scholarly journals The Extent of Interlayer Bond Strength during Fused Filament Fabrication of Nylon Copolymers: An Interplay between Thermal History and Crystalline Morphology

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2677
Author(s):  
Dries Vaes ◽  
Margot Coppens ◽  
Bart Goderis ◽  
Wim Zoetelief ◽  
Peter Van Puyvelde
Keyword(s):  
Molecular Weight ◽  
Bond Strength ◽  
Thermal History ◽  
Degree Of Crystallinity ◽  
Crystalline Morphology ◽  
Fused Filament Fabrication ◽  
Plate Temperature ◽  
Weld Time ◽  
Interlayer Bonding ◽  
Interlayer Bond

One of the main drawbacks of Fused Filament Fabrication is the often-inadequate mechanical performance of printed parts due to a lack of sufficient interlayer bonding between successively deposited layers. The phenomenon of interlayer bonding becomes especially complex for semi-crystalline polymers, as, besides the extremely non-isothermal temperature history experienced by the extruded layers, the ongoing crystallization process will greatly complicate its analysis. This work attempts to elucidate a possible relation between the degree of crystallinity attained during printing by mimicking the experienced thermal history with Fast Scanning Chip Calorimetry, the extent of interlayer bonding by performing trouser tear fracture tests on printed specimens, and the resulting crystalline morphology at the weld interface through visualization with polarized light microscopy. Different printing conditions are defined, which all vary in terms of processing parameters or feedstock molecular weight. The concept of an equivalent isothermal weld time is utilized to validate whether an amorphous healing theory is capable of explaining the observed trends in weld strength. Interlayer bond strength was found to be positively impacted by an increased liquefier temperature and reduced feedstock molecular weight as predicted by the weld time. An increase in liquefier temperature of 40 °C brings about a tear energy value that is three to four times higher. The print speed was found to have a negligible effect. An elevated build plate temperature will lead to an increased degree of crystallinity, generally resulting in about a 1.5 times larger crystalline fraction compared to when printing occurs at a lower build plate temperature, as well as larger spherulites attained during printing, as it allows crystallization to occur at higher temperatures. Due to slower crystal growth, a lower tie chain density in the amorphous interlamellar regions is believed to be created, which will negatively impact interlayer bond strength.

scholarly journals Chitosan-Based Adhesive: Optimization of Tensile Shear Strength in Dry and Wet Conditions

2021 ◽  
Vol 2 (1) ◽  
pp. 110-120
Author(s):  
Maisa Abdelmoula ◽  
Hajer Ben Hlima ◽  
Frédéric Michalet ◽  
Gérard Bourduche ◽  
Jean-Yves Chavant ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Strength ◽  
Bond Strength ◽  
Water Resistance ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Spread Rate ◽  
Assembly Time ◽  
Deacetylation Degree ◽  
Dry And Wet Conditions

Commercial adhesives present a high bond strength and water resistance, but they are considered non-healthier products. Chitosan can be considered as an interesting biosourced and biodegradable alternative, despite its low water resistance. Here, its wood bonding implementation and its tensile shear strength in dry and wet conditions were investigated depending on its structural characteristics. Firstly, the spread rate, open assembly time, drying pressure, drying temperature, and drying time have been determined for two chitosans of European pine double lap specimens. An adhesive solution spread rate of 1000 g·m−2, an open assembly time of 10 min, and a pressure temperature of 55 °C for 105 min led to a bond strength of 2.82 MPa. Secondly, a comparison between a high molecular weight/low deacetylation degree chitosan and a lower molecular weight/higher deacetylation degree chitosan was conducted. Tests were conducted with beech simple lap specimens in accordance with the implementation conditions and the conditioning treatments in wet and dry environments required for thermoplastic wood adhesive standards used in non-structural applications (EN 204 and EN 205). The results clearly revealed the dependence of adhesive properties and water resistance on the structural features of chitosans (molecular weight and deacetylation degree), explaining the heterogeneity of results published notably in this field.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

Stereo-chemical contributions to the glass transition and liquid–liquid phase separation in high molecular weight poly(N-vinyl carbazole)

RSC Advances ◽  
2016 ◽  
Vol 6 (35) ◽  
pp. 29326-29333 ◽  
Author(s):  
Abdul G. Al Lafi ◽  
James N. Hay
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Liquid Phase ◽  
High Molecular Weight ◽  
Structural Properties ◽  
Thermal History ◽  
Liquid Phase Separation ◽  
High Molecular Weight Poly ◽  
Liquid Liquid Phase Separation

Thermal history and purification effects on the structural properties of PVK were investigated. Liquid–liquid phase separation is suggested to occur by separation of isotactic rich segments from a matrix which is predominantly atactic.

