacillus subtilis and Escherichia coli are 98.85% and 99.99%, respectively. In addition, the enhanced compatibility of Cu2O-GO-NH2 with the PA6 matrix improves the orientation and crystallinity of the composite fibers. Compared with PA6/Cu2O-GO fibers, the fracture strength of PA6/Cu2O-GO-NH2 fibers increases from 3.0 to 4.2 cN/dtex when the addition of Cu2O-GO-NH2 is 0.2 wt%. Chemical modification and in situ concepts help to improve the compatibility of inorganic antimicrobial agents with organic polymers, which can be applied to the development of medical textiles.

Electromagnetic Interference Shielding Performances of Carbon-Fiber-Reinforced PA11/PLA Composites in the X-Band Frequency Range

To solve the problem of increasing electromagnetic pollution, it is crucial to develop electromagnetic interference (EMI) shielding materials. Using lightweight, inexpensive polymeric composites instead of currently used metal shielding materials is promising. Therefore, bio-based polyamide 11/poly(lactic acid) composites with various carbon fiber (CF) amounts were prepared using commercial extrusion and injection/compression molding methods. The prepared composites' morphological, thermal, electrical conductivity, dielectric, and EMI shielding characteristics were investigated. The strong adhesion between the matrix and CF is confirmed by scanning electron microscopy. The addition of CF led to an increase in thermal stability. As CFs formed a conductive network in the matrix, direct current (DC) and alternative current (AC) conductivities of the matrix increased. Dielectric spectroscopy measurements showed an increase in the dielectric permittivity/energy-storage capability of the composites. Thus, the EMI shielding effectiveness (EMI SE) has also increased with the inclusion of CF. The EMI SE of the matrix increased to 15, 23, and 28 dB, respectively, with the addition of 10-20-30 wt % CF at 10 GHz, and these values are comparable or higher than other CF-reinforced polymer composites. Further analysis revealed that shielding was primarily accomplished by the reflection mechanism similar to the literature data. As a result, an EMI shielding material has been developed that can be used in commercially practical applications in the X-band region.

Evaluation and Comparison of Mechanical Properties of Heat Polymerized Acrylic Resin After Reinforcement of Different Fibers in Different Patterns: An In Vitro Study

INTRODUCTION

Most denture fractures occur within the mouth due to resin flexural fatigue. For example, the deep labial notch at the high labial frenum causes denture breakage, as can deep scratches and generated processing stresses. The rising cost of annual prosthetic repairs is evidence that the problem of total denture fracture has not been solved. The purpose of this investigation was to evaluate the relative improvement in flexural strength between heat-cured polymethyl methacrylate (PMMA) resin reinforced with glass fibers (GF) and basalt fibers (BF) of varied orientations.

MATERIAL AND METHODS

A total of 150 heat-cured acrylic resin specimens of 65x10x3 mm dimension were prepared, 30 of which were left unreinforced (Group A), 30 of which were reinforced with GF in transverse pattern (Group B), 30 of which were reinforced with GF in meshwork pattern (Group C), 30 of which were reinforced with BF in transverse pattern (Group D), and 30 of which were reinforced with BF in meshwork pattern (Group E). All of the samples were put through flexural strength testing on the universal testing machine. One-way ANOVA and the Tukey-Kramer various correlation test (= 0.05) were used in SPSS for Windows to look at the facts.

RESULTS

The mean flexural strength for Group A was 46.26±2.26 MPa, 64.98±1.53 MPa for Group B, 76.45±2.67 MPa for Group C, 54.22±2.24 MPa for Group D, and 59.02±2.38 MPa for Group E. Flexural strength was impacted by both the kind of BF and GF reinforcement (F = 768.316, P = 0.001).

CONCLUSION

Within the limitation of the current research, BF reinforcement outperforms GF reinforcement and unreinforced heat-cured acrylic resin in terms of flexural strength.

Non-isothermal crystallization kinetics of ethylene-tetrafluoroethylene copolymer using integral Avrami equation

The non-isothermal crystallization kinetics of ethylene-tetrafluoroethylene copolymer (ETFE, Fluon®C-88AXP) was studied by using differential scanning calorimetry (DSC). The Jeziorny, Ozawa, Mo, and Kissinger equations have been used to describe the crystallization data. The Ozawa and Kissinger plots show downward curves instead of the linear relationship as predicted. Good linear relationship was obtained using the Jeziorny and Mo equations but no vital model parameters concerned with the crystallization kinetics could be acquired. The integral Avrami equation combining with Hoffman equation has been used to describe the crystallization data through nonlinear regression method and kinetic parameters have been acquired. The fitting quality improves when the thermal lag effect was taken into consideration. Meanwhile, the linearity of the Ozawa and Kissinger analysis is improved greatly and the Ozawa exponent and crystallization activity energy of the copolymer have been obtained.

