Cold Curing Research Articles

A versatile cold-curing wood adhesive derived from butylphenyl polyester

Although there have been notable advances in wood-based adhesive materials, the ability to rapidly bond wood under cold curing conditions at room temperature remains a challenge in these adhesives. Here, we report a new butylphenyl-derived polymer that can achieve super strong adhesion at room temperature by fast response at the wood interface. This behavior is achieved by the external reactive groups to create strong interfacial forces and the internal construction of organic-inorganic hybrid structures to reduce energy dissipation. Our research has established an effective method to modulate the viscoelasticity of the copolymer and optimize the adhesion properties of the adhesive at room temperature. The adhesive has a lap shear strength of 4.2 ± 0.17 MPa and also has a repair function that allows the repaired wood to withstand tensile forces of up to 470 N. It is anticipated that this dry, self-supporting, low-cost functional latex will be used as a commercial product for furniture restoration, wood industry and other applications.

Open time studies of cold curing polyurethane adhesives using a standardized spatula test setup suitable for near-production conditions

The presented studies introduce a new set-up and method to analyse the maximum open time of cold curing adhesives in a production environment. By using this new set-up, a manual spatula test, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) and a rheological method, the curing reaction of two cold curing two component polyurethane adhesives, were investigated. Furthermore, the effect of different joining times on the bonding behaviour were investigated using single lap shear samples.The lap shear tests showed that the prior problem for industrial applications is the dimensional accuracy rather than the adhesion to the substrates as all samples showed cohesive or substrate near cohesive failure even when joined after the maximum open time. All used methods showed a coherent curing behaviour for both adhesives. However, the derived times as well as their accuracies vary depending on the used method. Using the easy manual spatula test, the open time is determined by the sensory feelings of the testing person while pressing a wooden spatula into the adhesive bead and is often used in industrial applications. However, the accuracy lies only within 10–20 s especially for slow curing adhesives. In comparison, the ATR-FTIR method, which is based on the decrease of the isocyanate group during the reaction, showed shorter times, whereas longer times were determined by observing the complex viscosity increase of the rheological measurements. Even though the ATR-FTIR and rheological measurements showed reproducible times due to the required laboratory environment and testing procedure, they are therefore not suitable for production conditions. As the introduced new method is based on the manual spatula test, it is suitable for the production environment with the advantage of a good reproducibility. Furthermore, with this method decreasing maximum open times were observed for increasing bead cross sections.

The analysis of innovative manufacturing method of complete removable dentures

BACKGROUND: The optimization of the digital protocol in the manufacture of complete removable dentures to obtain milled dentures with design close to those modeled using computer-aided design and computer-aided manufacturing software is an urgent problem in dental prosthetics.
 AIM: To analyze the manufacturing of complete removable dentures and demonstrate the results of in vitro studies of prostheses obtained according to the developed protocol using the Kravets verticulator and prostheses in which the bases are bonded to the teeth with resins of cold and hot polymerization.
 MATERIALS AND METHODS: With digital technologies, using the proposed modernized Wieland Digital Denture (Ivoclar Vivadent) protocol, 10 bases and 10 corresponding dentitions were obtained by milling, according to pre-made templates obtained using 3D printing. Then, five samples were bonded with cold cure resin using the verticulator, and five samples were made with hot cure resin and verticulator.
 RESULTS: On most of the tooth treated with hot cure resin, the interlayer between the structures of the base and dentition was not observed, or interlayers had a thickness of 804 microns. The thickness of the interlayer of the cold curing specimens was 27325 microns. Pores are not observed for plastic bonded specimens, both cold and hot cured.
 CONCLUSION: The proposed method allows the use of digital technologies to obtain a monolithic plastic prosthesis, which eliminates inaccuracies in tooth positioning, during placement in the base of the prosthesis, and bind the base of the prosthesis and teeth using hot-curing acrylic plastic.

