Study On Polypropylene Microfoaming Technology

Polypropylene is a general-purpose plastics with good performances and has a wide range of applications.But because of it's linear structure and crystalline properties,it has low melt strength,and in foaming engineering,would cause bubble hole rupture and rough surface of extrusion molding products.The testing method of the melt strength,the preparation of high melt strength polypropylene(HMSPP)by crosslinking and by some recycled PP,and the processing conditions of the microfoaming PP profiles wrer studied in this paper.It was proved that the toque mechod can be used to test the melt strength of polymers.This method is more convenient than other methods founded in some references and is high precision and wide applications.The melt strength is affected by the temperature.The high temperature,the low melt strength,vice versa.Crosslinking can be used to remove the vice versa melt strength of PP.The crosslinking effect of PP is affected by resin type,the type and content of the crosslinking agent and the auxiliary crosslinking agent used.PPR 5003 is the best PP can be used to prepare HMSPP by this method.The compound crosslinking agents is better than the single crosslinking agent for PP's crosslinking.The best compound crosslinking agents we found is DTBP/DVB/ KH-570 = 0.5/0.5/2.The auxiliary crosslinking agent has some affect on the crosslinking of PP.When we use DCP as the the crosslinking agent,a little of TAIC can remove the melt streng of PP.The compound crosslinking agent CuB-1 is a valid agent for the crosslinking of the recycled PP.When the content of CuB-1 increases,the melting index of the recycled PP will decrease obviously,meanwhile the gel content and the melt strength of the recycled PP will increase notably.The microfoaming extruding of PP is affected by the content of foaming agent,the extruding temperatue and the length of the straight section of the die.The proper dosage of AC foaming agent is between0.1~0.2phr.Excess dosage of the foaming agent will cause the low-grade microfoaming products.It was prefer to choose the lower extuding temperature but should ensure the plastify of the plastics.In this paper,the proper temperature of the barrels is 1sec./145,2sec./155,3sec./165,and die/170?.The excess temperature will decrease the melt strength and cause the poor qualities of the profiles.The apparent density of the microfoaming profiles will decrease and the surface of them will be improved when the length of the straight section of the die is increased.