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
The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/c...The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.展开更多
Objective: To develop the characterization of the polymorphs and the best preparation method of two forms of the title compound (SU2162). After SU2162 was prepared in accordance with the patent process, the crystal fo...Objective: To develop the characterization of the polymorphs and the best preparation method of two forms of the title compound (SU2162). After SU2162 was prepared in accordance with the patent process, the crystal form I was recrystallized by ethyl acetate and the crystal form II was obtained by the recrystal in acetone. And the two crystal forms were characterized with differential scanning calorimetry (DSC) and X-ray powder diffraction (PXRD). The melting point of crystal form I (triclinic) is at 158°C, and the melting point of crystal form II (monoclinic) is at 163°C. The PXRD studies of the two crystalline samples indicate that they have the distinct diffraction patterns. The method herein can be stably prepared for the two crystal forms of the title compound.展开更多
1 Introduction Many kinds of nanocrystalline alloys have been prepared after crystallization of the corresponding amorphous alloys and their typical compositions are Fe-M’-M'-Si-B, where M’=Cu and M'=Nb, Mo,...1 Introduction Many kinds of nanocrystalline alloys have been prepared after crystallization of the corresponding amorphous alloys and their typical compositions are Fe-M’-M'-Si-B, where M’=Cu and M'=Nb, Mo, V, Hf, Ta, etc. which are called the nanocrystalline structure formation(NSF) elements. They have become a new kind of soft magnetic alloys with excellent magnetic properties. So far, much significant progress has been achieved in展开更多
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.
基金This work was supported by the Science Foundation of Polymer Physics Laboratory, Chinese Academy of Sciences.
文摘The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.
文摘Objective: To develop the characterization of the polymorphs and the best preparation method of two forms of the title compound (SU2162). After SU2162 was prepared in accordance with the patent process, the crystal form I was recrystallized by ethyl acetate and the crystal form II was obtained by the recrystal in acetone. And the two crystal forms were characterized with differential scanning calorimetry (DSC) and X-ray powder diffraction (PXRD). The melting point of crystal form I (triclinic) is at 158°C, and the melting point of crystal form II (monoclinic) is at 163°C. The PXRD studies of the two crystalline samples indicate that they have the distinct diffraction patterns. The method herein can be stably prepared for the two crystal forms of the title compound.
文摘1 Introduction Many kinds of nanocrystalline alloys have been prepared after crystallization of the corresponding amorphous alloys and their typical compositions are Fe-M’-M'-Si-B, where M’=Cu and M'=Nb, Mo, V, Hf, Ta, etc. which are called the nanocrystalline structure formation(NSF) elements. They have become a new kind of soft magnetic alloys with excellent magnetic properties. So far, much significant progress has been achieved in
