Vega Juan F, Souza-Egipsy Virginia, Expósito M Teresa, Ramos Javier
BIOPHYM, Departamento de Física Macromolecular, Instituto de Estructura de la Materia, IEM-CSIC, c/Serrano 113 bis, 28006 Madrid, Spain.
Interdisciplinary Platform for Sustainable Plastics towards a Circular Economy, SUSPLAST-CSIC, 28006 Madrid, Spain.
Polymers (Basel). 2022 Apr 17;14(8):1622. doi: 10.3390/polym14081622.
In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter's molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler-Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler-Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material.
在本文中，我们描述了一种确定聚合物相容性的方法，这将有助于确定聚烯烃材料在多层薄膜机械回收生态设计中的要求，同时避免使用反应性粘结层。我们的最终目标是确定聚烯烃结构层的分子特征，以提高其在机械回收过程中与粘结层的相容性。我们研究了嵌入具有各种功能（酯、丙烯酸酯、醋酸酯和甲基丙烯酸钠离聚物）的商业聚合物基质中的各种聚乙烯单晶的熔点降低情况，这些聚合物基质有可能用作粘结层。我们展示了基质的浓度和分子结构如何根据后者的分子结构不同地影响嵌入单晶的熔点。主要发现表明，粘结层与线性聚乙烯的相容性比与支化聚乙烯的相容性更好。事实上，我们的结果表明，非均相齐格勒-纳塔线性低密度聚乙烯与所有测试的粘结层都不相容。观察到的熔点降低与通过研究溶液混合共混物的流变行为和形态特征获得的结果非常一致，在理论上，聚合物链之间的链段相互作用在溶液混合共混物中已最大化。由于齐格勒-纳塔线性密度聚乙烯是多层应用中最常用的作为结构层的聚合物之一，这项研究的结果很有用，因为它们从生态设计的角度清楚地表明了这种类型的聚乙烯不适合回收利用。可以指定聚乙烯层的具体分子要求（支化含量小于0.5/100个碳原子）用于包装，指导含有这种材料的回收多层薄膜的生态设计和增值利用。
