scholarly journals Carbon / Epoxy Resin Based Elastic Memory Composites

2012 ◽  
Vol 14 (3) ◽  
pp. 227 ◽  
Author(s):  
J. Dyana Merline ◽  
C.P. Reghunadhan Nair
Keyword(s):  
Glass Transition ◽  
Flexural Strength ◽  
Shape Memory ◽  
Shape Recovery ◽  
Diglycidyl Ether ◽  
Bending Test ◽  
Different Types ◽  
Elastic Memory Composites ◽  
Memory Characteristics ◽  
Epoxy Systems

Elastic memory composites were processed from shape memory epoxy resins and carbon fabric reinforcements. Three different types of epoxies (diglycidyl ether of bisphenol-A, tris(4-glycidyloxy phenyl)methane, and epoxy novolac) were used as matrices. Developed composites were evaluated for flexural strength and analyzed by Dynamic Mechanical Thermal analysis. Of the three different epoxy systems with carbon: resin ratio of 50:50, the composite with diepoxy system exhibited maximum glass transition value of 119 °C, epoxy novalac system exhibited a low glass transition value of 54 °C and the tris epoxy system exhibited a glass transition of 100 °C respectively. The flexural strength and modulus of the composites were optimised at a concentration of 40 wt.%. The transition temperature also showed a maximum at around this composition. Bending test was adopted for the shape memory evaluation. All the developed composites exhibited more than 90% shape recovery. The diepoxy resin series of composites exhibited the maximum shape recovery of 97%. The shape recovery properties of the tris epoxy and epoxy novolac-based composites were inferior. For the diepoxy resin-based system, the shape recovery time was proportional to the resin content. The shape recovery of composite with 80% resin was demonstrated experimentally. The properties of the composites show that these systems have the required elastic memory characteristics for possible use in thermo-responsive self-deployable applications.

scholarly journals Nanoclay Modification of Shape Memory Polyurethane

2015 ◽  
Vol 15 (4) ◽  
pp. 327
Author(s):  
J. Dyana Merline ◽  
Reghunadhan Nair, C.P.
Keyword(s):  
Shape Memory ◽  
Shape Recovery ◽  
Clay Content ◽  
Bending Test ◽  
Modulus Ratio ◽  
Tem Analysis ◽  
Shape Memory Property ◽  
Nanoclay Content ◽  
Shape Memory Polyurethane ◽  
Memory Characteristics

Effect of nanoclay modification on the properties of  polytetramethylene oxide-based polyurethane was examined. Nanoclay was dispersed in polyurethane wherein the clay content was varied from 1 to 5 wt.%. The nanocomposites were characterized by thermal, FTIR, XRD and thermo-mechanical analyses and their shape memory properties were evaluated. Morphology was examined by TEM analysis. Bending test<br />was adopted for the evaluation of shape memory property. Increase in clay content resulted an increase in transition temperature. Tensile strength and modulus increased proportional to nanoclay content. The elongation decreased with clay content. Intercalated structure of clay in the PU matrix was observed<br />from XRD studies, which was confirmed by TEM analysis. Modulus ratio showed a decreasing trend with nanoclay content. This resulted in decreased shape recovery characteristics. Highest shape recovery of 92% was observed for PU with 1 wt.% clay content. Moderate nanoclay leveling is conducive to deriving<br />mechanically stronger PU without loss of shape memory characteristics.

scholarly journals A Large-Deformation Theory for Thermally-Actuated Shape-Memory Polymers and its Application

2010 ◽  
Author(s):  
Shawn A. Chester ◽  
Vikas Srivastava ◽  
Claudio V. Di Leo ◽  
Lallit Anand
Keyword(s):  
Glass Transition ◽  
Shape Memory ◽  
Deformation Theory ◽  
Shape Recovery ◽  
Large Deformations ◽  
Shape Memory Polymers ◽  
The Body ◽  
Thermally Induced ◽  
Thermally Actuated ◽  
Common Shape

The most common shape-memory polymers are those in which the shape-recovery is thermally-induced. A body made from such a material may be subjected to large deformations at an elevated temperature above its glass transition temperature &Vthgr;g. Cooling the deformed body to a temperature below &Vthgr;g under active kinematical constraints fixes the deformed shape of the body. The original shape of the body may be recovered if the material is heated back to a temperature above &Vthgr;g without the kinematical constraints. This phenomenon is known as the shape-memory effect. If the shape recovery is partially constrained, the material exerts a recovery force and the phenomenon is known as constrained-recovery.

