Reparation, Characterization And Grafting Modification Of Solid Phase High Chlorinated Polyethylene With Low Viscosity

The present work is concerned with the preparation of low viscosity highchlorinated polyethylene (HCPE) by solid-phase chlorination, which is with goodsolubility and the using viscosity of coating. For the sake of clarity, the reactionproducts from this system will be named as LHCPE. To improve the adhesion ofLHCPE film, maleic anhydride (MAH) was grafted onto the main chain of LHCPEvia in-situ chlorinating graft copolymerization (ISCGC), the anhydride modifiedLHCPE with good film adhesion was prepared and be named as LHCPE-cg-MAH.Firstly, the feasibility of the preparation of LHCPE by solid-phase chlorinationwas demonstrated with LDPE as raw material, and the preliminary chlorinatedprogram of LDPE was designed. LHCPE was prepared according to the design,which had overcame some problems such as low molecular weight of raw material,low melting temperature, difficulties with controlling the chlorination temperatureand the chlorination degree, and so on. The optimum reaction conditions wereexplored, including initiation methods, initiator content, the effect of swelling, earlyreaction temperature and chlorine flow. The results indicate that the chlorinationreaction rate reaches the fastest under the conditions of3%BPO,28mmol·min-1chlorine flow, swelled by DOP for12h before reaction, and at70℃at the earlystage. Then, the molecular structure of LHCPE was characterized by FTIR,1H-NMR,DSC and GPC. The main reaction was that the hydrogen atoms on the main chainwere replaced by chloride atoms, and there maybe mild side effects ofdehydrochlorination in the meanwhile because of the weak absorption peak at1647cm-1. The chlorine distribution uniformity of LHCPE is worse than that of HHCPE.Tg was101.2℃. The molecular weight was less than HHCPE, and the distribution is narrower. The viscosity test of LHCPE, the gel content and the preliminaryperformance of the film were the main points. Tu-4cup viscosity of LHCPE is36.3s,the lowest gel content is6%and the film adhesion is poor.Lastly, in order to increase film adhesion the anhydride modified LHCPE wasprepared by grafting maleic anhydride (MAH) onto macromolecular chain ofLHCPE via in-situ chlorinating graft copolymerization (ISCGC). The process ofMAH grafted onto LHCPE via ISCGC was inferred according to the reactionmechanism. In addition, the structure of modified product (LHCPE-cg-MAH) wascharacterized by FTIR,1H-NMR, DSC and GPC. The anhydride modified productLHCPE-cg-MAH was obtained by ISCGC of LHCPE and MAH, Tg is77.4℃.Thenumber-average molecular weight (Mn) and weight-average molecular weight (Mw)of LHCPE-cg-MAH are increased, but distribution of molecular weight (Mw/Mn) isdecreased. Furthermore, the film adhesion and impact strength of LHCPE-cg-MAHwas tested. The results showed that the film adhesion and impact strength ofLHCPE-cg-MAH reached the performance requirements of HCPE coating.