Study On Preparation Of Aluminum Hydroxide Microcapsule And Its Application In WPC

Aluminum Hydroxide (ATH) can replace halogen flame retardants as composite flame retardant additives for its excellent characteristics, such as nonhygroscopic, smoke suppression, non-poisonous and environmental protection performance.But there exsit some negative effect on mechanical properties of the composite materials due to its low flam retardant efficiency and poor compatibility with the polymer.So it is critical to modify Aluminum Hydroxide. This paper was based on the existing literature on the use of microencapsulation technology to encapsulate ATH and its compound with ammonium polyphosphate (APP), and explored the influence on wood-plastic composites (WPC) performance before and after ATH microencapsulation modification.Melamine and formaldehyde as raw materials, effects of the prepolymer temperature (X1), time (X2), pH value (X3) and their interactions on melamine formaldehyde resin (MF) prepolymer viscosity were studied by response surface analysis method, the model equationY=0.71+0.00575X1+0.017X2-0.035X3+0.0065X1X2-0.01X1X3-0.016X2X3-0.031X12+0.018X22-0.0017X32was gain-ed.Variance test showed that prepolymerization time, pH value and their interactions had extremely significant effects on the viscosity of the prepolymer, temperature and its interaction with pH value were significantly affected. On this basis, the better aluminum hydroxide microcapsule(MATH) product with good morphology and smaller diameter was gained under the condition of70℃,60min,1200rpm, core/wall=1.0and pH value=5.0through orthogonal analysis method. Characterization for chemical structure, surface morphology of MATH was analyzed with Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM). The results showed that FTIR spectrum of MATH include characteristic absorption peaks of ATH and MF decreased, XRD diffraction peak intensity decreased,too, compared with ATH, indicating that ATH was encapsulated by MF, this conclusion could be confirmed by ESEM micrographs.In order to overcome shortcomings of single flame retardant with low flame retardant efficiency, the synergistic complex (ATH/APP) with different mass ratio of ATH and APP was used as core material in this paper, MF was used as wall material to prepare microcapsule. Characterization was conducted by FTIR, XRD, ESEM and TG/DTG. The results showed that, both decrease of FTIR spectra absorption (including ATH, APP, MF) and XRD crystallinity diffraction peaks intensity of microcapsule indicated that (ATH/APP) was encapsulated by MF, which can be confirmed from ESEM micrographs, TG/DTG analysis showed that thermal decomposition properties of microcapsules with different mass ratio of ATH and APP changed a little, but char yield (%) in700℃were slightly lower than MATH.ATH, MATH and M (ATH/APP=1:1) were added into mixture of fir wood flour and HDPE to prepare flame retarding wood plastic composite materials, effects of different dosage of flame retardant on properties of composite materials were investigated. The results showed that, tensile strength of WPC decreased with addition content increasing of ATH, but showed a first increased,and then decreased trend when added MATH and M(ATH/APP=1:1),both of this two WPC with microcapsules had maximum tensile strength when addition content of flam retardant was20%, increased by7.87%and6.91%, respectively, compared with WPC,flexural strength of WPC increased with addition content increasing of ATH,while WPC with MATH and M(ATH/APP=1:1) had maximum flexural strength when addition content of two microcapsules were20%and30%, respectively,and the increasing percentage were11.33%and14.74%compared with WPC, impact strength of WPC decreased with addition content increasing of flam retardant;After ATH microencapsulation, compatibility between microcapsules and HDPE matrix has been significantly improved, while compatibility between M (ATH/APP) and HDPE matrix was slightly worse than MATH; Oxygen index of WPC increased with addition content increasing of three different kinds of flam retardant, WPC with M (ATH/APP) had the maximum oxygen index compared with other composite materials in the same addition content, and its thermal stablility was higher than composite material with MATH,indicating that after complex retardant microencapsulation,ATH and APP can play a synergistic role, both ATH, MATH and M(ATH/APP=1:1)could improve the final char yield of WPC.