Degradable foam tableware
DATE：2021/11/23 8:31:20 / READ： / SOURCE：This station
Degradable foam tableware
The plant cellulose is mixed into the polystyrene starch resin to promote multi-component cross-linking, so that the partial chain is transformed from the original linear or slightly branched structure to a three-dimensional network structure to form a fiber-reinforced starch foam. Effectively improve the degradation performance, mechanical properties, and processing performance of fast food products, and reduce costs.
In 1994, AC Albertson of Sweden pointed out that synthetic polymers such as PE and PS are not completely affective to microorganisms, but show a certain (although limited) long-term biodegradability, and the speed is faster than previously expected. . It can be seen that the measures to increase the degradation rate of degradable plastics such as starch/PE and starch/PS are to focus on the synergistic effect of microbial degradation and general oxidative degradation, and promote oxidative degradation, while promoting biological degradation on the surface of PE and PS. Activities create good conditions. In addition, in order to strengthen market competitiveness, it is also necessary to improve its performance and reduce costs, so the effort to find the best solution and implementation should be a long-term task.
1. The problems of degradable PS starch plastic foaming snack utensils
The light and biodegradability of the degradable PS starch plastic foam snack utensils exceeds the requirements for environmental certification degradable plastic packaging products issued by the National Environmental Protection Agency (HJBZ12-1997). In early 1998, it was tested by the China Environmental Labeling Certification Committee and obtained the certification. However, from the viewpoint of sustainable development, the following problems still exist.
①In order to obtain high degradation performance, the amount of starch should be added as much as possible. After reaching 25%, the physical properties of the product will be significantly reduced. Compared with PS foam tableware, there are obvious differences in strength, rigidity, surface quality and use performance. Market competitiveness is not strong. For this reason, the method of increasing the wall thickness of the product (that is, increasing the thickness of the sheet) has to be adopted to increase the quality of each fast food utensil and increase the production cost. For example, a medium-sized foaming snack utensil has a PS of about 5g, while the degraded PS can reach 6.5-7g.
②In the process of extruding the foamed sheet, the higher the starch content, the lower the melt strength, resulting in insufficient cell wall strength, which makes it difficult to withstand bubble expansion. As a result, the foam is easy to rupture, and the product has a high open cell rate, which causes a decrease in cell density and compression resistance.
③In order to protect the environment, butane is used in the production process to replace "Freon" (CFC11), which has a destructive effect on the atmospheric ozone layer. Because the permeability of butane is higher than that of CFC1 and the higher the starch content, the more easily the butane escapes and is lost during the inflation, which causes the collapse of the cells, the obvious shrinkage of the sheet, and the obvious reduction of the expansion ratio, which not only increases the production cost, but also makes Wrinkles appear on the surface of the product, which affects the appearance quality.
④The fluidity of PS with high starch content is significantly reduced, and the viscoelasticity of the melt suitable for foaming is difficult to maintain stably, and the melt viscosity cannot be reduced by increasing the material temperature (it is easy to make the starch zoom and the collapse of the foam aggravate) , So that the production capacity of the extruder is significantly reduced, and the quality stability is poor.
Author：admin