Two low density polyethylene resins (sample A and sample B) were fractionated through temperature rising elution fractionation (TREF)

and GPC

13C-NMR

DSC and SSA are exploited to study the chain structure of original resins and their fractions.The two resins with unimodal distribution have different properties.Compared with sample B

sample A possesses higher tensile break strength and film puncture resistance.By13C-NMR

the total branch contents of samples A and B are 3.93 mol% and 4.82 mol%

respectively.Both resins have short chain branch and long chain branch structures.It is also found that the branching content of the fractions decreases with the elution temperature

which is in accordance with TREF mechanism.By the TREF-GPC cross-fractionation results

the fractions of two resins focus on higher temperature region.The dominant fraction of sample A is eluted at 80 ℃

and its molecular weight is concentrated at 32104.The dominant fraction of sample B is eluted at 75 ℃

and its molecular weight is concentrated at 18104.Sample A has a slightly higher molecular weight

more content on high molecular weight

broader molecular weight distribution.In DSC results

the melting temperatures of samples A and B are 110.5 ℃ and 110.2 ℃

respectively.Both samples have broader melting range corresponding to 50~120 ℃.In the SSA thermal fractionation

each fraction of the two samples shows a broad range endotherm with multiple melting peaks (more than eight peaks).The arithmetic mean methylene sequence length of fractions for the two samples gradually increases from 34 to 86 and from 32 to 84 with the increase in the elution temperature

respectively.In addition

the characteristics of chain microstructure and the relationship of structure and properties were discussed.