Cross-linked thermoplastics

CO2-Based Polycarbonates with Low Glass Transition Temperatures Sourced from Long-Chain Terpenes

“…A common challenge encountered in polymers featuring double bond content in their side chains is cross-linking. − , This can be mitigated by the use of stabilizers or by reducing the double bonds. , Also in the case of PGeraGEC and PNerGEC, cross-linking tends to occur when stored at room temperature and exposed to light and oxygen over several weeks. Consequently, the polymers become insoluble in any solvent.…”

Molecular scale-driven upgrading of extrusion technology for sustainable polymer processing and recycling

“…Thermoplastic (quasi-linear polymer) materials are prone to thermal and/or oxidative degradation, and creep. Sufficient crosslinking improves the thermal stability and mechanical properties, such as impact strength, tensile strength, stress cracking, and resistance to creep [66]. Several crosslinked polymers therefore exist, with a broad range of applications, as shown in Figure 4.…”

Covalent Adaptable Networks Made by Reactive Processing of Highly Entangled Polymer: Synthesis-Structure-Thermomechanical Property-Reprocessing Relationship in Covalent Adaptable Networks

“…Thermoplastic polymers can be cross-linked into permanent networks, known as thermosets, to enhance their properties and expand their applicability. 1,2 For example, polyethylene (PE) can be processed into cross-linked PE (PEX, also called XLPE) by reactive extrusion of PE in the presence of a radical initiator; PEX is better suited than PE for applications like piping, cable insulation, and automotive ducts requiring substantial thermal stability, impact strength, and stress crack resistance. 1−3 Typical radical-based cross-linking of PE involves mixing a peroxide initiator with melted PE and curing the mixture at temperatures between 160 and 250 °C.…”

“…Thermoplastic polymers can be cross-linked into permanent networks, known as thermosets, to enhance their properties and expand their applicability. , For example, polyethylene (PE) can be processed into cross-linked PE (PEX, also called XLPE) by reactive extrusion of PE in the presence of a radical initiator; PEX is better suited than PE for applications like piping, cable insulation, and automotive ducts requiring substantial thermal stability, impact strength, and stress crack resistance. − Typical radical-based cross-linking of PE involves mixing a peroxide initiator with melted PE and curing the mixture at temperatures between 160 and 250 °C. − During this process, the peroxide decomposes into radicals that abstract hydrogen atoms from PE backbone chains, creating PE macroradicals. Cross-linking occurs when macroradicals present on secondary carbons (CH 2 units prior to hydrogen atom abstraction) terminate by combination, resulting in a bond between adjacent chains. − Alternatively, as a result of macroradicals present on tertiary carbons (CH units prior to hydrogen abstraction), chain scission can occur. − This is most notable with polypropylene. It occurs to a much lesser extent in low-density PE (LDPE); chain transfer and branching are the predominant mechanisms with LDPE. − CH 2 units in branches off the LDPE backbone also serve as sites for radical formation and cross-linking. − Similarly, radicals may form on CH 2 units in the side chains of other polymers and, thus, cause further branching, cross-linking, and chain scission .…”

“…Cross-linking occurs when macroradicals present on secondary carbons (CH 2 units prior to hydrogen atom abstraction) terminate by combination, resulting in a bond between adjacent chains. − Alternatively, as a result of macroradicals present on tertiary carbons (CH units prior to hydrogen abstraction), chain scission can occur. − This is most notable with polypropylene. It occurs to a much lesser extent in low-density PE (LDPE); chain transfer and branching are the predominant mechanisms with LDPE. − CH 2 units in branches off the LDPE backbone also serve as sites for radical formation and cross-linking. − Similarly, radicals may form on CH 2 units in the side chains of other polymers and, thus, cause further branching, cross-linking, and chain scission . This phenomenon has been observed in ethylene-vinyl acetate copolymer (EVA), , poly­(vinyl ethers), − polyacrylates, − and polymethacrylates. − In these polymers, cross-linking efficiency (moles of generated cross-links per mole of decomposed initiator) and the proportion of cross-linking to chain scission after radical formation have been studied as functions of side-chain length, isomerism, and average molecular weight. − …”