Toughening Modification Of PMMA For Laser Marking

Poly(methyl methacrylate) (PMMA) is widely used in industry equipment and people's daily life,due to its excellent optical property and well technic-economy properity property.However,PMMA exhibits drawbacks,such as poor impact resistant and brittle,which limits its use areas.To be used more widely,toughening modification needs to be applied.In this thesis these toughening methods are systemically reviewed,which include: copolymerization toughening,blending toughening ,fiber toughening and stratification toughening,etc.. As a laser marking material, PMMA accorded with the most performance requirements except the low impact strength.Based on the previous study of toughrning PMMA,and conbined that laser marking materials need to add laser functional pigments,the author adopted the means of melt blending to get toughened PMMA.Therefor, PEG,ACR impact-modifier and modified nano-SiO₂ were used to modify PMMA.Ground on the performances of modified PMMA samples,then selected the optimal PMMA composite system,added laser functional pigments,and prepared laser marking material.Study shows that:(1)Blending with PEG and ACR impact-modified are effective to improve the toughness of PMMA,but the impact value will then degress when overstepping the certain range and the tensile strength and flexural strength may get a little declined.(2)The nano-SiO₂ were reacted with silane coupling agent, which have double bond in the end of molecular chain,surface of alklaed-nano-SiO₂ particles are covered with PMMA by emulsifier-ree polymerization.The structure of modified particle is made of a core(SiO₂) and a shell(PMMA). The modified particles could be dispersed evenly in PMMA by the method of melting compositing.(3)The mechanical properties of PMMA/nano-SiO₂ composite material significantly improved. The notched impact strength, tensile strength and flexural strength increased with the increase of the content of modified nano-SiO₂.It could achieve the best overall mechanical properties when the content was 4%,the notched impact strength,tensile strength and flexural strength increased respectively by a factor of 94.7%, 28.0% and 24.1% comparing with that without nano-SiO₂. Not only these, PMMA/nano-SiO₂ composite materials have also enhanced thermal stability, glass transition temperature increased from 104.85℃to 119.3℃, vicat softening temperature increased by 13℃.(4)PMMA/nano-SiO₂ modified composite material can be applied to laser marking industry,and has ascendant effect compared with other laser marking materials,such as ABS.