Resistência a tração (por compressão diametral) em gessos odontológicos: influência da espessura dos corpos de prova

The influence of different specimen thicknesses on the tensile strenght (by diametral compression method 11) of dental stones has been studdied. It was observed that there was greater reproducibility os results as the thickness of the samples decreased. This leads us to recommend the latter type os samples when conducting diametral compression tensile strenght tests. A relationship between the compression strenght and tensile strenght was also studdied. It was found that the difference between the two strenghts decrenses as the thickness os the diametral compression strenght samples increases. The results were expressed in stress values.

Retenção ou "adesividade" do acréscimo de misturas de ZnO/Eugenol ao material já endurecido, nas moldagens de próteses totais

ln the techniques for obtaining impressions of edentulous mouths with zinc oxide - eugenol impression materials it is common procedure to add newly mixed material to the already hardened impression in order to improve or "correct" the impression. It was our purpose to find out about the retentive or "adhesive" qualities of the above mentioned "additions" to the hardened material. To obtain this information weused a tensile strenght test in which the "added" material remained in the geometrical center of the test samples. As a comparison, test samples were also used, without added material. Five of the most widely used zinc-oxide/eugenol impression materials in Brazil were utilized throughout the experiments. The results, presented through Graphs and Tables, were statistically analysed. The addition of newly mixed material to already hardened material caused a reduction in tensile strenght values in all live impression pastes. This reduction, however, was not significant in paste "C"; it was significant (.05) in pasle "A” and highly significant (.01) in pastes,"B", "D"and "E”.

EDIBLE FILM DARI KARAGENAN DAN MINYAK CENGKEH SEBAGAI ANTIMIKROBA PADA IKAN SEGAR

Edible film is a type of packagingthat is both effective and safe. Edible film maked using natural ingredients such as carrageenan. Clove oil addetional to enhance its antimicrobial function. This study puposed to determine the effect of using carrageenan and clove oil concentrations in the organoleptic and ALT test. The design used was used was CRD with test parameter namely thikness tset, elongation, tensile strenght, organoleptic quality obcervation and ALT. Thikness test result 0.02-0.13 mm, elongation 1.027-1.117%, tensile strength 0.088-0.095 MPa, the best organoleptic is A2 on parameter (eyes, smell and texture), ALT A1 value (1.4x103 koloni/g) amd A2 (9.4x102 koloni/g). the reduction of carrageenan and additional of clove oil resulted in increased thikness and tensile strenht, while decreasing elongation. Based on the organoleptic test, the best the best treatment was edible film A2. ALT A1 and A2 test result do not exceed the threshold.

Pengaruh Jenis dan Konsentrasi Filler terhadap Karakteristik Bioplastik dari Tepung Maizena

This study aims to determine the effect of filler types and concentrations and their interactions on the characteristics of bioplastics and to determine the concentrations and types of fillers that produce bioplastics with the best characteristics. This research used factorial randomized block design. The first factor is the type of filler consisting of 3 levels that is ZnO, clay, CaCO3. The second factor is the filler concentration consisting of 3 levels 0, 3, 6, and 9% (w/w). Each treatment are grouped into two time-based of making bioplastics, so there are 24 experimental units. The variabels observed were tensil strength, elongation at break, modulus young, swelling, and biodegradation. The data obtained were analyzed of variant and test Tukey’s. The results showed that the concentration and type of filler had a very significant effect on tensile strenght, elongation at break, modulus young and swelling but had no significant effect on the biodegradation value. The 9% concentration with ZnO filler produced the best bioplastic characteristics with a tensile strength value 4.11 MPa, elongation at break 31.16%, modulus young 7.06 MPa, swelling 55.01%, and biodegradability for 6-7 days. Keywords: Bioplastics, filler concentration, ZnO, clay, CaCO3

Hybrid Dental Composites Biomechanical Properties

In the last two decades, both general and oral health status became more important for individuals, being associated to their quality of life, social provenance and income. Society�s evolution is associated to high expectations regarding edentulous and decays treatment. Metal filling such as gaudent or amalgam have been replaced by aesthetic materials, to achieve similarity to the patient�s genuine biological tissue. Along with the aesthetic demand, dental materials have to fulfill biocompatibility and mechanical properties proximate to healthy soft either hard tissues. Composite materials have the advantages of accomplishing biological and mechanical demands and to be accessible financially, compared to ceramics. Composites are classified according to the main monomer, filling, particles� dimension, addition of external molecules, this entirety having a direct influence on materials� properties. The objective of this prospective interventional in vitro study was to evaluate biomechanical properties of four different hybrid composites: Premise direct™ - Premise indirect™ (Kerr, Orange, California, USA), Gradia� Direct (GC, Alsip, Illinois, USA) and Ceramage� (SHOFU Dental, Ratinger, Germany). Vickers microhardness, compressive strenght, direct tensile strenght, water absorption and solubility were assessed. The results showed that microfilled hybrid composites UDMA (urethane dimethacrylate)-based monomer had the highest evaluations regarding Vickers microhardness, compressive strenght and tensile strenght, whereas water absorption was the highest for nanofilled hybrid Bis-GMA (bisphenol A-glycidyl methacrylate)/TEGDMA (triethylene glycol dimethacrylate), and solubility for microfilled hybrid UDMA based monomer.

