Effect of thermal shock on mechanical properties of injection-molded thermoplastic denture base resins

This work describes the production of a spherical polybutylene terephthalate (PBT) powder and its processing with selective laser sintering (SLS). The powder was produced via melt emulsification, a continuous extrusion-based process. PBT was melt blended with polyethylene glycol (PEG), creating an emulsion of spherical PBT droplets in a PEG matrix. Powder could be extracted after dissolving the PEG matrix phase in water. The extrusion settings were adjusted to optimize the size and yield of PBT particles. After classification, 79 vol. % of particles fell within a range of 10–100 µm. Owing to its spherical shape, the powder exhibited excellent flowability and packing properties. After powder production, the width of the thermal processing (sintering) window was reduced by 7.6 °C. Processing of the powder on a laser sintering machine was only possible with difficulties. The parts exhibited mechanical properties inferior to injection-molded specimens. The main reason lied in the PBT being prone to thermal degradation and hydrolysis during the powder production process. Melt emulsification in general is a process well suited to produce a large variety of SLS powders with exceptional flowability.

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Research on cellular morphology and mechanical properties of microcellular injection–molded BCPP and its blends

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-021-07389-5 ◽

2021 ◽

Author(s):

Jiachang Wang ◽

Guilong Wang ◽

Jinchuan Zhao ◽

Aimin Zhang ◽

Guiwei Dong ◽

...

Keyword(s):

Mechanical Properties ◽

Cellular Morphology ◽

Injection Molded ◽

Morphology And Mechanical Properties

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Micro-Injection Molding of Polymer Nanocomposites Composition-Process-Properties Relationship

International Polymer Processing ◽

10.1515/ipp-2020-4065 ◽

2021 ◽

Vol 36 (3) ◽

pp. 276-286

Author(s):

Z. Dekel ◽

S. Kenig

Keyword(s):

Mechanical Properties ◽

Plug Flow ◽

Volume Resistivity ◽

Process Conditions ◽

Polyamide 66 ◽

Fountain Flow ◽

Microinjection Molding ◽

Injection Molded ◽

Composition Process ◽

Rheological Percolation

Abstract The mechanical, electrical, thermal, and rheological properties of micro injection molded nanocomposites comprising 2% and 5% carbon nanotubes (CNTs) incorporated in polycarbonate (PC), and polyamide 66 (PA) were studied. The design of experiments method was used to investigate the composition-process – properties relationship. Results indicated that the process variables significantly affected the flow patterns and resulting morphology during the filling stage of the microinjection molding (lIM) process, using 0.45 mm diameter lIM samples. Two distinct flow regimes have been identified in lIM using the low cross-section samples. The first was a conventional “fountain flow,” which resulted in a skin/core structure and reduced volume resistivity up to 10 X cm in the case of 5% CNTs and up to 100 X cm in 2% CNTs, in both polymers, respectively. In addition, inferior mechanical properties were obtained, attributed to polymer degradation under high shear rate conditions, when practicing high injection speeds, high mold temperatures, and high screw rotation velocities. The second was a “plug flow” due to wall slippage, obtained under low injection speeds, low mold temperatures, and low rotation velocities, leading to a substantial increase in modulus of elasticity (60%) with increased electrical resistivity up to 103 X cm for 5% CNTs and 105 X cm for 2% CNTs, respectively. The rheological percolation threshold was obtained at 2% CNTs while the electrical threshold was attained at 0.4% CNTs, in both polymers. It was concluded that in lIM, the process conditions should be closely monitored. In the case of high viscous heating, degradation of mechanical properties was obtained, while skin- core morphology formation enhanced electrical conductivity.

