| Pressure-sensitive adhesives(PSAs)have always played an irreplaceable role in our life.As people’s awareness of environmental protection and health increases,more and more attention has been paid to emulsion adhesives with simple polymerization process and small environmental pollution.Acrylate emulsion PSAs have many advantages in terms of polymerization process,environmental protection and adhesiveness.More and more attention has been paid to the development of PSA and have become one of the important directions of PSA development.The use of PSA reflects all aspects of life such as: packaging,hygiene,labeling and other fields.However,due to the structural characteristics of acrylate emulsion polymer,poor wettability of polar substrate and low cohesion strength in the coating process,resulting in small peeling strength and other defects,the application range of PSAs is limited.In order to solve the above problems,this experiment adopted pre-emulsification emulsion polymerization method,selected appropriate polymerization process and polymerization monomer,auxiliary agent,to improve the peel strength of acrylic emulsion pressure sensitive adhesive,and prepared a good stability of acrylic emulsion PSAs to ensure the balance of three strengths of PSAs.For improving the adhesion of PSA to substrate,especially the non-polar substrates with low free energy,it is often necessary to add some substances for modification.In this thesis,it was modified by silane coupling agent to further improve the water resistance and peel strength of acrylic emulsion PSA,and meet the requirements of use.In the process of emulsion polymerization,the reaction time,temperature,stirring speed and so on will affect the stability of acrylate emulsion and the properties of PSA.Through the experiments,the reaction temperature was selected as the pre-emulsion drop adding at 73°C for an hour,and then the temperature was raised to 82°C.The total time of the pre-emulsion drop adding was 3-3.5h,and then the reaction was carried out at this temperature for 1.5h more.In the experiment,the ratio of soft monomers to hard monomers,the introduction of functional monomers to change the amount,and the appropriate amount of emulsifiers,initiator,etc.are beneficial to the stability of acrylate emulsion and improve the 180° peel strength.The experimental results show that when soft monomer: hard monomer: functional monomer =76:16:8,the glass transition temperature is-30.4°C,the 180° peel strength is 6.39N/25 mm.And when the percentage of emulsifier is 0.48% of the total monomer,and that of the initiator is 0.4%,PSA with moderate viscosity,and good stability of the latex and good peel strength is got.In order to further increase the peel strength and improve the water resistance and heat resistance of PSA,the acrylate emulsion was modified by adding coupling agent.The coupling agent of KH-560 which with epoxy functional group is used in the polymerization process.When the amount of KH-560 is 3% of the total amount of monomers,the peel strength of the acrylic emulsion PSA is increased from 6.39N/25 mm to 7.85N/25 mm,and the water absorption rate decreases from 15.6% to 8.9%,which improves the water resistance,alkali resistance and heat resistance of the peel strength of the PSA.FT-IR analysis showed that the acrylate emulsion PSA modified by silane coupling agent was successfully synthesized.The laser particle size analyzer and TEM are used to analyze the particle size and emulsion of the latex,and the synthesized coupling agent is modified.The average particle size of the synthesized acrylate emulsion modified by coupling agent was435.1nm.The thermogravimetric analysis showed that the acrylate PSA modified by KH-560 had better hear temperature resistance than that of before the modification. |
PDF Full Text Request