Effect Of Protective Wax Structure On Properties Of Sidewall Rubber

Rubber protective wax is prepared from paraffin wax and microcrystalline wax in a certain proportion.It is a common physical antioxidant in rubber formula.Its function is to migrate to the rubber surface to form a dense wax film to protect the rubber from reacting with ozone^[1].The factors affecting the migration and protective performance of protective wax mainly include the chemical structure of protective wax,the amount of protective wax,other formulation systems,mixing and parking processes,etc.Starting from these factors,this paper will comprehensively explain which factors are related to the migration and protection performance of protective wax by testing the chemical structure and crystal morphology of original wax,the migration amount of protective wax,the micro morphology of wax film,the ozone aging resistance and flexion fatigue resistance of sidewall rubber.In the first part,four kinds of protective waxes provided by Hansheng company,including NEGOZONE9349,NEGOZONE3457F,NEGOZONE9360(later NG omitted to replace NEGOZONE)and market brand PW,were used to study the effect of protective wax structure on the properties of sidewall rubber.The results show that with the increase of the proportion of isoalkanes in the protective wax structure,the wax crystal morphology gradually changes from large and complete fibrous to fine needle shape,and the spherical crystal distribution similar to the island phase in the island structure becomes more in the wax film components on the rubber surface;Among the four kinds of protective waxes,medium and high temperature protective waxes NG9349 and NG3457F with carbon number distribution range of C₃₀-C₄₀ and isomeric alkane ratio of about 40%are easy to migrate to the rubber surface at 40?,and the formed wax film has toughness and good adhesion to the rubber surface,which is suitable for ozone protection near 40?.In the second part,low-temperature wax NG9345F and high-temperature wax NG9347F were used to study the effect of wax structure and dosage on the properties of sidewall rubber.The research shows that the thickness of wax film formed on the rubber surface increases rapidly with the increase of wax dosage before the wax dosage is 4 phr,and the protection ability is also enhanced.When the wax dosage reaches 5 phr,it basically reaches equilibrium.When the dosage exceeds 3 phr,it is easy to spray frost and affect the appearance.The dosage is generally 2 phr;The low-temperature protective wax NG9345F with carbon number distribution range of C₂₆-C₃₂ and isomeric alkane ratio of about 25%is easy to migrate to the rubber surface at low temperature(near 25?).The wax film is mainly composed of normal alkanes,and the formed wax film is complete and thick,which is suitable for ozone protection near 25?.In the third part,the protective wax NG9332F was used to study the effects of raw rubber system,plasticizing system and vulcanization system on the migration behavior of wax and the properties of sidewall rubber.The results show that the protective wax NG9332F is easier to spray out of the sidewall rubber with high br content,low amount of plasticizer V700 and high crosslinking density.It is suggested that the ratio of NR to br in the formula of sidewall rubber is close to 1:1,the dosage of plasticizer is 3-7phr,and the dosage of vulcanizing agent is 2.5phr or more,which can make the sidewall rubber not only have the necessary mechanical strength and good flexural fatigue resistance,but also have good ozone aging resistance.In the fourth part,NG9332F was used to study the effects of mixing and parking process on the migration behavior of wax and the properties of sidewall rubber.In a500ml internal mixer,when the rotor speed is about 80r/min,it can ensure better filler dispersion and better ozone resistance.The carbon number distribution range is concentrated in the C₃₀-C₄₀ range.The migration rate and wax film density of medium and high temperature protective wax such as NG9332F at 35?or 40?are much higher than 25?,so it is more suitable for protection at higher temperatures.