| Weft-knitted spacer fabric is a kind of novel cushioning material for personal protection,which contains two outer layers and a spacer layer.Compared with traditional personal protective cushioning materials,the knitted structure of spacer fabrics offers better thermal and moisture comfort and body fit,and is also more environmentally friendly.However,the current research on weft-knitted spacer fabrics still mostly stays at the theoretical level,with few practical applications and a low degree of industrialization.The purpose of this thesis is to develop high-energy-absorbing,comfortable and breathable one-piece sports protective equipment based on weft-knitted spacer fabrics.Four polymeric monofilaments with the same diameter(0.12 mm)including PET,PA6,PBT and PE,which widely used in industrialization,were selected as spacer yarns.Polyester spandex double covered yarn(100 D/100 D/210 D)was selected for the surface layer.Four weft-knitted spacer fabric structures with four stitch connecting distance of the spacer pattern were prepared on a computerized flat knitting machine(E7.2).A series of tests were conducted to study the relationship between the spacer monofilaments properties and the compression characteristics of spacer fabrics.To investigate the influence of heat steaming on the tensile,bending and compression properties of spacer fabrics,a low melting point(85°C)nylon thermal fuse(110 dtex)was introduced into the upper and lower layers of the spacer fabrics by using plating technique,and the surfaces of fabric samples were heat treated for 30 s,1 min and 2min,respectively.Oval with segmented weft-knitted spacer fabric protective kneepad was knitted on the computerized flat knitting machine.It was observed from side view of the fabrics that there are obvious morphological differences among the fabrics on the machine and off the machine.The yarn consumption of PET monofilament was lower than those of the others,so the post-buckling of the spacer monofilament of the other fabrics are more evident than that of the PET fabric.The fabrics were subjected to 50 cycles of compression testing on a INSTRON universal material testing machine,and the maximum strain was 75%.The single and multiple compression properties of the fabrics were analyzed and compared.It was found that the energy absorption and compression resistance of PET fabric were about 40–50% higher than other fabrics in the first40% strain of single compression.PA6 and PBT fabrics had the best compression resilience,and the overall energy absorption were about 20% higher than PET fabrics after 50 cycles of compression.PE fabric showed compressive resistance only in the first three compression cycles and had the lowest energy absorption.The tensile properties and surface morphology of the monofilaments after knitted and compression test were analyzed.It was found that monofilaments with good tensile recovery had positive effect on the compression recovery of fabrics,and the fractured surface morphology of PE monofilaments were observed.The effects of different heat steaming durations on the mechanical properties of the spacer fabrics were studied.After heat steaming,the horizontal and vertical ductility and stability of the fabric surface were improved,the bending stiffness of the fabric increased,and the energy absorption of the fabric at the first compression was increased from 4 J up to 8 J.However,long heat steaming time led to significantly decrease both compression resilience and air permeability of the spacer fabrics.Combining the plating-intarsia technique with the spacer fabric,the plating spacer fabric was successfully embedded into the interlock rib fabric.The curved edge and segmented knitting method were designed,which solved the problem of high bending stiffness of plating fabric and improved the overall flexural flexibility of the fabrics.It is expected that the findings from this thesis would provide useful information for developing high quality weft-knitted spacer fabrics for personal protection for human body. |
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