High Melt Strength Polypropylene Prepared By Solid Phase Method

High melt strength polypropylene(HMSPP)has been studied since 1980 s.It has a high melt strength and a perfect melt elasticity.The finding of high melt strength polypropylene expands applications in foam,thermoforming and extrusion coating.Thereforce,It is greatly significant studying on high melt strength polypropylene.The purpose of this study was to obtain modified HMSPP to investigate the technique of its Production Process via studying some influential factors.The hinges of this study included introduceing appropriate cross-linking or branching structures onto the PP backbone in order to acquire higher bath strength and the control of degradation of PP reactions.High melt strength polypropylene was prepared by cross-linking and grafting modification of PP using ethyl ether as the impregnating agent,benzoyl peroxide as initiator and divinylbenzene as the difunctional monomer,so that its melt strength can significantly increase.The effects of experimental parameters such as monomer and initiator concentration,impregnating agent content,interface agent content,swelling temperature,swelling time,reaction time and temperature,PP particle size on melt flow rate,melt strength and gel content were studied,and the products were characterized by TG,XRD,FTIR,DSC,PLM,ect.The experimental results show that the feed stock was w(BPO): w(PP)=0.03%,w(DVB): w(PP)=0.2%,impregnated in 20 mL ethyl ether at 30 for 10 h,then reacted at 100 for 2? ? h.The melt strength of the product has increased to 6.5 kPa·s that was 11 times of that of the pure PP,4.9 kPa·s increase form not swelling PP.Because in the process of using impregnated swelling agent assistance PP solid phase graft and crosslink,initiator and monomer enter into the PP matrix,it can effectively improve MS of the modified products and make up for the shortcoming of the traditional solid phase that mainly react in the surface of PP particles and monomer uneven distribute.The modified products FTIR spectra displayed monomer DVB was grafted onto the backbone of PP.The modified products DSC and PLM showed the branched cross-linking structure promoted crystallization,which made the crystallization temperature of the modified PP increased significantly,however,the crystallinity and the spherulites size of the modified PP decreased,while the number of spherulites increased and the modified PP boundary blurred.The modified products TG shows that the thermal stability of the modified products is improved compared with pure PP.The modified products XRD showed that the modified high melt strength polypropylene didn't change its crystal form,which is the same as common polypropylenes,they are ?crystal structure.Secondly,high melt strength polypropylene was successfully prepared by co monomers HDDA-DVB.The effects of comonomer(HDDA)concentration on melt flow rate,melt strength and gel content were studied,and the products were characterized.When the feed stock was w(DVB)/ w(HDDA)=1/2,the melt strength of the product has increased to 10 kPa·s.With the increasing concentrations of comonomer,the melt strength of the product increase,while the effect of gel content is not big.The modified products FTIR spectra displayed monomer DVB and HDDA were grafted onto the backbone of PP.The modified products TG shows that after adding HDDA comonomer,the thermal stability of the modified products is further improved.The modified products XRD showed that afer adding HDDA comonomer,crystal form of the product didn't change,which is the same as common polypropylenes,they are ?crystal structure.