Preparation And Properties Of Recycled Fibers Filled Wood Plastic Composites

As a new environmental friendly material, wood plastic composite (WPC) has been paidmuch attention in recent years because of wide material sources, low cost, nice appearance andlight quality, which has been widely used in automobile, furniture, packaging and constructionindustry. However, the application of WPC in structural engineering area is still restricted becauseof its low mechanical strength and bad impact resistance. Therefore, how to improve themechanical properties of wood plastic composites has become one of the main research directionsin the study WPC.In this study, recycled fibers were successfully obtained from waste textiles using a PFI mill,and high density polyethylene (HDPE)-based wood plastic composites reinforced with recycledfibers were manufactured. The properties of the WPC were investigated by mechanical propertytest, Thermo-gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and ScanningElectron Microscopy (SEM). All these researchs were aiming at exploring innovation methods torecycle waste textiles, and getting composites with well general mechanical properties. The mainwork and results are as follows:1. Waste polyester (PET) fabrics and cotton textiles were chosen as recycling materials, andthe beating process of waste textiles with PFI mill was studied. We found that several controllablefactors existed in the beating process, including rotation number, beating spacing, beating pressureand beating concentration, among them rotation number and beating spacing were the mostimportant parameters that influenced the dispersion of recycled fibers. Too small beating spacinglead fibers tangling together easily, while too big one lead plenty of fiber bundles not broke up.The increase of rotation number is helpful for fibers dispersion, but too much will be inefficient.The optimal processing parameters were rotation number of3000r, beating spacing of2.4mm,beating pressure of3.37N/mm and beating concentration of10%. Under the optimal processingparameters, recycled fibers were well dispersed after beating.2. HDPE-based composites reinforced with different content of recycled fibers weremanufactured. The affections of fiber content and fiber length on the mechanical behavior ofcomposites were studied, also the thermal stability and crystalline properties were observed, andtwo different surface modification methods were compared with each other. The results showedthat the recycled PET fibers and cotton fibers dispersed well in HDPE matrix with the help ofMAH-g-PP as a compatibilizer. The mechanical performance of composites was enhanced withthe adding of PET fibers, whereas the cotton fiber caused decrease in the impact strength whenimproving the tensile and flexural performance. Thermal analysis revealed that PET fibers causeda increase in the degree of crystallinity, while the thermal stability remained stable. Conversely,cotton fiber made the thermal stability of the composites decreased significantly, but had no significant effect on the crystallinity. Moreover, the better overall performance could be obtainedwhen the mass fraction of MAH-g-PP was5%and the length of the fiber was10mm.3. Based on previously study, wood flour and HDPE were used as main starting materials,and a series of recycled fibers reinforced WPC were manufactured. The effects of fiber contentand heat treatment conditions on the mechanical properties and crystalline behavior of thecomposites were studied, respectively. The results showed that the recycled PET fibers, cottonfibers and wood flour dispersed well in the resin matrix, and PET fibers further improved thecomprehensive mechanical properties of WPC, while the tensile properties increased firstly andthen decreased with the further addition of cotton fibers, with an optimal value at10wt%cottonfibers. The flexural and impact strength tended to decrease with the increase of cotton fibercontent, which could be explained by the agglomeration of fibers. Thermal analysis revealed thatthe thermal stability of WPC had no obvious change with the incorporation of either recycledfibers, however the PET fibers increased the crystallinity and melting point of WPC. Thecrystallization properties of WPC were improved significantly after heat treatment with differenttemperatures. In the case of WPC reinforced with PET fibers, the flexural strength and moduluswere both decreased, the tensile strength changed little during the heat treatment, while the tensileand flexural performances of the WPC reinforced with cotton fibers tended to increase, with anoptimal heat temperature at120℃.