Effect of Formulation and Process on the Cree Properties of NR
|School||Qingdao University of Science and Technology|
|Keywords||natural rubber formulation process creep|
The creep would affect the dimensional stability and service life of rubber products. Creep is the important properties of the rubber shock-absorbing parts. The production will generate permanent deformation after a period, and will result the product size changes.For a motor vehicle, excessive creep deformation of rubber products,will affect driving safety. But there are less domestic research in this area.For the low creep production,the natural rubber (NR) is the first choice. In this research, natural rubber was chosen, and the dynamic mechanical spectrum analyzer (DMTS)was used to test its creep properties,and investigated formulations、processes and temperature on the creep properties of natural rubber to explore the best formulation and process for the creep properties of natural rubber.The paper studied the effect of the curing system, the reinforcement system, the sulfur dosage and antioxidant species on the creep properties of the natural rubber.The results show that:(1) the creep properties of natural rubber vulcanized by semi-efficient curing system which the proportion of the sulfur and accelerator is one is best, while the creep resistance of natural rubber vulcanized by the effective curing system with no sulfur is worst.(2)When the ratio of carbon black/silica is50/0, the cross-link density of the natural rubber is maximum, the creep resistance is best;while the ratio of the carbon black/silica is20/30, the cross-link density of the natural rubber is minimum, the creep resistance is worst.(3) When the sulfur dosage is2.0phr, the creep properties of natural rubber is better.With the increase of the sulfur dosage, the cross-linking density of natural rubber vulcanizates is increases.When the cross-link density is low,with its increasing the creep resistance of the natural rubber is increased.,but the cross-link density is high,with its increasing the creep resistance of the natural rubber is decreased. The results show that,when the cross-linking density exceeds a certain limit, the creep resistance is deteriorated.(4) In the selection of the three antioxidant, the creep deformation of natural rubber which the antioxidant is RD is minimum, the creep resistance is better than the antioxidant4020and MB.The paper studied the influence of the mastication times、carbon black mixing time and curing temperature on the creep properties of natural rubber. The results show that:(1)when the mastication times is10times and the carbon black mixing time is2min,the complexing agent is dispersed evenly in the natural rubber, the reinforcing effect is greater,the hardness is big, the creep resistance is better.(2)when the curing temperature is143℃, the creep resistance of the natural rubber is best.It was studied in this paper that the influence of the temperature on the creep properties of natural rubber.The results show that:(1)The influence of temperature on the natural rubber is significate.When the temperature is25℃,the creep deformation of the sample increased with the time increases.But when the temperature is45℃and70℃,it was found that some samples expansion,and the expansion value is greater than the compressive creep deformation,resulting the creep deformation decrease with the time increases,and the slope of the creep curve is negative.The reason is to be further explored.(2)The creep of rubber,which includes decelerated creep and steady-state creep, is a time-varying process., In the period of840-1050s,the samples have a accelerated creep process.The experiment results show that the formulation, mixing process and vulcanization process have a significant influence on the creep properties of natural rubber.It is very important to select appropriate formulations and processes to study of low-creep rubber products.