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خلفية البحث و هدفه: يعتبر الاستقرار اللوني للوجوه الخزفية من العوامل الجوهرية لبقاء الوجوه الخزفية و المحافظه على ديمومة الناحية الجمالية. تمت دراسة الاستقرار اللوني للوجوه الخزفية مخبرياً وفقط بما يخص الاسمنت الراتنجي بشكل رئيسي ، أما سريرياً فلم نجد دراسات تدرس الاستقرار اللوني للوجوه الخزفية الرقيقة بأنواعها المختلفة . تهدف هذه الدراسة إلى دراسة تأثير اختلاف أشيع طريقتين في صنع الوجوه الخزفية الرقيقة (CAD/CAM,Hot Press) على الاستقرار اللوني السريري لهذه الوجوه. المواد و الطرائق: تألفت عينة البحث من 10 مرضى تم تعويض القواطع الأمامية لهم ب 32 وجه خزفي رقيق وفق الاَتي : المجموعة الاولى و شملت 5 مرضى تم التعويض لهم ب 16 وجه خزفي مصنع بطريقة (IPS e.max CAD) و المجموعه الثانية تم التعويض لهم ب 16 وجه خزفي مصنع بطريقة (IPS e.max Press). تم تقييم و قياس اللون للوجوه الخزفية بعد الإلصاق بواسطة جهاز قياس الطيف الضوئي Compact Vita Easyshade . تم حساب ∆a, ∆b, ∆L بين القياس الأولي و القياسات اللاحقة خلال الفترات الزمنية 24 ساعه, 6 اشهر , 12 شهر , 24 شهر ثم حساب CIE Lab (∆E ab) من أجل التحري عن التغير اللوني . النتائج: لا يوجد فروق معنوية ذات دلالة إحصائية بعد 6 و 12 و 24 شهر من الالصاق عند مستوى دلالة 0.05 في متوسطات التغير اللوني (∆E ab) بين مجموعتي (IPS e.max CAD, IPS e.max Press). درجة قبول التغير اللوني السريري كانت ≥ 3.5 لدى كلا الطرقتين بعد 6 و 12 شهرو 24 شهر . الاستنتاج: الاستقرار اللوني للوجوه الخزفية المصنعة بطريقتي (IPS e.max CAD, IPS e.max Press) كان محققاً سريرياً خلال كل فترات المراقبة.

خلفية البحث و هدفه: يعتبر الاستقرار اللوني للوجوه الخزفية من العوامل الجوهرية لبقاء الوجوه الخزفية و المحافظه على ديمومة الناحية الجمالية. تمت دراسة الاستقرار اللوني للوجوه الخزفية مخبرياً وفقط بما يخص الاسمنت الراتنجي بشكل رئيسي ، أما سريرياً فلم نجد دراسات تدرس الاستقرار اللوني للوجوه الخزفية الرقيقة بأنواعها المختلفة . تهدف هذه الدراسة إلى دراسة تأثير اختلاف أشيع طريقتين في صنع الوجوه الخزفية الرقيقة (CAD/CAM,Hot Press) على الاستقرار اللوني السريري لهذه الوجوه. المواد و الطرائق: تألفت عينة البحث من 10 مرضى تم تعويض القواطع الأمامية لهم ب 32 وجه خزفي رقيق وفق الاَتي : المجموعة الاولى و شملت 5 مرضى تم التعويض لهم ب 16 وجه خزفي مصنع بطريقة (IPS e.max CAD) و المجموعه الثانية تم التعويض لهم ب 16 وجه خزفي مصنع بطريقة (IPS e.max Press). تم تقييم و قياس اللون للوجوه الخزفية بعد الإلصاق بواسطة جهاز قياس الطيف الضوئي Compact Vita Easyshade . تم حساب ∆a, ∆b, ∆L بين القياس الأولي و القياسات اللاحقة خلال الفترات الزمنية 24 ساعه, 6 اشهر , 12 شهر , 24 شهر ثم حساب CIE Lab (∆E ab) من أجل التحري عن التغير اللوني . النتائج: لا يوجد فروق معنوية ذات دلالة إحصائية بعد 6 و 12 و 24 شهر من الالصاق عند مستوى دلالة 0.05 في متوسطات التغير اللوني (∆E ab) بين مجموعتي (IPS e.max CAD, IPS e.max Press). درجة قبول التغير اللوني السريري كانت ≥ 3.5 لدى كلا الطرقتين بعد 6 و 12 شهرو 24 شهر . الاستنتاج: الاستقرار اللوني للوجوه الخزفية المصنعة بطريقتي (IPS e.max CAD, IPS e.max Press) كان محققاً سريرياً خلال كل فترات المراقبة.

