Chemical crosslink densit and network structure of natural rubber vulcanizates modified with phosphorylated cardnol prepolymer

Abstract

The chemical crosslink density (CLD) and network structure of natural rubber ( N R ) vulcanizates, modified with phosphorylated cardanol prepolymer (PCP) , have been studied by equilibrium swelling and other chemical methods. The PCP-modified NR vulcanizates showed lower CLD, as compared to the unmodified NR samples, the decrease being lesser for the semiefficient vulcanization (SEV) system, as compared to the conventional (CV) and efficient (EV) vulcanization systems. The superior tensile characteristics of the PCPmodified vulcanizates of the SEV system is presumed to be partly due to the presence of an entangled network structure between the aliphatic segment of PCP and the isoprene chains, as evident from X-ray diffraction studies. The critical role of Zn++ ions in the crosslinking reactions, especially at higher concentrations of PCP, was evident from the increase in CLD a t higher concentrations of ZnO. The reduction in the IR absorption intensity, in the presence of ZnO, indicated the probable complex formation of Zn++ ions with the phosphate groups of PCP.

Physicomechanical properties of filled natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid

“…This has been ascribed to the residual acidity of PCNSL and the probable complex formation of Cure Characteristics Zn 2/ ions of the cure activator (ZnO) with the phosphate groups of PCNSL. 9 The effect of PCNSL dosage on the cure character-…”

“…9 It is possithe HAF-black-filled vulcanizate decreased at a higher rate compared to that containing silica ble that these mechanisms may also operate in the filled samples. Besides, the plasticizing effect and china clay with the increase in concentration of PCNSL.…”

Challenges for Natural Monomers and Polymers: Novel Design Strategies and Engineering to Develop Advanced Polymers

“…The phosphorus-modified CNSL prepolymer has been found to act as a multifunctional additive in NR in various roles. It can act as cross-linkable plasticizer, softener, tackifier, antidegradant and improver of thermal stability, improver of mechanical properties of vulcanizates, such astensile strength, tear strength and fatigue resistance, and coupling agent between filler and rubber [166][167][168][169][170][171][172][173][174][175][176][177][178][179][180][181][182]. Introducing free radical polymerizable moieties would enable cardanol to become a potential monomer for the molecular design of high-value polymers [183][184][185].…”

Studies on blends of natural rubber and ethylene propylene diene rubber modified with phosphorylated cardanol prepolymer: Processability, physico‐mechanical properties, and morphology

“…Previous studies have shown that PCNSL/PCP 12 could function as a multifunctional additive in NR and synthetic rubbers in various roles as a crosslinkable plasticizer, a softener, a tackifier, an antidegradant, an improver of the thermal stability and mechanical properties of vulcanizates (tensile strength, tear strength, and fatigue resistance), and a coupling agent between silica filler and NR, leading to improvement in resistance to crack propagation. [12][13][14][15][16][17][18][19][20] It has been reported previously that carbon-blackfilled EPDM vulcanizates containing PCNSL showed improvements in cure rate, tear strength, thermal stability, and resistance to thermo-oxidative decomposi-tion as compared to a commercial plasticizer. 18 A recent study on the melt rheology of EPDM modified with 5-10 phr of PCNSL on a capillary rheometer over a wide range of temperatures and shear rates showed the plasticizing effect of the additive on the rubber and the consequent improvement in melt processability.…”