Torsional Fiber Actuators from Shape-memory Polymer

MRS Advances ◽  
2018 ◽  
Vol 3 (63) ◽  
pp. 3861-3868 ◽  
Author(s):  
Muhammad Farhan ◽  
Tobias Rudolph ◽  
Karl Kratz ◽  
Andreas Lendlein
Keyword(s):  
Vinyl Acetate ◽  
Shape Memory Polymer ◽  
Circular Cross Section ◽  
Humanoid Robots ◽  
Melting Transition ◽  
Heating And Cooling ◽  
Rotary Motors ◽  
Temperature Ranges ◽  
Poly Ethylene ◽  
Soft Actuators

ABSTRACT:Humanoid robots, prosthetic limbs and exoskeletons require soft actuators to perform their primary function, which is controlled movement. In this work, we explored whether crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, with different vinyl acetate (VA) content can serve as torsional fiber actuators, exhibiting temperature controlled reversible rotational changes. Broad melting transitions ranging from 50 to 90 °C for cPEVA18-165 or from 40 to 80 °C for cPEVA28-165 fibers in combination with complete crystallization at temperatures around 10 °C make them suitable actuating materials with adjustable actuation temperature ranges between 10 and 70 °C during repetitive cooling and heating. The obtained fibers exhibited a circular cross section with diameters around 0.4±0.1 mm, while a length of 4 cm was employed for the investigation of reversible rotational actuation after programming by twist insertion using 30 complete rotations at a temperature above melting transition. Repetitive heating and cooling between 10 to 60 °C or 70 °C of one-end-tethered programmed fibers revealed reversible rotations and torsional force. During cooling 3±1 complete rotations (Δθr = + 1080±360°) in twisting direction were observed, while 4±1 turns in the opposite direction (Δθr = - 1440±360°) were found during heating. Such torsional fiber actuators, which are capable of approximately one rotation per cm fiber length, can serve as miniaturized rotary motors to provide rotational actuation in futuristic humanoid robots.

Achieving multimodal locomotion by a crosslinked poly(ethylene-co-vinyl acetate)-based two-way shape memory polymer

2021 ◽  
Author(s):  
Yao Zhao ◽  
Kaiyuan Peng ◽  
Jiaxin Xi ◽  
Shima Shahab ◽  
Reza Mirzaeifar
Keyword(s):  
Shape Memory ◽  
Vinyl Acetate ◽  
Smart Materials ◽  
Shape Memory Polymer ◽  
Soft Actuator ◽  
Output Force ◽  
Poly Ethylene ◽  
Underlying Mechanisms ◽  
Soft Actuators ◽  
Hot Surface

Abstract Locomotion is a critically important topic for soft actuators and robotics, however, the locomotion applications based on two-way shape memory polymers have not been well explored so far. In this work, a crosslinked poly(ethylene-co-vinyl acetate) (cPEVA)-based two-way shape memory polymer is synthesized using dicumyl peroxide (DCP) as the crosslinker. The influence of the DCP concentration on the mechanical properties and the two-way shape memory properties is systematically studied. A Venus flytrap-inspired soft actuator is made by cPEVA, and it is shown that the actuator can efficiently perform gripping movements, indicating that the resultant cPEVA SMP is capable of producing large output force and recovering from large deformations. This polymer is also utilized to make a self-rolling pentagon-shaped device. It is shown that the structure will efficiently roll on a hot surface, proving the applicability of the material in making sophisticated actuators. With introducing an energy barrier, jumping can be accomplished when the stored energy is fast released. Finite element simulations are also conducted to further understand the underlying mechanisms in the complex behavior of actuators based on cPEVA SMP. This work provides critical insights in designing smart materials with external stimulus responsive programmable function for soft actuator applications.

