Synthesis Of Hyperbranched Polymer Emulsion And Its Assistance In Improving The Water Resistance Of Medium Density Fiberboard

Medium density fiberboard?MDF?has developed rapidly and smoothly with good mechanical properties,high flexural strength and high impact strength.It has developed rapidly.Water molecules will enter the gap of MDF due to the many pores between wood fibers,which results in deformation,expansion,and the mechanical strength will be weakened,affecting the application field and service life of MDF.Therefore,it is necessary to add water repellent to improve the water resistance of MDF,which is the main purpose of the paper:Hyperbranched polymer?HBP?has a three-dimensional network structure,a large number of cavities in the interior,and a large number of active groups at the end,which can be modified well,giving it more excellent performance.The application and development of HBP have been actively promoted due to the special structure of HBP and its broad application prospects.The main work of the research:1.The synthesis and characterization of hyperbranched paraffin emulsionFirstly,the AB₂ type monomer was synthesized from succinic anhydride and diethanolamine,and then trimethylolpropane was used as the core molecule to synthesize a terminal hydroxyl group HPAE by controlling the nuclear molecule and AB_2.The second,third and fourth generation terminal hydroxyl HPAE were obtained at ratios of 1:9,1:21 and1:45.The final synthesized terminal hydroxyl HPAE was characterized of by Fourier transform infrared spectroscopy,nuclear magnetic resonance spectroscopy,hydroxyl value determination,elemental analysis and so on.The synthesized terminal hydroxyl group HPAE is then modified with acrylic acid?AA?to synthesize a double bond-terminated hyperbranched polymer.The final synthesized hyperbranched polymer is characterized by Fourier transform infrared spectroscopy,hydroxyl value determination,double bond content,etc.;The synthesized double bond terminated HPAE undergoes free radical initiation under the action of an initiator,and then it is grafted with paraffin?PF?,and then the hyperbranched paraffin?HBPF?synthesized,which was tested by Fourier infrared test,double bond content and so on.The hyperbranched paraffin emulsion?HBPFE?was synthesized by adding an appropriate amount of emulsifier to the hyperbranched paraffin,and was characterized byFTIR,and the properties was tested by viscosity and dry film water absorption rate were tested.2.Synthesis and characterization of hyperbranched polyacrylate emulsionThe above-mentioned synthesized double-bonded HPAE is used as a monomer to react with methyl methacrylate?MMA?and butyl acrylate?BA?to polymerize under the action of an initiator and an emulsifier to synthesize a hyperbranched polyacrylate emulsion?HBAAE?,then the synthesized HBAAE was subjected to Fourier infrared test,double bond content test,and performance tests was was tested by viscosity and dry film water absorption.3.MDF water resistance testIn the process of MDF molding,commercially available PF emulsion and HBPFE were added as water repellent,comparing the effect of commercially available PF emulsion and HBPFE on MDF performance by the water swelling ratio and mechanics of the molded MDF;Commercially available AA emulsion and HBAAE were added as water repellent,comparing the effect of commercially available AA emulsion and HBAAE on MDF performance by the water swelling ratio and mechanics of the molded MDF.Finally,comparing the effect of HBPE and commercial emulsion on MDF performance;and analyzing the optimal amount of HBPE to produce the best effect on MDF.We can know from the experimental results:1.The commercially available PF emulsion can improve the water resistance of MDF,and the water absorption thickness expansion rate can reach up to 9.5%,but the addition of the commercially available PF emulsion reduces the internal bonding strength of MDF to some extent;Adding HBPFE can not only improve the water resistance of MDF?the water absorption thickness expansion rate reaches 9.4%?,but also has less influence on the bond strength in MDF than the commercially available PF emulsion.2.The commercially available AA emulsion can improve the water resistance of MDF,and the water absorption thickness expansion rate can reach 10.0%,but the addition of a commercially available AA emulsion reduces the internal bond strength of MDF to some extent;Adding HBAAE can not only improve the water resistance of MDF?the water absorption thickness expansion rate reaches 9.5%?,but also has less influence on the bond strength in MDF than the commercially available AA emulsion.We can apply the successfully synthesized HBPE to improve the water resistance of MDF from comprehensive analysis,the water resistance of HBPE is better than the commercial emulsion,but in the case of achieving the same water resistance,the amount of HBPE added is generally smaller than that of the commercially available emulsion,and its effect on the mechanical properties of MDF is also smaller than that of the commercially available emulsion.