Study On Silicate Minerals-toughened And Reinforced Polypropylene

Polypropylene(PP),as a general-purpose thermoplastics,has a number of excellent mechanical properties,but there are also some other shortcomings,such as low-temperature brittleness,large molding shrinkage and easy to aging.Polyethylene(PE) has a good processing performance,with a certain degree of rigidity and a good impact property at low temperature.So it is a good modifier of PP.There is no double bonds in the molecular structure of the elastomer POE.It has a number of properties,such as good weatherability,smaller cohesive energy, higher sheafing sensitivity and the sheafing viscosity on the temperature witch is close to PP.So it has the unparable advantage of the thermal Stability and the processing.In this paper,PP-g-MAH,LDPE or POE and ultra-fine mineral powder were added as compatibilizer,flexibilizer and reinforcing agent in the PP matrix,respectively.PP/LDPE/muscovite composites and PP/POE / PP-g-MAH/muscovite/wollastonite composites have been prepared by melt blending process.The tensile properties of composite materials,bending properties, impact properties were studied.The Morphology and the Crystallization Behaviorof the composites were investigated by starting electron microscopy (SEM) and differential scanning calorimeter(DSC),respectively.The study draws the following conclusions:(1) Though modifying the surface of muscovite and wollastonite,the caking capability between mineral particles and PP was improved.The proper modification agent,dosage and modified technology have been decided.(2)The optimum recipe of PP/muscovite/PP-g-MAH/LDPE composite is determined by orthogonal test and single factor experiments.The mechanical properties,fluidity and thermal properties were investigatied.The flexural strength, notched impact strength,Rockwell hardness,melt flow rate and Vicat softening temperature have increased by 11.1%,13.2%,31.3%,91.89%and 0.64% respectively.Tensile strength decrease from 30.72MPa to 30.50MPa slightly and bending modulus decrease by 1.43%.The effect of muscovite particle size on the properties of the composites was studied,and the appropriate size of muscovite is d₉₀＝16.26μm.It is found that the composites should be prepared by directly-blending through the study of the blending-modes.Trough the surly of the surface morphology of the impact fracture by means of SEM,we also find that the small partical size of the modified muscovite and the little dosage can help the powder to disperse.With the increase of the amount of the LDPE,the impact strengh increase.Heat resistance of the composites have been improved through the study of TG-DSC.(3) The optimum processing condition of PP/wollastonite/muscovite/POE is determined by orthogonal test and single factor experiments.Through the researches of the mechanical properties,flowablity and thermal properties,we have found that tensile strength,flexural strength,flexural modulus,Rockwell hardness and vicat sorting point are increased to 30.16MPa,31.13MPa, 1220.11MPa,18.76.,91.7℃,increaced by 21.27%,64.97%,64.97%,22.61%,24.93%. However,the Charpy notched impact strength keeps steady and the fracture elongation decreases dramatically.The interface between the fillers and the matrix and the cause,which improves their performance,are explained through analyzing the surface morphology of the impact fracture by means of SEM.The analysis of the specimen fracture also indicates that the interface between the muscovite and wollastonite and the matrix is strong enough to transmit loads to the mineral particles,so as to play the reinforcing role of the mineral particles.The layered distribution of muscovite,which has large particle-size and the orientation of the wollastonite which has lager LD ratio,are apt to improve the strength of the composite.POE is distributed in the matrix in the form of spherical particle and boned well with the matrix,so as to improve the impact strength.But POE could't improve the caking capability of the mineral particles and PP.DSC is used to characterize the melting and crystallization behavior of the composites.The results of non-thermal crystallization data show that the composites have a higher erystallinity.And the inorganic particles have an obvious induced crystallization of PP during cooling,so it is theoretically explained the cause of improved properties. Through the non isotheirmal heating curves,we can see that the melting temperature and heat resistance are enhanced.Toughening mechanism of the composite was preliminary investigated, founding that the improved strength and toughness was not the result of wollastonite,mica or POE,but the outcome of synergisms of the three in the matix.