Structure And Properties Of Polypropylene/waste Plastics Multilayer Plates Composites

Plastics multilayer plate is extruded by polymethyl methacrylate (PMMA) and acrylonitrile-butadiene-styrene (ABS) terpolymer and then coated by unsaturated polyester resin (UPR) which is reinforced by glass fibre. The composites have bright and clean appearance, high hardness, excellent impact strength and flexural strength, good aging resistance. The waste of plastics multilayer plate (WGFRP) is difficult to be recycled because it contains thermoplastics and thermosetplastics. The traditional recycling ways, burying and burning, do not comply with the concept of continuous development, so it is necessary to seek a new recycling way.In order to solve the problem of WGFRP recycling,WGFRP, which was modified by silane coupling agents and compatibilizer, was added to PP by melt compounding. The processing conditions of PP composites were studied. The mechanical properties of the composites were tested. The optimal composition of the composites was selected. The microstructure and toughening mechanism of the PP composites were investigated. The PP composites with better mechanical properties and higher thermal stability were obtained. The research contents and main achievements are as follows:(i) The PP/WGFRP/PP-g-MAH composites were prepared by adding compatibilizer PP-g-MAH and WGFRP which was treated by silane coupling agents (KH550, KH560, KH570). The effects of WGFRP mesh and contents, types of silane coupling agents, compatibilizer contents on the tensile strength, impact strength, flexural strength, flexural modulus of the composites were investigated. The crystallinity and thermal stabitlity of the PP composites were studied by differential scanning calorimetry (DSC) and thermogravimetric analyzer(TGA), respectively. The morphology of the PP composites was observed by scanning electron microscope (SEM),and the toughening and reinforcing mechanism of the PP composites were discussed.The results show that when WGFRP(100 mesh and modified by 1wt% KH570)was 20 phr, compatibilizer PP-g-MAH was 2 phr,the impact strength of the composites was 7.66 kJ/m2,25% higher than the composites without compatibilizer, 113% higher than pure PP; The tensile strength was 29.37 MPa, 11% lower than pure PP. The results of DSC indicat that the addition of WGFRP reduces the crystallinity of PP, but does not change the crystal morphology of PP. TGA results suggest that thermal stability of PP increases with the increase amount of WGFRP and increase with the increase mesh of WGFRP.(ii) The double-surface orgno-modified montmorillonite(OMMT-3) was prepared by cetyltrimethyl ammonium bromide(CTAB) and KH550. The amount of OMMT-3 on the mechanical properties of the composites was investigated. The micro-structure of montmorilllonite,modified montmorillonite and their composites was studied by XRD; The thermal stability of PP/WGFRP/PP-g-MAH/OMMT-3 composites was studied by TGA; The morphology of the composites contaning double-surface orgno-modified montmorillonite was observed by SEM and transmission electron microscopy (TEM).When the weight ratio of PP,WGFRP,PP-g-MAH and OMMT-3 was 100∶20∶2∶5, the tensile strength, impact strength, flexural strength and flexural modulus of the PP/WGFRP/PP-g-MAH/OMMT-3 were 34.22 MPa, 46.88 MPa, 1650.22 MPa respectively, reached the maximium values, and impact strength was 7.94 kJ/ m2, closed to the value of the composites filled with pristine montmorillonite. The double-surface orgno-modified montmorillonit(eOMMT-3)has the best toughening and reinforcing effects for the composites. XRD results reveal that the interlayer spacings of CTAB modified montmorillonite (OMMT-1),KH550 modified montmorillonite (OMMT-2) are 2.41 nm and 1.55 nm. The double-surface orgno-modified montmorillonite(OMMT-3)presents a wider reflection peak at about 2θ= 3.68 ~ 4.52°, which corresponds to interlayer distance of d001=1.96 ~ 2.40 nm(the interlayer spacings of MMT is 1.54 nm). For PP/WGFRP/PP-g-MAH/OMMT-3 composites, a peak due to the clay layer spacing was nearly disappeared,a wide and weak peak appeared from2θ=2.3°to 3.3°. It suggests that some intercalated structure have not been exfoliated. TGA results show that the thermal stability of the composites increased by the increase amount of OMMT-3. SEM reveals that the impact fracture surface of composites became coarse when OMMT-3 was added. The results of XRD and TEM show that PP/PP-g-MAH/OMMT-3 (100/20/2/5) composites are nanocomposites in which exfoliated structure and intercalated structure coexist.