| Silane crosslinked polyethylene is more and more popular because of its excellent comprehensive properties and high cost performance.However,the traditional production process requires high-temperature boiling,which is time-consuming and energy consuming.Therefore,it is proposed to add water producing agent to realize self crosslinking at room temperature,which can save the process of high-temperature boiling in practical application and achieve the purpose of energy conservation and emission reduction.In this paper,linear low density polyethylene(LLDPE)was used as the matrix.Firstly,the effects of different process conditions on the properties of silane crosslinked polyethylene were studied.By studying the effects of plasticizing time,shear force and processing temperature on the gel content and mechanical properties of the products,the optimal process parameters were determined.When the rotational speed of Huck torque rheometer is 30 rpm and the reaction time is 5min,the silane crosslinked polyethylene product has good comprehensive properties,the highest grafting efficiency is 1.72,the gel content is 72.62%,the tensile strength is 22.98 mpa,and the elongation at break is 737.2%.The grafting reaction can be accelerated by increasing the temperature.When the processing temperature is increased,the melt flow rate of the product is reduced from 1.2g/10 min to 0.69g/10 min.Proper addition of catalyst can accelerate the hydrolysis condensation process of crosslinked polyethylene and improve the crosslinking efficiency of crosslinked polyethylene.In the aging resistance experiment,when the content of silane coupling agent is 1.8phr and the content of initiator is 0.1phr,the aging resistance of silane crosslinked polyethylene is excellent.Then Poe elastomer was added to the blend for toughening.When the ratio of LLDPE to Poe was 50:50,the gel content of silane crosslinked polyethylene was 76.9%,which improved the thermal stability of the product by 12.3%,and the two also had good compatibility.In addition,the addition of lubricant can prevent the pre crosslinking of the product,so that the gel content of the product is increased from 75.9% to 79.36.Secondly,several water producing agents were screened,and zinc oxide(Zn O)was selected as the final research object.The effects of Zn O content on the gel content,mechanical properties,crystallization properties,thermal stability and rheological properties of silane self crosslinked polyethylene were systematically studied.The experimental results show that the addition of Zn O can accelerate the silane hydrolysis and self crosslinking reaction of LLDPE;The comprehensive properties of silane self crosslinked polyethylene with 2% Zn O were the best,the gel content was 75.61%,the tensile strength was 24.43 mpa,and the elongation at break was 703.8%,which was equivalent to the properties of crosslinked polyethylene treated by traditional boiling process;The increase of gel content will increase the thermal stability of the blends,but the crystallinity will decrease;Through scanning electron microscope,it is found that the addition of water producing agent accelerates the growth and diffusion of water tree channel,makes the diffusion of water in the sample and the absorption of water in the air faster,and the water channel becomes more and more prominent and obvious.Finally,the self crosslinking characteristics of silane crosslinked polyethylene were measured under different temperature and humidity conditions.The relationship among gel content,temperature and humidity was successfully fitted by python,and the correlation equation was obtained. |
