| Oxygen is one of the important factors that can cause food decaying. It can cause food oxidation, bacteria reproduction, thus causing the discoloration, stale and loss of nutrients. Therefore the oxygen content in food packaging must not exceed the allowable values. The traditional ways to reduce the oxygen content are modified atmosphere packaging and vacuum packaging, but these methods cannot completely remove oxygen in the package with 0.1%~2% residential oxygen. Oxygen scavenging packaging is a new kind of packaging technologies which excels the traditional vacuum packaging and modified atmosphere packaging. It can actively remove oxygen in package.The core of oxygen scavenging packaging materials is the study of active oxygen scavenging ingredient. The cyclized styrene-butadiene copolymer(cyclized SBS) was prepared with SBS as raw material and p-toluene sulphonic acid as catalyst. The cyclized SBS oxygen scavenging blend were prepared by blending cyclized SBS, photoinitiator and transition metal catalyst. The oxygen scavenging reaction was triggered after UV irradiation. The cyclized SBS-α-pinene oxygen scavenging resin blend was prepared by blending cyclized SBS, α-pinene resin, photoinitiator, and transition metal catalyst. The oxygen scavenging single LDPE films were prepared with these two oxygen scavenging blend. The main contents and research results are as followings:(1) The optimal conditions for preparation of cyclized SBS were investigated by orthogonal array design. The oxygen scavenging property was determined to optimize the key factors that affect oxygen scavenging property of cyclized SBS oxygen scavenging blend, to achieve the appropriate and technologic conditions. The results showed that the optimal conditions were as follows: the concentration of SBS was 20%, the concentration of toluene sulfonic acid was 2%, the reaction temperature was 75℃ and the reaction time was 3h. Under these conditions, the oxygen scavenging ability could achieve 40.5 m L/g, and the oxygen scavenging rate achieved 0.129 m L?g-1?cm-2?d-1. Meanwhile, the influences of storage conditions such as the storage environment time, the storage environment temperature and the storage environment humidity on the oxygen scavenging property of cyclized SBS oxygen scavenging blend were evaluated. The results showed that the oxygen scavenging property of cyclized SBS oxygen scavenging blend decreased as the storage time and temperature increased, and while the humidity influence less on it.(2) The influence of the additive amount of α-pinene resin on oxygen scavenging property of the blend was studied. The results showed that the maximal oxygen uptake achieved 36.2 m L/g and 35.6 m L/g under 23℃ and 4℃ respectively. In addition, there was a measurable reduction in the oxygen scavenging property of the blend during storage. But the magnitude of the reduction will be weakened over the storage time or as the storage temperature rose.(3) The two kinds of oxygen scavenging LDPE films were prepared with these two oxygen scavenging blend as active oxygen scavenging ingredient. The oxygen scavenging properties of the kinds of films were studied. And the results showed that the films had achieved the desired results, and the oxygen scavenging property would not change over time. In addition, the films still had heat-sealed properties, and the seal strength changed not much when compared to LDPE film. But the oxygen scavenging blend does weaken the mechanical properties and the barrier properties to some extent. |
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