Study On Surface Modification Of Ground Calcium Carbonate And Its Blending With PBAT Copolymer

Polybutylene terephthalate（PBAT）has good biodegradability in nature and can be a good alternative to low density polyethylene materials,but its promotion is limited by its high price.Heavy Ca CO₃ filling in PBAT can reduce the product cost,but the compatibility between Ca CO₃ and PBAT matrix is poor,so the mechanical and thermal properties of PBAT/Ca CO₃ composites are poor.In this thesis,different types of coupling agents,surfactants and composite modifiers were selected to modify the surface of heavy Ca CO₃,and the capacity enhancer（ADR）was selected to optimize the composite formulations,and a series of PBAT/modified Ca CO₃ composites were prepared by melt blending method,and various performance tests were conducted on the composites to investigate the surface modification methods,modifier types and contents,PBAT and The composites were tested to investigate the effects of surface modification method,modifier type and content,the ratio of PBAT and Ca CO₃ and the content of ADR on the comprehensive performance of PBAT/Ca CO₃ composites.Firstly,three coupling agents,aluminate coupling agent（DL-411）,titanate coupling agent（NDZ-201）and silane coupling agent（KH-550）,were used to modify the surface of heavy Ca CO₃,and the PBAT/modified Ca CO₃ composite system was prepared by melt blending method.The results showed that the addition of the coupling agents effectively improved the agglomeration of Ca CO₃ compared with the unmodified Ca CO₃,and the wet modification was more effective than the dry modification,and the compatibility between the modified Ca CO₃ and PBAT matrix was good.The mechanical properties,hydrophobicity and thermal stability of PBAT/modified Ca CO₃ composites were significantly improved,with increased crystallization temperature and crystallinity,higher heat resistance,and higher melt flow rate.The PBAT/DL-Ca CO₃ composite has the best overall performance,with the tensile strength and elongation at break of PBAT/10%DL-Ca CO₃ reaching 17.57 MPa and 1280.09%respectively;the Vicat softening point of PBAT/50%DL-Ca CO₃ reached 100.6℃,compared to 86.5℃ for pure PBAT,an increase of 16.30%.Next,six surfactants,namely stearic acid（SA）,sodium dodecyl sulphate（SDS）,glutamic acid（GLU）,cetyl phosphate（PO16）,octadecyl phosphate（PO18）and cetyl trimethyl ammonium bromide（CTAB）,were selected to modify the surface of heavy Ca CO₃by wet process,and PBAT/modified Ca CO₃ composites were prepared by melt blending method.The PBAT/modified Ca CO₃ composites were prepared by the melt blending method,and the composites were characterized by various properties.The results showed that SA,SDS and PO16 were most effective in modifying Ca CO₃ at 3%.Compared with the unmodified Ca CO₃,the addition of these three surfactants effectively improved the compatibility between Ca CO₃ and the PBAT matrix.The mechanical properties,hydrophobicity and thermal stability of the PBAT/modified Ca CO₃ composites were significantly improved,the crystallisation temperature and crystallinity increased,the heat resistance temperature increased and the melt flow rate became higher.The PBAT/SDS-Ca CO₃ composite had the best overall performance,with a tensile strength of 17.99 MPa for PBAT/10%SDS-Ca CO₃,an increase of 19.22%compared to PBAT/10%Ca CO₃;the contact angle number of PBAT/10%SDS-Ca CO₃ reached 90.38°,which is a hydrophobic material.Then,DL-411 and SDS were used to modify Ca CO₃,and the PBAT/modified Ca CO₃composite system was prepared by melt blending method,and the properties of the composite system were characterized.The results showed that the best modification of Ca CO₃ was achieved when the compound modifier ratio（DL:SDS）was 3:2,the reaction time was 40min,the reaction temperature was 80℃ and the amount of compound modifier added was 3%.Compared with the single modifier,the mechanical properties of the composites prepared by blending Ca CO₃ and PBAT modified by the composite modifier were significantly improved,with higher crystallization temperature and crystallinity and increased hydrophobicity.The tensile strength of PBAT/30%CM-Ca CO₃ reached 13.75 MPa and the elongation at break reached 895.52%.the contact angle number of PBAT/10%CM-Ca CO₃ reached 93.82°.Finally,the PBAT/30%CM-Ca CO₃ composites were modified with the bulking agent ADR,and the PBAT/30%CM-Ca CO₃/ADR composites were prepared by the melt blending method.The results showed that with the increase of ADR content,the tensile strength of the composites increased,the crystallization temperature and crystallinity increased and then decreased,the melt flow rate decreased,and the heat resistance temperature and contact angle increased and then decreased.When ADR is added at 0.6%,the phase interface of the composite is tightly bound and the overall mechanical properties are optimal,the tensile strength of PBAT/30%CM-Ca CO₃/0.6%ADR was 14.37 MPa,the elongation at break was797.67%and the Vicat softening point reached a maximum of 96.5℃.