Crystallization kinetics and polymorphic transformations in polybutene-1

Abstract

\ Vh e n s u bcooled fro m the m elt to any tempera t ure between abou t 90 t o lJ 0 °C, polybu te l1!'-l tra nsform s at a r eadily m eas ura ble rate to a cr ys talline phase de noted "form 2," wh ich is t yp ically sphe ruli t ic. The kinetics of this process have bee n m eas ured by op t ical and d ihtometric t ech ni ques . The r es ults are consistent w ith th e cOlleepts t h a t th e ini tia tion is het erogeneo us, that the in it iation is followed by spherical g row t h (Avrami n = 3), and that t he growth rate is nucleation controlled. Va lu es a rc ob ta in ed for t he s urface fr ee e nergi es and r elated qU:l nt it ies t hat ar c cons is tent with crystalli zation by cha in folding: (J = 7.2 er g/ cm 2 or 7.2 mJ/ m 2 , (J , = 15.5 er g/cm 2 or 15.5 mJ/ m2, a nd wor k of chain folding q= 1.7 X 10-13 ero-/fold. (For comparison, q is 2.1 X 10-13 e rg/fold for polyeth ylene.) The work of ch a in foldin g of polybu te ne-l is also compa red with t hat of polych lor ot rifluoroethy lene, and it is shown t ha t an in crease of q is conn ec Led with a n increase of equi librium me lt ing t cmperat ure. Crys ta l form 2 s ubseque ntly convcr ts s lowly n car room tempcrature to a cr ys t alline phase denoted " form 1" of diffcre nt hcli city a nd d ens ity, and Lh e ratc of t his crystal-crystal t ransform a t ion is also studi cd . The A vrami p ar a meter fo r t he form 2 form 1 process is n = 2. T he process a ppears t o be nucleaLion cont rolled. It is s hown t ha t form 1 is, everywhere below its melting point, t he stable form. The equili brium mel t ing temper ature for form 2 is es t im ated t o be a bou t 128°C, a nd for form 1 a bou t 141 °C . A deg ree of cr ys t allini ty scale bascd on sp cci fic volum e is establis hed. Th e degr ee of crystalli ni ty of form 2 is a bou t 52 per ce nt, a nd a fter convers ion t o form 1, th e crystaJl ini ty is a bout 77 p cr cen t .

Crystal Growth of Isotactic Poly(butene-1) in the Melt. I. Kinetic Roughening

“…The value of we obtained in this work is almost half the value of ¼ 7:2 Â 10 À3 J m À2 estimated by Powers et al 21 from the value of Áh f using an empirical relation 22 which is given by the following equation.…”

Direct melt crystal growth of isotactic polybutene‐1 trigonal phase

“…The earliest challengers were Powers et al [8], who used trigonal crystals obtained by solid-state transformation from the tetragonal phase as nuclei and attempted to observe the growth of trigonal crystals in the melt. This was, unfortunately, not successful and they hypothesized that the growth rate of trigonal crystals is "exceedingly" slower than that of tetragonal crystals.…”

High pressure dilatometry on polybutene-1

“…The latter seems to be relatively low (there exist data as high as 0.169 cmZ/g [24]. One possible explanation might be that if one compares in reference [6] the experimental curves with the tabulated numbers one finds a crystallinity of about 83% for the sample used at 1 bar which is unusually high (though possible [10]). Assuming a crystallinity similar to that of our samples or of the samples used in reference [6] at higher pressure would yield A Vm-values also similar to ours.…”

“…This transition is fastest near room temperature at 1 bar [9][10][11]6] and has a half-time of more than one day, but can be accelerated by some orders of magnitude by the application of mechanical stress [12,13] or hydrostatic pressure [6]. By the second method the temperature of minimum half-time is increased slightly.…”