| Ultra High Molecular Weight Polyethylene?UHMWPE?is an engineering thermoplastic with excellent comprehensive properties and its products are widely used.However,UHMWPE has many shortages,such as:poor processability and abrasive wear properties,low surface hardness and thermal deformation temperature,which limit its application.Cellulose is the most abundant organic polymer in nature.Nanocrystalline cellulose?CNC?is obtained from natural cellulose,with large surface area,high crystallinity,high strength,biodegradability and regeneration.CNC has great potential in the application of high-performance composites.In this work,the processability of UHMWPE is improved by the addition of polyethylene glycol?PEG?and high-density polyethylene?HDPE?.Then,CNC and organic-inorganic hybrids are prepared by acidic hydrolysis,sol-gel method and ultrasound-wet blending technique.The effects of nanofillers on the processability,mechanical properties,thermal properties and tribological properties of the UHMWPE composites are systematically investigated.Firstly,the effects of PEG on the properties of UHMWPE are studied and the results show that PEG play a role of unwrapping and lubrication in UHMWPE matrix.With the increasing PEG content,the processability of UHMWPE is improved while the mechanical properties are impaired.On this basis,the effects of HDPE on the properties of UHMWPE/PEG blends are researched.With the addition of HDPE,the processability of the materials is improved due to the good processability of HDPE and its compatibility with UHMWPE,but the tribological properties of the materials are deteriorated.The mechanical properties of the materials are optimal when UHMWPE/HDPE is 60/40.The CNC is prepared from microcrystalline cellulose?MCC?by sulfuric acid hydrolysis.The length,diameter and crystallinity of CNC are about 200 nm,10 nm and 73.9%,respectively.The one-dimensional-zero-dimensional Nanocrystalline cellulose-silica hybrid?CNC-Si O2?is prepared by sol-gel method.TEM and FTIR analysis show that Si O2 with a diameter of 20-30nm are tightly adsorbed on CNC through the covalent bond and hydrogen bond interaction between Si O2 and CNC,which forms a special“beaded structure”.TG analysis shows that the T5%,T10%and Tmax of the hybrid are 3.7%?6.48%?11.70%higher than CNC.Then,the UHMWPE/PEG composites are modified by blending with CNC and CNC-Si O2hybrid.It turns out that adding CNC or hybrid impair the processability of the composites,but no pressure oscillation occurs.Hybrid is superior to CNC in the modification of the mechanical properties,thermal properties,anti-friction and wear resistance of the UHMWPE/PEG composites.With the addition of 4 phr hybrid,the flexural strength,flexural modulus and hardness of the composites increase by 27.2%,82.4%,and 21.0%,and the friction coefficient,wear scar width and wear volume decrease by 43.3%,18.9%and 21.2%.The interface combination between the hybrid and matrix is better and the phase interface is fuzzier.The CNC effectively intercalates into the montmorillonite?MMT?sheets through ultrasound-wet blending technique.FTIR analysis shows that the CNC-MMT hybrid exists certain interactions?hydrogen bond,covalent bond and coordination?.TEM indicates that the most MMT sheets of the hybrid with a size of about 100 nm adsorb on the CNC,and only a few exist individually.TG analysis shows that,compared with CNC,T5%,T10%and Tmax of the one-dimensional-two-dimensional CNC-MMT hybrid are 20.4%,11.3%and 6.6%higher.The effects of CNC and CNC-MMT hybrid on the UHMWPE/HDPE/PEG composites are investigated.It turns out that the addition of CNC damage the processability of the composites,but the influence of the hybrid is not obvious.The addition of CNC and hybrid both increase the mechanical properties of the composites first and then decrease,and the optimum amount of the fillers is 3phr.With the increasing amount of CNC and hybrid,the heat resistance and tribological properties of the composites are gradually improved.The interfacial strength between the hybrid and matrix is stronger and the modifying effects of the hybrid are better.The flexural modulus and hardness of the composites increase by 64.3%and 30.2%,and the friction coefficient,wear scar width,and wear volume decrease by 32.1%,22.3%,and 29.7%with the addition of 4phr hybrid. |
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