Influence of Surface Crystalline Structures on DSC Analysis of PTFE

Sciuti, Vinicius Fiocco; Melo, Caiuã Caldeira de; Canto, Leonardo Bresciani; Canto, Rodrigo Bresciani

doi:10.1590/1980-5373-mr-2017-0326

Cited by 13 publications

(8 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The high-modulus samples exhibited a uniformly distributed fibrillar microstructure. We attribute these distinct features to the fusion and coalescence of the PTFE nanoparticles during the thermal treatment, , which was also confirmed by the SEM characterization of the thermally treated PTFE dispersion without any GG present (Figure S5). In contrast, the low Young’s modulus samples were heterogeneous with two distinct microstructures, one with fibrillar features similar to the high-modulus samples but another highly porous region where the PTFE nanoparticles had not completely coalesced.…”

Section: Resultssupporting

confidence: 66%

Direct Ink Writing of Poly(tetrafluoroethylene) (PTFE) with Tunable Mechanical Properties

Jiang

Erol

Chatterjee

et al. 2019

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

Poly(tetrafluoroethylene) (PTFE) is a unique polymer with highly desirable properties such as resistance to chemical degradation, biocompatibility, hydrophobicity, antistiction, and low friction coefficient. However, due to its high melt viscosity, it is not possible to three-dimensional (3D)-print PTFE structures using nozzle-based extrusion. Here, we report a new and versatile strategy for 3D-printing PTFE structures using direct ink writing (DIW). Our approach is based on a newly formulated PTFE nanoparticle ink and thermal treatment process. The ink was formulated by mixing an aqueous dispersion of surfactant-stabilized PTFE nanoparticles with a binding gum to optimize its shear-thinning properties required for DIW. We developed a multistage thermal treatment to fuse the PTFE nanoparticles, solidify the printed structures, and remove the additives. We have extensively characterized the rheological and mechanical properties and processing parameters of these structures using imaging, mechanical testing, and statistical design of experiments. Importantly, several of the mechanical and structural properties of the final-printed PTFE structures resemble that of compression-molded PTFE, and additionally, the mechanical properties are tunable. We anticipate that this versatile approach facilitates the production of 3D-printed PTFE components using DIW with significant potential applications in engineering and medicine.

show abstract

Section: Resultssupporting

confidence: 66%

Direct Ink Writing of Poly(tetrafluoroethylene) (PTFE) with Tunable Mechanical Properties

Jiang

Erol

Chatterjee

et al. 2019

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…Our results also revealed that one side of each type of membrane contained micrometre-sized topological artefacts: “warts” on PTFE-W and thread-like structures on PTFE-B. Both artifacts are pure PTFE in different forms arising from distinct production processes [ 28 , 30 , 45 ]. The results indicated that these artifacts present a major contribution to early bacterial adhesion.…”

Section: Discussionmentioning

confidence: 66%

“…It has been shown that such beadlike structures occur when the concentration of the polymer solution, from which the material is prepared, is sufficiently low [ 30 ]. This type of crystallites, so-called “warts”, has been observed in several cases, for instance when they were used as a means of PTFE texturing [ 28 , 45 ]. Larger magnifications ( Figure 4 i,j) revealed the coexistence of “warts” (yellow arrows) and dendrites (red arrow), which has been reported before [ 45 ].…”

Section: Resultsmentioning

confidence: 99%

“…This type of crystallites, so-called “warts”, has been observed in several cases, for instance when they were used as a means of PTFE texturing [ 28 , 45 ]. Larger magnifications ( Figure 4 i,j) revealed the coexistence of “warts” (yellow arrows) and dendrites (red arrow), which has been reported before [ 45 ]. The dendrites are similar in shape but larger in size compared to the ones seen on the PTFE-B surface.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference

Begić

Didović

Blagojević

et al. 2022

IJMS

View full text Add to dashboard Cite

Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, and Veilonella parvula) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites (“warts”), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log10CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.

show abstract

“…The maximum density of the specimens is 2.43353 g/cm 3 when the holding time is 4 h, which is 0.512% higher than that of the samples with a holding time of 5 h. When the holding time is more than 5 h, the density of the specimen does not decrease but increases, which may be due to the fact that too long a holding time aggravated the decomposition of the PTFE molecular chain and decreased the molecular weight. The smaller the entanglement between and within molecules, the stronger the activity of the molecular chain and the stronger the crystallization ability, which leads to the increase of crystallinity [ 27 , 28 ]. It can be seen from Figure 10 b,c and Table 8 that the specimens with holding times of 3 h, 4 h, 5 h and 6 h at 360 °C respectively experienced elastic-plastic deformation, yield, strain hardening and fracture failure during static compression [ 29 ], and the deformation of the specimens was relatively large.…”

Section: Resultsmentioning

confidence: 99%

Effect of Sintering Factors on Properties of Al-Rich PTFE/Al/TiH2 Active Materials

2021

View full text Add to dashboard Cite

Sintering process is an important part of the specimen preparation process, which directly affects the properties of materials. In order to obtain the best sintering control factors of Al-rich PTFE/Al/TiH2 active materials, Al-rich PTFE/Al/TiH2 active specimens with different sintering control factors were prepared using a mold pressing sintering method. A quasi-static compression experiment was carried out on a universal material testing machine, and a real stress-strain curve was obtained. The effects of sintering control factors on the properties of Al-rich PTFE/Al/TiH2 active materials were analyzed by means of mechanical parameters such as compressive strength, failure strain and toughness. SEM and XRD were used to analyze the microstructure and phase of the sintered samples. The results show that: (1) With the increase of cooling rate, the density, yield strength, strain hardening modulus, compressive strength and toughness of Al-rich Al/PTFE/TiH2 specimens decrease gradually, while the failure strain and pores of the specimens increase gradually. (2) With the increase of sintering temperature, the density, maximum true strain and toughness of the specimens first increase and then decrease, and the failure strain of the specimens gradually increases. When the sintering temperature is 360 °C, the PTFE matrix and particles inside the specimen are closely combined, a small number of particles are exposed on the PTFE matrix and there are a small number of voids. (3) With the increase of holding time at 360 °C, the strength and toughness of the material first decrease and then increase. When the holding time is 6 h, the interface between particles and matrix inside the specimen is the strongest, and the crack propagation inside the specimen is less. (4) When the sintering time increased from 1 h to 4 h at 315 °C, the compressive strength of the specimen increased by 1.62%, the toughness of the specimen decreased by 0.55% and the failure strain of the specimen decreased by 0.54%. The interface between PTFE matrix and particles is the strongest and the crack propagation is less in the specimen with a holding time of 4 h. (5) Above all, the optimum sintering parameters of Al-rich Al/PTFE/TiH2 materials are cooling rate of 25 °C/h, sintering temperature of 360 °C, holding time of 6 h and holding time of 4 h at 315 °C. (6) The reactivity of Al-rich Al/PTFE/TiH2 specimens with 10% content of TiH2 under static compression is not significantly affected by sintering parameters.

show abstract

Influence of Surface Crystalline Structures on DSC Analysis of PTFE

Cited by 13 publications

References 21 publications

Direct Ink Writing of Poly(tetrafluoroethylene) (PTFE) with Tunable Mechanical Properties

Direct Ink Writing of Poly(tetrafluoroethylene) (PTFE) with Tunable Mechanical Properties

Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference

Effect of Sintering Factors on Properties of Al-Rich PTFE/Al/TiH2 Active Materials

Contact Info

Product

Resources

About