Shape Memory Acrylate Polymers Enabled by Radiation Crosslinking

Transcription

1 Shape Memory Acrylate Polymers Enabled by Radiation Crosslinking Kejia Yang, Hongbo Fan 2, Wyatt Archer, Benjamin Lund 3, Walter Voit,2,3 The University of Texas at Dallas, Department of Chemistry and Biochemistry, Richardson, TX The University of Texas at Dallas, Department of Materials Science and Engineering, Richardson, TX Adaptive 3D Technologies, Dallas, TX CIRMS meeting 26 April 8 th, 26

2 Shape Memory Polymers (SMPs) Shape memory polymers (SMPs): smart materials which can recover from the temporary shape to the permanent shape upon an external stimulus. Two types: Thermoplastic SMP: polyurethane Thermosetting SMP: chemically crosslinked polymers SMP manufacturing Thermoplastic SMP: conventional processing Thermosetting SMP: reactive processing R post manufacturing processing ionizing radiation

3 Ionizing radiation Two competitive processes during the exposure to radiation Chain scissioning Crosslinking Charlesby Pinner equation s: sol fraction p : degradation density q : crosslinking density d: radiation dose µ : starting molecular weight

4 Earlier work on radiation on acrylate polymers Previously, we have studied several acrylate polymer systems. Neat poly(methyl acrylate) (PMA) and its blends with sensitizers (TMPTA and TAIC) 2. PMA copolymers: to study specific targets of radiation crosslinking of acrylates Methyl acrylate (MA) Main chain hydrogen Side chain α hydrogen 4 tert Butylcyclohexyl acrylate (tbcha) Trimethylolpropane triacrylate (TMPTA) 2 Carboxyethyl acrylate (CXEA) Triallyl isocyanurate (TAIC) Figure. Gel fraction as a function of radiation dose for PMA blended with increasing concentrations of a) TAIC; b) TMPTA. Figure c. Gel fraction as a function of radiation dose Voit, W.; Ware, Y.; Gall, K. Polymer 2, 5(5), pp

5 Earlier work on radiation on acrylate polymers 3. MA IBoA copolymer and PLA: To study radiation temperature effects Storage modulus (MPa) Irradiation Temperature C 2 C 4 C 6 C 2 Polylactic acid (PLA) 3 Tan δ 3 Isobornyl acrylate (IBoA) Methyl acrylate (MA) Storage modulus (MPa) 2 Not irradiated Irradiated with% 2 C, 5kGy - -2 Irradiated with% 6 C, 5kGy 3 2 Tan δ poly(methyl-co-isobornyl acrylate) ratio [3:] 2.5% TMPTA by mass, irradiated at kgy 5 Temperature ( C) Temperature ( C) 2 Fig.2 DMA curves of copolymers of 75% MA and 25% IBoA Fig.3 DMA curves of PLA blends Shaffer, S.; Yang, K.; Vargas, J.; Di Prima, M.A.; Voit, W. Polymer 24, 55(23), pp

6 Continuing work Acrylate copolymer synthesis BuA IBoA Sample # composition (wt%) n Butyl acrylate (BuA) Sample #2 composition (wt%) E beam radiation Isobornyl acrylate (IBoA) R R n E-beam radiation n n R R

7 Thermogravemetric Analysis (TGA) Decomposition temperature: 38 C Decomposition temperature: 323 C Weight% Before e-beam radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation Weight% Before radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation Temperature (ºC) Temperature (ºC) 6 7 Fig.4 TGA curves of copolymers of 25% BuA and 75% IBoA Fig.5 TGA curves of copolymers of 33% BuA and 67% IBoA No obvious difference in thermal decomposition temperature before and after irradiation Radiation did not change samples thermal decomposition temperatures but improved the homogeneity. Crosslinking density may be low, if any.

8 Solvent test All samples were soaked in chloroform at room temperature for a week. None of the irradiated samples dissolved all swelled in chloroform All irradiated samples were lightly crosslinked Sample composition Dose (kgy) Swelling rate in chloroform (%) 25%BuA 75%IBoA %BuA 67%IBoA *Samples irradiated at 5 kgy: swelled samples difficult to separate out from solvent

9 Differential Scanning Calorimetry (DSC) Heat Flow ^exo T g 45 ºC T g 45 ºC T g 45 ºC Before e-beam radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation Heat Flow ^exo T g 29 ºC T g 29 ºC T g 29 ºC Before e-beam radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation T g 3 ºC T g 7 ºC Temperature (ºC) Temperature (ºC) Fig.6 DSC curves of copolymers of 25% BuA and 75% IBoA Fig.7 DSC curves of copolymers of 33% BuA and 67% IBoA All irradiated samples showed higher glass transition temperatures

10 Dynamic Mechanical Analysis (DMA) Storage modulus (MPa). Before e-beam radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation 3 2 Storage modulus (MPa). Before e-beam radiation 5 kgy e-beam radiation kgy e-beam radiation 2 kgy e-beam radiation 3 2. Tan δ. Tan δ Temperature (ºC) Fig.8 DMA curves of copolymers of 25% BuA and 75% IBoA Temperature (ºC) Fig.9 DMA curves of copolymers of 33% BuA and 67% IBoA In DMA, samples irradiated at 5 kgy showed the highest T g All rubbery modulus of irradiated samples dropped lower than kpa lightly crosslinked

11 Conclusion and future work BuA IBoAcopolymerswerecrosslinkedwhenexposedtoe beam radiation at 5,, and 2 kgy, and the crosslinking density was low TGA showed no difference in thermal decomposition temperature between unradiated and irradiated samples DSC showed all irradiated samples have similarly higher T g, while DMA showed samples irradiated at 5 kgy have the highest T g E beam radiation Future work: Investigate the specific targets of radiation crosslinking of BuA IBoA copolymers Employ TGA MS (mass spectroscopy) to study the side groups of irradiated polymers, in order to further investigate how the radiation at and 2 kgy affect the samples glass transition temperatures

12 Reference. Charlesby, A.; Pinner, S. P Roy Soc A-Math Phy 959, pp Voit, W.; Ware, Y.; Gall, K. Polymer 2, 5(5), pp Vijayabaskar, V.; Bhattacharya, S.; Bhowmick, AK. Radiat Phys Chem 24, 7(5), pp Shultz, A.R.; J Polym Sci 959, 35(29) pp Shaffer, S.; Yang, K.; Vargas, J.; Di Prima, M.A.; Voit, W. Polymer 24, 55(23), pp Burlant, W.; Hinsch, J.; Taylor C. Polymer Sci 964, 2, pp