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Young's modulus of biaxially oriented polypropylene (BOPP) films prepared with homemade film stretcher was investigated,which can be used to indicate the softness of fihns.It was found that the modulus of films was decreased by about 69% as the content of polyethylene (PE) added into polypropylene (PP) reached 30%.Also,increasing draw temperature can induce lower stress level during stretching,which may lead to the formation of crystals with low orientation level and thus decreased modulus of films.Based on laboratory study,BOPP films produced on commercial line were studied by differential scanning calorimetry (DSC),wide and small-angle X-ray scattering (WAXS,SAXS) with varying contents of PE.SAXS results show that the crystals are oriented in both machine direction (MD) and transverse direction (TD),and the crystals are more oriented in TD than MD according to the WAXS results for all films.Also,the orientation parameter of crystal along TD increases from 0.68 to 0.83 as the contents of PE increase from 0% to 25%.Meanwhile,the modulus of films in MD declines with increase of PE contents generally,improving the film softness.Orientation of crystals is thus an effective structure parameter to adjust the film softness.The relationship of processing-structure-property is also established. 相似文献
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A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors and scissorlike mechanism, all stretching modes, including uniaxial stretching with constant and free width, simultaneous and sequential biaxial stretching, can be applied to a square-shaped sheet. Parameters related to film stretching manufacturing, such as temperature, draw ratio and stretching speed can be set independently to meet the requirement of different polymers. The force information during stretching is recorded by two miniature tension sensors in two directions independently, which can monitor the mechanical stimulus and stress response. Using this equipment, experiments are conducted to investigate the influence of stretching parameters on the structure of polypropylene films, which provides an effective method to tailor the processing conditions to obtain the films with desired properties. 相似文献
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由付里叶分析到小波分析的进展 总被引:3,自引:0,他引:3
本文通过对付里叶分析和小波分析的详细比较 ,展示小波分析的特点和优越性 ,有助于深化对小波分析的认识和理解 相似文献
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