Synthesis of a novel UV-curable prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane and study on its UV-curing properties

Precursor 3-ethyl-3-hydroxymethyloxetane was synthesized with trihydroxypropane and diethyl carbonate as the main raw materials. Intermediate 3-ethyl-3-allylmethoxyoxetane was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide. Prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane was synthesized with 3-ethyl-3-allylmethoxyoxetane and 1,1,3,3-tetramethyldisiloxane. Cationic photoinitiator triarylsulfonium hexafluoroantimonate of 3 wt% was added to the prepolymer, and a novel kind of photosensitive resin was prepared. Structures of the compounds obtained at individual stages of the synthesis were analyzed and characterized by FTIR and 1H-NMR. Photo-DSC analysis showed that the prepolymer had excellent photosensitivity. Thermogravimetric analysis (TG) revealed that the ultraviolet (UV)-cured samples owned excellent thermal stabilities of up to 405°C. And the mechanical properties of the UV-cured samples were tested by the universal material testing machine, giving 25.95 MPa of tensile strength, 2,935.15 MPa of elastic modulus, and 4.09% of elongation at break.

Bending Resistance of Polylactic Acid Absorbable Root Canal Pile after Repairing Residual Roots

As we all know, tooth growth is very important for children. Whether it is the growth of new teeth or the loss of deciduous teeth, the residual roots of deciduous teeth will affect the physiological replacement of permanent teeth, and the repair of non-absorbable retention posts will also participate. Therefore, the purpose of this article is to explore the polylactic acid can absorb the bending resistance of the root canal pile after repairing the residual root. The method adopted in this paper is to randomly select 24 isolated mandibular premolars to ensure the morphological similarity of the sample as much as possible. After routine root canal treatment and filling, the crown is removed, and the sample is divided into 3 groups on average.. Respectively, polylactic acid absorbable root canal post, fiberglass post and composite resin short post retention, to perform post-core resin crown repair. Subsequently, the electronic universal material testing machine and formula were used to calculate the bending resistance of each material in the fracture mode, and then LSD two-sided inspection was used for comprehensive comparison. Corresponding conclusions are drawn through data comparison. The research results show that the bending strength of the polylactic acid absorbable root canal pile group is 1031.44±359.78N, the bending strength of the glass fiber pile group is 1121.34±193.50N, and the composite resin short pile The group was 1581.36±677.20N, and the differences were statistically significant (P<0.05). The three groups of samples in the experiment are all favorable tooth creases. Therefore, it can be concluded from the experimental results that the bending resistance of the polylactic acid absorbable root canal pile after restoring the residual root is lower than that of the composite resin short pile, which can also meet the clinical needs.

Preparation of Bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane and Investigation of Its Cationic UV-Curing Material Properties

Precusor EHO(3-ethyl-3-hydroxymethyloxetane) was synthesized with diethyl carbonate and trihydroxypropane as the main raw materials. Intermediate AllyEHO(3-ethyl-3-allylmethoxyoxetane) was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide as the main raw materials. Prepolymer bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane was synthesized with 3-ethyl-3-methoxyoxetane)propyl and diphenylsilane. Photoinitiator triarylsulfonium hexafluoroantimonate of 3% was added to the prepolymer, and a novel kind of the photosensitive resin was prepared. They were analyzed and characterized with FTIR and 1H-NMR. Photo-DSC examination revealed that the bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane has great photosensitivity. The thermal properties and mechanical properties of the photosensitive resin were examined by TGA and a microcomputer-controlled universal material testing machine, with thermal stabilities of up to 446 °C. The tensile strength was 75.5 MPa and the bending strength was 49.5 MPa. The light transmittance remained above 98%.

Characterization and antibacterial property of epsilon-poly-L-lysine grafted cellulose films

In order to obtain a stable, biodegradable and cost-effective antibacterial food package materials, this study developed a facile route to immobilize epsilon-poly-L-lysine (EPL) on films. Cellulose films were prepared via a sol-gel transition method and activated by epoxy chloropropane (ECH) to form epoxide group. EPL was covalently immobilized on the surface of the cellulose films (ECFs) by reacting the amino groups of the EPL molecules with the epoxy groups of the epoxidized cellulose films. The structure, morphology and properties of films were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, universal material testing machine, ultraviolet-visible spectrophotometer and static water contact angle. The results showed that EPL was immobilized successfully in the cellulose films. ECFs exhibited 80% transmittance through 300 nm to 1100 nm and the excellent thermal degradation temperature of 240°C. Moreover, good antimicrobial activity against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus and Alicyclobacillus acidoterrestris were confirmed within 12 h, which is expected to provide a novel material for potential applications in the food industry.

A Study on the Improvement of Using Raw Lacquer and Electrospinning on Properties of PVP Nanofilms

Raw lacquer (RL), ethanol being used as the solvent, was added to polyvinyl pyrrolidone (PVP) and then electrospun into RL/PVP nanofilms. Manufacturing parameters such as RL/PVP ratio, voltage, flow velocity, needle type, and the distance between syringe and the collection board were systematically investigated. A scanning electronic microscope (SEM) was used to observe the surface morphology of nanofilms; the block drop method was used to measure the water contact angle; the mechanical properties of RL/PVP nanofilms of different proportions were tested by universal material testing machine; and Fourier-transform infrared spectroscopy (FT-IR) was used to characterize the structure. Based on the water resistance and acid resistance measurements, the proposed nanofilms demonstrated to be water and acid resistant were successfully produced. The results show that PVP that melts in water becomes incompatible with water after adding raw lacquer, and the acid resistance is greatly improved. Furthermore, the smaller the fiber diameter, the better the mechanical properties of the nanofilms are under low ratio of RL/PVP. With a high proportion of RL/PVP, the inner structure of the nanofilm is denser, and the water resistance and acid resistance are better. The dense structure can protect the inner material of the nanofilms.

