Construction And Performance Study Of Flexible Sensors Based On Polyethylene Packaging Materials

Polyethylene(PE)material,as the world’s largest general-purpose plastic,has excellent characteristics such as low cost,low density,corrosion resistance,easy processing,etc.It has been widely used in the field of packaging,and PE tape and bags can be seen everywhere in daily life.If these daily necessities are intelligent,it is of great significance to portable people’s life and the intelligence of packaging field.As an information detection device,the sensor can transform the sensed chemical,physical or biological information into electrical signals or other required forms of information output according to certain laws to meet the requirements of information transmission,processing,storage,display,recording and control.Combining PE materials with sensors makes the application of PE materials more convenient,faster and smarter on the basis of meeting people’s daily needs.On the other hand.Making PE material intelligent greatly reduces the production cost of flexible sensors and is more flexible and extensive in terms of depth and breadth of information collection compared with traditional rigid sensors.However,the preparation of PE-based flexible sensors is limited by the inert surface and low surface energy of PE materials,and it is still challenging to realize the intelligence of PE materials without changing their own structure and properties.In this thesis,we develop a series of PE-based flexible sensors with sensing functions based on Norrish Ⅱ hydrogen capture reaction using different types of PE materials,and validate the functions of the sensors when they are used as "universal adhesive tape" and "smart bags".The main work of this thesis is as follows:(1)Low density polyethylene(LDPE)tape as a reaction substrate,isopropylthioanthrone(ITX)as a photoinitiator,polyethylene glycol diacrylate(PEGDA)as a cross-linked polymerization monomer in a sandwich structure to produce cross-linked polymerization reaction grafted PEG three-dimensional molecular mesh to fix the conductive material in situ,to achieve the preparation of flexible sensors without destroying the structure and properties of the material itself.A self-adhesive multifunctional sensor was designed.A self-adhesive multifunctional flexible sensor LDPE tape-g-P(PEGDA)/PEDOT:PSS(L T-3(P))was designed as a "smart tape".The obtained L T-3(P)has a conductivity of 0.053 S/m and a square resistance as low as 3.06 KΩ/sq.It is a polymer-based flexible sensor with high sensitivity(bending strain(GF1=8.4),compression strain(GF2=4.4),and torsion strain(GF3=3.1)),a wide dynamic response range(42 Pa～12 KPa),and a short response time(150 ms),etc.The self-adhesive properties of the L T-3(P)enable direct adhesion to the target object and successful monitoring of deformation in product packaging.At the same time,the sensors are independent of each other and interconnected,so that multidimensional bending deformation can be accurately determined in complex bending deformation by analyzing the signals expressed by the sensor group as a whole.Here,we designed and implemented the "smart tape" L T-3(P)as a single "pixel" and constructed a"multi-pixel" sensor complex by freely combining multiple sensors.In this case,the "smart tape" L T-3(P)is designed and implemented as a single "pixel",and a"multi-pixel" sensor complex is constructed by freely combining multiple sensors to achieve accurate multi-dimensional monitoring of product packaging and transportation.(2)The L T-3(P)sensor complex monitors deformation mostly in two dimensions,and it is challenging to extend this directional sensing capability to three-dimensional stimuli to improve the accuracy of monitoring material packaging.Herein,an LDPE-based reactive substrate,based on the "activity" and"controllability" of visible-light reactive radical grafting polymerization reaction,is designed for monitoring three-dimensional stimuli by grafting four different functional PEG three-dimensional molecular mesh layers in a sandwich structure.The "all-in-one" multilayer flexible sensor LDPE(P Ⅳ)is used as a "smart bag"for intelligent monitoring of product weight and gripping status.The reaction mechanism of the "active" visible light cross-linked graft polymerization was investigated by quantitative analysis of the type and content of elements in each graft layer by Fourier Infrared Transform Spectroscopy(FT-IR)and X-ray Photoelectron Spectroscopy(XPS);the distribution of each element in each graft layer was investigated by energy spectrometry(EDS).The "controlled" reaction mechanism of visible light cross-linked graft polymerization was investigated by energy spectrometry(EDS)on the distribution of each element in each graft layer;the LDPE(P Ⅳ)sensor model proved that LDPE(P Ⅳ)can achieve accurate monitoring of horizontal shear and vertical normal forces.At the same time,LDPE(P Ⅳ)as a "smart bag" can achieve the vertical gravity of the target object and horizontal gripping force feedback,to further achieve the monitoring of the state of the object inside the bag provides a design idea.The flexible sensor designed in this work based on PE material is flexible in operation,low in production cost and can be mass produced.The design of sensors in packaging experiments provides new ideas for the future development of flexible sensor devices with different functions and helps to promote the development of "intelligence" in the packaging industry.