Allan H. Fawcett

Blends of Bitumen with Polyethylenes

Blends of a 100 penetration grade bitumen with four different polyethylenes having up to 40 pph or 29% of polymer by weight were prepared using a Z-blade mixer at more than 160°C. The blends were studied by fluorescence optical microscopy, differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The optical measurements indicated the presence of bitumen-rich and polymer-rich phases. The DSC showed that the melting point of the crystallites was lowered and within the polymer-rich phases, the extent of crystallinity reduced by the presence of the bitumen. Annealing made significant changes to crystallite size, suggested by the raising of the melting point of the polymer crystallites. The DMTA measurements show that these polymers lower the temperature at which the glass transition softens the material, but raises the temperature at which the blend undergoes viscous flow. When the polymer fraction is over 20% to 28% the flow starts only when the crystallites melt, so the polymer then provides an associating junction network.

Step growth of an AB2 monomer, with cycle formation

A computer-based lattice model of the step growth reaction of an AB2 monomer, the next elaborate system after an AB monomer, has been devised that allows the simultaneous and explicit occurrence of inter- and intramolecular reactions of A and B groups of the flexible and moving molecules according to Monte Carlo selections of pairs adjacent on the lattice. Though cyclizations are infrequent in comparison to the reactions that develop the branched structures, they do occur, as they accumulate they consume a proportion of the A groups, and so they prevent the development of infinite branched molecules with fractal characteristics. Growth stops when each molecule contains a cycle. For the model explored, in which six lattice sites are used for each monomer, the limiting value of the number average degree of polymerization, 〈x〉n,∞, is 14.6(±0.3) (after infinite time). The occurrence within the system of rings of m residues (m=1,2,3,…) is found to depend upon m and the extent of reaction of the A groups, pa, a...

Studies on membranes composed of polymer-bitumen blends

Abstract A computer-controlled bending system has been constructed for characterizing the bending properties of commercial membranes composed of polymer-bitumen blends supported by a non-woven polyester type base. The system allows the bending elasticity and yield point to be obtained for a membrane, and also permits the stress relaxation after a distortion to be characterized. These properties are related to the polymer present in the bitumen.

Terpolymers of styrene, hex-1-ene and SO2

Abstract Terpolymers of styrene, hex-1-ene and sulphur dioxide have been prepared at temperatures between 67 and −63° and their microstructure characterized by 13C NMR spectroscopy. The main chains consist of sequences in which hex-1-ene residues alternate with sulphone groups, and sequences in which styrene runs are terminated by sulphone groups. The mole fraction of styrene residues, the mean length of styrene runs 〈m〉, and the fraction of single, double and triple runs of styrenes have been found by analysis of the 13C NMR spectra. 〈m〉 fell with temperature. At 45° there is a tendency in favour of homopolymerization of each type of alkylsulphone radical. The reactivity of the styrene relative to hex-1-ene rises a little as the temperature is raised to 67°, but rises also by a factor of 20 as the temperature is lowered to −63°.

Modification of a Bitumen with Various Polymers for Use in Built Up Roofing Membranes

Bitumen, a mixture of aromatics, paraffins, asphaltenes and resins that remain after crude oil has been fractionally distilled, finds applications in blends with a proportion of a polymer, in built up membranes for the roofing industry. Blends of three commercially used polymers with a 100 penetration grade Nynas bitumen at levels between 9% and 29% w/w were prepared using a Z-blade mixer. The morphology, thermal and dynamic mechanical properties of these blends were examined using fluorescence optical microscopy, differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The blends prepared with these polymers displayed low temperature flexibility and an onset of flow at high temperatures. The former characteristic is required for use in cold environments the latter feature being a critical property when the membrane is manufactured and later when applied by the torching process on a roof. It may be seen how the different blends function in a manner that makes them suitable for the production of built-up roofing membranes.