Vapor-grown carbon nanofiber/poly(ethylene-co-vinyl acetate) composites with electrical-active two-way shape memory behavior

2017 ◽  
Vol 28 (19) ◽  
pp. 2749-2756 ◽  
Author(s):  
Chen Qian ◽  
Yaofeng Zhu ◽  
Yubing Dong ◽  
Yaqin Fu
Keyword(s):  
Shape Memory ◽  
Vinyl Acetate ◽  
Carbon Nanofibers ◽  
Carbon Nanofiber ◽  
Analytical Techniques ◽  
Heating And Cooling ◽  
The Matrix ◽  
Device Applications ◽  
Poly Ethylene ◽  
Vapor Grown Carbon Nanofiber

Vapor-grown carbon nanofibers were filled into poly(ethylene-co-vinyl acetate) through solution mixing to achieve electrical-active two-way shape memory. The vapor-grown carbon nanofiber/poly(ethylene-co-vinyl acetate) nanocomposites were systematically and explicitly investigated through combined analytical techniques. Experimental results showed an increase in crystallization temperature ( Tc) and a decrease in melting temperature ( Tm) as the vapor-grown carbon nanofiber concentration in the nanocomposites increased. This result indicates that carbon nanofibers can act as nucleating agents during crystallization but may hinder the formation of thermodynamically stable crystals. The nanocomposites had a higher modulus but a lower strength than pure poly(ethylene-co-vinyl acetate). In two-way shape memory testing, a decrease in reversible strain and shape recovery occurred in the nanocomposites. Nevertheless, obvious two-way shape switching was observed in all samples during cyclic heating and cooling. The nanocomposite with 15% vapor-grown carbon nanofibers could be electrically heated rapidly and uniformly because of the high conductivity of vapor-grown carbon nanofibers and their uniform distribution in the matrix. Finally, the electrical-active two-way shape memory effect was achieved. This work contributes to the design of electrical-active two-way shape memory polymers in device applications for advanced functions.

scholarly journals The Thermal and Mechanical Properties of Poly(ethylene-co-vinyl acetate) Random Copolymers (PEVA) and its Covalently Crosslinked Analogues (cPEVA)

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1055 ◽  
Author(s):  
Ke Wang ◽  
Qibo Deng
Keyword(s):  
Mechanical Properties ◽  
Thermogravimetric Analysis ◽  
Vinyl Acetate ◽  
Polymer Networks ◽  
Crosslinking Density ◽  
Random Copolymers ◽  
Melting Transition ◽  
Thermal And Mechanical Properties ◽  
Scanning Calorimetry ◽  
Poly Ethylene

The thermal and mechanical properties of poly(ethylene-co-vinyl acetate) random copolymers (PEVA) and its covalently crosslinked analogues (cPEVA) were controlled by the overall crystallinity of the polymer networks. The cPEVAs with different VA-content were synthesized by thermally-induced crosslinking of linear PEVA with dicumyl peroxide (DCP). This work was mainly concerned with the effect of vinyl acetate (VA) content on the crosslinking density, thermal and mechanical properties of PEVAs and cPEVAs, respectively. The chemical composition was analyzed by thermogravimetric analysis and 1H-NMR. The thermal and mechanical properties of PEVAs and cPEVAs have been studied through a series of conventional analytical methods, including gel content determination, different scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis and traditional mechanical measurements. The experimental results show that the thermal and mechanical properties of PEVAs and cPEVAs increase with decreasing the VA-content. A broad melting transition with a ΔTm in the range from 78 °C to 95 °C was observed for all polymer networks.