Development of high-strength rammed earth walls with alkali-activated ground granulated blast furnace slag (GGBFS) and waste tire textile fiber (WTTF) as a step towards low-carbon building materials

Rammed earth (RE) structures are cost-effective and eco-friendly substitutes for low-rise buildings, but their low compressive and tensile strengths are a concern. Cement stabilization is often used to improve these properties, but this practice has negative environmental consequences. This study investigates the use of green alkali-activated mortar made with industrial waste materials, including ground granulated blast furnace slag (GGBFS) and waste tire textile fiber (WTTF), as a sustainable alternative to cement. The study involves testing the compressive and tensile strengths of the modified mortar under different climatic conditions (i.e., hot-dry, moderate, and cold curing environments). The results showed that the best improvement performance of the modified specimens in terms of both compressive and tensile strengths was obtained in hot-dry and moderate conditions, particularly GGBFS-based geopolymers, as confirmed by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses. In addition, the tensile strength of the specimens is notably enhanced by the addition of WTTF as a reinforcing agent. The change in the failure modes and the brittleness index values of the modified samples indicated the ductility characteristics, particularly in the hot-dry condition. Moreover, although reinforcing with WTTF remarkably increases the soil ductility, it is shown to barely affect the elastic modulus.

Study of the Effect of Epoxy Reinforcement with C60 on the Rheological and Adhesion Properties

Cold curing was used to evaluate the rheological properties of epoxy resin which was reinforcedwith fullerene (C60) at different concentrations (0, 0.07, 0.11, 0.16, 0.25, 0.33, and 0.66 wt%).The kinetics of changes at complex viscosities was studied, by investigating the relationshipbetween resin viscosity and resin with nanoparticles temperature dependency, the effect offullerene reinforcements on the viscosity of the constituent epoxy-polymer compositions wasevaluated. We steadied how the complex viscosity changed with time when adhesivecompositions doped with C60 at various concentrations polymerized. By changing theconcentrations of fullerenes, the time to reach the gel-point was determined for the mixturesand materials used. It was observed that the reinforcement at the beginning of the mixture withreinforcement changes with the time curing of the composition at a concentration of 0.16 wt.%,the maximum effect (30%) is achieved. The Young's modulus is shown to increase when thepolymer is doped with fullerenes at 0.15 wt.% and decrease when the polymer is without filler

Comparative Evaluation of Bacterial Colonization Color Stability and Halitosis of Oral Appliances Fabricated Using Cold Cure Acrylics, Heat Cure Acrylics and Thermoforming Sheets: An In Vivo Study.

Removable oral appliances form an integral part of interceptive orthodontic procedures. Bacterial colonization leading to halitosis and poor color stability are the major disadvantages of the same in spite of patient acceptability. The aim of the present study was to evaluate bacterial colonization, color stability, and halitosis from the oral appliances fabricated using cold cure, cold cure under pressure pot, heat cure acrylics, thermoforming sheet, Erkodur and antibacterial thermoforming sheet, Erkodur-bz. A group of 40 children was divided into five groups and the appliances were delivered. Bacterial colonization and halitosis were evaluated before giving the appliance to the patient after 1 and 2 months. Color stability was evaluated before giving the appliance to the patient and then after 2 months. This study was designed as a single-blinded randomized clinical trial. Results have shown that after 1 and 2 months, bacterial colonization was higher from the appliances fabricated with cold cure and was lower for the Erkodur group, which was statistically significant. Color stability was more from the appliances fabricated with Erkodur and was less for cold cure, which was statistically significant. Halitosis after 1 month was more from the appliances fabricated with cold cure and less from Erkodur group, which was statistically significant. After 2 months, halitosis was more from the cold cure group and less from Erkodur group, which was not statistically significant. Thermoforming sheet, Erkodur showed better results than other groups in terms of bacterial colonization, color stability, and halitosis. When removable appliances are indicated for minor orthodontic tooth movement, Erkodur is preferable due to the advantages of easy fabrication and less bacterial colonization. Madhuri L, Puppala R, Kethineni B, et al. Comparative Evaluation of Bacterial Colonization Color Stability and Halitosis of Oral Appliances Fabricated Using Cold Cure Acrylics, Heat Cure Acrylics and Thermoforming Sheets: An In Vivo Study. Int J Clin Pediatr Dent 2022;15(5):499-503.

