scholarly journals A novel fibre-ensemble level constitutive model for exogenous cross-linked collagenous tissues

2016 ◽  
Vol 6 (1) ◽  
pp. 20150090 ◽  
Author(s):  
Michael S. Sacks ◽  
Will Zhang ◽  
Silvia Wognum
Keyword(s):  
Constitutive Model ◽  
Soft Tissues ◽  
Fibrous Tissue ◽  
Collagen Fibre ◽  
Tissue Response ◽  
Loading Path ◽  
Cross Linking ◽  
The Matrix ◽  
The Cross ◽  
Collagenous Tissues

Exogenous cross-linking of soft collagenous tissues is a common method for biomaterial development and medical therapies. To enable improved applications through computational methods, physically realistic constitutive models are required. Yet, despite decades of research, development and clinical use, no such model exists. In this study, we develop the first rigorous full structural model (i.e. explicitly incorporating various features of the collagen fibre architecture) for exogenously cross-linked soft tissues. This was made possible, in-part, with the use of native to cross-linked matched experimental datasets and an extension to the collagenous structural constitutive model so that the uncross-linked collagen fibre responses could be mapped to the cross-linked configuration. This allowed us to separate the effects of cross-linking from kinematic changes induced in the cross-linking process, which in turn allowed the non-fibrous tissue matrix component and the interaction effects to be identified. It was determined that the matrix could be modelled as an isotropic material using a modified Yeoh model. The most novel findings of this study were that: (i) the effective collagen fibre modulus was unaffected by cross-linking and (ii) fibre-ensemble interactions played a large role in stress development, often dominating the total tissue response (depending on the stress component and loading path considered). An important utility of the present model is its ability to separate the effects of exogenous cross-linking on the fibres from changes due to the matrix. Applications of this approach include the utilization in the design of novel chemical treatments to produce specific mechanical responses and the study of fatigue damage in bioprosthetic heart valve biomaterials.

Chemiluminescence measurement of gel times for amine-cured epoxy resins

1995 ◽  
Vol 7 (2) ◽  
pp. 219-236 ◽  
Author(s):  
K A Kozielski ◽  
N C Billingham ◽  
G A George ◽  
D C L Greenfield ◽  
J M Barton
Keyword(s):  
Chemical Reactions ◽  
Epoxy Resins ◽  
Physical State ◽  
Glycidyl Ether ◽  
Cross Linking ◽  
Gel Time ◽  
The Matrix ◽  
Effect Of Impurities ◽  
The Cross

The cross-linking reactions of 4,4'-diaminodiphenyl sulphone (DDS) with stoichiometric quantities of glycidyl ether- or tetraglycidyl amine-based epoxy resins were monitored using chemiluminescence (CL) and rheometry. It was found that, when a sample was cured isothermally in air, the CL profile increased to a maximum, then decreased again. The maximum was found to correspond well with the gel time (tgel), as measured by rheometry. This observation is discussed in relation to the chemical reactions occurring within the material and the physical state of the matrix. The effect of impurities in DDS on the gel time of these epoxy resins is reported.

Creep and dynamic mechanical behavior of cross-linked polyvinyl alcohol reinforced with cotton fiber laminate composites

2019 ◽  
Vol 39 (4) ◽  
pp. 326-335 ◽  
Author(s):  
Naman Jain ◽  
Shubhan Ali ◽  
Vinay K. Singh ◽  
Komal Singh ◽  
Nitesh Bisht ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Cotton Fiber ◽  
Water Solubility ◽  
Mechanical Analysis ◽  
Cross Linking ◽  
Laminate Composites ◽  
Dynamic Mechanical ◽  
The Matrix ◽  
The Cross ◽  
Uptake Test

AbstractThe objective of this investigation was to fabricate cross-linked polyvinyl alcohol (PVA) based laminate composites reinforced with biaxial cotton sheets. Cross-linking was done with sulfuric acid, to overcome the water solubility of PVA. A water uptake test was performed to evaluate the effect of cross-linking on the water absorption properties of the composites. Morphology, distribution and bonding between the matrix and reinforcement of the fabricated composites were studied using scanning electron microscopy. Mechanical properties such as the tensile strength (TS), modulus of elasticity and elongation of the fabricated composites material were evaluated. There was about a 56.25% increase in the TS of the cross-linked composite as compared to the neat PVA, and at 64 wt.% of cotton fiber, there was about a 56% increase in the TS as compared to the cross-linked PVA. The thermal degradation analysis of fabricated composites material was carried out by thermogravimetric analysis. The thermal stability increased with increase in cotton fiber wt.%. The viscoelastic properties of the fabricated composites material were determined by dynamic mechanical analysis. The effects of stress (4 MPa, 6 MPa and 8 MPa) and temperature (20°C and 40°C) on creep and recovery behavior of the laminated composites were studied.

scholarly journals Plugging mechanisms of polymer gel used for hydraulic fracture water shutoff

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 411-422
Author(s):  
Song Zhang ◽  
Falin Wei ◽  
Pingde Liu ◽  
Liming Shao ◽  
Weitao Li
Keyword(s):  
Hydraulic Fracture ◽  
Physical Simulation ◽  
Distribution Patterns ◽  
Cross Linking ◽  
Polymer Gel ◽  
Gel Layer ◽  
The Matrix ◽  
The Cross ◽  
The Difference ◽  
Flow Leak

