Characterization of PVAc Adhesive Penetration and its Effect on Wood Properties

Penetration of adhesive into the wood cell and lumens is an important factor that may enhance the durability of the adhesive bonds. In this study, the diffusion of adhesive polyvinyl acetate (PVAc) into the cell wall of various types of wood was evaluated making use of micro-CT. Compression shear block tests were also applied to examine the mechanical performance of the bond. In adhesive assemblies examined, cell walls at the immediate surface which were damaged during machine planning were full of adhesives. As the penetration of PVAc increased, the variation in the observed bind strengths was not substantial. Bonded with the same type of glue, black spruce appeared to have lower shear strength than Douglas fir and lodgepole pine. Moreover, gravity seemed to play a role in the glue penetration. During clamping and adhesive curing, the substrate on the lower of the shear block specimen had a deeper glue penetration. There are some correlations between glue penetration and glue line thickness measured using micro-CT.

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Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling

Polymers ◽

10.3390/polym13132091 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2091

Author(s):

Daniela Mileva ◽

Jingbo Wang ◽

René Androsch ◽

Katalee Jariyavidyanont ◽

Markus Gahleitner ◽

...

Keyword(s):

Mechanical Performance ◽

Metallocene Catalyst ◽

Nucleating Agent ◽

Random Copolymers ◽

Rapid Cooling ◽

Significant Difference ◽

Chip Calorimetry ◽

High Cooling Rates ◽

Fast Scanning Chip Calorimetry

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

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Design and Characterization of Microscale Auxetic and Anisotropic Structures Fabricated by Multiphoton Lithography

Nanomaterials ◽

10.3390/nano11020446 ◽

2021 ◽

Vol 11 (2) ◽

pp. 446

Author(s):

Ioannis Spanos ◽

Zacharias Vangelatos ◽

Costas Grigoropoulos ◽

Maria Farsari

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Mechanical Performance ◽

Element Analysis ◽

Mechanical Responses ◽

Multiphoton Lithography ◽

Anisotropic Structures ◽

Scanning Electron

The need for control of the elastic properties of architected materials has been accentuated due to the advances in modelling and characterization. Among the plethora of unconventional mechanical responses, controlled anisotropy and auxeticity have been promulgated as a new avenue in bioengineering applications. This paper aims to delineate the mechanical performance of characteristic auxetic and anisotropic designs fabricated by multiphoton lithography. Through finite element analysis the distinct responses of representative topologies are conveyed. In addition, nanoindentation experiments observed in-situ through scanning electron microscopy enable the validation of the modeling and the observation of the anisotropic or auxetic phenomena. Our results herald how these categories of architected materials can be investigated at the microscale.

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Experimental and numerical characterization of 3D-printed scaffolds under monotonic compression with the aid of micro-CT volume reconstruction

Bio-Design and Manufacturing ◽

10.1007/s42242-020-00122-3 ◽

2021 ◽

Author(s):

R. Baptista ◽

M. F. C. Pereira ◽

A. Maurício ◽

D. Rechena ◽

V. Infante ◽

...

Keyword(s):

Micro Ct ◽

Volume Reconstruction ◽

Numerical Characterization ◽

3D Printed ◽

Ct Volume

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A Comprehensive Investigation on 3D Printing of Polyamide 11 and Thermoplastic Polyurethane via Multi Jet Fusion

Polymers ◽

10.3390/polym13132139 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2139

Author(s):

Wei Shian Tey ◽

Chao Cai ◽

Kun Zhou

Keyword(s):

Tensile Strength ◽

Flexural Strength ◽

Wear Rate ◽

Mechanical Performance ◽

Thermoplastic Polyurethane ◽

Print Quality ◽

Polyamide 11 ◽

Powder Bed

Multi Jet Fusion (MJF) is a recently developed polymeric powder bed fusion (PBF) additive manufacturing technique that has received considerable attention in the industrial and scientific community due to its ability to fabricate functional and complex polymeric parts efficiently. In this work, a systematic characterization of the physicochemical properties of MJF-certified polyamide 11 (PA11) and thermoplastic polyurethane (TPU) powder was conducted. The mechanical performance and print quality of the specimens printed using both powders were then evaluated. Both PA11 and TPU powders showed irregular morphology with sharp features and had broad particle size distribution, but such features did not impair their printability significantly. According to the DSC scans, the PA11 specimen exhibited two endothermic peaks, while the TPU specimen exhibited a broad endothermic peak (116–150 °C). The PA11 specimens possessed the highest tensile strength in the Z orientation, as opposed to the TPU specimens which possessed the lowest tensile strength along the same orientation. The flexural properties of the PA11 and TPU specimens displayed a similar anisotropy where the flexural strength was highest in the Z orientation and lowest in the X orientation. The porosity values of both the PA11 and the TPU specimens were observed to be the lowest in the Z orientation and highest in the X orientation, which was the opposite of the trend observed for the flexural strength of the specimens. The PA11 specimen possessed a low coefficient of friction (COF) of 0.13 and wear rate of 8.68 × 10−5 mm3/Nm as compared to the TPU specimen, which had a COF of 0.55 and wear rate of 0.012 mm3/Nm. The PA11 specimens generally had lower roughness values on their surfaces (Ra < 25 μm), while the TPU specimens had much rougher surfaces (Ra > 40 μm). This investigation aims to uncover and explain phenomena that are unique to the MJF process of PA11 and TPU while also serving as a benchmark against similar polymeric parts printed using other PBF processes.

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