Vinylidene Chloride Polymers

Goggin, W. C.; Lowry, R. D.

doi:10.1021/ie50387a015

Cited by 21 publications

(7 citation statements)

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“…Ethylene [36,37,38) and vinylid ene chloride [39,40) bo th form polym er s th at are r ath er highly cryst allin e. Th e polym ers of ethylen e oxide a nd acrylonitrile also are probably crystalline. The apparen t heat of polym erization t o solid polym er mu st then include a sm all quan tity represen ting the h eat of crystallization, depending on th e percentage of crystallini ty.…”

Section: Heats Of Polymerizationmentioning

confidence: 99%

Heats of polymerization - a summary of published values and their relation to structure

Roberts¹

1950

J. RES. NATL. BUR. STAN.

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This paper contain s a table showing values of heats of polymerization assembl ed from a survey of t h e li terature. There are 42 substit uted vin yl compounds arranged as follows: vinyl alkyls, vinyl aryls, other vinyls, vi nyl acids and esters, dienes and copoly m ers. Values reported by differen t authors are gi ven for each com pound, wi th correspondin g states of monomers and ploym ers and a notation on t he methods used in obtaining t he values. A second table gives structural formulas of monomers.Some values of heats of polymeri zation to hypothetical polymers having no ste ri c hindrance are calculated from published values of heats of form ation of hydrocarbon s, making ce rtain ass4mptions regardin g branch groups. Th e m ethod of calculation is expla in ed. H eat of polymerization is a rbi t rari ly assigned to four energy effects : (1 ) t he reaction I I I IC= C ---> -C-C-; (2) t he eff ect of side g ro ups on bond energies wh en t he re is no in te r- I I I I .action between the groups; (3) thc eff cct of ste ri c hindrance between ide g roups ; and (4) thc "e nd eff ect" a r isin g from the nearn css of t he double bond to the en d of t he monomer molec ule. Values of hcats of polymerization a re compared , and t he ir relation to s t r ucture is examined, with particular emphasis on t he effect of s teric hindrance. Etyhlene has t he highest and alpha-methylsty rene t he lowes t heat of pol y me ri zation ; isobute nc and the methac rylates also are low. D isubstitution on the same vinyl carbon is a frequent cause of ste ri c interference, with consequent recluctionin heat of polymerization . Large b ra nched substi tuents may causc ste ri c inte rfe rence. The substit u tion of chlorin e on the aromatic ring of styrene has little effect on heat of polym eri zation. Steric interferen ce may prcvent polymerization above the dim e r. The heat of copolymer ization of butadien e an d styrene lics between the values for t he separate monom ers. H eat of copolymeri zation of other monom cr pairs may be higher or lower than the val ue for t he separate compon ents. H eat of polymeriza tion depends somewhat on t he ratio of 1,2-a nd 1,4-addition, and on t he amount of crystallinity of the polymers.

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Section: Heats Of Polymerizationmentioning

confidence: 99%

Heats of polymerization - a summary of published values and their relation to structure

Roberts¹

1950

J. RES. NATL. BUR. STAN.

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“…The bending of the beam, particularly under impact, is too large to be described by the simple bending equations which assume the deformation to be small. 3. The dynamic bending of the beam differs from the slow bending, as discussed later in connection with the bending of plates, and as was found with the vibration of glass beams.…”

Section: The Breaking Strength Of Beams By Loading and By Imfactmentioning

confidence: 84%

XCIV. The behaviour of glass under impact and static loading

B.Sc¹

1945

The London, Edinburgh, and Dublin Philosophical Magazine and Jo

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Plates VIII.-X.]ABSTRACT. l~umerous experiments have been performed on the strength of glass in the form of beams and plates. The beams, cut from sheet glass approximately 0.28 era. thick, were tested by a slow loading test and by the impact of a pendulum. The squares were tested both by pressing a steel ball against the square and also by the impact of a falling ball.It was shown that in the case of slow impact when using objects much heavier than the glass, the energy required to break the glass is greater than that needed under static conditions. The difference can be explained * The following symbols used in this paper generally follow the British Standard Handbook No. 560, 1934. Where they differ from those used by Professor S. Timoshenko, to whose book several references are made, his symbols are given in brackets afterwards. V, velocity ; t, the time ; E, Young's modulus of elasticity ; f, the modulus of rupture or bending strength ; P, the aggregate normal force ; ~, the deflection of a plate or beam ; a, (v) Poisson's ratio ; n, the frequency of vibration ; L, the length of a beam ; h, the thickness of a beam or plate ; a, the side of a square plate ; p, the specific gravity ; Pm (a max.), the ~standard deviation ) ma~mum stress ; v, the coefficient of variation \ average value × 100 for a series of measurements.if the known changes in the modulus of rupture of glass with time are taken into account. As the velocity of impact is increased, however, the energy required to shatter a glass plate generally diminishes markedly. This decrease in strength is ascribed to the operation of stresses, due to the weight of the glass, the initial value of which is given approximately by the relation V~/Ep. When glass is broken by small balls at high velocites characteristic cone or " shell '° fractures are produced, which appear to be an extension of the statically formed ring cracks along lines perpendicular to the maximum tension in the glass.The coefficients of variation of the measured quantities are given in a number of cases. Impact tests give a larger variation in the results than static tests since the former give estimates of the energy required to break and hence contain the term (f(l~v)) 2, where v is the coefficient of variation of the stress required to break.

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“…The Saran fibers were stretched in the manufacturing processes-e.g., the extrusion, &dquo;orientation,&dquo; and &dquo;elongation&dquo; [4]. Consequently, the Saran fibers are in a strained state and begin to relax, resulting in shrinkage.…”

Section: Mechanism Of Shrinkagementioning

confidence: 99%

“…It was found that shrinkage accompanies the weight loss. 4. The weight loss was caused by the loss of the plasticizer which the fibers contained.…”

Section: Mechanism Of Shrinkagementioning

confidence: 99%