PMMA Application in Piezo Actuation Jet for Dissipating Heat of Electronic Devices

The present study utilizes an acrylic (PMMA) plate with circular piezoelectric ceramics (PC) as an actuator to design and investigate five different types of piezo actuation jets (PAJs) with operating conditions. The results show that the heat transfer coefficient of a device of PAJ is 200% greater than that of a traditional rotary fan when PAJ is placed at the proper distance of 10 to 20 mm from the heat source, avoiding the suck back of surrounding fluids. The cooling effect of these five PAJs was calculated by employing the thermal analysis method and the convection thermal resistance of the optimal PAJ can be reduced by about 36%, while the voltage frequency, wind speed, and noise were all positively correlated. When the supplied piezoelectric frequency is 300 Hz, the decibel level of the noise is similar to that of a commercial rotary fan. The piezoelectric sheets had one of two diameters of 31 mm or 41 mm depending on the size of the tested PAJs. The power consumption of a single PAJ was less than 10% of that of a rotary fan. Among the five types of PAJ, the optimal one has the characteristics that the diameter of the piezoelectric sheet is 41 mm, the piezoelectric spacing is 2 mm, and the length of the opening is 4 mm. Furthermore, the optimal operating conditions are a voltage frequency of 300 Hz and a placement distance of 20 mm in the present study.

Non-isothermal crystallization, yellowing resistance and mechanical properties of heat-resistant nylon 10T/66/titania dioxide/glass fibre composites

Herein, we report novel heat-resistant nylon 10T/66/titania dioxide/glass fibre (nylon 10T/66/TiO₂/GF) composites based on as-synthesised nylon 10T/66, which is a copolymer of poly(decamethylene terephthalamide) (nylon 10T). The non-isothermal crystallization behaviors of nylon 10T/66 and nylon 10T/66/TiO₂/GF composites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo equations were used to analyse the crystallization kinetics, whereas the Kissinger method was applied to calculate the activation energy. It turned out that the introduction of TiO₂ and GF could accelerate the crystallization of nylon 10T/66 and exhibited an effective heterogeneous nucleation effect. In addition, we conducted yellowing resistance and mechanical property analysis of the nylon 10T/66/TiO₂/GF composites. The above results successfully demonstrated that the heat-resistant nylon 10T/66/TiO₂/GF composites possess higher crystallization temperature and crystallization rate, whiter color, and better yellowing resistance and mechanical properties than previously as-synthesised nylon 10T/66. Consequently, nylon 10T/66/TiO₂/GF composites have great potential to be used as a heat-resistant engineering plastic.

Herein, we report novel heat-resistant nylon 10T/66/titania dioxide/glass fibre (nylon 10T/66/TiO₂/GF) composites based on as-synthesised nylon 10T/66, which is a copolymer of poly(decamethylene terephthalamide) (nylon 10T).

Integrating Nano-Cu₂O@ZrP into In Situ Polymerized Polyethylene Terephthalate (PET) Fibers with Enhanced Mechanical Properties and Antibacterial Activities

The approach of in situ polymerization modification has proven to be an effective route for introducing functions for polyester materials. In this work, Cu₂O@ZrP nanosheets with excellent dispersity and high antibacterial activity were integrated into in situ polymerized polyethylene terephthalate (PET) fibers, revealing an enhanced mechanical performance in comparison with the PET fibers fabricated directly via a traditional melt blending method. Additionally, such an in situ polymerized PET/Cu₂O@ZrP fibers displayed highly enhanced mechanical properties; and great antibacterial activities against multi-types of bacterium, including S. aureus, E. coli and C. albicans. For the as-obtained two types of PET/Cu₂O@ZrP fibers, we have detailed their molecular weight (detailed molecular weight) and dispersibility of nano-Cu₂O@ZrP and fibers crystallinity was investigated by Gel chromatography (GPC), Scanning electron microscope (SEM), and X-ray diffractometer (XRD), respectively. The results showed that the aggregation of the nano-Cu₂O@ZrP in the resultant PET matrix could be effectively prevented during its in situ polymerization process, hence we attribute its highly enhanced mechanical properties to its superior dispersion of nano-Cu₂O@ZrP.