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Characterization on Moso Bamboo Bonding Interface on Microscale

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Tutor: GuanMingJie
School: Nanjing Forestry University
Course: Wood Science and Technology
Keywords: Carbonized bamboo,Bleached bamboo,Properties of bonding interface,Polyvinylalcoh
CLC: TS652
Type: Master's thesis
Year:  2013
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Abstract:
The resources of bamboo are abundant in our country. And lots of researches about bamboohave been done on the product development, process modification and so on. But there are fewresearches about interface characterization in microscale of bamboo composites. In this paper, weused carbonized bamboo and bleached bamboo as our raw materials, common used PF modifiedby different proportion of low molecule PF and PVA as our adhesives, and had an analysis ofheating effect changing under adhesive curing and molecule weight distribution. In addition,many testing ways had been conducted on comparison between microscopic bamboo interfacemorphology, strain distribution with macroscopic bamboo shear strength such as fluorescenttrack technology, electronic speckle pattern interferometry and bonding strength test. Researchmethods and results were as follows:1) Heating effect changing of three adhesives: ordinary PF, low molecule PF and20%PVAhad been studied under adhesive curing by the method of DSC (differential scanning calorimetry).It indicated that glass transition point of low molecule PF was lower than the other two adhesives,and20%PVA got the maximum glass transition point with sharp exothermic peak and fiercereaction.Molecule weight distribution of ordinary PF and low molecule PF had been studied. Resultsshowed that under the premise of slowing down activating reaction temperature, dispersivity ofadhesive was prone to be uniform by the method of extending activating reaction time.2) Adhesive permeability of two kinds of modified PF had been studied in the carbonizedbamboo bonding interface and bleached bamboo bonding interface by using fluorescencemicroscope. These two kinds of adhesives were ordinary PF with low molecule PF and PVArespectively in various proportions. Results showed that with the percentage of low molecule PFincreasing, modified PF with low molecule PF got the better permeability effect with sufficientadhesive in bonding interface; under different content of PVA, we could see the obvious reducedpenetration effect as the percentage of PVA increasing; And also, by and large penetration effectof adhesive in carbonized bamboo bonding interface was better than that in bleached bamboobonding interface.3£©Strain distribution in the bleached bamboo bonding interface had been studied by themethod of electronic speckle pattern interferometry in the shear strength testing. The resultsshowed that under different content of low molecule PF, strain distribution in bonding interfaceglued by modified PF with10%low molecule PF was obviously lower than the others whichmight lead to larger elasticity modulus; under different content of PVA, we could see the apparent larger strain distribution as the percentage of PVA reaching20%which indicated that additionalPVAmight lead to microscopic interface slipping and energy releasing.4) In this chapter, it had been discussed about the macroscopic shear strength of carbonizedbamboo and bleached bamboo glued by modified PF with low molecule PF and PVArespectivelyin different proportions. The results showed that under different content of low molecule PF, dryshear strength of specimens glued by modified PF with10%low molecule PF reached themaximum value while wet shear strength was prone to decline as the percentage of PVAincreasing. Under different content of PVA, we got the optimal dry shear strength as thepercentage of PVA increasing to20%while wet shear strength decreased with the percentage ofPVA increasing, for hydroxyl was prone to absorb moisture on hydro-thermal treatment whichwould lead to more stress concentration in bonding interface. Moreover shear strength variationtendency had little difference with two kinds of modified adhesives, it meant that there was nocorrelation between shear strength variation tendency and treatment process; but shear strength ofcarbonized bamboo was generally larger than that of bleached bamboo glued by the sameadhesive, which was concerned to material itself strength changing by different processingtreatment.
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