In the study, the bonding strength of phenol-formaldehyde (PF) adhesive on plywood under different hot press temperature and time was evaluated. A mechanical mathematical model was established to analyze the curing process of PF adhesive, in which the parameters of model could be used to predict the bonding strength and change rate of plywood. The thermal curing degree of the adhesive was determined by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) as well as Nuclear magnetic resonance (NMR) were used to analyze the chemical structure of adhesives with different curing degree. The results show that higher of hot press temperature, the shorter of time to reach the target temperature. The changed rate constant of bonding strength and the maximum bonding strength of plywood could be calculated by the mechanical mathematical model accurately, and the temperature at 130°C was the optimal temperature for plywood manufacture in the study. FTIR analysis indicated that the primary reaction of PF adhesive in the alkaline medium was the condensation occurring between hydroxymethyl groups and residual active position of other phenolic rings. NMR data presented that the ratio of -CH2- (34.5–35.1 ppm)/CH2-OH (62.4–63.1 ppm) could be used to evaluate the curing degree of PF adhesive. [ABSTRACT FROM AUTHOR]

In this research, the silk web was hot-pressed for various times, the effect of press time on the structure and mechanical properties of silk non-woven fabric was also investigated. The yellowing appeared in the silk non-woven fabric and became more apparent as press time was increased. The crystallinity of silk was decreased by the hot press treatment and it did not change significantly with an increase of hot press time. The porosity of silk non-woven fabric was constantly decreased until 120 s and it did not change much after that. The thickness of silk non-woven fabric was significantly decreased by a press time of 10 s and slightly decreased with a further increase of hot press time. The hot press treatment increased the maximum stress and elongation of silk non-woven fabrics. The press time had a significant impact on the mechanical properties of silk non-woven fabric, with 90 s being the optimum condition for the best work of rupture of silk non-woven fabric. [ABSTRACT FROM AUTHOR]

Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength ( a uc ) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS] 4 . To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing 3 . To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing a uc at each accumulative probability, P f . Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron microscopy (SEM) and electron dispersive X-ray (EDS) mapping showed PPS adhering to CF. Electron spin resonance (ESR) of a 5 kGy sample indicated lengthening of PPS chains as evidenced by a reduction in dangling bond peak. It Is assumed that 5 kGy HLEBI creates strong bonds at the interface while strengthening the PPS bulk. A model is proposed to illustrate the possible strengthening mechanism.

In this study, electrical steel laminated composites with positive Si gradient (PO-G), counter Si gradient (CO-G), and cross Si gradient (CR-G) were fabricated by hot-press sintering, cold rolling and annealing. The microstructure evolution during processing, as well as the magnetic and mechanical properties were investigated. The results indicate that the microstructure of the high-silicon layer and medium-silicon layer in the hot-pressed composites featured columnar grains throughout the thickness. The microstructure of the low-silicon layer in the hot-pressed CO-G sample consisted of equiaxed grains. However, a mixed structure dominated by columnar grains with some equiaxed grains was observed in the inner low-silicon layer of the PO-G and CR-G samples. Following cold rolling, the thickness ratio of each layer remained largely unchanged. After annealing, the microstructure of each layer transformed into columnar grains. The average grain size of the high-silicon layer, medium-silicon layer, and low-silicon layers in the three composites were approximately 20–23 μm, 33–38 μm, and 42–49 μm, respectively. Compared with the CO-G and CR-G samples, the annealed PO-G composite exhibited lower core loss at 400–1000 Hz and superior tensile strength. Furthermore, the core loss of the three composites was greater than that of the initial medium-silicon and high-silicon materials. This can be attributed to the increased hysteresis loss due to the existence of multi-layer interface. [ABSTRACT FROM AUTHOR]