Effect of the Inclusion of Olive Cake in the Diet on the Physicochemical Characteristics of Dry-Cured Loin and Dry-Cured “Cachaço” of Bísaro Pig

The purpose of the present study was to characterize the dry-cured loin and dry-cured “cachaço” of Bísaro pork and evaluate the effect of the inclusion of olive cake in the animals’ diet on the cured products. For this purpose, forty loins and forty “cachaços” were used, followed by a process of cold curing with controlled ventilation, without adding nitrites or synthetic additives. The dry-cured loin and “cachaço” chemical compositions were significantly different in moisture, total fat, protein, chlorides, ash, and haem pigments. The “cachaço” showed a much higher value of total fat and a lower protein value. Its chloride content was lower and was related to the lower ash percentage. Neither product differed significantly in the water activity and collagen content. The proportions of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids were significantly different between these products. The dry-cured “cachaço” showed higher values of SFA and PUFA, and the dry-cured loin had higher MUFA content. No significant effect of different olive cakes on diet was observed in the chemical compositions. Both products are of high quality and with good nutritional and physicochemical characteristics, and the introduction of olive cake in the diet did not affect any of the quality parameters analyzed.

Influence of Upcycled Post-Treatment Bark Biomass Addition to the Binder on Produced Plywood Properties

The valorization of tree bark through chemical treatment into valuable products, such as bark acid, leads to the formation of process residues with a high solids content. Since they are of natural origin and are able to be suspended in water and acid, research was carried out on the recycling of suberic acid residues (SAR) as a bi-functional component of binder mixtures in the production of plywood. The 5%–20% (5%–30% for curing time) mass content of SAR has been investigated with urea-formaldehyde (UF) resin of about 66% of dry content. The results show that the curing time of the bonding mixture can be reduced to about 38% and 10%, respectively, for hot and cold curing, of the initial curing time for the lowest SAR content. The decreasing curing time of the tested binder mixtures with the increase in SAR content was caused by the increasing amount of acidic filler, since amine resins as UF require acidification hardening, and the curing dynamics are strongly dependent, among others, on the content of the acid medium (curing agent). In the case of hot curing, a SAR content of about 20% allowed us to achieve the curing time of bonding mass with an industrial hardener. Investigations into the mechanical properties of examined panels showed a significant modulus of elasticity (MOE) increase with filler content increase. Similar conclusions can be drawn when analyzing the results of the modulus of rupture (MOR) investigations; however, these were only significant regarding hot-pressed samples. The shear strength of the plywood samples increased with the SAR rise for both cold- and hot-pressed panels. The in-wood damage of samples with SAR filler, hot-pressed, rose up to about 30% for the highest SAR filler content. For cold-pressed samples, no in-wood damage was found. The positive effect of veneer impregnation limiter by resin was identified for SAR acting as a filler. Moreover, a higher density of SAR-containing bonding lines was reached for hot-pressed panels. Therefore, the results confirmed the ability to use the SAR as an upcycled component of the bonding mixture for plywood production.

Development of Energy-Efficient “Cold” Curing Method for Polypropylene Glycol Fumarate Using an Optimized Initiating System

The possibility of using the polymeric matrix obtained as a result of “cold” polymerization of polypropylene glycol fumarate (p-PGF) with methacrylic acid (MAA) as a polymeric base for obtaining new adhesives of domestic production was demonstrated. The starting reagent (p-PGF) was synthesized by condensation polymerization of fumaric acid with propylene glycol in the presence of a catalyst, which reduced the temperature and shortened the process time. A number of solutions of p-PGF in MAA of different mass compositions were obtained and their rheological properties were determined. Curing of the studied solutions was carried out by radical polymerization at room temperature in the presence of the “cold curing” initiating system. The optimum composition and amount of components of the “cold” curing initiating system consisting of an initiator (benzoyl peroxide) and a promoter (dimethylaniline) were established. Technological parameters of curing (temperature, lifetime and curing time, the value of volume shrinkage) were determined. The obtained compounds were identified by infrared spectroscopy. The surface morphology of the cured samples was studied by scanning electron microscopy. It was found that varying the composition of the initial polymermonomer mixture allows controlling the physicochemical properties.

Cold-curing mixtures based on biopolymer lignin complex for casting production in single and small-series conditions

