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The effect of polymer crystallization on cationic polymerization of trioxan in solution
POLYMER PHYSICS M E E T I N G -
S H R I V E N H A M APRIL 1964
discriminate between intralamellar folds and interlamellar links. Certainly folds are attacked as was demonstrated by an experiment on single crystals grown from solution. Careful control of the reaction conditions is necessary to obtain reproducible weight loss curves and a preliminary study of these suggests that it may be possible to estimate the amount of interlamellar amorphous material.
Some Observations on the Structure of Nylon 6.6 Spherulites Crystallized from the Melt P. H. HARRIS,British Nylon Spinners Ltd, Pontypool, Monmouthshire Thin melt-crystallized films of Nylon 6.6 have been examined by transmission electron microscopy. At low beam intensities little structure is observed but at normal intensities a marked contrast enhancement occurs apparently coincident with the loss of crystallinity. The structure observed after this change can be correlated with that observed previously in the polarizing microscope. Positively birefringent spherulites exhibit a conventional shearlike morphology but negatively birefringent and non-birefringent spherulites show no evidence of this. It is considered that the contrast enhancement induced by the electron beam is probably due to thickness'variations determined by the initial molecular orientation.
The Ef)'ect of Polymer Crystallization on Cationic Polymerization of Trioxan in Solution L. LEESEand M. W. BAUMBER,BX Plastics Ltd, Manningtree, Essex The work of Kern and Jaacks on polymerization of trioxan in methylene chloride has been extended by a study in ethylene dichloride. Kinetics have been investigated chemically and by adiabatic calorimetry and results indicate that during an induction period soluble low molecular weight polymer is produced which eventually forms crystal nuclei. These initiate an accelerating reaction whose rate depends on the area of crystal surface available for polymer deposition or formation and equations have been obtained which describe the observed kinetics. The kinetic arguments are supported by photomicrographs of crystals at the various stages of polymerization, which indicate a progressive increase in the size of the original crystals rather than constant formation of fresh nuclei. The evidence strongly suggests that polymerization takes place at the growing crystal surface.
Session on Molecular Structure and Radiation Damage
Introductory Talk: The Determination of Polymer Structure by X-ray Diffraction C. W. BuNN, Royal Institution, London W.1 In principle, X-ray diffraction methods can give detailed information on the structure of crystalline polymers--the chain conformation, the stereo positions of side-groups (for instance, whether vinyl polymers are isotactic or syndiotactic), the arrangement of the molecules and the density of crystalline regions. A detailed crystal structure determination is a lengthy task, but sometimes valuable information on some of the aspects mentioned can be obtained readily and quickly. The chain repeat distance (obtained straightforwardly from fibre photographs), together with basic stereochemical data like bond lengths and angles and the principle of staggered bonds, may point definitely to a particular chain conformation. The general distribution of intensity in the fibre diffraction pattern is also a valuable and powerful indication of the conformation, and may lead, for helical chains, to a knowledge of the number of monomer units and the number of turns of the helix
380
S H R I V E N H A M APRIL 1964
discriminate between intralamellar folds and interlamellar links. Certainly folds are attacked as was demonstrated by an experiment on single crystals grown from solution. Careful control of the reaction conditions is necessary to obtain reproducible weight loss curves and a preliminary study of these suggests that it may be possible to estimate the amount of interlamellar amorphous material.
Some Observations on the Structure of Nylon 6.6 Spherulites Crystallized from the Melt P. H. HARRIS,British Nylon Spinners Ltd, Pontypool, Monmouthshire Thin melt-crystallized films of Nylon 6.6 have been examined by transmission electron microscopy. At low beam intensities little structure is observed but at normal intensities a marked contrast enhancement occurs apparently coincident with the loss of crystallinity. The structure observed after this change can be correlated with that observed previously in the polarizing microscope. Positively birefringent spherulites exhibit a conventional shearlike morphology but negatively birefringent and non-birefringent spherulites show no evidence of this. It is considered that the contrast enhancement induced by the electron beam is probably due to thickness'variations determined by the initial molecular orientation.
The Ef)'ect of Polymer Crystallization on Cationic Polymerization of Trioxan in Solution L. LEESEand M. W. BAUMBER,BX Plastics Ltd, Manningtree, Essex The work of Kern and Jaacks on polymerization of trioxan in methylene chloride has been extended by a study in ethylene dichloride. Kinetics have been investigated chemically and by adiabatic calorimetry and results indicate that during an induction period soluble low molecular weight polymer is produced which eventually forms crystal nuclei. These initiate an accelerating reaction whose rate depends on the area of crystal surface available for polymer deposition or formation and equations have been obtained which describe the observed kinetics. The kinetic arguments are supported by photomicrographs of crystals at the various stages of polymerization, which indicate a progressive increase in the size of the original crystals rather than constant formation of fresh nuclei. The evidence strongly suggests that polymerization takes place at the growing crystal surface.
Session on Molecular Structure and Radiation Damage
Introductory Talk: The Determination of Polymer Structure by X-ray Diffraction C. W. BuNN, Royal Institution, London W.1 In principle, X-ray diffraction methods can give detailed information on the structure of crystalline polymers--the chain conformation, the stereo positions of side-groups (for instance, whether vinyl polymers are isotactic or syndiotactic), the arrangement of the molecules and the density of crystalline regions. A detailed crystal structure determination is a lengthy task, but sometimes valuable information on some of the aspects mentioned can be obtained readily and quickly. The chain repeat distance (obtained straightforwardly from fibre photographs), together with basic stereochemical data like bond lengths and angles and the principle of staggered bonds, may point definitely to a particular chain conformation. The general distribution of intensity in the fibre diffraction pattern is also a valuable and powerful indication of the conformation, and may lead, for helical chains, to a knowledge of the number of monomer units and the number of turns of the helix
380