Copolymers of acrylonitrile with some furans and their Diels-Alder adducts

Abstract Copolymers of acrylonitrile with furan, 2-methylfuran and with 2,5-dimethyl furan have been prepared by free radical copolymerizations, and their 13 C spectra examined for evidence of the three types of structure that formed, according to previous studies. We have characterized the Diels-Alder adducts of acrylonitrile with furan and with 2-methylfuran, and have found that they may also copolymerize with acrylonitrile by addition at their double bonds. The enchained adducts were most readily recognized in the 1 H spectrum by shifts at 4.8 and 4.6 ppm respectively from protons at the oxygen bridgehead. The 13 C spectra of these various polymers have been assigned with the aid of model compounds. Below δ =60 ppm the nitrile shift was dispersed over a larger range of shifts than is found in PAN itself, and was joined by the shifts of unsaturated carbon atoms and of carbon atoms linked to the oxygen atoms within these structures. Above 60 ppm the shifts of carbons in acrylonitrile units were found to be perturbed systematically from their normal places by the presence of neighbouring structures formed from the different furan-containing molecules. In both the 1 H and 13 C spectra shifts characteristic of the end groups from the AIBN initiator were noted. Fine structure in the spectra was attributed to monomer sequence effects and to the tactic structure of the polymer. Chiral centres appeared to be created from the furan rings at random, at least when protonated carbons were the site of initial attachment, but the mode of addition to the ring—whether cis, trans or both, was not certain. Assignments were made of bands in the i.r. spectra to modes of vibration of the units formed from the furan monomers.

Solution properties of polysulphones of some 1,2-disubstituted alkenes

Abstract Fractions of poly(cyclohexene sulphone), M n = 22 500–324 000 , and poly(cyclopentene sulphone), M n = 47 200–571 000 , were prepared. Unlike poly(hex-1-ene sulphone) and poly(2-methylpent-1-ene sulphone), neither of these polymers, nor poly(but-2-ene sulphone) nor poly(hex-2-ene sulphone), showed any dielectric dispersion in solution over the frequency range 2 × 102 to 1.2 × 107Hz. The dielectric increment was similar in magnitude to the high frequency value for poly(hex-1-ene sulphone) and poly(2-methylpent-1-ene sulphone), and was attributed entirely to distortion polarization. The absence of a permanent dipole indicates that in the polysulphones of 1,2-disubstituted alkenes the CC bonds are all in the trans conformation, whether or not the alkene has a cyclic structure. Unperturbed dimensions were calculated from viscosity data and compared with those calculated for free rotation about the two CS bonds in each repeat unit, the CC bonds being assumed to be all in the trans conformation. The observed values are not greatly in excess of the free-rotation values.

A model for structural inhomogeneities in hexagonal polyoxymethylene (POM)

Abstract Recently samples of POM have been prepared which have the X-ray powder diffraction pattern of the hexagonal form, but have a distinctly different i.r. spectrum. These observations are interpreted here as being due to a difference in the packing of the helical molecules, rather than to the presence of significantly non-standard conformations which is the usual interpretation.

Cross-polarization magic-angle spinning 13C nuclear magnetic resonance spectra of acrylonitrile—furfuryl alcohol copolymers

Abstract A copolymer consisting of nearly equal weights of residues from acrylonitrile and furfuryl alcohol has been subjected to heating to two different temperatures under nitrogen, and exposed to concentrated hydrochloric and sulphuric acids. The chemical changes thus caused have been monitored by cross-polarization magic-angle spinning 13 C nuclear magnetic resonance spectroscopy. Strong spinning sidebands from the nitrile carbons of the acrylonitrile residues and weaker spinning sidebands from the olefinic carbons of the furan residues were observed in the standard experiment. The structure of the material was completely altered by heating to 600°C, extensive aromatic structures being formed, but at 185°C only one type of furan residue was rearranged. This structure was also attacked by exposing the powdered copolymer to concentrated hydrochloric and sulphuric acids. The chemical changes within the copolymers were also characterized.

Conformational properties of poly(alkene sulphone)s in solution: 1. Relation between the dielectric properties in solution and the structure of the repeat unit

Abstract A survey of the available evidence shows that the central CC bonds in β-disulphones and polysulphones have a mainly trans , and sometimes an exclusively trans , conformation. Calculations of the coulombic interactions in the 27 possible conformational sequences in SO 2 CH 2 CH 2 SO 2  show that certain sequences having gauche CC bonds are unlikely to be significantly populated. Others such as ( t , g − , g + ) and ( g − , g − , g + ) involve a certain amount of steric interaction but are likely to be comparable in energy with those having a trans CC bond. One alkyl substituent or two at the same carbon atom eliminates some but not all of the accessible sequences having a gauche CC bond. Substituents at both carbon atoms cause such strong steric interactions that only trans CC bonds are allowed. It is shown how such considerations account satisfactorily for the two types of dielectric behaviour of poly(alkene sulphone)s in solution. Preliminary experiments indicate that poly(norbornene sulphone), unlike polysulphones of other 1,2-disubstituted alkenes, does have a permanent dipole because of the inability of adjacent CS bonds to take up anti-parallel positions. A close resemblance is noted between the conformation about the main-chain CC bond in poly(cyclohexene sulphone) and that about the main-chain CC bond in poly(but-2-ene sulphone) in its most stable configuration.