Research On The Interface Structure And Properties Of Cellulose/polycaprolactone Composites

In this thesis,a series of novel interface structure of cellulose/polycaprolactone(PCL)composites used PCL-based polyurethane prepolymer(PCLPU)as a compatibilizer were successfully prepared in an intensive mixer by the method of melting reaction.Firstly,the compatibilizing mechanism of interface structure and properties of cellulose/PCL composites were investigated.Secondly,the effects of different PCLPU content on the structure and properties of cellulose/PCL composites were researched.Finally,the effects of different cellulose content on the structure and properties of cellulose/PCL composites were further studied.This paper consists of three parts:(1)Structure and properties of cellulose/PCL composites compatibilized with PCLPU:The results of a variety of tests and characterization showed that the multifunctional polyurethane layer(PCLPU layer)was located at the interface between the cellulose and PCL matrix.On the one hand,urethane linkages was formed from the reaction between multiisocyanates of PCLPU layer and the hydroxyl groups of cellulose,which improved the adhesion force between the PCLPU and cellulose;On the other hand,the PCL soft segments in PCLPU layer could interact with PCL matrix through PCL crystallinity to enhance the interface adhesion force between PCL matrix and PCLPU.The multifunctional PCLPU was thus deemed effective in improving the compatibility of cellulose/PCL composites.The results revealed that,owing to the good compatibilizer PCLPU used,composites with PCLPU were superior in terms of morphological structure,thermal degradation stability and mechanical properties when compared with the non-compatibilized cellulose/PCL composites.(2)The effects of different PCLPU content on the structure and properties of cellulose/PCL composites:A series of cellulose/PCL composites with different PCLPU content were successfully prepared in an intensive mixer by the method of melting reaction.The characterization results revealed that the thermal degradation stability of composites improved with the increase of PCLPU content and the crystallization performance in the composites declined.When the content of PCLPU was below 15%,the mechanical properties of the composites enhanced with the increase of PCLPU content,but slightly down when the content was up to 20%.It may be ascribed to that the PCLPU itself was an elastomer and the effect of PCLPU content had dominance over the effect of crosslinking degree.Therefore,the content of PCLPU was indeed as an important factor for improving the compatibility and properties of cellulose/PCL composites.(3)The effects of different cellulose content on the structure and properties of cellulose/PCL composites:A series of cellulose/PCL composites with different cellulose content were successfully prepared in an intensive mixer by the method of melting reaction.The results of a variety of tests and characterization indicated that the interface compatibility between cellulose and PCL decreased with the increase of cellulose content.It is worth noting that thermal degradation stability and elongation at break of cellulose/PCL composites also reduced with the increase of cellulose content.It is mainly because more cellulose content may lead to lower degree of crosslinking between cellulose and PCLPU and decrease of interface adhesion force with the same PCLPU compatibilization;meanwhile,the breaking strength of composites increased with the increase of cellulose content since the cellulose itself had high strength.Based on the above,the content of cellulose was also an indispensible factor for improving the compatibility and properties of cellulose/PCL composites.