The Influence of Thermo-Oxidative Degradation on the Behavior of Epoxy Shape Memory Polymers

2014 ◽  
Author(s):  
Kannan Dasharathi ◽  
John A. Shaw
Keyword(s):  
Glass Transition ◽  
Shape Memory ◽  
Residual Strain ◽  
Oxidative Degradation ◽  
Viscoelastic Behavior ◽  
Diglycidyl Ether ◽  
Strain Recovery ◽  
Recovery Ratio ◽  
Chemical Aging ◽  
Residual Strains

Results are reported from an ongoing experimental investigation of the effects of thermo-oxidative aging on the mechanical behavior of an epoxy shape memory polymer (SMP). Chemo-rheological degradation due to macromolecular scission and cross-linking is one of the main factors contributing to the chemical aging of thermo-responsive SMPs. This aging may manifest as residual strain or irreversible material property changes, which can affect the performance and limit the useful life of a SMP. A relatively new epoxy SMP based on the diglycidyl ether of bisphenol A is synthesized, and specimens are tested under uni-axial tension using a dynamic mechanical analyzer. Fundamental viscoelastic behavior and thermal expansion coefficients are first characterized, showing a glass transition near 60 °C. Shape memory cycle experiments are performed at shape fixing temperatures of 80, 125, 150 and 175 °C, and the effect of fixing time at each temperature is examined upon subsequent strain recovery at 80 °C. Performance parameters such as recovery ratio, speed of recovery and residual strain are quantified as a function of shape fixing time and temperature. No effect of chemical aging was seen at a fixing temperature of 80 °C, although the recovery ratio decreases initially with increasing fixing time and stabilizes near 92 %. Only minor effects of chemical aging are seen in the mechanical responses for fixing temperatures of 125 and 150 °C, but specimens exhibit progressively more noticeable color changes that indicate oxidation. Significant effects are observed at the highest fixing temperature of 175 °C, where chemical aging at longer fixing times results in a reduction in recovery rate across the rubber-glass transition temperature, progressively larger residual strains, lack of complete strain recovery at 80 °C, and higher temperatures to achieve 90 % strain recovery.

scholarly journals Bio-Based Epoxy Shape-Memory Thermosets from Triglycidyl Phloroglucinol

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 542 ◽  
Author(s):  
David Santiago ◽  
Dailyn Guzmán ◽  
Francesc Ferrando ◽  
Àngels Serra ◽  
Silvia De la Flor
Keyword(s):  
Shape Memory ◽  
Shape Recovery ◽  
Memory Performance ◽  
Crosslinking Agent ◽  
Shape Memory Polymers ◽  
Crosslinking Density ◽  
Mechanical Analysis ◽  
Diglycidyl Ether ◽  
Partial Substitution ◽  
Scanning Calorimetry

A series of bio-based epoxy shape-memory thermosetting polymers were synthesized starting from a triglycidyl phloroglucinol (3EPOPh) and trimethylolpropane triglycidyl ether (TPTE) as epoxy monomers and a polyetheramine (JEF) as crosslinking agent. The evolution of the curing process was studied by differential scanning calorimetry (DSC) and the materials obtained were characterized by means of DSC, thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), stress-strain tests, and microindentation. Shape-memory properties were evaluated under free and totally constrained conditions. All results were compared with an industrial epoxy thermoset prepared from standard diglycidyl ether of Bisphenol A (DGEBA). Results revealed that materials prepared from 3EPOPh were more reactive and showed a tighter network with higher crosslinking density and glass transition temperatures than the prepared from DGEBA. The partial substitution of 3EPOPh by TPTE as epoxy comonomer caused an increase in the molecular mobility of the materials but without worsening the thermal stability. The shape-memory polymers (SMPs) prepared from 3EPOPh showed good mechanical properties as well as an excellent shape-memory performance. They showed almost complete shape-recovery and shape-fixation, fast shape-recovery rates, and recovery stress up to 7 MPa. The results obtained in this study allow us to conclude that the triglycidyl phloroglucinol derivative of eugenol is a safe and environmentally friendly alternative to DGEBA for preparing thermosetting shape-memory polymers.

Study on the Shape Memory Behavior of Poly (L-Lactide)

2005 ◽  
Vol 475-479 ◽  
pp. 2399-2402 ◽  
Author(s):  
Xili Lu ◽  
Wei Cai ◽  
Lian Cheng Zhao
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Amorphous Phase ◽  
Memory Effect ◽  
Crystalline Phase ◽  
Ring Opening ◽  
Shape Recovery ◽  
Ring Opening Polymerization ◽  
Bending Test ◽  
Shape Memory Behavior

Poly(L-lactide) (PLLA) was synthesized by the ring-opening polymerization of L-lactide and the shape memory behavior was studied using DSC and bending test experiments. The results indicate that the specimen shows the shape memory effect (SME), the small crystalline phase of PLLA and the mobility of amorphous phase may be responsible for the SME. The shape recovery of samples decreases and approaches to steady with the testing number increases.

