Study On Ramie Knitted Composites

In this work. Ramie yarn was chose as reinforcement, polypropylene filament and polylacticacid was chose as matrix to prepared ramie/ PP, ramie/ PLA knitted composites usedcompression molding technique. The knitted structure prefabricate was weaved half-milanorib stitch, milano rib stitch, half-gauge rib stitch, full needle rib stitch. The factors of precaststructure, fiber content, curved yarn depth and molding process parameters affect tensileproperties and impact properties were discussed on ramie/ PP. The factors of fiber content,curved yarn depth and molding process parameters and different ways of surface treatmentaffect tensile properties and impact properties were studied on ramie/ PLA, the tensile fracturecross-section shape of composites were observed by SEM.Through the analysis of prefabricate: When the knitted structure was half-milano rib stitch,ramie fiber content was 50%, curved yarn depth was 9, the tensile strength of ramie/ PPprefabricate were best. When the ramie fiber content was 33%, curved yarn depth was 8, thetensile strength of ramie/ PLA prefabricate were best.Through the analysis of ramie/ PP composites: The technology of composites reachedthe best when the molding pressure was 10MPa, holding time was 10min, temperature was185℃. Half-milano rib stitch composites transverse tensile strength(16.4MPa) and tensilemodulus(1432.2MPa), longitudinal tensile strength(33.3MPa) and tensilemodulus(2156.4MPa), transverse impact strength(21.3KJ/m2) and longitudinal impactstrength(28.3KJ/m2) were the best when the curved yarn depth was 9 and fiber content was50%. The elongation at break was same rule as curved yarn depth and declined as the increaseof fiber content.Through the analysis of half-milano rib stitch ramie/ PLA composites: The technology ofcomposites reached the best when the molding pressure was 10MPa, holding time was 8min,temperature was190℃. The composites transverse tensile strength(22.4MPa) and tensilemodulus(2128.7MPa), longitudinal tensile strength(36.6MPa) and tensilemodulus(2858.3MPa), transverse impact strength(24.5KJ/m2) and longitudinal impactstrength(33.4KJ/m2) were the best when the curved yarn depth was 8 and fiber content was33%. The transverse elongation at break was 7.5% and the longitudinal was 5.1%.Through the observe on SEM: The mechanical properties of the ramie/ PLA compositeswere improved under these different fiber surface treatments, and surface of fiber wasgranulated. By comparison, 8% NaOH treatment 40 minutes improved the mechanicalproperties of composites which transverse tensile strength could increased to 27.7 MPa andlongitudinal to 40.1 MPa, transverse impact strength could increased to 28.3KJ/m2andlongitudinal to 37.6KJ/m2. 3% A-151 treatment 20 minutes improved the mechanical properties of composites which transverse tensile strength could increased to 28.2 MPa andlongitudinal to 41.6 MPa, transverse impact strength could increased to 30.8KJ/m2andlongitudinal to 39.2KJ/m2.