Response Surface Methodology Approach to Recycling Aluminium Chips AA6061 by Optimum Hot Extrusion Parameter

A method for recycling aluminium alloy chips by hot extrusion was studied as well as the possibility of using to recycle aluminium chips. As a result, according to an ANOVA analysis, preheat temperature is the most significant factor influencing the response variables investigated. Preheat temperature and the quadratic effect of factor preheat temperature provided a primary contribution to the responses investigated. Additionally, factor preheat time did not provide a significant contributing factor to the Ultimate Tensile Strenght. This developed the Response Surface Methodology (RSM) model for ER12, which can now be used for analysis and predicting the Ultimate Tensile Strenght for recycling aluminium chip using the hot extrusion process. The Miscellaneous Design and Response Surface Methodology enabled the determination of optimal operating conditions for obtaining hot extrusion production. The optimization of the analyzed responses demonstrated that the best results for hot extrusion process parameter. It reveals the empirical models developed were reasonably accurate, particularly for UTS at 550°C temperature and 3 hours preheating time. All the actual values for the confirmation run are within the 95% prediction interval.

PENGARUH BENTUK SALURAN PADA PROSES PENGECORAN DENGAN MODEL DARI STYROFOAM TERHADAP SIFAT MEKANIS ALUMINIUM PADUAN Al-Si-Cu

Proses pengecoran masih banyak menjadi pilihan utama pada proses produksi di industri. Pilihan pada pengecoran ini disebabkan karena proses pengerjaan lain sangat tidak mungkin dilakukan, misalnya pada pembuatan komponen-komponen otomotif, seperti bottom, dudukan shock dll. Metode pengecoran dengan menggunakan polystyrene foam sebagai pola cetakan yang ditimbun dalam pasir cetak merupakan metode pengecoran evaporative. Metode ini akan menghasilkan coran yang sesuai dengan pola cetakan yang dibentuk. Tujuan penelitian ini adalah mengkaji struktur mikro, kekerasan, dan kekuatan tarik paduan Al-16.4Si-5.59Cu hasil coran yang dilakukan dengan metode evaporative / lost foam casting. Bahan utama penelitian ini adalah paduan Al-16.4Si- 5.59Cu, polystyrene foam sebagai pola cetakan dan pasir cetak. Pengecoran paduan Al- 16.4Si-5.59Cu dilakukan dengan cara proses peleburan pada temperatur tuang 800°C serta menggunakan 5 variabel saluran dengan beberapa perubahan bentuk variasi saluran turun dan masuk serta beberapa penambahan riser. Pengujian hasil coran meliputi pengujian foto struktur mikro, uji kekerasan dan uji tarik (tensile strength).Hasil pengujian kekerasan adalah variasi saluran yang mempunyai saluran penambah lebih banyak dan saluran penuangan tinggi mempunyai nilai kekerasan yang tertinggi dengan 77.83 HRF dan berbanding terbalik dengan nilai kekuatan tarik yang rendah 62.95 M.Pa (tensile strenght) pada Variasi E. Serta variasi saluran C yang mempunyai sistem saluran yang mengakibtkan perlambatan pembekuan dan laju aliran lebih lama mempunyai kekuatan tarik bahan tinggi 98.75M.Pa (tensile strenght) tetapi lunak 69.17 HRF. Beberapa variasi mengalami penurunan kekerasan dan kekuatan tarik oleh cacat porositas seperti saluran langsung pada saluran turun variasi saluran A 73.05 HRF, 66.02 M.Pa. Hasil beberapa variasi saluran B 69.95 HRF, 73.58 M.Pa mendekati nilai variasi saluran C dan variasi saluran D 76.45 HRF, 7.76 M.Pa mendekati nilai saluran Variasi E dengan masing-masing sistem saluran yang berbeda.

Studi Perbandingan Kuat Tarik Tidak Langsung terhadap Campuran Aspal Beton dengan menggunakan Limbah Marmer dan Abu Sekam Padi sebagai Filler

