Heats of reaction of natural rubber with sulfur

Abstract

An adiabatiecopper ca l? rim e ter wa s used to determine th e heats of vul ca niza ti o n of pal e c re~e natura l rubber wIth s ulfur for mIxtures varying in com pos iti o n from 0 to 32 pe rce nt added s ulfur. The s id e rea ction that produces hydroge n s ulfide was avoided by us in " reacti on te mpe ratures near 155°C. Heat s of reac tion at 25°C and at ] 55 °C are re ported. Th e e nth~py c han ge at 25°C for co mpound s con talllln g up to about 18 pe rce nt s ulfur is given in joules per gra m of vu lca nizate by th e eq uatlon , !::J.H1o =-2 1. ]· 5 with a s tandard dev iation of 11 J ig. He re 5 is th e percentage of co mbin ed s ulfur. Above 18 pe rcen t s ulfur th e heat of reacti o n at 25°C remains app roxima te ly co ns tant a t 380 :!: 8 J ig. A co m~ari so n is made between th e hea t of vu lca nization and th e vo lu me c han "e on vulca ni zation , both as fun c tion s of com bin ed s ulfur , b y making use of data in th e lit e rature. 0 Key words: Aneroid ca lorim e ter; ca lorimeter; hea t of vu lca niza tion; hea t meas ure me nts; rubb er; rubb er-s ulfur reactIon ; vo lum e chan ge on vul ca nintion ; vu lca ni za tion.

Characterization of the Mechanical, Biodegradation, and Morphological Properties of NBR/Biopolymer Blend, Integrated with a Risk Evaluation

“…Thus, the vulcanization of the NGP/NBR blend took place by the endothermic reaction. 33 The chemical structure of NGP/NBR is shown in Figure 1. Figure 2 depicts the overview of the evaluation methods used to compare the NGP-blended NBR and pure NBR samples, comprising mechanical, morphological, chemical composition, and biodegradation characterization tests.…”

“…Following, the dispersed NGP was added to NBR and the samples (10 wt % NGP and 90 wt % NBR blend) were prepared in the form of thin films (<2 mm thick) by casting process and at a reaction temperature near 160–170 °C using an oven. Thus, the vulcanization of the NGP/NBR blend took place by the endothermic reaction . The chemical structure of NGP/NBR is shown in Figure .…”

A Novel Approach for Simulation and Optimization of Rubber Vulcanization

“…As the curing reaction is exothermic, the heat obtained from the curing reactions is generated per unit material volume ( Q ), and defined by Equation ( 2 ), where is the vulcanization specific heat ( = 13 kJ kg [ 40 ]). The heat of reversion was neglected due to the slow rate of reversion reactions.…”