<abstract> <p>This study proves that lignin-based biopolymer materials can be employed as starting materials for the synthesis of novel casting binders that fulfill the current level of characteristics. The optimal concentration of the binder in the mixture was experimentally determined to be 5.8%–6.2%. It has been demonstrated in practice that the employment of ammonium salts as a technical lignosulfonate (TLS) modifier can result in the provision of cold (room temperature) curing of a mixture based on them. It was proposed to use as a technological additive that boosts the strength characteristics of a mixture of substances carboxymethyl cellulose (CMC). In a variety of adhesive materials, it is utilized as an active polymer base. The concentration limits for using CMC in the mixture are set at 0.15%–0.25%. To improve the moldability of the combination, it was suggested that kaolin clay be used as a plasticizing addition. The concentration limits for using a plasticizing additive are set at 3.5%–4.0%. The produced mixture was compared to the analog of the alpha-set method in a comparative analysis. It was discovered that the proposed composition is less expensive, more environmentally friendly, and enables the production of high-quality castings. In terms of physical, mechanical, and technological properties, the created composition of the cold curing mixture is not inferior to analogs from the alpha-set method. For the first time, a biopolymer-based binder system containing technical lignosulfonate with the addition of ammonium sulfate and carboxymethyl cellulose was used in the production of cast iron castings on the case of a cylinder casting weighing 18.3 kg from gray cast iron grade SCh20. Thus, it has been proved possible for the first time to replace phenol-based resin binders with products based on natural polymer combinations. For the first time, a cold-hardening mixture based on technological lignosulfonates has been developed without using hardeners made of very hazardous and cancer-causing hexavalent chromium compounds. But is achieved through a combination of specialized additives, including kaolin clay to ensure the mixture can be manufactured, ammonium sulfate to ensure the mixture cures, and carboxymethyl cellulose to enhance the strength properties of the binder composition. The study's importance stems from the substitution of biopolymer natural materials for costly and environmentally harmful binders based on phenolic resins. This development's execution serves as an illustration of how green technology can be used in the foundry sector. Reducing the amount of resin used in foundry manufacturing and substituting it with biopolymer binders based on technological lignosulfonates results in lower product costs as well as the preservation of the environment. Using lignin products judiciously can reduce environmental harm by using technical lignosulfonates, or compounds based on technical lignin. The combination is concentrated on businesses with single and small-scale manufacturing because it is presumable that this is merely the beginning of the investigation. This study confirms the viability of creating a cold-hardening combination based on technical lignosulfonates in practical applications and supports this with the castings produced, using the creation of a gray cast iron cylinder casting as an example.</p> </abstract>

Adhesive and impact strength of hybrid layered metal-polymer composites reinforced by basalt fiber

This work shows the possibility of obtaining hybrid layered metal-polymer composites based on low-carbon steel and aluminum alloys with interlayers of basalt fiber reinforced thermoplastic polymer — polyetheretherketone by methods of hot and cold bonding with the use of hot and cold curing adhesives, respectively. The adhesive tear and shear strength of composites obtained by two alternative methods and the impact strength of steel-polymer and aluminum alloy-polymer joints were evaluated. The tests of five-layered composites for impact bending on samples with “crack-arrester” type V-notch (with the orientation of the notch line across the composite layers) at temperatures of −60, +20, and +200°С were carried out. The analysis of the test results showed that the composites have increased strength at shear loads and resistance to brittle fracture at low climatic and high working temperatures. Fractographic analysis of the fracture surface of composites allowed to determine that the fracture proceeds through adhesive, cohesive, and mixed mechanisms. Cohesive fracture is initiated in the polymer layer by nucleation and crack growth along the fiber-matrix interface, as well as cracking of the basalt fibers.

Novel Cold Cure Acrylic Denture Base with Recycled Zirconia Nano-Fillers That Were Functionalized by HEMA Agent Incorporation: Using the Sprinkle Approach.

BackgroundThough acrylic resins possess many useful properties, denture fracture is nevertheless a familiar issue.ObjectiveThis study aimed to determine the effect of low-percent recycled Zirconia nanoparticles as filler on the transverse strength, impact strength, surface hardness, water sorption, and solubility of resin using the sprinkle cold-curing technique.Materials and MethodsVarious formulae were prepared and mixed with PMMA (polymer) powder containing varying percentages (0.01%, 0.1%, 0.3%, and 0.5%) of recycled ZrO2NPs to mono-methyl methacrylate (MMA monomer). A 2-hydroxyethyl-methacrylate (HEMA) agent was used to functionalize recycled zirconia (ZrO2) nano-fillers. X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and dynamic light scattering were used to characterize the samples. For mechanical tests, standard metallic moulds (according to American Dental Association specification no. 27) were machined for 60 specimens’ preparation, 12 for each percent (zero, 0.01%, 0.1%, 0.3%, and 0.5%). A one-way ANOVA test was used to compare the five groups for parametric data, while the Kruskal–Wallis test was employed for nonparametric data. The P 0.05 value was accepted as the significance level. All formulae were tested for cytotoxicity at 24 and 48 hours on WI38 normal lung cell lines.ResultsThe XRD analysis demonstrated the tetragonal crystallographic structure of the recycled zirconia nanoparticles. Incorporating a low percentage of recycled ZrO2 nanoparticles (0.01%, 0.1%, 0.3%, and 0.5%) improved the tested properties of PMMA to different degrees in a significant and non-significant pattern, while the optimal tested percent was 0.3%.ConclusionThe 0.3% percentage of recycled zirconia nanoparticles maintained and improved the physical and mechanical properties of acrylic resin. Recycled ZrO2/PMMA nanocomposite is a synergistic candidate due to its economic return and clinical application safety.