Process-structure-property effects on ABS bond strength in fused filament fabrication

2018 ◽  
Vol 19 ◽  
pp. 29-38 ◽  
Author(s):  
A.C. Abbott ◽  
G.P. Tandon ◽  
R.L. Bradford ◽  
H. Koerner ◽  
J.W. Baur
Keyword(s):  
Bond Strength ◽  
Structure Property ◽  
Fused Filament Fabrication ◽  
Process Structure

scholarly journals Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2352 ◽  
Author(s):  
Behzad Nematollahi ◽  
Praful Vijay ◽  
Jay Sanjayan ◽  
Ali Nazari ◽  
Ming Xia ◽  
...  
Keyword(s):  
3D Printing ◽  
Bond Strength ◽  
Fibre Volume ◽  
Interface Plane ◽  
Flexural Performance ◽  
Fresh State ◽  
Hardened State ◽  
3D Printed ◽  
Shape Retention ◽  
Interlayer Bond

This paper investigates the effect of polypropylene (PP) fibres on the fresh and hardened properties of 3D-printed fibre-reinforced geopolymer mortars. Different percentages of PP fibres ranging between 0.25% and 1.00% by volume were added to an optimised geopolymer mixture. All samples showed reasonable workability and extrudability. In addition, shape-retention ability in the fresh state was investigated as a major requirement for 3D-printing. The compressive strength of the printed specimens was tested in the hardened state in three loading directions, viz. longitudinal, perpendicular, and lateral. The flexural strength of samples was also tested in the longitudinal and lateral directions. In addition, the interlayer bond strength was investigated. Fibre addition seems to influence compressive strengths positively only when the loading is perpendicular to the interface plane. This is due to the preferential fibre alignment parallel to the direction of extrusion. The addition of fibre significantly enhanced the flexural performance of the printed samples. The use of fibre dosages of 0.75 and 1.00 vol % caused deflection-hardening behaviour of the 3D-printed geopolymers and, hence, a significantly higher fracture energy in comparison to specimens without fibre or with lower fibre content. However, an increase in the fibre volume caused some minor reduction in interlayer bond strength. With respect to properties in the fresh state, higher fibre volumes caused better shape-retention ability in the printed samples. The results indicate the possibility of printing fibre-reinforced geopolymers which meet all the necessary properties in both the fresh and hardened states.

Structure-Property Relationship of Dodecylbenzenesulfonic Acid Doped Polyaniline

2013 ◽  
Vol 721 ◽  
pp. 199-205 ◽  
Author(s):  
Ying Liu ◽  
Qi Wen ◽  
Jia Li Guan ◽  
Shi Jie Zhao ◽  
Qi Xing Hu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ammonium Persulfate ◽  
Degree Of Crystallinity ◽  
Structure Property ◽  
X Ray Diffraction ◽  
Electrospinning Technique ◽  
Dodecylbenzenesulfonic Acid ◽  
Molar Ratios ◽  
Liquid Crystal Property ◽  
Relationship Of

Dodecylbenzenesulfonic acid (DBSA) doped polypanilines (PANIs) were chemically synthesized in different molar ratios of aniline (An) to ammonium persulfate (APS) and An to DBSA. The microstructures of these PANIs were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR). UV-Vis spectrometer, semiconductor parameter analyzer, ubbelohde viscometer and electrospinning technique were used to characterize the optical, electrical properties, viscosity and solubility of these PANIs. The results show that the molar rations of An to APS and An to DBSA had strong effect on the microstructure, molecular weight, degree of crystallinity, optical property, solubility and conductivity of obtained DBSA doped PANI. With the increase of the molar ratios of An to APS and An to DBSA, the conductivities and molecular weight of DBSA doped PANIs decreased, while the degree of crystallinity and solubility of DBSA doped PANIs increased. The DBSA doped PANI could dissolve in dichloromethane or HFIP and could be fabricated short fibers by electrospinning. Moreover, the solution of DBSA doped PANIs in concentrated sulphuric acid showed liquid crystal property.

