On programming of polyvinylidene fluoride–limestone composite for four-dimensional printing applications in heritage structures

Abstract

Heritage structures are under the effect of chemical, physical and biological weathering, and out of these common effects, chemical weathering has a significant impact (as it results in nifty formation and causes fractures in heritage structures). Chemical weathering may include carbonation, oxidation, hydration, hydrolysis, and acidification. Most heritage structures are made up of limestone, which is more susceptible to carbonation. According to the reported literature, commercial practices for the maintenance and repair of these heritage structures use epoxy-based solutions, which may not be best suited as per the various regulations imposed by different government/public authorities. But so far little has been reported on the use of innovative, programmable thermoplastic composites for the maintenance and repair of such structures. This study highlights the effect of chemical treatment (as a stimulus) using a one-way programming of three-dimensional-printed thermoplastic composite-based (polyvinylidene fluoride–6% limestone) functional prototype as a solution for the maintenance and repair of heritage structures (grade III). For one-way programming, three-dimensional-printed substrate is exposed to dimethylformamide, and the changes in morphological and surface properties are noticed. After this, carbonation cycle (with carbonic acid) is performed and the changes in morphological and surface properties are compared to ascertain the stimulus effect for one-way programming (of polyvinylidene fluoride–6% limestone composite). The results of the study outline that the prepared composite may be programmed by controlling the exposure of dimethylformamide and carbonic acid (as a stimulus). Further best settings for preparing feedstock filament (for three-dimensional printing of functional prototypes in case of a selected heritage structure) are 200 °C screw temperature, 0.35 N m torque and an applied load of 8 kg in terms of better mechanical properties and shore D hardness.

Multi-material printing of PVDF composites: A customized solution for maintenance of heritage structures

“…Two PVDF polymer-based composites: PVDF-CaCO 3 (P-CC) and PVDF-graphene-Mn doped ZnO (P-GM) were prepared by the chemical-assisted mechanical blending process (based upon previous studies. 23,24 ) Dimethylformamide (DMF) solvent was used to blend the reinforcement in the PVDF matrix. A total of 80g of composition/proportion were prepared for both types of composite matrix.…”

“…The blending proportion of CaCO 3 reinforcement for the first composite was ascertained at 6% by weight for acceptable 3D printing and one-way programming as an extension of a previous study conducted. 24 Similarly, 6% graphene power and 3%Mn doped ZnO was blended in PVDF to prepare 80g P-6G3M composite for 3D printing and electro-active response. 23 In this study, the blend was obtained by uniform stirring at 55°C for 2 h, and the prepared composite was put in a vacuum oven for another 2 h at 70°C.…”

“…The literature review also revealed that significant studies have been reported on the use of 3D technologies for the conservation and restoration of cultural heritage. 24–29 But hitherto little has been explored for the application of 3D printing-based repair of heritage buildings.…”

“…20,21 As regards repairing heritage structures by the 3D printing approach, composite prepared from recycled plastic waste with electro-active and one-way programming features has been reportedly proposed acceptable as a customized repair solution. [22][23][24] Figure 2 also shows that very less work is reported on the repair of heritage structures by integrating 3D printing technology to fabricate cost-effective solutions for the maintenance of irregular non-structural cracks.…”

“…The literature review also revealed that significant studies have been reported on the use of 3D technologies for the conservation and restoration of cultural heritage. [24][25][26][27][28][29] But hitherto little has been explored for the application of 3D printingbased repair of heritage buildings. The present work is on investigations of 4D properties in multi-material 3D printed thermoplastic composites of PVDF base polymer matrix for fabrication of smart 3D repair solution.…”