Polímeros com memória de forma: características, tipos e aplicações

Abstract

De forma geral, diversos materiais entre eles poliméricos, cerâmicos e metálicos, podem apresentar propriedades de memória de forma. O efeito memória de forma é a propriedade onde os materiais apresentam uma “memória” de sua forma, ou seja, apresentam a capacidade de retornar a sua forma inicial após sofrer algum tipo de deformação, entretanto, esse efeito depende da aplicação de um estimulo externo para que o retorno aconteça, como o calor, eletricidade, luz, entre outros. Esses materiais são classificados como materiais inteligentes, pois apresentam propriedades que respondem a um estimulo externo de ordem química, física ou biológica. Este trabalho pretende realizar uma revisão da literatura sobre polímeros com memória de forma, abordando suas características gerais, teorias termomecânicas, mecanismos de ativação e aplicações. Deste modo, deseja-se divulgar a temática pouco discutida no Brasil, contribuindo para o desenvolvimento de novas tecnologias e síntese de polímeros com memória de forma.

4D printing of shape memory polylactic acid/ethylene-glycidyl methacrylate (PLA/E-GMA) blends

“…In figure 4(a), the evolution of the storage modulus (G ′ ) with respect to the angular frequency (ω) is depicted for PLA, E-GMA, and PLA/E-GMA blends. PLA showed liquidlike behavior, whereas E-GMA copolymer and PLA/E-GMA blends exhibited predominantly solid-like behavior [1,16,38]. The copolymer and blends demonstrated significantly higher storage modulus values than PLA at low frequencies.…”

“…When E-GMA is incorporated into the blend, it increases the mobility of the polymer chains, allowing for easier deformation and molecular rearrangement during the shape memory cycle. This increased flexibility enables better fixation of the temporary shape and more complete recovery of the original shape [1,2,66,69,70]. Secondly, E-GMA plays a crucial role in the transfer of stress and strain within the material.…”

“…The shape memory cycle encompasses a series of stages (figures 8 and 9): (1). the polymer is heated to the switch temperature and subjected to a predetermined strain or stress.…”

“…Shape memory polymers (SMPs) have garnered significant attention in recent years due to their unique properties and robotics [4,[7][8][9]. SMPs are typically thermally or chemically triggered, enabling them to undergo reversible changes in their physical properties, such as shape, size, and modulus [1,[10][11][12]. These materials offer the advantage of being lightweight, mechanically robust, and adaptable to a wide range of shapes and structures.…”

Influence of crystallization on the shape memory effect of poly (lactic acid)

“…As the temperature rises, molecular agitation increases, favoring chain mobility. At this point, when chain mobility is facilitated with the temperature increase, the polymer can be easily deformed and elongated, leading to a decrease in randomness and entropy of the system [25][26][27]. The degree of crystallinity of the polymer directly influences the shape recovery behavior, and the understanding of this relationship is essential to improve the performance of SMPs.…”