The Effect Of Properties Of Luffa Sponge Mattresses On The Pressure Distribution On Human-bed Interface

Luffa sponge?LS?is the natural plant fiber materials with rich resources,low carbon,environmentally friendly,renewable and biodegradable.It is of great significance for the development of low carbon economy to expand the application of luffa sponge.In this paper,the LS fiber bundles and columnar LS are used as filling materials to develop LS mattresses.The transmission electron microscope?TEM?,scanning electron microscope?SEM?,polarized light microscopy?PLM?,fourier infrared spectrometer?FTIR?,X-ray diffraction?XRD?are used to study the micro/nano-structure and chemical component of luffa sponge.In addition,the tensile properties and moisture regain of LS fiber bundles were tested according the ASTM.And these results would provide scientific theoretical basis for the development and design of the filling material of LS mattress.Three methods of alkali treatment were used to soften the LS fiber bundles and one optimal solution which could enhance,toughen and soften the LS fiber bundles were found and the mechanism were studied.Furthermore,as a sleeping platform,mattresses have an important influence on the human body.The pressure distribution of human-bed interface is an important aspect of sleep comfort.Therefore,in thia paper,on the basis of research of mattress filling materials,the effect of mechanical properties,material characteristics,and structure feature on the human-bed interface were studied with taking gender and body types into full consideration.It provided a scientific basis for the establishment of the human-bed matching relationship and the humanized design and customized production of the mattress?The main conclusions of this paper are as follows:?1?LS is a kind of fiber bundles with irregular holes in the axial direction and abundant grooves and micro cracks on the surface of fiber bundles.The diameter of LS of high density?H.D?is about 450-640um,which is larger than that of low density?L.D??280-450um?.Microscopical observation showed that there is 1 cavity in the middle part of the low density Luffa fiber bundles,and there are 2 or 3 cavity in the high density Luffa fiber bundles,and the distribution was irregular.The proportion of fiber in LS fiber bundles of H.D is about 72%-80%,and that of L.D is 75%-87%.LS fiber are shuttle type and easy to bend,of which the length is between 1050-1700um,the diameter is between17-28um,the fiber wall thickness is between 3-8um.There is little difference between the length and diameter of the luffa fiber of H.D and L.D,but the wall cavity ratio of luffa fiber of H.D?0.29-0.39?is significantly higher than that of LS fiber of L.D?0.18-0.20?.In addition,the wall layer of luffa fiber cell is mainly composed of intercellular layer,primary wall and secondary wall,and the secondary wall consists of two layers?S1 and S2?.?2?The 24 hour moisture regain of the LS fiber bundle is higher than that of jute and Arenga engleri fiber,which is related to the groove,micropore and microcrack structure on the surface and the axial hollow structure of the fiber bundle.The moisture regain of LS fiber bundles of L.D is between 10.2%-10.9%,and the moisture regain of LS fiber bundles of H.D is relatively low,with a range of 7.1%-9.3%.The tensile strength of LS fiber bundles of L.D has excellent tensile properties,of which the tensile strength is between 53.82-91.63MPa,the elongation at break is between 4.98-9.81%,and the young's modulus is between 918-1897MPa.What's more,the fiber bundles of the LS has a high specific modulus between 2.07-4.05MPa*m³/Kg,and superior to Arenga engleri fiber.In addition,the mechanical properties of LS fiber bundle of L.D are relatively better than that of H.D,Which is related to the relatively high fiber tissue ratio of LS fiber bundles of L.D and the uneven cavity formed by the abscission of the phloem tissue of LS fiber bundles of H.D,which will reduce the tensile mechanical properties of the fiber bundles.?4?Three softening methods have changed the structural characteristics,mechanical properties and moisture regain of LS fiber bundles to a certain extent.The tensile strength and elongation at break of LS fiber bundles of H.D treated by10%NaOH-20%CH₃COOH increased by 121.3%and 296%respectively,while young's modulus decreased by 54.9%.This indicated that stiffness of LS fiber bundles decreases,while elasticity and flexibility increase.The cellulose crystallinity of LS was 36.4%and increased by 49.2%than that of the untreated LS,which promotes the mechanical properties and durability of the LS fiber.Thus,it was beneficial to the processing and utilization of the filling material of the LS mattress.After treatment,the moisture regain of LS fiber bundles is 7.34%,which is still higher than jute fiber.When used as mattress filling material,it can ensure the dry interface of the mattress.?5?The structure and material of Luffa mattress cushion have significant influence on the pressure distribution of Luffa mattress bed.The memory cotton mattress has good pressure reduction property.Adding the flocculus luffa cushion to the bottom of the memory cotton can further improve the pressure reduction property of shoulder and buttocks in supine position.Adding the columnar luffa cushion to the bottom of the memory cotton can increase the fitting degree of the mattress and the body in the supine and lateral position,and improve the pressure reduction property of the shoulder in supine posture.The addition of latex cotton on the top of these cushions can not only improve the pressure reduction property of the shoulders and buttocks,but also improve the fitting degree of mattress.Adding the columnar luffa cushion to the bottom of latex cotton would decrease the fitting degree of mattress,but it had better pressure reduction property on the shoulder and buttocks.?6?With the increase of BMI,the average pressure of human bed interface increased and the maximum pressure and pressure index decreased.The maximum pressure and contact area of high pressure threshold range of the Hourglass type subjects was higher than that of the Apple type in lateral state.This is due to the obvious body curve of the hourglass type subjects,and the pressure concentration in the shoulder and buttocks is easy to produce in the lateral state.However,in the supine condition,the maximum pressure of shoulder of Apple subjects on palm mattress was higher than that of Hourglass type subjects.Due to excessive body subsidence,the softer cotton mattress squeezed on both sides of the body of Hourglass subjects resulted in greater average pressure,while towel gourd mattress could better support Hourglass subjects.The pressure reducing effect of Luffa mattress is slightly worse than that of cotton,but far better than that of brown mattress.?7?There is a difference in the pressure distribution between men and women,and the maximum and average pressure of men are higher than that of women,but the sensitivity of male to mattress hardness is stronger than that of women.