Preparation And Property Test Of PVC/NBR Reversible Crosslinking Material

Polyvinyl chloride(PVC)is a cheap resin material with various formulations and extensive applications,which,however,still has problems such as poor thermal stability,low toughness and weak cold resistance.To improve its performance,a PVC modification is often required.Traditional cross-linking modification can improve the performance of PVC,which,nonethless,will lose its thermoplastic material.In view of this,the borate bond with reversible characteristics is introduced into the macromolecular chain of polymer to improve the performance of PVC while endowing it with the characteristics of secondary processing and recycling.Since there is relatively small active chlorine content inside PVC,nitrile rubber(NBR)and PVC are mixed and modified in this experiment.Besides,a borate crosslinker containing dithiol group is prepared and introduced into the PVC / NBR mixing system,so as to improve the crosslinking density of the mixing system.(1)A boronate crosslinking agent containing bis-mercapto groups was synthesized,its structure was characterized,and its thermodynamic properties were investigated at the same time.(2)The feasibility of dimercapborate crosslinking PVC is verified by infrared and swelling experiments.Through analyzing torque images,using small molecule alcohol as a assistant crosslinker and 4-dimethylamine pyridine as an ester exchange catalyst produces best effects.Then,DMA is tested on the polymers,showing that the PVC can release more stress for somea certain period of time after the introduction of a reversible crosslinking structure.The limit processing number of reversible cross-linking P VC is 3 times,and the tensile performance after processing for multiple times only varies slightly from the control sample.(3)The feasibility of dimercapborate crosslinking NBR is verified by infrared and swelling experiments.Through the determination of rotor-free sulcanizer and gel rate,it is found that 180℃ is the suitable temperature for forming sampling products and its multiple processability is verified on the opening machine.By comparing with the mechanical properties of pure NBR samples,it is figured out that the tensile properties of NBR have been improved significantly after crosslinking.(4)The absorption effect of NBR on dioctyphthalate(DOP)is significantly stronger than that of PVC.Therefore,PVC is pre-infiltrated and remixed with NBR to explore the effect of DOP amount on mixed polymer.The results show that the appropriate amount of DOP is 30 parts.Then by analyzing the insoluble material of the conmixed polymer by the gel degree and infrared test,the formation of the co-crosslinking network is verified and the tensile performance of the co-crosslinked polymer is found to decrease with the increasing decomposition degree of P VC,which,however,is still better than the control sample after multiple processes.