AbstractThe performance of polymer gel to plug a hydraulic fracture is greatly affected by its distribution patterns and gelling effect. In this study, the migration of a gel plugging agent in a fracture and its plugging after gelling were investigated by physical simulation experiments. In addition, the distribution patterns of the gel plugging agent and its plugging mechanism after gelling were investigated in detail. The results of this study revealed that the migration flowing behavior of the gel solution in a fracture can be divided into three streams: fracture flow, leak off flow, and matrix flow. Such behavior distributed the gel in three different patterns after gelling: gel clusters in the fracture, gel layer on the fracture surface, and dispersed gel lumps in the matrix pores-throats. Because of the leak off flow and the difference in components, the gel solution has apparent disproportional leak off–diffusion of components during its migration in a fracture, with less polymer molecules and loss of more cross-linking agent ions. The leak off of the cross-linking agent significantly deteriorates the gelling strength of the polymer gel, affecting its performance to plug a hydraulic fracture. The results also show that when the normalized concentration of the cross-linking agent ions in a fracture is less than 0.6, gel fails to plug the fracture effectively after gelling. When gelling was carried out by in situ cross-linking, polymer gel provided more satisfactory plugging performance than the gelling via ground pre-cross-linking.

scholarly journals Impact of Cross-Linking of Collagen Matrices on Tissue Regeneration in a Rabbit Calvarial Bone Defect

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3740
Author(s):  
Masako Fujioka-Kobayashi ◽  
Elena Andrejova ◽  
Hiroki Katagiri ◽  
Benoit Schaller ◽  
Anton Sculean ◽  
...  
Keyword(s):  
Bone Formation ◽  
Tissue Regeneration ◽  
Fibrous Tissue ◽  
Giant Cells ◽  
Cross Linking ◽  
Tissue Formation ◽  
Calvarial Bone ◽  
Collagen Matrices ◽  
Post Surgery ◽  
The Cross

The cross-linking of collagen matrices (Cl_CM) may provide volume-stable enhanced defect regeneration when compared to non-cross-linked matrices (Ncl_CM). The aim of the present study was to investigate the bone forming potential of collagen matrices (CMs) and the effects of cross-linking CMs in a rabbit calvaria defect model. (1) Empty controls (n = 6), (2) Ncl_CM (n = 8), and (3) Cl_CM (n = 8) were selected to be observed for the healing in 10 mm critical-sized calvarial bone defects. The potential for the bone as well as the connective tissue formation were evaluated by micro-CT and histomorphometry at three months post-surgery. There were no statistically significant differences in terms of new bone volume in the defects between the groups. However, the Cl_CM induced significantly greater fibrous tissue regeneration (5.29 ± 1.57 mm2) when compared to the controls (3.51 ± 0.93 mm2) by histomorphometry. The remnants of collagen fibers with immune cells, including macrophages and giant cells, were occasionally observed in the Cl_CM group but not in the Ncl_CM group. In conclusion, the cross-linking of collagen did not influence the potential for bone formation. Nevertheless, Cl_CM might be advantageous for the maintenance of fibrous tissue volume without disturbing bone formation in the defects.

A Structurally Motivated Constitutive Model for Bat Wing Skin

2014 ◽  
Author(s):  
Alyssa J. Skulborstad ◽  
N. C. Goulbourne
Keyword(s):  
Constitutive Model ◽  
Deformation Gradient ◽  
Compressive Loading ◽  
Strain Energy Function ◽  
Tissue Response ◽  
Material Behavior ◽  
Elastin Fiber ◽  
The Matrix ◽  
Wing Skin ◽  
Bat Wing

Unique among animal flyers, bats have highly flexible and stretchable thin wing membranes. The connection between the structural constituents of bat wing skin, its material behavior, and flight abilities is not yet known. In this work we propose a structurally motivated constitutive model for the wing skin. Within a continuum mechanics framework, the proposed strain energy function for the wing skin is the sum of contributions due to the matrix and two mesoscopic fiber families, one oriented primarily spanwise consisting of elastin fiber bundles and the other family oriented chordwise consisting of muscle fibers. While the fibers are flat and straight when the wing is somewhat open, the matrix exhibits corrugations due to compressive loading from the pre-stretched spanwise fibers. This mismatch in the natural configurations of components is accounted for in the model by a decomposition of the deformation gradient of the spanwise fibers. The material parameters are fit with a procedure motivated by the underlying deformation mechanisms of the tissue corresponding to the regions of the j-shaped constitutive curves. The proposed model is fit to the first set of biaxial experimental stress-strain data for bat wing skin and captures the general features of the tissue response well.

A Comparative Study of the in vivo Distribution of 32P-Polyphosphates and 32P-Orthophosphate

1972 ◽  
Vol 11 (01) ◽  
pp. 70-78
Author(s):  
Esther Miller ◽  
Leopoldo Anghileri
Keyword(s):  
Radiation Dose ◽  
Comparative Study ◽  
Soft Tissues ◽  
Tumor Bearing ◽  
In Vivo Distribution ◽  
The Cross ◽  
Total Body

SummaryThe distribution of 32P-polyphosphates (lineal and cross-linked) and 32Porthophosphate in normal and tumor bearing animals has been studied. Differences between the cross-linked and the lineal form are related to a different degree of susceptibility to the hydrolysis by the phosphatases. In contrast to orthophosphate, the polyphosphates showed a lower accumulation in soft tissues which gives an advantageous reduction of the total body radiation dose.

scholarly journals Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

2021 ◽  
Author(s):  
Istebreq A. Saeedi ◽  
Sunny Chaudhary ◽  
Thomas Andritsch ◽  
Alun S. Vaughan
Keyword(s):  
Glass Transition ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Epoxy Resins ◽  
Functional Network ◽  
Cross Linking ◽  
Network Modifier ◽  
Epoxy Resin System ◽  
The Cross ◽  
The Impact

AbstractReactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

scholarly journals The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2623
Author(s):  
Monika Wójcik-Bania ◽  
Jakub Matusik
Keyword(s):  
Total Pore Volume ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Cross ◽  
Chain Lengths ◽  
First Time ◽  
Substituent Influence ◽  
Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

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