Preparation And Properities Of Polyurethane Packaging Materials

Polyurethane(PU)is widely used in coatings,textiles and medical fields because of its excellent properties,but its properties are affected by many factors.Therefore,it is of great significance to study the factors affecting the performance of PU.And PU material is easy to be polluted by bacteria,which limits its application in the field of antibacterial packaging.Quaternary ammonium salt has good antibacterial properties and biocompatibility.Compounding it with PU has attracted extensive attention in the field of food preservation.In this study,isophorone diisocyanate(IPDI),polycarbonate diol(PCDL)and diethylene glycol(DEG)were selected as raw materials to synthesize a new polyurethane material.Using dodecyl dimethyl benzyl ammonium chloride as antibacterial agent to prepare PU antibacterial films and carrying out the experiment of packing and keeping fresh citrus.The PU films can be used as a new antibacterial packaging films.The results are as follows:Diethylene glycol(DEG),1,6-hexanediol(HDO),1,4-butanediol(BDO),2,2-dihydroxymethylpropionic acid(DMPA)and 2,2-dihydroxymethylbutyric acid(DMBA)were used as chain extenders to study the effects of chain extenders on the properties of PU films.The analysis of FT-IR and ~1H NMR showed that IPDI,PCDL and DEG had successfully synthesized new PU.PU-DEG has excellent barrier performance and thermal stability.Its elongation at break and tensile strength are 858%and 41mpa respectively,and its water contact angle is 99.5°.The effect of R value on the properties of the films was studied by changing the ratio of n(-NCO)/N(-OH)(R value).With the increase of R value,the breaking elongation of the film first increased and then decreased,the tensile strength gradually decreased,the water contact angle,thermal stability and barrier properties gradually improved,and the transparency decreased.The effect of DEG content on the properties of the film was studied.With the increase of DEG content,the elongation at break decreased,the tensile strength increased first and then decreased,the water contact angle,thermal stability and barrier properties increased,and the transparency decreased.Change the film-forming temperature and study the effect of film-forming temperature on the properties of the film.With the increase of film forming temperature,the elongation at break,tensile strength and water contact angle of the film increased first and then decreased,and the transparency decreased gradually.In order to make PU films play an antibacterial role in packaging and preservation,dodecyl dimethyl benzyl ammonium chloride was introduced into PU to prepare antibacterial PU films.The effect of antibacterial agent content on the properties of the film was studied.The results showed that with the increase of antibacterial agent content,the change of elongation at break and tensile strength of the film was irregular,the water contact angle and transparency decreased,and the thermal stability and barrier property increased.The antibacterial experiment showed that when the content of antibacterial agent was 0.8%,it had obvious inhibitory effect on Escherichia coli and Staphylococcus aureus,and the antibacterial effect on Aspergillus niger and Penicillium was not as good as that of bacteria.The effect of antibacterial film on the freshness of citrus was studied.The results showed that the sensory evaluation of Citrus packaged with antibacterial film was higher than that of the control group.The weight loss rate was lower than that of the control group.At 20 days,the weight loss rate was 3.88%lower than that of the control group,and the consumption rate of sugar content and vitamin C content decreased.The results showed that antibacterial PU film could effectively prolong the shelf life of citrus.