| Cotton fibers are one of the highest yielding natural fibers and the most important textile raw materials.With the continuous improvement of people's life,the life cycle of cotton textiles has been greatly shortened,so the waste cotton textiles are also increasing day by day.At present,the recycling methods on them still remain as rags or are directly discarded,buried,burned,etc.,which has a very low value of reuse,but also causes environmental pollution and enormous waste of resources.In response to this problem,the study uses waste cottom rags as raw materials.First,the rags are defibrated into a fiber form by a defibration process.Then,based on defibrated cotton fibers which are the substrate and the isocyanate-based adhesive PM-50 which is the adhesive component,by using the self-designed sizing system,pre-pressing mold and hot-pressing mold,a high-performance and high-density cotton fiber-based composite is prepared with compression molding process.The content of cotton fiber in the composite is higher more than 80 wt%,the physical and mechanical properties meet the highest requirements in GB-T31765-2015,especially,the internal bond strength and water resistance are far better than those of similar composites.It provides new ideas and solid experimental foundations for the high-value use of waste cottons.The main contents and results of the study are as follows:(1)The defibration of waste cotton rags is performed by alkaline peroxide mechanical pulping method.The effects of cooking temperature,cooking time,NaOH concentration,and H2O2 concentration on the defibration process are studied,as well as the length,width,fiber screening value,fiber morphology,cell wall thickness,cell diameter,chemical composition and surface active groups of defibrated cotton fibers.The study shows that when the amount of NaOH is 12 wt%,the amount of H2O2 is 3 wt%,the cooking temperature is 130°C,and the cooking time is 5 h,the cotton fibers with good dissociation can be obtained.The average length of the fiber is 1.01 mm and the average width is 12.72?m;the fiber length distribution is reasonable,and the surface of the fiber has a large number of active groups such as hydroxyl.In summary,it is theoretically a good substrate for composites based on plant fibers.(2)The defibrated cotton fibers are used as substrate,PM-50,which is the mixture prepared with a certain ratio of MDI and PMDI,is selected as the adhesive component,by using the self-designed sizing system,pre-pressing mold and hot pressing mold,a high-density cotton fiber-based composite is constructed.Then the orthogonal experimental method is adopted to study the effect of fiber moisture content,hot-pressing time,hot-pressing temperature,composite's density,and adhesive amount on the static bending strength,elastic modulus,internal bond strength,24-hour thickness swelling and the wet static bending strength of the composites.The results show that the composite prepared with 8 wt%water content,density of 1.08 g/cm~3,20 wt%adhesive content,hot-pressing temperature of160°C,and hot-pressing time of 2 min has the best performance,the static bending strength is47.2 MPa,the elastic modulus is 4040.6 MPa,the internal bond strength is 3.6 MPa,the thickness swelling is 11.1%,and the wet static bending strength is 20.6 MPa.(3)The chlorinated paraffin waterproofing agent and the reactive silicone waterproofing agent are prepared,the influence of heat treaTent conditions,the soaking time of reactive silicone waterproofing agent,amount of adhesive and chlorinated paraffin on the thickness swelling and the static bending strength of the the composite are further studied.The results show that increasing the adhesive content to 50 wt%,heating the composite at 200°C for 4 h,or dipping the composite with the reactive silicone waterproofing agent for 4 h are the effective ways to improve the water resistance of high density cotton fiber-based composites,the thickness swelling can be reduced to 5.8%,7.4%,and 7.3%respectively. |
PDF Full Text Request