To develop a material with strong impact resistance, bending direction and in‐plane direction, the tensile and bending properties of sandwich films obtained by placing and re‐pressing a compression‐molded polypropylene sheet between two sheets of carbon‐fiber‐reinforced thermoplastics (CFRTPs) were evaluated. Three types of CFRTP were investigated, and thermoplastic nylon 66, polyurethane, and polyphenylene sulfite were used as the resin base materials to wrap the carbon fiber. Regarding the tensile properties of the sandwich films, the Young's modulus and maximum stress values were lower compared with those of the CFRTP sheets, regardless of the resin base material. However, improvements in elongation properties of 97%, 109%, and 156%, respectively were found, transforming the film into a softer and stronger film. Regarding the bending properties of the sandwich films, the Young's modulus and maximum stress values were higher compared with those of the CFRTP sheet. To examine the influence of the number of layers, the five‐layer sheet, in which the sandwich film was placed in two CFRTP sheets, exhibited inferior elongation properties to the three‐layer sheet during the tensile test. However, the results of the bending test found a significant improvement in Young's modulus of approximately 2.5 times and final strength of approximately three times. We anticipate that this material could be applicable to components requiring specific mechanical properties in both bending and in‐plane directions in future applications. Highlights: CFRTP sandwich sheets were fabricated using a simple hot‐press method.The sandwich sheet showed improved mechanical properties in the in‐plane directions.Both the tensile modulus and the bending modulus have reached the GPa‐order.The sandwich film in question had particularly excellent bending properties.The sandwich film showed dependence on the number of layers.In‐plane elasticity of the films was evaluated using a falling ball test. [ABSTRACT FROM AUTHOR]

In this study, the effects of density profile and hot press diagram on the technological properties of particleboard were analyzed. Physical and mechanical properties of particleboards were evaluated. Density profile was found a main parameter affecting quality properties of particleboard. While increasing entrance pressure improved the modulus of rupture and elasticity, and thickness swelling of the panels, increasing exit pressure was found to be effective on the bonding strength and thickness swelling. Exit pressure did not statistically affect the bending properties. Decreasing feeding speed of the hot press significantly improved all of the properties. While high surface density improved the modulus of rupture and elasticity, and thickness swelling, high core density caused better internal bond strength and thickness swelling. Entrance pressure was found to be effective on the surface density of particleboard. Exit pressure did not statistically affect the surface density, however, increased the core density.

The effects of periodic hot-press drying on drying behavior and mechanical damage to Chinese fir lumber were investigated by taking the heating platens' temperature (TP) and compression ratio (Rc) as experimental factors. The temperature and pressure inside lumber were analyzed during drying process. The results were as follows. The drying rate of lumber was significantly increased with increasing TP and Rc. Scanning electron microscope (SEM) micrographs showed that bordered pit membranes, cross-field pits, middle lamella between adjacent cells, and tracheid walls were damaged after drying, and the damage became more severe with higher TP and Rc. Detachments between ray parenchyma cells and tracheids were observed at 170 °C. Nitrogen-adsorption measurement results demonstrated that more cell wall pores in the 2.5~6.2 nm pore diameter range were generated at higher TP, resulting in an enlarged specific surface area and pore volume of cell walls. These structural changes contributed to accelerating moisture migration and decreasing the drying time. Furthermore, fluctuating pressure inside lumber was the main driving force leading to moisture migration and cell tissue damage in lumber during drying. The influence of TP on internal temperature (TM) and pressure (PM) was greater than Rc. With the increase in TP from 130 to 170 °C at the Rc of 10%, the maximum TM and PM were increased by 30.90% and 39.84%, respectively. However, TP should not be too high to prevent the formation of macro-cracks caused by high pressure, which may significantly affect wood's mechanical properties. These results provide theoretical support for periodic hot-press drying processes' improvement and high-value utilization of Chinese fir. [ABSTRACT FROM AUTHOR]

