Yong Zhou Wang

Study on Effective Storage Time of Constant Viscosity Natural Rubber

The effective storage time (i.e. storage life) of constant viscosity natural rubbers prepared with hydroxylamine hydrochloride, hydroxylammonium sulphate, hydrazine hydrate, aniline and semicarbazide hydrochloride respectively were investigated with heat accelerated storage aging combined with differential scanning calorimeter(DSC) method as well as the heat aging life equation. The results show that the effective storage time of constant viscosity natural rubber prepared with hydroxylamine hydrochloride is 19.2 years at 30°C, 39.4 years at 25°C and 82.9 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with hydroxylammonium sulphate is 16.3 years at 30°C, 32.6 years at 25°C and 66.5 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with hydrazine hydrate is 42.5 years at 30°C, 85.9 years at 25°C and 177.9 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with aniline is 30.4 years at 30°C, 66.7 years at 25°C and 150.2 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with semicarbazide hydrochloride is 13.5 years at 30°C, 27.4 years at 25°C and 57.1 years at 20°C.

Effect of Tackifier on Thermal Oxidation Kinetics and Effective Storage Time of Raw Natural Rubber

The thermal oxidation kinetics of natural rubber containing hydrazine dihydrochloride or hydrazine sulfate used as tackifier were studied, and the effective storage time of natural rubber containing tackifier was predicted with a method of heat accelerated storage aging. The results show that the thermal oxidation activation energy of natural rubber containing hydrazine dihydrochloride is 105.6kJ/ mol, being a little higher than that (104.7 kJ/ mol) of the control. The thermal oxidation activation energy of natural rubber containing hydrazine sulfate is 103.1kJ/ mol, being a little lower than that of the control. The effective storage time of natural rubber containing hydrazine dihydrochloride is 13.4 years at 30°C,27.0years at 25°C, and 55.9years at 20°C. The effective storage time of natural rubber containing hydrazine sulfate is 11.6years at 30°C,23.0 at 25°C, and 46.8years at 20°C.The effective storage times of natural rubber containing two tackifiers hydrazine dihydrochloride or hydrazine sulfate are higher than that of the control at the same condition.

Study on Aging Resistance Properties of Natural Rubber Dried by Microwave

In this work, thermogravimetry (TG) and Wallace plastometer were used to study the thermal-oxidative aging resistance properties of natural rubber (NR) dried by microwave and hot-air. Showed from the results, thermal degradation temperature, primary thermal-oxidative degradation temperature, the value of P0, PRI and VR for NR dried by microwave were higher than those of NR dried by hot-air; the thermal-oxidative aging resistance properties of NR vulcanizes dried by microwave improved significantly, and the rate of change for elongation at break (-26.76%) and tensile strength (-38.6%) of NR vulcanizes dried by microwave before and after aging were apparently higher than those of NR vulcanizes dried by hot-air, which were (-60.29%) and (-82.11), respectively.

Study on Curing Kinetics of Natural Rubber Dried by Microwave

In this article, the curing kinetics of natural rubber (NR) dried by microwave at frequency of 2450MHz was studied using vulcameter, as well as molecular weight. Seen from the results, the molecular weight distribution of NR dried by microwave was wide, the reaction rate of NR dried by microwave at any temperatures increased with conversion degree (α) increment and passed through a maximum at the value of α between 0.1 and 0.3, the peak height of α was increased with a shift in peak position towards a higher α value, which provided evidences that the curing behavior illustrated autocatalytic characteristics and depended on curing temperature.

Effect of Viscosity Stabilizer on the Properties and Structure of Raw Constant Viscosity Rubber

The properties of raw constant viscosity natural rubber were measured using a rubber processing analyzer. The results show that the rubber processing analyzer can characterize well the effect of viscosity stabilizer on the dynamic mechanical properties of raw constant viscosity rubber by applied strain sweep or frequency sweep. In linear viscoelastic region, the increment of the dynamic torque S’ of the constant viscosity natural rubber prepared with hydroxylamine hydrochloride decreases with the increase in the level of hydroxylamine hydrochloride . In the range of low frequency, the increment of the dynamic modulus G’ of constant viscosity natural rubber prepared with hydroxylamine hydrochloride is obvious lower than those of natural rubber and constant viscosity natural rubber prepared with aniline. G’ of the constant viscosity natural rubber prepared with aniline is just only a little higher than that of natural rubber. Hydroxylamine hydrochloride and aniline can decrease the molecular weight of rubber, and change the molecular weight distribution. The dynamical properties of constant viscosity natural rubber are dependent on the molecular weight and the molecular weight distribution.

Effect of Hot Air Aging on Structure and Properties of Raw Natural Rubber

The molecular structure, molecular weight and its distribution, P0, PRI, Mooney viscosity, processibility of raw natural rubber, curing characteristics of compounds and mechanical properties of vulcanites were studied by hot air aging. The results show that for raw natural rubber after heating at 70°C for 20 days, C = C bond of molecular chains was broken, the numbers of the C = C bond decreased, methyl oxidized, and –OH and –COOH formed. The number-average molecular weight, weight-average molecular weight and viscosity-average molecular weight decreased, the molecular weight distribution became wide. P0, PRI, Mooney viscosity, rubber elastic torque S , viscous torque S , elastic modulus G, viscous modulus G and complex viscosity η* decreased, loss factor tanδ increased. The curing rate of compound reduced and curing characteristics were inferior. The elongation at break and tensile strength decreased, and tensile stress at 300% modulus and 500% modulus did not change obvious. Anti-aging property became deteriorate.