Phenolic rigid organic filler/isotactic polypropylene composites.I.Preparation

A novel phenolic rigid organic filler(KT)was melt-mixed with an isotactic polypropylene(iPP)to prepare a series of PP/KT composites,with or without maleic anhydride grafted polypropylene(MAPP)as compatilizer.The evolution of filler morphology during melt-mixing and melt-pressure processes was monitored by scanning electron microscope(SEM)and polarized optical microscope(POM).The influences of shear force,pressure time,filler content and MAPP concentration on the final filler dispersion were studied.We found that this rigid organic filler readily melted and dispersed homogenously into the iPP matrix through a fission-fusion process during the melt-mixing process.Thus a balanced dispersion,which was closely related to shear force and MAPP concentration,can be achieved.During the meltpressure process,parts of the filler particles combined gradually through a coalescence process.However,the incorporation of MAPP can effectively inhibit the tendency to coalesce and refine the filler particles sizes into nanoscale.Thus,a series of PP/KT composites with controllable filler particles size and narrow size distribution can be obtained just by adjusting process conditions and MAPP concentration.In addition,due to the in-situ formation mechanism,the filler phase possessed a typical solid true-spherical shape.

Phenolic rigid organic filler/isotactic polypropylene composites. Ⅱ. Tensile properties

A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the tensile properties of PP/KT micro-composites was studied by uniaxial tensile test and the mor-phological structures of the stretched specimens were observed by scanning electron microscopy(SEM)and polarized optical microscopy(POM).We found that the Young's modulus of PP/KT specimens increased with filler content,while the yield and break of the specimens are related to the filler particles size.The yield stress,the break-ing stress and the ultimate elongation of PP/KT specimens were close to those of unfilled iPP specimens when the max-imal filler particles size is less than a critical value,which is 7μm at a crosshead speed of 10 mm/min and 3μm at 200 mm/min,close to that of glass bead but far more than those of other rigid inorganic filler particles.The interfacial interaction was further estimated from yield stress,indi-cating that KT particles have a moderate interracial inter-action with iPP matrix.Thus,the incorporation of small KT particles can reinforce iPP matrix and simultaneously cause few detrimental effects on the other excellent tensile properties of iPP matrix,due to their organic nature,higher specific area,solid true-spherical shape and the homogen-ous dispersion of the ROF particles in microcomposites.

Phenolic rigid organic filler/isotactic polypropylene composites. Ⅲ. Impact resistance property

A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the impact resistance property of PP/KT specimens(with similar interparticles distance,1.8μm)was studied by notched izod impact tests.It was found that the brittle-ductile transition(BDT)of the PP/KT microcomposites took place at the filler content of about 4%,and the impact strength attains the maximum at 5%(with filler particles size of 1.5μm),which is about 2.5 times that of unfilled iPP specimens.The impact fracture morphology was investigated by scanning electron micro-scopy(SEM).For the PP/KT specimens and the high-density polyethylene/KT(HDPE/KT)specimens in ductile fracture mode,many microfibers could be found on the whole impact fracture surface.It was the filler particles that induced the plastic deformation of interparticles ligament and hence improved the capability of iPP matrix on absorbing impact energy dramatically.The determinants on the BDT were further discussed on the basis of stress concentration and debonding resistance.It can be con-cluded that aside from the interparticle distance,the filler particles size also plays an important role in semicrystal-line polymer toughening.

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing and melt-mixing

A novel phenolic rigid organic filler （named KD） with a high melting point was dispersed in an isotactic polypropylene （iPP） matrix by solution-mixing and/or melt-mixing. A series of KD/iPP blends was prepared with or without addition of maleic anhydride-grafted polypro- pylene （MAPP） as a compatibilizer. Influences of MAPP and mixing methods on the filler dispersion were studied using polaried optical microscope （POM）, scanning electron microscope （SEM） and tensile test. The filler particles are always inclined to form large irregular aggregates in the iPP matrix due to their significant differences in polarity and solubility in solvent. However, an iPP/MAPP/KD （PMK） blend containing filler particles with a quasi-spherical shape （-97.8 nm in diameter） and narrow particle size distribution （polydispersity index = 1.076） was successfully prepared by incorporating MAPP to reduce the interfacial tension and surface free energy between the dispersion phase and the continuous phase, and adopting a spray-drying method after solution-mixing to suppress the increase of the size of the dispersed phase during the removal of solvent.