Remanufacturing Of Vitrimers Based On Transesterification Reaction

Thermosetting polymers crosslinked by covalent bonds are capable of maintain their integrity upon heating,and thus possess excellent properties including superior chemical resistance,and stable thermal and mechanical properties at high temperatures.Thes e excellent properties make them ideal choices in a variety of engineering fields ranging from electronics and aerospace to the automotive industry.However,structures formed with the traditional thermosetting polymers cannot be reprocessed as the polymer networks are covalent crosslinked.This unprocessable nature,combined with the explosion in thermosetting polymers globally,is leading to vast waste of thermosetting polymers materials with serious environmental implications.Vitrimers have covalent adaptive networks(CANs)based on bond exchange reactions(BERs),which can achieve reprocessability including self-healing,remolding,and welding.Vitrimers behave like traditional thermosets at room temperature but are malleable like thermoplastics at high temperatures due to the thermally induced bond exchange reactions(BERs)between hydroxyl and ester groups.The simultaneous breaking and reconnecting between hydroxyl and ester groups reshuffles the macromolecular chains and essentially allows the polyme r network to switch between multiple equilibrium states.Such behavior makes vitrimers not only maintain the properties of traditional thermosetting polymers,such as excellent mechanical performance,chemical resistance,and thermal stability,but also thermally malleable like thermoplastics.At present,there are still deficiencies in the research on the remanufacturing of glass-like polymers.First,in the post-processing and recycling process,it is important to select appropriate processing conditions to promote the dynamic reorganization of cross-linked bonds in the network,which can determine the thermo-mechanical properties of the recycled materials,thereby further affecting the application of recycled glass polymers in engineering Subsequent use i n.Therefore,it is necessary to study the mechanical properties of recycled materials by studying processing conditions,and to save processing energy by optimizing processing conditions.Second,in order to meet the requirements of different working cond itions,the adjustability of the thermo-mechanical properties of the glass-like polymer is highly needed in the application of recycling and remanufacturing.Third,although thermosetting photosensitive resins account for nearly half of the market share of 3D printing materials,and are widely used due to their excellent mechanical stability at high temperatures,excellent chemical resistance,and good compatibility with high-resolution 3D printing technology Used in various fields.However,once these thermosetting photosensitive resins form three-dimensional parts through photopolymerization,the covalent network is permanent and cannot be reprocessed,that is,reshaped,repaired or recycled.Therefore,it is necessary to develop a glass-like polymer material capable of high-resolution and sustainable 3D printing.Fourth,currently only the cyclic 3D printing of soft epoxy acid glass polymers has been realized,and a new method of cyclic 3D printing of glass-like polymers needs to be developed for the cycli c 3D printing of various glass-like polymers.In order to solve the above problems,this article first conducted an experimental study on the recovery rate of glass-like polymer powders with different particle sizes.The glass-like polymer powders with different particle size distributions were prepared and characterized.Through dynamic mechanical analysis and uniaxial tensile test,the influence of particle size on the mechanical properties of recycled glass polymers was studied.In addition,other proces sing parameters such as temperature,time and pressure,and their interaction with particle size are discussed.The experimental results show that the recovery of rubber modulus and ultimate tensile strength is very important for evaluating recovery efficiency and selecting recovery process parameters.Acceptable performance recovery(above 80%)requires the smallest particle size and the highest temperature,time and pressure values.Moving away from these conditions will result in a significant decrease i n the recovery rate of ultimate tensile strength.The impact of particle size on molding quality is significant.Finer polymer powder can increase the contact area of recycled materials,thereby reducing the requirements for other processing conditions.In addition,the particle size changes other conditions(temperature,time,and pressure)required to achieve the same mechanical properties.The interface welding of glass-like polymer powder follows the Arrhenius-type superimposed effect of time and temper ature.In order to improve the post-processing efficiency,large-particle powders can be reproduced at a higher processing temperature or longer processing time.Adjusting these processing parameters can help design optimized remanufacturing procedures to meet actual engineering applications.Secondly,a simple strategy based on composite materials is proposed.This method can avoid complex chemical reactions,so as to prepare glass-like polymers with adjustable thermomechanical properties by virtue of the good weldability of basic glass-like polymers.Blend.The effect of processing parameters(such as temperature and time)on the properties of recycled glass polymer blends was experimentally studied.The results show that sufficient heat treatment with hig her processing temperature and longer processing time can enhance the interfacial adhesion between the glass-like polymer blend particles,resulting in higher modulus and greater stretchability.Through multi-generation recycling experiments,the reasonable recycling capacity of glass-like polymer blends is proved.A calculation model was established,which considered the temperature-dependent thermomechanical behavior of pure glass-like polymers and the random distribution of each group of classified glass polymer particles to predict recycled glass-like polymers with various components Thermomechanical properties of blends.The good agreement between the recycled glass polymer blends of various components obtained in the experiment and the prediction of th e calculation model proves the validity of the calculation model.This shows that the adjustable thermomechanical properties of the glass-like polymer blend can be achieved by adjusting the components of the basic glass-like polymer powder,which provides a flexible and environmentally friendly way to recycle waste materials for practical engineering applications.Through the use of calculation models to further study the parameters to explore the designability of recycled glass polymer blends,showing the ability to increase the glass modulus while reducing the rubber modulus,and by reducing the glass transition temperature difference and Expand the width of the tan ? curve to produce a blend with good miscibility.Third,a two-step polymerization strategy is proposed for the development of3 D printed reworkable thermoset materials(3DPRTs).The product forms a compliant material with a Young's modulus of 7.4 MPa at room temperature in the first step of light curing,and after the second step of heating and curing,it turns into a hard material with a Young's modulus of about 900 MPa,so This material allows users to reshape the printed three-dimensional structure into a new arbitrary shape through buckling deformation and heating and secondary curing.This material is based on the transesterification reaction to achieve dynamic balance,so you only need to simply 3D print ing a new material on the damaged part of the material to repair the damaged part.Unnecessary printed parts can also be recycled through the thermoforming process,so that the material can be reused in other applications,and the mechanical properties after multiple generations of recycling are still maintained above 80%.3DPRTs provide a practical solution to the environmental challenges associated with the rapid increase in the consumption of3 D printing materials.Finally,a new method for recycling printing glass polymers is proposed.This method uses the light curing properties of 3DPRTs to achieve resin recycling by mixing resin powder with 3DPRTs and then 3D printing.Three glass-like polymers based on transesterification were used to explore the feasibility of this recovery method through experiments.The 3D printing of a mixture with a volume content of up to 25% of the glass-like polymer powder is realized through digital light processing technology.The recycled materials have thermomechanical properties between 3DPRTs and glass-like polymer powder raw materials.This recycling method provides a completely new path for resin recyclin g.