Thermomechanical Characterization of a Series of Crosslinked Poly[ethylene-co-(vinyl acetate)] (PEVA) Copolymers

2015 ◽  
Vol 1718 ◽  
pp. 123-130 ◽  
Author(s):  
Matthias Heuchel ◽  
Laith Al-Qaisi ◽  
Karl Kratz ◽  
Ulrich Nöchel ◽  
Marc Behl ◽  
...  
Keyword(s):  
Shape Memory ◽  
Vinyl Acetate ◽  
Mechanical Stability ◽  
Shape Memory Polymer ◽  
Thermomechanical Properties ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Shape Memory Effects ◽  
Cross Links ◽  
Poly Ethylene

ABSTRACTCrosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) has been recently introduced as a polymer material, which can be functionalized with various shape-memory effects by solely altering the thermomechanical treatment called programming.In this study two series of cPEVAs with different vinyl acetate contents of 18 wt% (cPEVA18) and 28 wt% (cPEVA28) comprising different crosslink densities were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) in the temperature range of -130 °C to 120 °C. DMTA tests were performed in torsion mode, because such movements are highly relevant in the context of complex shape changes in shape-memory polymer based devices. Finally, the obtained DMTA results were compared with DMTA conducted in tension mode. Swelling experiments revealed a gel content in the range from 81% to 90% for cPEVA18 samples while for cPEVA28s a complete conversion was observed. The degree of swelling was found to decrease substantially with increasing crosslink density for both cPEVA series.The influence of VA content and extent of crosslinking on the appearance of the respective melting (Tm) and glass transition (Tg) as well as the thermomechanical properties of cPEVA systems could be demonstrated by discussing both DSC and DMTA results. The temperature range of mechanical stability correlates with the VA content and is determined by decreasing Tm values. The cross links do barely alter the stiffness of a PEVA up to the Tm rang, but lead to constant mechanical rigidity in the rubbery range above Tm.

Thermally stimulated depolarization current characteristic of EVA–conductive PPy composites

2019 ◽  
Vol 54 (2) ◽  
pp. 205-214 ◽  
Author(s):  
F. S. Thabet ◽  
A. M. AbdElbary ◽  
G. M. Nasr
Keyword(s):  
Vinyl Acetate ◽  
Relaxation Times ◽  
Peak Height ◽  
Depolarization Current ◽  
Thermally Stimulated Depolarization Current ◽  
Poling Temperature ◽  
Temperature Ranges ◽  
Poly Ethylene ◽  
Thermally Stimulated Depolarization ◽  
Pure Poly

Thermally stimulated depolarization current in pure poly(ethylene-co-vinyl acetate) and poly(ethylene-co-vinyl acetate) composites with different amounts of polypyrrole/carbon nanoparticles (of various weight ratios, 100:0, 95:5, 90:10, 85:15, 80:20, and 70:30) have been investigated at poling temperature 363 K using different polarizing voltage. Thermograms of pure and composite samples have two or three peaks over all temperature ranges depending on the polarizing voltage. The decrease in peak height with increased polarized voltage is observed in pure poly(ethylene-co-vinyl acetate) samples loaded with 5%, 10%, 15%, and 30% polypyrrole due to the detrapping of the large amounts of charge results in electrode blocking and decrease in thermally stimulated depolarization current in those samples. The molecular parameters, such as activation energy E, charge released Q, and relaxation times τ0 and τ m for thermally stimulated depolarization current peaks have been estimated.

Contribution to the determination of relative increment of internal energy at low deformation of cross-linked rubber

1980 ◽  
Vol 45 (8) ◽  
pp. 2315-2318 ◽  
Author(s):  
Vladimír Pollák ◽  
Andrej Romanov
Keyword(s):  
Internal Energy ◽  
Vinyl Acetate ◽  
Temperature Changes ◽  
Relative Increment ◽  
Poly Ethylene ◽  
Small Deformations

The relative charge of the internal energy, fU/f, during deformation of cross-linked elastomers, poly(ethylene-co-propylene) and poly(ethylene-co-vinyl acetate), was determined at various temperatures. Anomalies in the dependence of fU/f on relative dilatation in the region of small deformations ( 35%) are to a large extent besides other factors due to the sensibility of the formula used to calculate fU/f to temperature changes.

Sign in / Sign up

Export Citation Format

Share Document