Curing Effect on Durability of Cement Mortar with GGBS: Experimental and Numerical Study.

In this paper, supplementary cementitious materials are used as a substitute for cement to decrease carbon dioxide emissions. A by-product of the iron manufacturing industry, ground granulated blast-furnace slag (GGBS), known to improve some performance characteristics of concrete, is used as an effective cement replacement to manufacture mortar samples. Here, the influence of curing conditions on the durability of samples including various amounts of GGBS is investigated experimentally and numerically. Twelve high-strength Portland cement CEM I 52.5 N samples were prepared, in which 0%, 45%, 60%, and 80% of cement were substituted by GGBS. In addition, three curing conditions (standard, dry, and cold curing) were applied to the samples. Durability aspects were studied through porosity, permeability, and water absorption. Experimental results indicate that samples cured in standard conditions gave the best performance in comparison to other curing conditions. Furthermore, samples incorporating of GGBS have superior durability properties. Permeability and water absorption were improved by and , respectively, compared to the reference sample. Thereafter, data from capillary suction experiments were used to numerically determine the hydraulic properties based on a Bayesian inversion approach, namely the Markov Chain Monte Carlo method. Finally, the developed numerical model accurately estimates the hydraulic characteristics of mortar samples and greatly matches the measured water inflow over time through the samples.

Methods for studying the ductus venosus in animals

The ductus venosus is a physiological vascular shunt to the umbilical and caudal vena cava in the fetus. The umbilical vein (vena umbilicalis) leaves the placenta, enters the fetus through the foramen umbilical, and goes to the liver hilum. It carries oxygenated and nutrient‐rich blood from the placenta to the fetus. Part of the blood enters the liver through the umbilical vein, through the shunt ‐ the ductus vein enters the central venous line ‐ the caudal vena cava. This mechanism of blood redistribution is necessary for feeding the fetal brain with blood that is more saturated with oxygen. Given the scarce data on the topography, shape, and morphometric parameters of the venous duct in animals, we set the goal of revealing the methods used for its postmortem study. For a complete and comprehensive study of the topography of the venous duct, it is necessary to use a set of anatomical methods: thin anatomical preparation, vasoradiography, production of corrosive preparations, and morphometry. When conducting vasoradiography, a mass for injection prepared according to the recipe was used as a radio‐opaque mass: 45% ‐ lead white, 45% ‐ gum turpentine, 10% ‐ medical gypsum powder (M.V. Shchipakina, A.V. Prusakova, D.S. Bylinskaya, S.A. Kuga, 2013). In the manufacture of corrosive preparations, self‐hardening dental plastic was used. It belongs to the acrylic group of cold curing plastics and consists of powder and solvent components. In both cases, the injection of these substances was carried out through the umbilical vein, without opening the abdominal cavity, by accessing through the umbilical cord. After introducing the X‐ray contrast mass, the objects of study were placed in a fixing solution (10% formalin solution) and left in it for up to 5 days. Subsequently, thin anatomical preparation and photography, as well as radiography, were performed. After introducing a plastic solution, the objects were placed in chambers with a temperature of +4°C for two days. Subsequently, corrosion treatment was carried out in an aqueous potassium hydroxide solution for 4 ‐ 5 days. The morphometry of the venous duct in the study of vaso‐radiographs was carried out in the RadiAnt computer program, in the study of a corrosive preparation ‐ using an electronic caliper (Stainless hardened). On vaso‐radiographs, the ductus venous is identified as a sizeable cone‐shaped vessel located in the area of the liver hilum. The ductus venosus is identified as a craniodorsal blood vessel that flows into the caudal vena cava on the casts of the vascular bed. The proposed methods for studying the ductus venosus make it possible to accurately anatomically describe the position, shape, and size of the ductus venosus in fetuses.

