Hydrolysis Resistant Modification And Fiber Application Of Phosphorus Containing Flame Retardant Copolyester

Polyester fiber has excellent performance,large output and affordable price.It has been widely used.However,it is a kind of flammable materials.It burns violently after being ignited by a fire source,and it is not easy to be extinguished.This phenomenon brings a huge threat to the life and assets of people.Therefore,flame-retardant polyester fiber materials gradually appear in the market.From the point of view of the processing and application of flame retardant polyester fiber,there are not many varieties in mass production at present.There are still some problems in subsequent processing and application.The post-processing process of flame retardant polyester fiber,such as the dyeing process under the hot and humid environment with high temperature and high pressure.In such an environment,the ester bond and phosphorus-oxygen bond in the flame retardant polyester fiber structure are prone to be broken,resulting in the hydrolysis of the fiber.It affects the performance and subsequent use of the flame retardant polyester fiber products.Based on the above issues,it is of practical significance to explore the structural performance changes and the performance degradation mechanisms of flame-retardant polyester fibers in hot and wet environments,aiming to provide optimization schemes for application performance.Carbodiimide is a commonly used hydrolysis-resistant agent.Carbodiimide can obtain excellent hydrolysis-resistant effect with slight content in polyester.In this paper,flame retardant copolyesters were blend-modified with carbodiimide hydrolysis resistance agent to enhance its hydrolysis resistance.The basic properties of the blend-modified hydrolysis-resistant and flame-retardant copolyester slices were evaluated,and their thermal humidity resistance and thermal oxidation resistance were explored and studied.On this basis,the flame-retardant copolyester and the hydrolysis-resistant masterbatch were melt blended and spun.The basic properties of the hydrolysis-resistant modified flame-retardant copolyester fibers were tested,and the flame retardant performance and hydrolysis resistance properties were evaluated.The specific research contents are as follows:(1)The main product of the commercially available flame retardant copolyester slices is the copolyester modified by CEPPA flame retardant.The phosphorus-oxygen bond and ester bond contained in the main chain are easily broken under the action of moisture.The acidic structure is generated by hydrolysis and high temperature conditions,further promoting the accelerated development of hydrolysis.The addition of carbodiimide has little effect on the basic properties of the flame retardant copolyester.The crystallization and the heat resistance is improved and crystallization temperature is increased.Testing of rheological properties shows that flame retardant copolyesters are more temperature sensitive than conventional PET melts.Blended spinning process of adding carbodiimide hydrolysis-resistant components can refer to the spinning process of flame retardant copolyester,and the spinning temperature can be lowered.(2)Under the same conditions,the conventional PET,flame retardant copolyester and blended slices are thermally processed.Each sample has different degrees of degradation.It is occurred that the molecular weight decreases,and the polydispersity coefficient increases.The degradation of the blended slices was relieved compared with the flame retardant copolyester.The hydrolysis resistant flame retardant copolyester blend slices with effective content of 0 wt%,0.5wt%,1.0 wt% and 1.5 wt% decreased by 6855 g/mol,5130 g/mol,4371 g/mol and 4084 g/mol respectively.And the increase of polydispersity coefficient also decreased gradually.While the increase of polydispersity coefficient also decreases gradually.Using conventional PET and high content of anti-hydrolysis masterbatch blended,the test shows that the addition of carbodiimide can consume the terminal carboxyl groups in the system during thermal processing The reduction of terminal carboxyl groups is beneficial to inhibit thermal degradation and the occurrence of hydrolysis reactions.When each sample was treated in the same heat and humidity environment,their molecular weight and phosphorus content decrease with the increase of treatment time.Adding carbodiimide into polyester has a good effect on the heat and moisture resistance of phosphorus-containing flame retardant copolyester.Among the blended slices,the sample with 0.5wt% effective content of carbodiimide has a better effect.The retention rate of the number average molecular weight of the pure sample and 0.5 wt% blended slices increase by 18.64 % and 10.3 %respectively.The addition of carbodiimide could improve the resistance to humidity and heat and thermal oxidation resistance.(3)The flame retardant copolyester fibers were prepared by melt spinning.The limiting oxygen index is about 29 %,the vertical combustion UL-94 level is V-2,and the flame retardant performance is good.Compared with the conventional PET fiber,the breaking strength decreases.The comprehensive performance changes little after adding the hydrolysis-resistant component.On the whole,the addition of hydrolysis-resistant components has no obviously effect on the use effect of flame retardant copolyester fibers.From the hydrolysis results,the strength of the phosphorus-containing flame-retardant copolyester fiber decreases more seriously than that of the conventional PET fiber.The addition of 0.5 wt% carbodiimide into flame retardant copolyester improves the strength retention of the phosphorus-containing after hydrolysis.The retention rate of strength and limiting oxygen index after 72 and 36 hours of hot and humid hydrolysis reached reached more than 83% and 92 % respectively.It can be seen that a small amount of carbodiimide can increase the hydrolysis resistance of the fiber and improve the performance of the phosphorus-containing flame retardant copolyester fiber.