Calcium Carbonate Nanoparticles In Situ Modification Of Bamboo Fibers And Their Composites

China has abundant resources of bamboo. Bamboo fiber reinforced composites, withhigh economic value and potential market, is one of the most important branches ofbamboo industry. As a reinforcing phase, bamboo fibers' surfaces and mechanicalproperties have a major impact on the interface and mechanical properties of composites.As the performance testing methods of single plant fibers have gained momentum inrecent years, the study of surface modification's effects on surface morphology, wettingand mechanical properties and other aspects of plant fibers, is the focus of currentresearches, to reveal surface modification's impacts on the mechanism of plant fibesreinforced composites'interfaces.The study applied an ironic solution reaction to in situ deposit calcium carbonate(CaCO₃) particles onto bamboo fibers. The situation of CaCO₃adsorbance, surfacefeatures of bamboo fibers (Neosinoealamus affinis) and tensile properties of individualbamboo fibers and fiber reinforced polypropylene composites were investigated. Optimalmodification process for the composites were obtained. Three kinds of fibers of bamboo,chinese fir and jute were modified with the optimal modification process. The fibersurface modification technology could provide theoretical basis for the application ofplant fibers in composites' field.The conclusions are summarized as follows:(1) The process parameters of temperature, additive (ethylene diamine tetraaceticacid disodium) amount, calcium chloride (CaCl₂) molarity have significant impacts onCaCO₃particles adsorbance, particle sizes and size distribution on bamboo fibers'surfaces. Nanoscale and submicron crystals could be obtained by controlling theparameters.(2) As CaCO₃adsorbance (below2.54%bamboo fibers' dry weight) increases, thebamboo fibers got reduced surface roughness (Rq value) and increased static contactangles. while CaCO₃adsorbances continued to increase, Rq increased and static contactreduced. CaCO₃particles filled bamboo fibers' pores, resulted in an increase of thedensity of the fibers, which could prevent the rapid deformation and rupture of the pitwith stretching test, thus, tensile properties of the modified single bamboo fibers were allimproved. (3) The conditions of optimal modification process for laminated bamboo fiberreinforced polypropylene composites were as followings: temperature at25°C, additiveamount at2.5×10^-3g/ml, CaCl₂molarity at0.2mol/l. The CaCO₃adsorbance, Rq, staticcontact angle, tensile strength and modulus of elasticity of modified single bamboo fiberswere6.96%,226.75,66.89°,1134.83MPa,37.25GPa, respectively. The tensile strength andmodulus of elasticity of of the treated bamboo fiber composites were54.04MPa,2.08GPa,10.49%,16.85%higher than those of the untreated bamboo fiber composites.(4) With the above optimum conditions, the trend for CaCO₃adsorbance of threekinds of modified plant fibers were as followings: chinese fir fiber (16.08%)> jute fiber(11.45%)> bamboo fiber (6.96%). After the treatment of in situ deposition of CaCO₃particles, bamboo fibers' Rq lowered while that of chinese fir fibers and jute fibersincreased, and the static contact angle of the bamboo fibers and chinese fir fibers reducedwhile that of jute fibers increasesd. The tensile properties of all three kinds of singleplants fiber were improved, with main increments of36.15%for the elastic modulus ofbamboo fibers, when tensile strengths of chinese fir fibers and jute fibers weresignificantly increased by29.28%,20.37%, seperately. The tensile properties of threekinds of modified plant fiber reinforced composites have been improved, with smallincrements of about10%in tensile strength, while the elastic modulus of plant fibercomposites improved significantly, the trend of which was similar as CaCO₃adsorbance'strend: chinese fir fibers (45.22%)> jute fibers (34.96%)> bamboo fibers (16.85%).