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Article
An Evaluation of Some Mechanical Properties of Autopolymerizing Acrylic Resin with the Modified One after Changing the Curing Environment: (In vitro Study)

Author: Intisar J. Ismail
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2015 Volume: 27 Issue: 4 Pages: 62-71
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Studying and investigating the transverse strength(Ts), impact strength(Is), hardness (Hr) and surfaceroughness(Ra) of conventional and modified autopolymerizing acrylic resin with different weight percentages ofbiopolymer kraftlignin, after curing in different water temperatures; 40°C and 80°C.Material and Methods: Standard acrylic specimens were fabricated according to ADA specification No.12 fortransverse strength, ISO 179 was used for impact testing, Shore D for hardness and profilometerfor surface roughness.The material lignin first dispersed in the monomer, then the powder PMMA is immediately added. Lignin added indifferent weight percentages. Then cured using pressure pot (Ivomet) in two temperatures;40°C and 80°C under 2bar pressure, for 30 minutes.Atotal of 144samples were prepared for this study. Ts, Is, Ra, and Hr were tested, by usingInstron universal testing machine, charpy impact tester, shore D tester, and profilometer respectively.Results: The transverse strength increased in both the conventional and modified onewhen compared with thatcured in air. The addition of 0.5wt% lignin gave the higher effect (78.0017MPa) with highly significant difference foundbetween groups at 40°C polymerizing temperature. While the impact strength in both temperatures in the modifiedresin revealed increased results than conventional one, 1.25wt% of kraft lignin gave the highest value (12.7355KJ/m2)with highly significant differences found between groups at 80°C polymerizing temperature. Hardness and surfaceroughness showed also highly significant differences found between groups at 40°C polymerizing temperature, allthe groups had increased Hr. than the control one (78.95), while the Ra. decreased for 1.0% ,1.25,1.50 and 1.75 wt%lignin content to (0.26,0.10,0.063, 0.12μm) respectively in 40°C polymerizing temperature, the lowest value present in1.75 wt% lignin (0.05 μm) at 80°Cpolymerizing temperature.Conclusions: It seems that increasing the polymerizing temperature to 40°C had a positive effect on the mechanicalproperties of autopolymerizing acrylic resin and the one enforced by kraft lignin biopolymer in low percentages.Increasing the polymerizing temperature to 80°C will doesn’t have much positive effect but it doesn’t deteriorate themechanical properties. However, when submitted to increasing the temperature to 80°C, specimens showed asignificantincrease in impact strength


Article
Rheological Behavior of Isothermal Cured Epoxy/1,4-Diaminobenzene Systems

Authors: Muataz H. Ismael --- Salah N. Farhan صلاح نوري فرحان --- Ayad Dari Jaafar اياد داري جعفر
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2018 Volume: 11 Issue: 1 Pages: 38-43
Publisher: Diyala University جامعة ديالى

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Abstract

A novel curing agent (1,4-diaminobenzene) was used to enhance behavior of the epoxy resin system. The effect of the curing agent content (12 to 21 wt%) subjected to the isothermal curing temperatures at 80 °C to 110 °C were performed. Results indicate that the gel time was effected slightly on the viscosity when the curing temperature was higher than 90 °C and curing material consist over from 18wt %. These results explain that reaction rates caused by higher curing temperature.


Article
The Effect Of Curing Types On Compressive Strength Of High Performance Concrete
تأثير طرق الانضاج على مقاومة الانضغاط للخرسانة العالية الاداء

Authors: Nada Mahdi Fawzi ندى مهدي فوزي --- Ahmed Saher Tawfeeq Agha أحمد ساهر توفيق آغا
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2012 Volume: 18 Issue: 7 Pages: 768-783
Publisher: Baghdad University جامعة بغداد

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Abstract

The present investigation considers the effect of curing temperatures (30, 40, and 50˚C) and curing compound method on compressive strength development of high performance concrete, and compares the results with concrete cured at standard conditions and curing temperature (21˚C). The experimental results showed that at early ages, the rate of strength development at high curing temperature is greater than at lower curing temperature, the maximum increasing percentage in compressive strength is 10.83% at 50C˚ compared with 21C˚ in 7days curing age. However, at later ages, the strength achieved at higher curing temperature has been less, and the maximum percentage of reduction has been 5.70% at curing temperature 50C˚ compared with 21C˚curing temperature in 91 days curing age. Also, the results showed that the specimens which are cured under field condition (using curing compound) have a various strength development rate, and the results indicate 92.11% as minimum field-standard curing strength ratio.

هذا البحث اخذ بنظر الاعتبار تأثير درجات حرارة الانضاج (30، 40، 50 ˚م) وكذلك طريقة الانضاج الذاتي باستخدام المركبات الكيميائية على تطور مقاومة الانضغاط للخرسانة العالية الاداء، ومقارنة النتائج مع خرسانة منضجة تحت ظروف ودرجة حرارة قياسية (21˚م). النتائج المختبرية اظهرت، في الاعمار المبكرة، بان معدل تطور مقاومة الانضغاط في درجات حرارة الانضاج العالية اعلى من درجات الانضاج الواطئة، حيث يصل نسبة الزيادة في مقاومة الانضغاط الى 10,83% عند درجة حرارة انضاج 50˚م مقارنة بالدرجة القياسية (21˚) بعمر 7 ايام. اما في الاعمار المتأخرة، فان مقاومة الانضغاط في درجات الحرارة العالية تكون اقل، حيث تصل نسبة النقصان الى 5,70% عند درجة حرارة 50˚م مقارنة بالدرجة القياسية (21˚م) بعمر 91 يوم. وكذلك النتائج اظهرت, بان النماذج المنضجة تحت الظروف الحقلية باستخدام المركبات الكيميائية, تمتلك معدلات متغيرة في تطور مقاومة الانضغاط وان اقل نسبة مقاومة حقلية الى قياسية كانت 92,11%.

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