The Effects of Incorporating Ag-Zn Zeolite on the Surface Roughness and Hardness of Heat and Cold Cure Acrylic Resins

One of the most widely used materials for the fabrication of prosthetic dental parts is acrylic resin. Its reasonable mechanical and physical properties make it a popular material for a wide range of dental applications. Recently, many attempts have been made to improve the mechanical and biological properties of this material, such as by adding fibres, nanoparticles, and nanotubes. The current study aimed to evaluate the effects of adding an antimicrobial agent, Ag-Zn zeolite, on the surface roughness and hardness of the denture base resins. Ag-Zn zeolite particles were chemically prepared and added at different concentrations (0.50 wt.% and 0.75 wt.%) to the heat cure (HC) and cold cure (CC) acrylic resins. Zeolite particles were characterized and confirmed using X-ray diffraction (XRD) and Energy-Dispersive X-ray Spectroscopy (EDX) attached with a Scanning Electron Microscope (SEM). Sixty disk shape specimens (40 mm diameter and 2 mm thickness) were fabricated from the HC and CC resins with and without the zeolite. All the specimens were divided into two main groups based on the acrylic resins, then each was subdivided into three groups (n = 10) according to the concentration of the Ag-Zn zeolite. A surface roughness and a hardness tester were used to measure the surface finish and hardness of the specimens. The analysed data showed that the surface roughness values significantly decreased when 0.50 wt.% and 0.75 wt.% zeolite were incorporated in the HC resin specimens compared to the control group. However, this reduction was not significant in the case of CC resin, while the surface hardness was significantly improved after incorporating 0.50 wt.% and 0.75 wt.% zeolite for both the CC and HC resins. Incorporating Ag-Zn zeolite with acrylic resin materials could be beneficial for improving their surface finish and resistance to surface damage as defined by the higher hardness.

“Cold Curing” of Polyethylene Glycol Maleate with Acrylic Acid and Some Physicochemical Properties of Their Solutions

The possibility of using the copolymers based on unsaturated polyesters with acrylic acid (AA) as the main component (polymeric basis) for the creation of novel highly effective sealants and glues of domestic produc-tion was demonstrated. Polyethylene glycol maleate (p-EGM) was synthesized by step-growth polymeriza-tion of maleic anhydride with ethylene glycol using the catalyst, which shortened the process duration. A number of solutions of p-EGM with AA were obtained. Physicochemical characteristics of initial solutions were determined. Some rheological properties of the solutions of p-EGM in unsaturated carboxylic acid were studied. Radical polymerization — the process of “cold curing” of the solutions of p-EGM with AA at room temperature was carried out. The combination of initiating a system of cold curing consisting of initiator (benzoyl peroxide) and promoter (dimethylaniline) was selected and their optimal content in the initial mon-omer mixture was established. The main parameters of curing, namely gelation time and curing time, were determined. Identification of the copolymers was performed using IR-spectroscopy. The morphology of the surfaces of cured samples of p-EGM with AA was studied using SEM. The optimal composition requiring further studies as highly filled compositional polymeric materials for using as sealants and glue basis was es-tablished.

Study of the Aging of Cold-Cured SKU-PFL Type Polyurethane Filled with Waste Products

The article describes the results of aging of samples of cold-cured molded polyurethanes of SKU-PFL brand filled with zeolite and silica gel - wastes of petrochemical production. The samples were aged under normal climatic conditions for 5 years. Filling of the samples varied from 10 to 50 %wt. Investigations of physical and mechanical properties of the samples before and after aging were carried out, the basic indicators of material quality were calculated using Microsoft Office Excel package. As a result of researches it was established that after aging the basic physical and mechanical properties of cast polyurethanes of SKU-PFL brand of cold curing filled with zeolite and silica gel change insignificantly, however the best resistance to aging are in samples with 20 %wt. zeolite and 10 %wt. silica gel filling both before and after aging that allowed to recommend them for long-term use of articles.

