Study On Preparation And Performance Of High-efficiency And Long-lasting LLDPE Drip Shed Film

Thermal insulation and light transmission are the basic characteristics of plastic films used in the field of agricultural greenhouse films.Greenhouse films are often used in spring or winter.When the climate gets colder,there is a huge difference in temperature and humidity between the inside and outside of the greenhouse film.The phenomenon results in a large number of droplets on the inner surface of the film.The presence of droplets refracts the incident light and reduces the transmittance of agricultural films,therefore affects the growth and yield of crops.And these droplets absorb heat and the thermal insulation effect becomes poor.In order to solve the above problems,it is the current research focus to prepare a hydrophilic and long-lasting drop film.There are two methods for preparing the drip film:physical blending and covalent bonding.The drip film prepared by the grafting method has excellent dripping performance and a long shelf life,but the processing steps are cumbersome,the production efficiency is low and the environment is polluted.Therefore,only a simpler method can be used to produce an excellent drip film,in order to make further progress in this field.This article considers factors such as cost and process simplicity,It is of great practical significance to develop an efficient and durable drip film based on LLDPE as the matrix resin.In this paper,LLDPE is used as the matrix,GMS,Tween 60 and Span 20 as the dropping agent,and LLDPE-g-MA as the compatibilizer.Secondly,the use of ethylene-vinyl acetate copolymer?EVA?to increase the compatibility of the base resin and the drip agent and reduce the polymer crystallinity,Prepared LLDPE/EVA composite drip shed film to improve the retention period and light transmittance of the drip film.Finally,the film with the best retention period of drip is selected,and the TA/SA mixed coating is coated on the surface to prepare the outer drip shed film.Characterize the wettability,first drop time,dripping property,self-healing performance,drop retention period,mechanical properties and light transmittance of the above film,to explore the influence of the content of LLDPE-g-MA,the amount of dripping agent and the mixed coating on the performance of the drip film,The main contents and conclusions are as follows:?1?The dried LLDPE and LLDPE-g-MA were melt blended with GMS,Tween60 and Span20 to prepare LLDPE drip shed film with LLDPE-g-MA content of0-20 w%,explore the effect of the content of LLDPE-g-MA on the performance of the drip film.Results show,The film thickness is 0.08mm,When the content of LLDPE-g-MA is 20 w%,the contact angle of the drip film is 73.8°,the first dropping time is 229 s,and the dripping duration is 6 days,which meets the national standard.When the content of LLDPE-g-MA is 10 w%,the contact angle of the drip film is61.7°,and the first dripping time is 132 s,both of which are minimum values,This indicates that the smaller the contact angle,the shorter the first drop time.When the content of LLDPE-g-MA is 20 w%,the light transmittance of the film is 86.9%.Compared with the drip film with the added amount of 0 w%,the light transmittance decreases by 0.5%.Repeated tests of the first dropping time of the film showed that when the dropping agent was in contact with water,it was not easy to lose with the water,and the reproducibility of the dropping performance was relatively high.?2?Using orthogonal experiment method,design L₁₂?6×2²?orthogonal table,Explore the influence of the three factors of GMS,Tween60 and Span20compounding ratio,LLDPE-g-MA content,LLDPE and EVA mixing ratio on the drip shelf life of drip shed film.The results show that the proportion of GMS,Tween60and Span20 is the main influencing factor.When the total amount of the drops is 4w%,the mixing ratio GMS:Tween60:Span20=1:1:1,the content of LLDPE-g-MA is30 w%,LLDPE:EVA=9:1,film had the longest holding period,with a holding period of 20 days.Compared with Tween60 and Span20,the migration rate of GMS is slower,and the antifogging duration is extended by 13%;Span20 has good wettability,the contact angle is reduced by 37%,and the initial dripping time is shortened by 38%;With the increase of EVA content from 10 w%to 20 w%,the antifogging duration decreased by 2%instead.Based on orthogonal experiments,the three conditions of fixed LLDPE-g-MA content are 30 w%,LLDPE:EVA=9:1,GMS:Tween60:Span20=1:1:1,An LLDPE/EVA composite dripping film with a total amount of drip agent of 3-5 w%was prepared.The test results showed that the drip film with containing 5 w%drop agents had a contact angle of 47.3o,the first dripping time was 112 s,and the dripping duration was extended to 22 days.As the content of dripping agent increases,the dripping duration of the dripping film gradually increases.However,if you continue to increase the content of the drip agent,the increase of the drip retention period will be weakened.The light transmittance of film is 85.1%.?3?Mixing Tannic acid?TA?and Sodium alginate?SA?solutions according to concentration of 3 wt%with 1:1 and 1:2 volume ratio,and then coated on LLDPE films.Characterize the wettability,hot mist retention period and adhesion ability of the externally coated PE film.The test results show that when V?TA?:V?SA?=1:1,the film has the longest duration of hot mist,which can reach 2 hours.The contact angle is 39.3°and the adhesion area reached 96.8%.On this basis,a mixed liquid with a volume ratio of 1:1 is selected to surface coat the drip film with the longest holding period to prepare an overcoated drip film.The results show that the duration of the outer coating drip film function is 23 days;Water droplets quickly spread on the surface of the film and penetrate into the coating;the outer coating mixed layer has the ability of water to trigger self-healing;The light transmittance of the film is87.4%.