For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the inte...For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.展开更多
Due to the mechanical stability of the PP layer,the oriented PP/PE double-layer film with a row-nucleated crystalline structure can be annealed at a higher temperature than the PE monolayer film.In this work,the effec...Due to the mechanical stability of the PP layer,the oriented PP/PE double-layer film with a row-nucleated crystalline structure can be annealed at a higher temperature than the PE monolayer film.In this work,the effects of annealing temperature within the melting range of PE on the crystalline structure and properties of PP/PE double-layer films were studied.When the annealing temperature is between 100 and 130℃,below the melting point of PE,the crystallinity,the long period,lateral dimension and orientation of the lamellae in the PE layer increase with the annealing temperature due to the melting of thin lamellae and the self-nucleated effect of partially-melted melts during annealing.With the annealing temperature further increasing to 138℃,near the melting ending point of PE,since the lamellae melt completely and the melt memory becomes weak during annealing,some spherulite structures are formed in the annealed sample,resulting in a decrease of orientation.In contrast,the annealing only causes the appearance of a low-temperature endothermic plateau in the PP layer.The improved size and orientation of lamellar structure in the PE layer increase the pore arrangement and porosity of the stretched PP/PE microporous membrane.This study successfully applies the self-nucleation effect of partially-melted polymer melt into the practical annealing process,which is helpful to guide the production of high-performance PP/PE/PP lithium batteries separator and the annealing process of other multilayer products.展开更多
The structural analysis of two PP/PE copolymer samples,1 and 2,was conducted by using^(13)C-NMR,GPC and crystallization segregation DSC(CSDSC)techniques.A pure polypropylene sample was also used for comparison.It was ...The structural analysis of two PP/PE copolymer samples,1 and 2,was conducted by using^(13)C-NMR,GPC and crystallization segregation DSC(CSDSC)techniques.A pure polypropylene sample was also used for comparison.It was found that the two copolymer samples are very close in composition(the ethylene mol content is 4.3%and 4.5%,respectively),stereoregularity(96%and 97%)and molecular weight(M_(w)=7.0 x 10^(4)and 7.3 x 10^(4);M-(w)/M_(n)=5.0 and 6.1,respectively).While the CSDSC thermograms of the two samples are quite different from each other.Sample 1 shows a higher average melting temperature and a broader distribution of its thermogram These phenomena were explained as an indication of a less uniform distribution of ethylene units along the PP chains for sample 1.It was noted that CSDSC is a very sensitive and convenient technique for structural studies of copolymers.展开更多
文摘For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.
基金the National Natural Science Foundation of China(Nos.52173033,51773044 and 51603047)Guangzhou Science and Technology Plan Project(No.202102020952)+2 种基金Research and Development Plan for Key Areas in Guangdong Province(No.2019B090914002)the Project of Science Foundation of Guangdong Province(No.2021A1515011914)Foshan Science and technology innovation project(No.FS0AA-KJ919-4402-0145).
文摘Due to the mechanical stability of the PP layer,the oriented PP/PE double-layer film with a row-nucleated crystalline structure can be annealed at a higher temperature than the PE monolayer film.In this work,the effects of annealing temperature within the melting range of PE on the crystalline structure and properties of PP/PE double-layer films were studied.When the annealing temperature is between 100 and 130℃,below the melting point of PE,the crystallinity,the long period,lateral dimension and orientation of the lamellae in the PE layer increase with the annealing temperature due to the melting of thin lamellae and the self-nucleated effect of partially-melted melts during annealing.With the annealing temperature further increasing to 138℃,near the melting ending point of PE,since the lamellae melt completely and the melt memory becomes weak during annealing,some spherulite structures are formed in the annealed sample,resulting in a decrease of orientation.In contrast,the annealing only causes the appearance of a low-temperature endothermic plateau in the PP layer.The improved size and orientation of lamellar structure in the PE layer increase the pore arrangement and porosity of the stretched PP/PE microporous membrane.This study successfully applies the self-nucleation effect of partially-melted polymer melt into the practical annealing process,which is helpful to guide the production of high-performance PP/PE/PP lithium batteries separator and the annealing process of other multilayer products.
文摘The structural analysis of two PP/PE copolymer samples,1 and 2,was conducted by using^(13)C-NMR,GPC and crystallization segregation DSC(CSDSC)techniques.A pure polypropylene sample was also used for comparison.It was found that the two copolymer samples are very close in composition(the ethylene mol content is 4.3%and 4.5%,respectively),stereoregularity(96%and 97%)and molecular weight(M_(w)=7.0 x 10^(4)and 7.3 x 10^(4);M-(w)/M_(n)=5.0 and 6.1,respectively).While the CSDSC thermograms of the two samples are quite different from each other.Sample 1 shows a higher average melting temperature and a broader distribution of its thermogram These phenomena were explained as an indication of a less uniform distribution of ethylene units along the PP chains for sample 1.It was noted that CSDSC is a very sensitive and convenient technique for structural studies of copolymers.