ДОСЛІДЖЕННЯ ВПЛИВУ ВМІСТУ ПІСКУ ТА МОДИФІКУЮЧИХ ДОБАВОК НА ВЛАСТИВОСТІ ПОЛІМЕРБЕТОННИХ КОМПОЗИЦІЙ

Purpose. Establishment of the influence of the content of sand and modifying additives on the hardness, compressive strength, and impact strength of polymer concrete compositions. Methodology. Polymer concrete compositions in the form of round pancakes, sticks and bars based on polyester resin of the CHROMOPLAST GP 2000 brand, hardener (organic peroxide for cold curing) of the Luperox K1 brand, cobalt stearate (cobalt salt of stearic acid), styrene and river sand were subject of investigation. Samples of polymer concrete composites were obtained in two stages: 1) mixing the resin with sand 2) the addition of hardener, styrene and cobalt stearate. To obtain a hardened polyester composition, metal forms with bent sides were used; ceramic boats (not enameled) metal molds 2 cm high. Preparation of the composition was carried out in the following sequence: first, resin was mixed with sand, then hardener, cobalt stearate and styrene were added. The following sequence of preparation of the composition also took place: first the resin and hardener were mixed, only then sand mixed with styrene and cobalt stearate was added. The forms were loaded into a heating cabinet and heated to a temperature of 100 °C for 30-40 minutes. After cooling in the form of the product was removed. The hardness, compressive strength and toughness of the developed compositions were investigated by standard methods. Results. It was found that an increase in sand content from 0 to 90% of the mass. in polymer concrete compositions leads to an increase in hardness by ~ 466%, as well as a decrease in compressive strength by ~ 62% and impact strength by ~ 50%. Scientific novelty. An increase in the hardness index and a decrease in the compressive strength and toughness of polymer concrete compositions with an increase in the sand content to 90 % of the mass was established. This is because the sand has a higher hardness than the polyester resin, and accordingly, an increase in its content leads to an increase in the hardness of the composition. The decrease in compressive strength and toughness is due to a decrease in the amount of binder, due to which the composition becomes more fragile. Practical value. The developed polymer concrete compositions can be used in construction, as well as for repairing damaged concrete surfaces and eliminating cracks.

Shear bond strength values of PEEK to dentin using different surface treatments

Aim: To compare the shear bond strength values to dentin using different surface treatment of PEEK by sandblasting and acid etching techniques. Methodology: Forty removed human molar teeth (maxillary/mandibular) were used in this investigation. Extracted teeth were cleaned with an ultrasonic scaler (EMS, Switzerland) and kept in a 10% formalin solution to eliminate surface debris. An acrylic resin block of dimensions 10mm x10mm was fabricated using autopolymerising acrylic resin (DPI-RR Cold Cure, India) and the teeth were embedded in the center of block upto complete submergence of the root. Two groups were made (group A and group B), each comprising of 20 blocks and colour coding was done to distinguish the groups. Group A comprised of clear acrylic resin blocks in which the PEEK surfaces were modified by acid etching and group B comprised of pink acrylic resin blocks in which PEEK surface was modified by sandblasting. Results: Mean ± SD of shear bond strength recorded for group A and B was 1.94 and 2.40 Mpa respectively with statistically significant difference as P

Gluing Techniques on Bond Performance and Mechanical Properties of Cross-Laminated Timber (CLT) Made from Larix kaempferi

Previous studies have proved that Larix kaempferi is a good material for preparing cross-laminated timber (CLT), but under bending shear stress, CLT made by Larix kaempferi is prone to the phenomenon of bonding face cracking, which seriously affects the shear performance of CLT. To solve this problem, this paper took Larix kaempferi as raw material, conducted experiments on the surface sanding conditions, gluing pressure and adhesive types of sawing timber, and explored the influence of these three factors on the bonding quality of CLT. The microscopic characteristics of the bonding layer were further studied. The results showed that for Larix kaempferi with a density of 0.68 g/cm3 used in this experiment, a high bonding pressure is required. Among the three cold curing adhesives selected in the experiment, emulsion polymer isocyanate (EPI) adhesive needs 1.5 MPa bonding pressure to ensure the bonding quality, while for polyurethane (PUR) and phenol resorcinol formaldehyde (PRF), 1.2 MPa can meet the need of adhesive pressure. This is concerned with the permeability of different adhesives under different pressures. The microscopic results of the bonding layer show that EPI adhesives have poor permeability, so it requires high bonding pressure. The influence of sanding surface of different sand-belt on block shear strength (BSS) and wood failure percentage (WFP) is not obvious, while the durability of bonding layer is better when sanding mesh number is 100. Hence, a high pressure should be used for CLT industrial production when the laminate density is higher, especially when the adhesive has poor permeability. Reasonable sanding surface treatment can be used in laminate surface treatment to improve the durability of CLT.