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Mechanical Properties and Biocompatibility of Urethane Acrylate-Based 3D-Printed Denture Base Resin

Polymers ◽

10.3390/polym13050822 ◽

2021 ◽

Vol 13 (5) ◽

pp. 822

Author(s):

Jy-Jiunn Tzeng ◽

Tzu-Sen Yang ◽

Wei-Fang Lee ◽

Hsuan Chen ◽

Hung-Ming Chang

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Flexural Modulus ◽

Measurement Data ◽

Uv Exposure ◽

Control Group ◽

Urethane Acrylate ◽

Shore Hardness ◽

Digital Light Processing ◽

Denture Base

In this study, five urethane acrylates (UAs), namely aliphatic urethane hexa-acrylate (87A), aromatic urethane hexa-acrylate (88A), aliphatic UA (588), aliphatic urethane triacrylate diluted in 15% HDD (594), and high-functional aliphatic UA (5812), were selected to formulate five UA-based photopolymer resins for digital light processing (DLP)-based 3D printing. Each UA (40 wt%) was added and blended homogenously with ethoxylated pentaerythritol tetraacrylate (40 wt%), isobornyl acrylate (12 wt%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (3 wt%), and a pink acrylic (5 wt%). Each UA-based resin specimen was designed using CAD software and fabricated using a DLP 3D printer to specific dimensions. Characteristics, mechanical properties, and cytotoxicity levels of these designed UA-based resins were investigated and compared with a commercial 3D printing denture base acrylic resin (BB base) control group at different UV exposure times. Shore hardness-measurement data and MTT assays were analyzed using a one-way analysis of variance with Bonferroni’s post hoc test, whereas viscosity, maximum strength, and modulus were analyzed using the Kruskal–Wallis test (α = 0.05). UA-based photopolymer resins with tunable mechanical properties were successfully prepared by replacing the UA materials and the UV exposure times. After 15 min of UV exposure, the 5812 and 594 groups exhibited higher viscosities, whereas the 88A and 87A groups exhibited lower viscosities compared with the BB base group. Maximum flexural strength, flexural modulus, and Shore hardness values also revealed significant differences among materials (p < 0.001). Based on MTT assay results, the UA-based photopolymer resins were nontoxic. In the present study, mechanical properties of the designed photopolymer resins could be adjusted by changing the UA or UV exposure time, suggesting that aliphatic urethane acrylate has good potential for use in the design of printable resins for DLP-type 3D printing in dental applications.

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Impact of thermal shock cycles on mechanical properties and microstructure of lithium disilicate dental glass-ceramic

Ceramics International ◽

10.1016/j.ceramint.2017.10.079 ◽

2018 ◽

Vol 44 (2) ◽

pp. 1589-1593 ◽

Cited By ~ 6

Author(s):

Dongdong Qian ◽

Lei Zhang ◽

Ying Zhang ◽

Pingying Liu ◽

Xizhang Wang ◽

...

Keyword(s):

Mechanical Properties ◽

Thermal Shock ◽

Glass Ceramic ◽

Lithium Disilicate

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Preparation of ZrO2 Composite Ceramics with High Thermal Shock Resistance

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.455-456.650 ◽

2012 ◽

Vol 455-456 ◽

pp. 650-654 ◽

Cited By ~ 1

Author(s):

He Yi Ge ◽

Jian Ye Liu ◽

Xian Qin Hou ◽

Dong Zhi Wang

Keyword(s):

Mechanical Properties ◽

Water Absorption ◽

Thermal Shock ◽

Thermal Shock Resistance ◽

Sintering Temperature ◽

Fiber Composite ◽

Physical And Mechanical Properties ◽

Composite Ceramics ◽

Shock Resistance ◽

Absorption Measurements

The physical and mechanical properties of nanometer ZrO2-ZrO2fiber composite ceramics were studied by introduction of ZrO2fiber. ZrO2composite ceramics at different sintering temperature was investigated by porosity and water absorption measurements, flexual strength and thermal shock resistance analysis. Results showed that ZrO2composite ceramics containing 15 wt% ZrO2fiber with sintering temperature of 1650°C exhibited good mechanical properties and thermal shock resistance. The porosity and the water absorption were 8.84% and 1.62%, respectively. The flexual strength was 975 MPa and the thermal shock times reached 31 times. Scanning electron microscope (SEM) was used to analyze the microstructure of ZrO2composite ceramics.

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