Urea-formaldehyde prepolymer and hot-press drying were used to improve the properties of poplar wood. The wood was impregnated with the prepolymer using a pulse-dipping machine. The impregnated timbers were compressed and dried by a multilayer hot-press drying kiln. The drying rate was more rapid during the chemical modification and hot-press drying than conventional kiln-drying. In addition, the properties of timber were also enhanced obviously. When the compression rate was 28.6%, the basic density, oven dry density and air-dried density of modified wood improved 22%, 71%, and 70%, respectively. The bending strength and compressive strength parallel to grain increased 60% and 40%. The water uptake of treated wood was significantly decreased compared with the untreated wood. The FTIR analysis successfully showed that the intensity of hydroxyl and carbonyl absorption peaks decreased significantly, which was attributed to a reaction of the NHCH2OH of urea-formaldehyde prepolymer with the wood carboxyl (C=O) and hydroxyl (-OH) groups. The XRD results indicated that the degree of crystallinity increased from 35.09% to 36.91%. The morphologic models of chemical within wood were discovered by SEM.

In order to manufacture complex curvilinear generatrix workpieces of high-temperature titanium alloy, the hot tensile behavior of Ti55 alloy sheet was tested and the hot press forming process was investigated using Finite Element Method (FEM) simulation and experiment. The hot tensile experiments of Ti55 rolled sheet were conducted at the temperatures of 800–900 °C with the strain rates of 0.001–0.1 s−1. According to the results of hot tensile tests and microstructure evolution, the proper hot press forming parameters were determined as the temperature of 850 °C and the strain rates of 0.001–0.01 s−1. The wrinkling mechanism in the transition region was analyzed and the initial blank sheet geometry was optimized by FE simulation of hot press forming. The two-step hot press forming process was better to produce the complex sheet workpiece of Ti55 alloy than the one-step hot forming scheme, which could restrain the wrinkling trend and ensure the microstructure and mechanical properties of the hot formed workpieces.

The metal and carbon fiber reinforced plastic (CFRP) hybrid parts are increasingly used in automobile industry to meet the demand for vehicle weight reduction. The interface bond strength between metal and CFRP is the key to the part properties. The effects of different surface treatments on the interface bond strength of DP780 Steel/CFRP composite laminate based on hot-press curing integration were studied. Single lap test and single-leg bending (SLB) test were used to characterize the interface bond strength of the hybrid composite laminate. Interface failure mechanism was analyzed through surface roughness, fracture mode and fracture morphology. The experimental results showed that the steel surface treated by laser exhibited the highest surface roughness and the greatest surface energy in contrast to other surface treatments, such as degreasing, acid corrosion and grinding. The single lap test results showed that the laser-treated specimen had the maximum interface bond strength and there were a lot of fibers residues on the steel fracture surface. In SLB tests, there was no gap between the laser-treated steel and CFRP interface. The interface was bonded finely, which greatly improved the interface bond strength. [ABSTRACT FROM AUTHOR]

