SYNOPSISUsing polycaprolactone (PCL) fibers drawn with various draw ratios, the effects of draw ratio on enzymatic degradation were studied in order to understand the influence of fine structure on biodegradation. Degradability of PCL fibers as monitored by total organic carbon (TOC) formation or weight loss decreased with increase in draw ratio due to higher crystalline content. There were some distinct features of degradation behavior among the fibers, because the fibers underwent significant change in molecular organization of the polymer, such as crystallinity and orientation, during drawing processes. From scanning electron microscopy (SEM) photographs showing that the enzyme preferentially attacked amorphous or less ordered regions rather than crystalline or more ordered regions of the fiber, spherulites were observed in the undrawn fiber, and on the other hand, fibrillar stripes along the fiber axis were observed in the drawn fibers, which suggest that the spherulites in the undrawn fiber were extended to be broken, and fibril structures were formed during the drawing processes. These SEM photographs suggest that there are differences of crystal structures in addition to crystallinity among the fibers with different draw ratio, which significantly affects the enzymatic degradation behavior of the fibers. The diameter of the fibers became gradually slim, macroscopically uniform, as enzymatic degradation proceeded although it was dependent on draw ratio. It is evident that the degradation proceeded in the crystalline regions as well as the amorphous regions. 0 1995 John Wiley & Sons, Inc.

Structure and properties of high-speed spun fibers of nylon 6 were studied in the range of take-up speeds from 5 to 12 kdmin. With increasing take-up speed, Young's modulus increased uniformly, while tenacity passed through a maximum at 8 km/min. WAXD data demonstrated the increase in the perfectness of the crystalline state with increasing take-up speed. First, the y-form crystal structure predominated up to 9 kdmin along with increase in its crystal size; second, in the range of 9 to 12 km/min, the a-form crystal structure appeared and developed as reflected by the increase in its crystal perfection. The structure-properties relationships are discussed, and it is indicated that the increasing tendency of Young's modulus over 9 kdmin can be attributed to the development of the a-form crystals.

SYNOPSISThermal shrinkage, viscoelastic properties, wide-and small-angle X-ray diffractions, and molecular orientation by fluorescence method were measured for fiber samples of nylon 46 [ poly (tetramethylene adipamide) ] as compared with nylon 66 [ poly (hexamethylene adipamide) ] . The structural study of nylon 46 fiber indicated that molecular chains are welloriented along the fiber axis in the interlamellar region whose thickness is relatively thin. It was also shown that the onset of thermal movement of nylon 46 molecules is shifted to the higher temperature than nylon 66. These characteristics will be attributed to the cause of good dimensional stability, a significant feature of nylon 46 fiber, attractive for its application to industrial usages.

SYNOPSISMeasurements of melting points were made for melt-polymerized aliphatic-aromatic copolyamides; ( i ) N66PT, (ii) N66CT, and (iii) N66ST, i.e., nylon 66 [ poly (hexamethylene adipamide ) ] copolymerized with three kinds of aromatic diamines, p -phenylenediamine ( P ) , bis(p-aminophenyl) methane ( C ) , and bis(p-aminophenyl) sulfone ( S ) , and terephthalic acid ( T ) . As the mole fraction of copolymerized component nl, increases in the case of (ii) or (iii) , the melting point decreases uniformly according to the relationship of Flory. In the case of ( i ) , the melting point first decreases and then begins to increase after passing a minimum a t nl N 0.2. A preliminary WAXD (wide-angle X-ray diffraction) study on N66PT crystals shows that the basal plane of the crystal lattice shifts from that of nylon 66 toward hexagonal packing with the increase of nl. It was suggested that the formation of mixed crystals for a series of N66PT will be attributed to their melting point behavior.

SynopsisElastomers, based on cellulose fibers, were synthesized by grafting ethyl acrylate onto fibers preirradiated by a high-energy electron beam. The rheological properties and fine structure of the elastomers were investigated in order to determine factors in development of rubber-like elastomeric behavior. Mechanical properties of the elastomers depended on (1) degree of polymerization of irradiated cellulose molecules, (2) extent of grafting, and (3) experimental methods of evaluation, particularly in varying environmental conditions, for example, in making measurements in air, water, or ethyl acetate. Glass transition temperatures of the elastomers were dependent on the environmental conditions of evaluation; stiffnesses of the elastomers levelled off a t about 0°C; and in all environments, a rubber-like plateau was observed. Poly(ethy1 acrylate) separated from the elastomers was not soluble in acetone. The mean molecular weight of the separated poly(ethy1 acrylate) of the elastomer was determined in ethyl acetate by the equilibrium swelling method. Electron microphotographs of cross sections of the elastomers, which exhibited rubber-like behavior, indicated that the fibrillar structure of the irradiated cellulose fibers formed a uniform network and that poly(ethy1 acrylate) was uniformly distributed among the fibrils.It was concluded that crosslinks existed in the elastomers.