超高压处理对LDPE、PA6食品包装材料包装性能可逆性的研究

Influence of High Pressure Processing on the Reversibility of LDPE and PA6 Food Packaging Materials

摘要:

本文在不同条件下对LDPE、PA6进行超高压(HPP)处理，测定不同压力、保压时间及存储时间对材料拉伸强度、热封性能、阻隔性能、热性能以及包装性能可逆性的影响。实验表明：处理压力、保压时间及存储时间对2种材料的热封性均未产生显著影响，但LDPE、PA6试样的拉伸强度随压力升高明显增大；当压力<300 MPa时LDPE的透湿性逐渐上升，当压力>300 MPa时LDPE的透湿性又逐渐降低，对PA6来说，当压力>100 MPa时，材料的透湿性明显下降由10.13 g/(m2?d)（0.1 MPa/10 min）降低到6.79 g/(m2?d)（200 MPa/10 min），但随压力增大透湿性下降的幅度并不明显；两种材料的熔融焓在HPP下均有升高，当存储24 h后，两种材料的ΔH又有所恢复；与0.1 MPa下相比，经过HPP后对异丙基甲苯在LDPE（500 MPa）和PA6 (100 MPa)薄膜中的渗透率分别降低约50%和58%，但随着存储时间的延长又逐渐恢复至常压下的渗透率。研究发现实验中采用的LDPE和PA6 2种薄膜的包装性能均有可逆现象出现。

Abstract:

This study investigated the tensile strength, heat-sealing properties, thermal properties, barrier properties, and reversibility of LDPE and PA6 films under different conditions of high-pressure processing (HPP) compared to control samples processed at atmospheric pressure. The results showed that the effects of pressure, dwell time, and storage time on the heat-sealing properties of LDPE and PA6 materials were not significant, but the tensile strength of LDPE and PA6 samples increased significantly as the pressure increased; When the pressure was lower than 300 MPa, the water vapor transmission rate (WVTR) of LDPE increased gradually, while the WVTR gradually decreased when the pressure was higher than 300 MPa. For PA6 samples, when the pressure was higher than 100 MPa, the WVTR decreased from 10.13 g/(m2?day) (0.1 MPa/10 min) to 6.79 g/(m2?day) (200 MPa/10 min), but the reduction was not significant with increasing pressure. The melting enthalpy of LDPE and PA6 samples increased under HPP treatment, which was recovered after storage for 24 h. Compared with 0.1 MPa, the permeation of p-cymene through LDPE and PA6 films was reduced by about 50% and 58%, respectively, under different HPP treatments, but returned to levels observed at atmospheric pressure almost immediately when the pressure was released. The results show that the properties of LDPE and PA6 films are reversible under HPP treatment, hence both are suitable for HPP.