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The maximum shear rates used in ref 9 ranged from 1.8 X lo4 s-' at 345 MPa (50000 psi) to 3.8 X lo5 s-' at atmospheric aressure.(18) 2.ABSTRACT: The viscoelastic properties of poly(pivalo1actone) (PPL) have been investigated in the linear range using stress-relaxation and dynamic-mechanical measurements. Under the conditions that the sample was isotropic and insensitive to relative humidity, Ferry's reduction method was applied without using translations along the vertical axis. A horizontal shift factor was determined at each temperature, which satisfactorily agreed with the WLF equation in the transition region. The apparent activation energy of PPL was temperature dependent and passed through a maximum near Tg whose value was found to be 369 f 3 K. The relaxation spectrum was calculated according to the first method of approximation of Schwarzl and Staverman, and it was found to be flat with a complicated fine structure. Two absorption peaks were determined. The low-temperature y peak, around 300 K, was ascribed to a relaxation process in the crystalline phase of the polymer while the high-temperature p peak was related to the glass-transition process.Among polylactones based on the skeletal formula (-CH2CR1R2C00-),, poly(pivalo1actone) ( P P L ) has been the most extensively studied because of its technological i m p~r t a n c e . ' -~ The practical and technological interests appeared since the polymer has been commercially spun to give fibers.Q Moreover PPL has been f o u n d to have reinforcing properties when prepared in copolymers of the general s t r u c t u r e ABA where A represents a PPL block and B an elastomer, for example, poly(cu-methyl-a-npropyl-P-propiolactone) ( P M P P L ) . The mechanical properties of PPL/PMPPL ABA copolymers were reported similar to those of commercial styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) copolymer^.^ More recently, it was shown that grafting of short ( M , -500-4000) chains of PPL onto various elastomeric backbone polymers, including ethylene-propylene-diene, a l t e r n a t i n g ethylene-ethyl a c r y l a t e copolymer, and poly(ethy1 acrylate), produced a new type of thermoplastic elastomer with outstanding physical properties, such as solvent resistance resilience, abrasion resistance, and h e a t and aging ~t a b i l i t y . "~ ABA triblock copolymers containing 35-45% PPL made f r o m polyisoprenes ( M , -40000) could be melt-spun into fibers showing excellent mechanical properties.1° In each case, t h e o u t s t a n d i n g properties of these P P L -g r a f t elastomers were related t o the hard segments of PPL which act as cross-linking sites and reinforcing filler particles. In view of the commercial importance of PPL, its thermal and crystalline properties have been investigated.11-19 But surprisingly, its mechanical properties have not been studied despite the importance of t h i s investigation i n order t o know the performance of PPL as a commercial film o r fiber.It is then the purpose of the present paper t o investigate the...

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SynopsisA method has been developed which permits the quantitative determination of fiber orientation in a cellulosic sample (paper, nonwoven or composite). From the measured fibril angle distribution function and the observed variation in intensity of the (002) plane of the x-ray pattern, a parameter governing the fiber distribution function is obtained analytically. The method is demonstrated for two different paper samples showing a narrow and a large fiber orientation distribution. The method is rapid for a series of samples involving the same fibers and does not involve any operator interpretation. It gives directly the average fiber orientation function from the bulk.of the sample, not just from its surface as microscopic methods do. It can be particularly useful in the analysis of paper-polymer laminates.

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