**1. Introduction**

Film mulching technology has the advantages of increasing temperature and moisture; preventing plant diseases, insects and weeds; and promoting crop growth [1]. In 2019, the amount of plastic film used in China reached 1.379 × <sup>10</sup><sup>6</sup> t, and the area covered by plastic film reached 1.76281 × <sup>10</sup><sup>7</sup> hm<sup>2</sup> [2], which ranked first in the world. However, the farmland residual film recycling technology in China started relatively late, and the long-term, large-scale use of ultra-thin and low-strength plastic film has caused a series of problems, such as soil compaction, a decreased seedling rate, and crop yield reduction [3].

At present, manual recycling is mainly adopted in the treatment of non-point source pollution of farmland residual film, mechanical recycling, and the use of degradable plastic

**Citation:** Liu, J.; Liu, X.; Jiang, Y.; Zhou, X.; Zhang, L.; Wang, X. Research on the Adaptability of High-Performance Film for Full Recycling to the Curl-Up Film Collecting Method. *Agriculture* **2022**, *12*, 1051. https://doi.org/10.3390/ agriculture12071051

Academic Editors: Jin Yuan, Wei Ji and Qingchun Feng

Received: 18 June 2022 Accepted: 16 July 2022 Published: 19 July 2022

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film. Manual recycling of residual film is time-consuming, laborious, and costly, and it is difficult to motivate farmers [4]. Residual film recycling is not required after laying degradable residual film, since the film can decompose through natural degradation [5], however, degradable plastic film is not yet mature in cost control and production technology; the high cost of use and the unpredictable degradation effect during use make it difficult to implement large-scale promotion and use [6,7]. Mechanical recycling of residual film is currently the most widely used method for its high operating efficiency and low operating cost. The mulch film widely used in China has two levels of thickness, 0.008 mm and 0.01 mm, and its tensile property is lower than the mulch film with a thickness of 0.025 mm or more, which is commonly used abroad. Residual plastic film collectors used abroad are mostly curl-up residual film recycling machines with a simple mechanical structure demanding a good tensile performance of plastic film [8], while development of the residual plastic film collectors used in China is restricted by the poor tensile properties of plastic film. According to the planting mode of crops, a variety of film collectors with different mechanical structures has been developed, mainly including drum type, spring tooth type, and tooth chain type [9], which are not only complex in structure but also have a lower film recycling rate than those developed in foreign countries. Marí et al. [10] studied the application of biodegradable plastic mulch films (BDMs) in strawberry planting, and the research results showed that BDMs are a viable alternative to PE mulch. However, Anunciado [6] pointed out in the study of BDMs that the extent of change to the physicochemical properties of BDMs, due to agricultural weathering, is greatly affected by the polymeric composition and is greater in warmer climates. Steinmetz [11] studied BDMs and mentioned that the high use cost restricted the popularization of BDM. Therefore, due to the high cost of agricultural weathering, the technology of BDMs cannot effectively solve the problem of non-point source pollution of residue film in fields. Zhang et al. [12] performed parameter optimization on the Arc-Shaped Nail-Tooth Roller-Type Recovery Machine for Sowing Layer Residual Film, and the field test results showed that this machine type could achieve a normal residual film collection rate of 66.8% on common polyethylene mulching film. Zhou et al. [13] developed a kind of film collector with a film-removing plate, and this device can achieve a film collection rate of 86.93% on common polyethylene mulching film in ideal conditions. However, in the process of collecting the polyethylene mulching film, there are still residue films uncollected in the field, thus, the film-collecting effect was not satisfactory. Qu et al. [14] replaced the traditional rheological processing of drag and shear on high polymer materials with plasticizing transport based on volume elongational rheology, which reduced the macromolecular chain breakage of high polymer materials and greatly improved the mechanical properties of film molded by processing extreme rheological plastics, such as polyethylene. Based on the complex blow-molding technology, through dynamic distribution, the film can be overlaid for 3–5 layers, and the macromolecules are oriented in different directions between the layers to achieve an interweaving effect; thus, the tensile performance of the film is greatly enhanced, and the "high-performance film for full recycling to the curl-up film recycling method" (which can be called "high-performance film") was developed [15,16]. Since the tensile performance of the high-performance film is better than that of common polyethylene film, laying the high-performance film for full recycling can greatly improve the film collecting rate, and the production cost of the high-performance film is very low compared with BDMs; therefore, this technology has become an effective means to solve non-point source pollution of residue films in agricultural fields.

A contrast test on the tensile property of high-performance film and ordinary polyethylene film under different test factors was carried out, and the variation rules of the tensile properties of both films during the film-laying period of 0–180 days, as well as the minimum tensile level for the 180-day film-laying period, were obtained. Moreover, the operation principles of the curl-up residual plastic film collector were analyzed, and the curl-up collecting of the film for the 180-day film-laying period was carried out. Through an analysis on overcoming the force between the soil and the film during curl-up collecting of the film, the tensile stresses on the film while the curl-up film collector pulled it up under different test factors were obtained. The field test on the curl-up collecting of film was carried out. By comparing the film recycling rate on the film laid in the same year and the working performance of the two residual plastic film collectors of different structures, the proper structure adaptable to the curl-up collecting of high-performance film was obtained. This research can provide theoretical support for simplifying the structure of residual plastic film collectors, enhancing the film recycling rate, and reducing the cost of film recycling.

### **2. Contrast Test on the Tensile Properties of High-Performance Film and Ordinary Polyethylene Film**

In order to obtain the variation law of the tensile properties of the high-performance film and the ordinary polyethylene film laid in a cotton field in Xinjiang within their service period and the minimum tensile level at the end of the service period, the film-laying period, the film thickness, sampling direction, and sampling position were used as test factors; the elongation at break and tensile yield stress were used as test indexes to carry out the contrast test on the two types of films.
