Quick answer
Ordinary thermoplastic insulation softens and can melt or drip as it gets hot. Electron-beam cross-linked insulation is different: the e-beam bonds the polymer chains into a thermoset structure that holds its shape at high temperature and will not melt or drip — which is why it is called melt-resistant.
This matters for safety and reliability: the wire keeps insulating even under overload or fire conditions, resists short circuits and lasts far longer. APAR's Anushakti Fire Protekt uses this e-beam technology for melt-resistant, long-life performance.
Related: XLPE insulation and HR-FR-LSH.