Bond Characteristics of Overlays Placed over Bridge Decks Sealed with High-Molecular-Weight Methacrylate

2000 ◽  
Vol 1697 (1) ◽  
pp. 24-30 ◽  
Author(s):  
Bahram M. Shahrooz ◽  
Arnol J. Gillum ◽  
Jeremiah Cole ◽  
Ahmet Turer
Keyword(s):  
Molecular Weight ◽  
Bond Strength ◽  
High Molecular Weight ◽  
Fatigue Testing ◽  
Bridge Decks ◽  
Limit State ◽  
Surface Preparation ◽  
Service Level ◽  
Preparation Techniques ◽  
Bond Characteristics

The bond strength between portland cement overlays and bridge decks treated with high-molecular-weight methacrylate sealers is examined. The data universally suggest that sealers reduce the available bond strength. However, extra surface preparation techniques, such as light sandblasting of the sealed surface or broadcasting sand over the surface immediately after sealing [at approximately 1 kg/m2 (20 lb/100 ft2)], restore the strengths to 80 or 85 percent, respectively, of the unsealed surface. Service-level fatigue testing and loading well beyond the serviceability limit state do not adversely affect the bond strength so long as the sealed surface is treated before the application of the overlay. Therefore, to seal the existing cracks, bridge decks may be sealed if either of the recommended secondary surface preparation techniques is followed.

scholarly journals Effect of Heterogeneous Deacetylation on the Properties of Northern Shrimp Chitin and Chitosan

2020 ◽  
Author(s):  
Nataliia Dolgopiatova ◽  
Yuliya Kuchina ◽  
Tatiana Dyakina ◽  
Tatiana Volkova
Keyword(s):  
Molecular Weight ◽  
Shear Stress ◽  
Alkaline Treatment ◽  
Degree Of Crystallinity ◽  
Repeated Treatment ◽  
Experimental Conditions ◽  
Northern Shrimp ◽  
Chitin And Chitosan ◽  
Chitosan Deacetylation ◽  
The Degree Of Crystallinity

The effect of alkaline treatment of shrimp chitin on the molecular weight, the degree of deacetylation and degree of crystallinity of the resulting chitosan is studied. The viscosity of chitosan solutions from repeatedly deacetylated chitin is studied. It is shown that repeated treatment of chitin/chitosan with alkali causes the destruction of polysaccharide macromolecules. After four-time deacetylation and one-time deacetylation of chitin/chitosan for four hours, the molecular weight of the polysaccharide decreases by ten times. The maximum degree of chitosan deacetylation under experimental conditions was 92.0 -92.5%. The diffractograms of chitin and chitosan from the Northern shrimp are of the form typical for samples containing an amorphous phase in addition to a crystalline phase. The degree of crystallinity of chitin from Northern shrimp was 40.8%, of chitosan samples after one-, two-, and three-time deacetylation was 62-65%. For a sample of chitosan obtained after four-time deacetylation, recrystallization, and drying in a freeze dryer, the degree of crystallinity is close to the degree of crystallinity of shrimp chitin. The investigated acetic acid chitosan solutions with a concentration of 5% (wt.) and the chitosan molecular weight of 250, 160 and 130 kDa in their rheological properties are liquid-like non-Newtonian systems, their viscosity decreasing with increasing shear stress. After four-time deacetylation of chitin, the viscosity of chitosan solutions practically does not change with increasing shear stress, which apparently can be due to a significant decrease in the molecular weight of chitosan under these conditions.

Temperature-compensated constitutive model of fused filament fabrication 3D printed PLA materials with full extrusion temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kaiyang Zhu ◽  
Zichen Deng ◽  
Shi Dai ◽  
Yajun Yu
Keyword(s):  
Mechanical Properties ◽  
Thermal Decomposition ◽  
Constitutive Model ◽  
Polylactic Acid ◽  
Extrusion Temperature ◽  
Fused Filament Fabrication ◽  
Printing Process ◽  
Content Type ◽  
3D Printed ◽  
Interlayer Bonding

Purpose This study aims to focus on the effect of interlayer bonding and thermal decomposition on the mechanical properties of fused filament fabrication-printed polylactic acid specimens at high extrusion temperatures. Design/methodology/approach A printing process, that is simultaneous manufacturing of contour and specimen, is used to improve the printing accuracy at high extrusion temperatures. The effects of the extrusion temperature on the mechanical properties of the interlayer and intra-layer are evaluated via tensile experiments. In addition, the microstructure evolution affected by the extrusion temperature is observed using scanning electron microscopy. Findings The results show that the extrusion temperature can effectively improve the interlayer bonding property; however, the mechanical properties of the specimen for extrusion temperatures higher than 270°C may worsen owing to the thermal decomposition of the polylactic acid (PLA) material. The optimum extrusion temperature of PLA material in the three-dimensional (3D) printing process is recommended to be 250–270°C. Originality/value A temperature-compensated constitutive model for 3D printed PLA material under different extrusion temperatures is proposed. The present work facilitates the prediction of the mechanical properties of specimens at an extrusion temperature for different printing temperatures and different layers.

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