An isotactic polypropylene/aluminum alloy hybrid was fabricated by a self-made ultrasonic-assisted hot press molding (UAHPM) technology, and the properties and structure at the plastic-metal interface were explored. The surface of aluminum alloy was chemically etched and anodized to form micro- and nano- pore structures. The field emission scanning electron microscopy (FE-SEM) was used to observe the strong micro-nano two-scale mechanical interlocking structures formed at the interface of PP/aluminum hybrid. The element diffusion at the plastic-metal interface was detected by the energy dispersive spectrum. The results showed the stronger isotactic polypropylene/aluminum hybrids were manufactured by the UAHPM technology compared with the traditional press-molded samples. The maximal tensile shear strength of the UAHPMed hybrid reached up to 18.96 MPa, compared with 9.77 MPa for the conventional hybrid. The bonding layer between isotactic polypropylene and the aluminum alloy was 3.7um prepared by the UAHPM technique against 6.2 um for the conventional press molding technology. The thermal property of polypropylene was examined by differential scanning calorimetry (DSC), and crystal structure was characterized by X-ray diffraction (XRD), and the β-crystal of PP existence at the PMH's interface contributes to the excellent plasticity and strong bonding strength. [ABSTRACT FROM AUTHOR]

BiFeO3 represents the most extensively investigated multiferroic due to its fascinating ferroelectric domain structures, large polarization, and multiferroic coupling, among many other emergent phenomena. Nevertheless, much less concern with the piezoelectricity has been raised while all these well addressed properties are identified in thin film BiFeO3, and bulk ceramic BiFeO3 has never been given priority of attention. In this paper, we report our experiments on the ferroelectric and piezoelectric properties as well as domain structures of BiFeO3 bulk ceramics synthesized by rapid hot-press sintering. It is revealed that these properties are strongly dependent on the microstructural quality, and the largest piezoelectric coefficient d33 = 55 pC/N with electric polarization as large as 45 μC/cm2 is obtained for the sample sintered at 800 °C, while they are only 30 pC/N and 14 μC/cm2 for the samples sintered in normal conditions at 800 °C. The two-level hierarchical stripe-like and irregular dendrite-like domain structures are observed in these hot-press sintered samples. It is suggested that the enhanced piezoelectric property is ascribed to the two-level hierarchical stripe-like domain structure which may respond more easily to electrical and strain stimuli than those irregular dendrite-like domains. The enhanced remnant polarization should be owing to the improved sample quality and large grains in the properly hot-press sintered samples. [ABSTRACT FROM AUTHOR]

This research investigates the performance of medium density fiberboard (MDF) with respect to hot press parameters. The performance of the board, type of glue, and production efficiency determine the optimum temperature and pressure for hot pressing. The actual temperature of the hot press inside the MDF board determines the properties of the final product. Hence, the optimal hot press parameters for the desired product are experimentally obtained. Moreover, MDF is experimentally investigated in terms of its vertical density profile, bending, and internal bonding under the various input parameters of temperature, pressure, cycle time, and moisture content during the manufacturing process. The experimental study is carried out by varying the temperature, pressure, cycle time, and moisture content in the ranges of 200–220 °C, 145–155 bar, 260–275 s, and 8–10%, respectively. Consequently, the optimum input parameters of a hot-pressing temperature of 220 °C, pressure of 155 bar, cycle time of 256 s, and moisture content of 8% are identified for the required internal bonding (0.64 N/mm2), bending (32 N/mm2), and increase in both the core and peak density of the vertical density profile as per the ASTM standard.

The cooling performance of a slice die is studied numerically and experimentally. The slice die is designed to improve the cooling performance compared to that of a conventional die that is generally used in the Hot Press Forming (HPF) process by modifying the cooling channel layout and arrangement. In order to understand the physical phenomenon of the slice die cooling performance, the cooling performance of the conventional die is also simulated and their results are compared with the slice die results. From the results of the maximum temperature of the blank and die and the temperature distribution of the blank, the slice die has considerably improved cooling performance. To validate the simulation results, the slice die is prototyped and a blank is produced by the HPF process. Blank temperatures are measured by a thermal imaging camera at several holding times. The simulation and experimental results of the blank temperatures are compared and agree with the error rate of 3%. In order to verify the quality of the produced blank, ultimate tensile stress, yield stress, and elongation tests are conducted for specimens that are extracted from the blank and are compared with existing literature results.