Dip Molding Of EPVC And Liquid Silicone Rubber

As a traditional molding method, dip molding has many advantages, such assimple molding process, low tooling costs, quick and inexpensive prototypes, shortlead-times on custom tooling, no internal stress molded into parts, large parts can bemade without significant tooling investment, etc. Dip molding plays an important rolein the processing of polymeric materials.In this paper, EPVC was molded via dip molding process, the effect of dipmolding temperature and plasticization time on the structure and properties of EPVChad been investigated. The results showed that EPVC formed a three-dimensionalphysical gel network during the molding process, with the increasing of dip moldingtemperature and plasticizing time, the gelation level of EPVC gradually increased, andthe molded EPVC was completely plasticized when the gelation level approached to100%. The molded EPVC had the combined performances, which the gelation levelwas98.62%, the tensile strength was11.63MPa, the elongation at break was435.09%,and the migration of plasticizer was8.34%, when EPVC was dip molded at220oC for5min..The effect of composition of plasticizers on the plasticization process andproperties of plasticized EPVC had been studied by two different systems, which wereDINP/TOTM and DINP/ESO. The results showed that the efficiency of plasticizingwas related to the molecular weight, polarity of the plasticizer, and the compatibility ofEPVC. At different stages of plasticization, these factors had different effect on themolding process, compound plasticizers had better plasticizing efficiency than a soloplasticizer. When DINP and TOTM was mixed on the ratio of40:20, the tensilestrength was14.44MPa, the elongation at break was496.51%, and the migration ofplasticizer was6.95%, it had the best plasticizing efficiency in the DINP/TOTMplasticizer system. When DINP and ESO was mixed on the ratio of20:40, the tensilestrength was14.47MPa, the elongation at break was598.53%, and the migration ofplasticizer was1.12%, it had the best plasticizing efficiency in the DINP/ESOplasticizer system.Liquid silicone rubber was used as a new dip molding material, the effect ofdifferent components on dip molding and the properties of LSR products was studied. The results showed that the proper formula of LSR which can be molded via dipmolding process were: viscosity of30000cp and2500cp of vinyl silicone oil mixedon a scale of100:50by weight as base rubber; hydrogen content of1.00%hydrogensilicone oil was the curing agent, the mixing ratio of Si-H/-CH=CH2was1.2:1;chloroplatinic acid as the catalyst, the dosage was6ppm; Alkynol compounds asinhibitors, the dosage was0.2phr, the specific surface area of fumed silica was175±20m2/g, treated by hexamethyldisilazane, was used as reinforcing filler, thedosage was20phr.The effect of dip molding temperature and vulcanizing time on the properties ofLSR had been investigated. The results showed that with the increasing of dip moldingtemperature, the gelation time of LSR gradually decreased, the proper temperature fordip molding of LSR was180oC. The molded LSR had the combined performances,which the Shore A hardness was40, the tensile strength was3.75MPa, the elongationat break was271.37%, the heat resistance was perfect, when LSR was dip molded at220oC and vulcanized for5min..