Lapisan perkerasan jalan mengalami dua pembebanan yaitu beban tekan dan beban tarik. Pada kondisi dilapangan beban tarik lebih sering menyebabkan retak, diawali dengan adanya retakawal (crackinitation) pada bagian bawah lapisan perkerasan yang kemudian akan menjalar kepermukaan. Salah satu upaya yang dapat dilakukan untuk mengatasinya yaitu dengan menambahkan bahan alternative yang dapat menunjang kekuatan perkerasan. Beberapa bahan tambah yang dapat digunakan yaitu limbah marmer dan abu sekam padi sebagai bahan pengisi (filler). Penelitian ini bertujuan untuk mengetahui kadaraspal optimum untuk pencampuran limah marmer dan abu sekam padi sebagai filler serta untuk mengetahui pengaruh limbah marmer dana buse kampa di pada campuran terhadap kuat tarik tidak langsung. Pengujian awal dengan alat Marshall Test untuk mendapatkan kadar aspal optimum (KAO). Pengujian selanjutnya dengan menggunakan alat Indirect Tensile Strenght. KAO yang digunakan yaitu 5,95% dan kadar filler yaitu 0,0%, 0,5%, 1,0%, 1,5%, dan 2,0%. Dari hasil pengujian kuat tarik tidak langsung, campuran dengan menggunakan filler limbah marmer mampu menahan beban sebesar 11969,37 KPa. Sedangkan campuran yang menggunakan abu sekam padi mampu menahan beban sebesar 11294,47 KPa. Berdasarkan hasil tersebut maka dapat disimpulkan bahwa campuran dengan menggunakan filler abu marmer lebih kuat menahan beban dibandingkan abu sekam padi. The pavement layer passes two loads: the compressive load and the tensile load. On surface conditions, itis discover ed by retrie ving the crack in itation at the bottom fthe layer which will then radiate to the surface. One of eff or that can be done to over come this is to add alternative material stoin crease the strength of it. Some of the ingredients added can beused are marble waste and rice husk ashas filler. This study aim stode termine the optimal asphalt content formixing marble andri cehuskash waste asa filler and also to know the marble and gray waste on in direct tensil emixture. Initial test with Marshall Test tool to obtain optimum bitumen content (KAO). Then exttestis by using the Indirect Tensile Strenght tool. KAO is 5.95% and filler content is 0.0%, 0.5%, 1.0%, 1.5%, and 2.0%. In directtax collection, using afiller of marble wast ecapable of with standing loads of 11969.37 KPa.While the mixture using rice huskas hable to with stand the load of 11294.47 KPa. Base on the results it can be concluded that the mixtureusing as hmarble filler is stronger to with stand the load than using rice husk ash.

KARAKTERISASI UJI KEKUATAN TARIK (TENSILE STRENGHT) FILM PLASTIK BIODEGRADABLE DARI TANDAN KOSONG KELAPA SAWIT DENGAN PENGUAT ZINK OKSIDA DAN GLISEROL

Telah dilakukan karakterisasi uji kekuatan tarik (tensile strength) film plastik biodegradable dari tandan kosong kelapa sawit dengan penguat zink oksida dan gliserol. Penelitian ini bertujuan untuk mengetahui kekuatan tarik film plastik biodegradable yang dihasilkan dari tandan kosong kelapa sawit dengan variasi ZnO dan gliserol (a) 0 % ZnO dan 50% gliserol; (b) 2% ZnO dan 25% gliserol; (c) 9% ZnO dan 25% gliserol; (d) 3% ZnO dan 50 % gliserol. Metode penelitian yang digunakan adalah analisis sifat mekanik dan uji kekuatan tarik film plastik menggunakan Universal Testing Machine (UTM). Hasil penelitian menunjukan bahwa kuat tarik pada film plastik biodegradable dipengaruhi oleh konsentrasi gliserol dan ZnO. Kuat tarik maksimal yang didapat dari penelitian yaitu 12,642 MPa dengan komposisi gliserol 25% dan ZnO 9%. Hal ini menunjukkan bahwa semakin banyak penambahan komposisi gliserol dan ZnO maka kuat tarik plasik akan semakin baik. Kata kunci : biodegradable film, kuat tarik, tandan kosong kelapa sawit

Pembuatan Bioplastik dari Kitosan dan Sorbitol dengan Penambahan Minyak Atsiri Serai

<em>Plastik merupakan bahan yang banyak digunakan dalam kehidupan, namun plastik juga menjadi permasalahan skala global yakni sampah plastik karena plastik yang bersal dari bahan baku minyak bumi sulit untuk diuraikan. Sehingga dibutuhkan plastik yang ramah lingkungan (bioplastik). Dalam penelitian ini dilakukan pembuatan bioplastik dari kitosan dan sobitol sebagai pemplastis serta minyak atsiri serai sebagai insektisida nabati. Tujuan dari penelitian ini adalah untuk mempelajari sifat mekanik bioplastik. Bioplastik yang dihasilkan dilakukan mengujian mekanik kuat tarik (tensile strenght) dan perpanjangan (elongasi).Hasil penelitian menunjukkan penambahan 1 mL minyak atsiri serai berpengaruh terhadap sifat mekanik bioplastik dengan nilai kuat tarik dan elongasi bioplastik eksperimen masing-masing sebesar 3.50 Mpa dan 7.54% dari nilai biplastik kontrol masing-masing sebesar 1.427 Mpa dan 3.97%</em>