Preparation Of Polyacrylic Core-shell Particles And Toughness On Polycarbonate

Acrylate core-shell particle(ACR)is an important toughening modified plastic additive,which has been successfully applied for nylon 6,polyethylene,polybutylene terephthalate,and epoxy resin engineering plastics.While the traditional ACR core-shell particle can play a certain extent toughening effect,it is now facing a problem that tension is so large at the surface.At the same time modified plastic has a drop in tensile strength.Then it is difficult to get modified materials with balanced mechanical properties.The aromatic polycarbonate(PC)is widely used in the industry optical materials,electronic appliances,automotive,packaging,building materials.It owes to its excellent performance,such as high transmittance,high refractive index,high impact resistance,dimensional stability and easy processing characteristics.With the advancement of technology and the time,the polycarbonate is subjected to certain restrictions in the application only because of its poor notch impact toughness.Therefore,an acrylate core-shell particle taking a certain crosslinked core and a rigid outer liner shell is designed and fabricated as a polyacrylate rubber elastomer additive.Moreover,according to the polar substrate of polycarbonate,a small amount of functional monomer was copolymerized to shell surface to improve the compatibility between the core-shell particles and the polycarbonate substrate,and then to improve the modification effect.The particle size,core-shell ratio,the amount and species of functional monomer at the shell,amount of core-shell particles of ACR all have a significant impact on the modification effect.So in this study,four series core-shell particles were prepared in accordance with the above factors.Those polyacrylic core-shell particles were prepared by seeded emulsion polymerization using thermal initiator system,in which the monomer's conversion was determined by gravitation and the particles size by laser dynamic light scattering(DLS)and transmission electron microscopy(TEM)was used to observe the particle diameters and the morphology.On the basis of the core-shell particles,PC/polyacrylic core-shell particles blends were prepared through a twin-screw extruder by melting extrusion.Blends with different amount of ACR were also prepared to observe the brittle-ductile transition.The mechanical properties of the blends were investigated.Scanning electron microscope(SEM)was used to observe the fractured surfaces.Rheological behavior of blends was also researched by capillary rheometer.It was found that the polymerization had a very high conversion(above 98%)and the particles had an obvious core-shell structure.The ACR with particle size 280 nm,core-shell ratio 70/30 by weight,the amount of functional monomer at the shell 0.25%,shell functional monomer methacrylate,was suitable for toughening PC.Finally,blends with 1.96% core-shell particle exhibit good mechanical properties.The notched impact strength was 4.97 times than pure PC;Elongation at break is 2.50 times than pure PC;the area under the curve is 2.60 times than pure PC.And the tensile strength of this blend showed almost no decline.It is a comprehensive material.We can analysis through the SEM cross-section and found that pure PC dissipate impact energy by craze triggered while blends by core-shell particles cavitation and matrix shear yielding in accordance with Wu theory.The rheological behavior of blends showed that viscosity of modifiers polycarbonate decreases with the amount of modified plastic additive.Blends showed good material processing performance.