Nano-silica modified phenolic resin film: manufacturing and properties

Nano-silica modified phenolic resin film is prepared using different mass fractions of nano-silica by liquid composites molding (LCM). The effects of nano-silica on the rheology and curing of phenolic resin are studied by rheometer and differential scanning calorimeter (DSC). The results show that the viscosity of nano-silica modified phenolic resin decreases with the increase of temperature, and the viscosity is lowest between 70°C and 90°C. The appropriate resin film infusion (RFI) process is investigated, and the stepped curing process system is established. In addition, the microstructures of modified phenolic film and composites are tested by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Nano-silica can be uniformly dispersed in phenolic resin when the amount of nano-silica added is ≤ 4%. And the mechanical properties of nano-silica modified phenolic composites are tested by universal material testing machine. The optimum nano-silica mass loading for the improvement of mechanical properties is found. This work provides an effective way to prepare the modified phenolic resin film suitable for resin film infusion (RFI) processes, and it maybe become a backbone of thermal protection material in aerospace.

Influence of Vanadium Microalloying on Microstructure and Property of Laser-Cladded Martensitic Stainless Steel Coating

Martensitic stainless steel (MSS) coatings with different vanadium (V) contents (0–1.0 wt%) by microalloying have been successfully fabricated utilizing a unique laser cladding technique. The microstructure and properties of the resulting MSS coatings, with and without element V addition, have been carefully investigated by various advanced techniques, including XRD, SEM, TEM, microhardness tester, universal material testing machine, and electrochemical workstation. It was found that the V-free coating was mainly composed of martensite (M) and ferrite (F), trace M23C6 and M2N, while the V-bearing coatings consisted of M, F, M23C6, and VN nano-precipitates, and their number density increased with the increase of V content. The V microalloying can produce a significant impact on the mechanical properties of the resulting MSS laser-cladded specimens. As the V content increased, the elongation of the specimen increased, while the tensile strength and microhardness increased firstly and then decreased. Specifically, the striking comprehensive performance can be optimized by microalloying 0.5 wt% V in the MSS coating, with microhardness, tensile strength, yield strength, and elongation of 500.1 HV, 1756 MPa, 1375 MPa, and 11.9%, respectively. However, the corrosion resistance of the specimens decreased successively with increasing V content. The microstructure mechanisms accounting for the property changes have been discussed in detail.

Study on the Dispersion of Aramid Pulp in Epoxy Resin System

In order to improve the uniformity of dispersion of aramid pulp (AP) in an epoxy resin (EP) system containing the EP and curing agent, a series of treatments including the surface cleaning, colloid mill grinding, freeze-drying of APs were carried out in this article. In addition, the composites were prepared by mixing the untreated and treated APs and EP system with the AP mass fractions of 0, 0.1, 0.3, 0.5 and 0.7%. The APs and their dispersion behaviors in EP system were characterized by scanning electron microscope (SEM), fiber quality analyzer, specific surface area tester and optical microscope, moreover, the impact strength and section morphology of composites after impact damage were tested and characterized by a universal material testing machine and SEM.

Effects of Zr, Y on the Microstructure and Properties of As-Cast Cu-0.5Y-xZr (wt.%) Alloys

In this paper, the microstructure and properties of as-cast Cu-Y-Zr alloys with different Zr content were studied in order to investigate whether the precipitates in copper alloys would interact with each other by adding Y and Zr simultaneously. As-cast Cu-0.5Y-xZr (wt.%, x = 0.05 and 0.1, nominal composition) alloys were prepared by vacuum melting in this study. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to observe the microstructure of the alloys. The mechanical properties of the alloys were tested by universal material testing machine at room temperature. The effects of Zr content on the microstructure and mechanical properties of the alloys were explored. As shown by the research results, in the as-cast Cu-0.5Y-xZr (wt.%) alloys, the precipitated phase was the Cu5Y/Cu5Zr phase and ranged from 10 nm to 70 nm in size; when the Zr content increased from 0.05 wt.% to 0.1 wt.%, both the tensile strength and elongation rate of the alloys increased; when the Zr content was 0.1 wt.%, the tensile strength was 225 MPa and the elongation rate was 22.5%.

ANALISIS KEKUATAN TARIK KAMPUH V DAN KAMPUH I SAMBUNGAN LAS BAJA KARBON RENDAH YANG TERDAPAT PADA BESI IWF 400

by using connection type I. To get a good welding result is determined several factors, including the properties of material welding, connection type, welding position, and electrode used. In a welding project, there is still a welder that only uses I in the weld IWF 400 connecting iron while the thickness of the material 13 mm. This study aims to determine the effect of the use of campuh against the strength of weld joint connection using LB 52U 2.6 mm Electrode and RD 7018 3.2 mm electrode with AC Flow. In this study using experimental method begins with making specimens. With the collection of 7 specimens consisting of 3 specimens with welding treatment using Camp V, 3 specimens with welding treatment using Camp I and 1 IWF 400 specimens without welding treatment. From the results of research conducted on specimens by making and testing specimens with a tensile test machine Hydraullic Universal Material Testing Machine then obtained on the specimen without welding average value of Maximum (max) 41,28 kgf/mm². In welded specimens with a connection of the V values the average value of the Maximum (max) 39,82 kgf/mm². On a welded specimen with a maximum I knot connection (max) 38,32 kgf/mm².The results of this study indicate the results of iron welding IWF 400 using camp V greater value voltage 39.82 kgf / mm². From the maximum voltage value obtained from this study it is recommended that iron welding IWF 400 uses V.