Thermal Behavior of Clay/Epoxy Nanocomposites

2012 ◽  
Vol 21 ◽  
pp. 23-28
Author(s):  
Artur S.C. Leal ◽  
Carlos José de Araújo ◽  
Suédina Maria L. Silva ◽  
Antônio Gilson Barbosa de Lima
Keyword(s):  
Thermal Stability ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elevated Temperatures ◽  
Mechanical Analysis ◽  
Diglycidyl Ether ◽  
X Ray Diffraction ◽  
Curing Conditions ◽  
The Matrix ◽  
Epoxy Systems

In this work, the effect of curing agent, curing conditions and the incorporation of small amounts of organoclay on the thermal properties of DGEBA (diglycidyl ether of bisphenol A) epoxy resin was evaluated in order to develop an epoxy system for application as the matrix in active composites whose dispersed phase consists of shape memory alloy wires. The DGEBA resin was prepared using three amine derivatives as hardeners (triethylenetetramine - TETA, diethylenetriamine - DETA and diaminodiphenylsulfone - DDS) under varied curing conditions, in the absence and presence of organoclay. Epoxy systems were characterized by dynamic mechanical analysis (DMA), optical microscopy and X-ray diffraction. According to the obtained results, the cured DETA and DDS epoxy systems at elevated temperatures, above 180°C, showed a higher glass transition temperature (Tg) and thermal stability values than the system cured at low temperature (TETA). In addition, when the post-cure treatment was used, an improvement of the thermal stability was verified. When 1 phr (parts hundred resin) of organoclay was incorporated in DETA and DDS cured epoxy systems and post-cured, either the increase in the Tg and thermal stability values were more significant, especially for the system cured with DDS. Hence, the epoxy/DDS/organoclay system (exfoliated nanocomposite) is the most appropriate to be used as the matrix in the preparation of active composites since this matrix is thermally stable in the Ni-Ti shape memory alloy working range whose phase transformation occurs between 70 and 80 °C.

Study on Shape Recovery Behaviors of Epoxy-Based Shape Memory Polymer

2011 ◽  
Vol 179-180 ◽  
pp. 325-328 ◽  
Author(s):  
Bo Zhou ◽  
Xue Lian Wu ◽  
Yan Ju Liu ◽  
Jin Song Leng
Keyword(s):  
Glass Transition ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Shape Recovery ◽  
Shape Memory Polymer ◽  
Shape Memory Polymers ◽  
Numerical Calculations ◽  
Glass Transition Temperatures ◽  
Recovery Experiment

The glass transition temperatures of epoxy-based shape memory polymers (SMPs), which contain a flexibilizer at various contents of 0%, 5%, 10% and 15% respectively, are determined through DMA tests. The shape memory effect of such materials is investigated through shape recovery experiments. Experimental results show that the content of flexibilizer has much influence on the shape memory effect of epoxy-based SMP. A shape recovery equation is developed based on the results of shape recovery experiment. Numerical calculations show that the developed shape recovery equation well predicts the shape recovery behaviors of epoxy-based SMP.

scholarly journals Comparative Evaluation of Flexural Strength and Flexural Modulus of Different Periodontal Splint Materials: An In Vitro Study

2019 ◽  
Vol 9 (19) ◽  
pp. 4197
Author(s):  
Shahabe Saquib ◽  
AlQarni Abdullah ◽  
Das Gotam ◽  
Naqash Talib ◽  
Sibghatullah Muhammad ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Flexural Modulus ◽  
In Vitro Study ◽  
Mean Value ◽  
Vitro Study ◽  
Bending Test ◽  
P Value ◽  
Significant Difference ◽  
Different Types

Splinting of the mobile teeth is a critical part of periodontal management to improve the prognosis and longevity of stable results of periodontally compromised teeth with increased mobility. Different types of splints are used in the dental field based on their mechanical and physical properties.The objective of the current in vitro study was to evaluate the flexure strength and flexural modulus of different types of splinting materials, such as: composite block, ligature wire, Ribbond®, InFibra®, and F-splint-Aid® bonded utilizing Flowable composites resin material. Seventy-five bar specimens were prepared with the dimensions of 25 × 4 × 2 mm, utilizing split metallic mold. Specimens were divided equally (n = 15) into five groups (one control group, four test groups). Different layers of splinting material were placed in between the layers of composite before curing. All the specimens were subjected to a three-point bending test by using a universal testing machine to calculate the flexural strength and flexural modulus. The entire data was subjected to statistical tests to evaluate the significance. Specimens from composite block groups showed the least mean value for flexural strength (89.15 ± 9.70 MPa) and flexural modulus (4.310 ± 0.912 GPa). Whereas, the highest mean value for flexural strength (168.04 ± 45.95 MPa) and flexural modulus (5.861 ± 0.501 GPa) were recorded by Ribbond® specimens. Inter group comparison of flexural strength showed statistically significant differences (P-value < 0.05), whereas comparison of flexural modulus showed non-significant difference among the groups (P-value > 0.05). Within the limitation of the present study, it was concluded that the Ribbond® exhibits maximum flexural strength and flexural modulus, whereas the composite blocks recorded the least values. Still, the decision making depends on the clinical scenario and the unique characteristic of each splint material.

Sign in / Sign up

Export Citation Format

Share Document