Study On The Properties Of Silvergrass Fibers Reinforced High Density Polyethylene Composites

In this study, the effects of different treatments and process methods on the properties ofsilvergrass reinforced HDPE composites were investigated as well as compared with those of thewood fiber reinforced HDPE composites. The main conclusions can be drawn as follows,1. The mechanical properties of the treated composites compared well with those ofuntreated composites. A marked improvement of49.0%in tensile strength and47.4%in flexuralstrength for40%silvergrass (SV) reinforced high density polyethylene (HDPE) composites canbe obtained. It is also found that the crystallinity of composites was increased due to the treatedfiber acted as nucleating agent. Compared with that of the untreated wood plastic composites(WPCs), the contact angels of NaOH and combined treated30%,40%and50%SV reinforcedWPCs were improved. At the same time, the water absorption of combined treated WPCs wasdecreased. And the interfacal compatibility of NaOH and polymeric methylene diphenyldiisocyanate (PMDI) treated WPCs was better than that of the untreated or NaOH treated WPCs.2. The mechanical properties of WPCs were improved due to the maleated polyethylene(MAPE) was effective for increasing the interfacial adhesion. When adding MAPE into thecomposites, the crystallinity and thermal stability of WPCs were improved. Moreover, the resultsshow that with MAPE adding, SV can act as heterogeneous nucleating agent. The tensile andflexural strengths of compression molded WPCs were greater than those of injection moldedones, when8%MAPE was added into the composites. However, the contact angels of injectionmolded WPCs were better than those of compression molded ones. Moreover, the waterresistance properties of injection molded composites were also better than those of compressionmolded ones.3. It can be concluded that, when SV: PMDI=6:1(mass ratio), the mechanical properties ofWPCs can be reached the maximum values at50%SV fibers. Compared with those of theuntreated WPCs, the tensile and flexural strengths of WPCs were improved126.1%and105.1%respectively. It is also found that the crystallinity of composites was increased due to the treatedfiber acted as nucleating agent. At the same time, the water absorption of PMDI treated WPCswas decreased by78.6%,80.3%79.8%and78.1%compared with those of the untreated WPCs.Moreover, the contact angels of WPCs were increased as well as the interfacial compatibility wasbetter.4. It can be found that, when SV: PMDI=6:1(mass ratio), the mechanical properties ofWPCs can be reached the maximum values at50%SV fibers with treated by8%MAPE. It alsoshowed that when the SV fibers were treated by MAPE or PMDI, SV can be an effectivenucleating agent. However, when SV fibers were treated by PMDI and MAPE, the SV fibers had a negative effect on the degree of crystallinity. Compared with that of the untreated or PMDItreated WPCs, the thermal stability of combined treated ones was improved,while the contactangels of distilled water on the surfaces of the combined treated WPCs were samller than onthose of PMDI treated ones, though still better than on those of untreated ones. Through thereaction mechanism of PMDI and MAPE modified silvergrass, it can be concluded that at thelow MAPE content, MAPE can be reacted with PMDI and–OH more easily.5. When adding8%MAPE, the mechanical properties and crystallinity of silvergrassreinforced composites were almost the same as those of the wood fibers reinforced composites.At the same as, the contact angels of MAPE treated50%silvergrass reinforced composites andwood fibers reinforced composites became91°and88°respectively. Compared with thatof theuntreated composites, the water absorption of treated composites were also decreased.Meanwhile, the interfacial compatibility of treated composites became well. Therefore,silvergrass can be applied to prepare WPCs substituting for the wood fibers.6. The mechanical properties of8%MAPE treated WPCs can be reached the maximumvalues when the injection pressure was110MPa. The crystallinity of composites was decreasedwith the injection pressure; the water absorption of the composites was affected by both the fibercontent and the injection pressure.