Effects of benzoxazine resin on property enhancement of shape memory epoxy: A dual function of benzoxazine resin as a curing agent and a stable network segment

Abstract

Abstract. An ability of bisphenol-A/aniline based benzoxazine resin (BA-a) to simultaneously acts as a curing agent and a stable or rigid network segment for shape memory epoxy, i.e. a two component system, is demonstrated. This significantly simplifies a formulation of present shape memory epoxy systems, i.e. a three or four component system. A suitable content of BA-a in the aliphatic epoxy (NGDE)/polybenzoxazine (PBA-a) samples for good shape memory performance is in a range of 30 to 50 mol%. The storage modulus of the obtained NGDE/PBA-a shape memory polymers (SMPs) was increased from 3.57 GPa for 30 mol% BA-a content to 4.50 GPa for 50 mol% BA-a content. Glass transition temperature of the sample was also substantially increased with increasing BA-a fraction, i.e. from 51°C to 140°C. Flexural modulus and strength at room temperature of the samples at 50 mol% BA-a were found to be as high as 3.97 GPa and 132 MPa compared to the maximum values of 2.54 GPa and 100 MPa of SMP based on cyanate ester-epoxy. All samples exhibited a high value of shape fixity close to 100%. A presence of the BA-a in the samples also imparted a greater recovery stress ranging from 0.25 to 1.59 MPa. Consequently, the obtained NGDE/PBA-a copolymers are highly attractive for shape memory materials to be used in a broader range of applications particularly at elevated temperature and a higher recovery stress value.

Shape memory polybenzoxazines based on a siloxane-containing diphenol

“…Benzoxazines are a class of thermosetting resins, and they can be used as shape memory materials because the corresponding polybenzoxazines can provide a chemical crosslinking structure to determine a permanent shape. Recently, bisphenol‐A/aniline type benzoxazine (BA‐a) was employed to copolymerize with prepolymer of polyurethane or epoxy to form SMPs, in which the polybenzoxazine (PBA‐a) is thought to serve as a second set of netpoints supporting a permanent shape. Jana and coworker reported that the shape memory properties of the BA‐a/urethane copolymers are higher than those of the neat polyurethane, and the polybenzoxazine phase in the BA‐a/urethane copolymers can induce shape memory behavior in nonshape memory polyurethane with amorphous soft segment and significantly improve the values of shape fixity, recovery ratio, and recovery stress in shape memory polyurethane .…”

“…Jana and coworker reported that the shape memory properties of the BA‐a/urethane copolymers are higher than those of the neat polyurethane, and the polybenzoxazine phase in the BA‐a/urethane copolymers can induce shape memory behavior in nonshape memory polyurethane with amorphous soft segment and significantly improve the values of shape fixity, recovery ratio, and recovery stress in shape memory polyurethane . Rimdusit et al prepared a series of BA‐a/epoxy copolymers, and they found that the BA‐a/epoxy copolymers exhibited a high value of shape fixity close to 100% and the thermo‐mechanical performance of epoxy SMPs was enhanced whereas the BA‐a/epoxy SMPs with higher BA‐a content provided a longer shape recovery time . However, to the best of our knowledge, the thermally induced SME has never been reported before for any known polybenzoxazine, whether main‐chain or side‐chain type.…”

Thermosetting Shape Memory Polymers and Composites Based on Polybenzoxazine Blends, Alloys and Copolymers

“…This SMP system was prepared by blending NGDE with BA‐a at BA‐a molar percentage in the range of 30 to 50 %. In the epoxy and benzoxazine system the reaction between phenolic and epoxide group was expected to occur after the ring opening reaction of benzoxazine and the emerging phenolic OH‐groups . They confirmed that (PBA‐a/NGDE) copolymers formed chemical crosslinks (Figure ).…”

“…Moreover, their recovery stress was increased with increasing BA-a content up to 33 mol %w ith the reported recovery stress of about 38 kPa comparedt o2 0.4 kPa of the unmodified shape memory epoxy. [41] The SMP systems ynthesized from binary mixtures based on polybenzoxazine/ aliphatic epoxy without aromatic epoxy and curing agent was continuously developed by Ta npitaksit et al [42] This SMP system was prepared by blendingN GDE with BA-a at BA-a molar percentage in the range of 30 to 50 %. In the epoxy and benzoxazine system the reaction betweenp henolic and epoxide group was expected to occur after the ring openingr eaction of benzoxazine andt he emerging phenolic OH-groups.…”

“…The SMP system synthesized from binary mixtures based on polybenzoxazine/ aliphatic epoxy without aromatic epoxy and curing agent was continuously developed by Tanpitaksit et al . This SMP system was prepared by blending NGDE with BA‐a at BA‐a molar percentage in the range of 30 to 50 %.…”