Preparation And Utilization Of Microcrystalline Cellulose From Wheat Straw

Recently,polymer materials have played an important role in daily life and industrial fields.This is due to the increased environmental pollution.It is necessary to find renewable,biodegradable polymer materials instead of petroleum-based products.Polylactic acid(PLA)is a versatile polymer made from renewable agricultural raw materials that has properties such as biodegradability,recyclability,transparency,and ease of processing.It is mainly used for food packaging,disposable cups,etc.However,it also has the defects of brittleness,poor impact resistance,instability to heat and high price,which limits its further development and application.Polyethylene(PE)is also a very commonly used polymer material and is widely used in the field of films.It also has disadvantages such as poor heat resistance,resistance to photooxidation and non-degradability.Some inexpensive and high-quality substances can be added to them to improve certain aspects of their defects.One of the most attractive natural fillers is cellulose.Natural fiber reinforced polymer composite technology focuses on low cost and high performance.China is a big agricultural country and produces a large amount of crop stalks every year.Among them,21% are wheat straw and straw contains a lot of cellulose components.Add cellulose or its derivatives to polylactic acid and polyethylene to improve the mechanical properties of PLA and the degradation properties of polyethylene.In this way,better polymer products can be obtained and at the same time agricultural waste can be utilized.The main research results are as follows.1.Preparation of microcrystalline cellulose(MCC).The raw material used was wheat straw cellulose.The method used was the dilute acid hydrolysis.Finally,the most suitable experimental conditions(reaction temperature 140 °C,sulfuric acid concentration 2%,reaction time 3 h,solid-liquid ratio 1:10)were used for SEM,XRD and FT-IR tests.SEM analysis of MCC showed very good removal of amorphous regions in cellulose.By calculating the crystallinity of the XRD pattern,a high crystallinity value of 67.33% was obtained.MCC had the same structure as cellulose by FT-IR.At this condition,the sugar content in the sugar liquid was 33.20%.Through thermal performance analysis,it was shown that MCC had more flame retardant type I crystalline cellulose at high temperatures.2.Composites of microcrystalline cellulose and polylactic acid.By adding different proportions of MCC(2 wt%,4 wt%,6 wt%,8 wt%)in combination with PLA,it was found that composites added by 4 wt% microcrystalline cellulose had the best tensile properties.The tensile strength was 73.01 MPa.Compared with PLA,this value was increased by 8.40% and the elastic modulus increased by 2.62%.Composites with different amounts of microcrystalline cellulose also exhibited the better flexural modulus(except PLA-8)and the flexural strength.XRD and DSC analysis,adding MCC increased the crystallinity of the PLA/MCC composites.3.Composites of microcrystalline cellulose and polyethylene.Different amounts of microcrystalline cellulose(2 wt%,4 wt%,6 wt%,8 wt%)were compounded with polyethylene.Finally,they were mainly physical composites from FT-IR.Through the XRD pattern,it was found that the addition of microcrystalline cellulose had a significant change in the crystallinity of polyethylene.The tensile properties of the test showed that the composites with microcrystalline cellulose added,there was some reduction in the tensile strength,but they still had the good tensile strength.