-F i v e d i f f e r e n t l a b o r a t o r i e s have c o l l a b o r a t e d i n a research programme on determination o f t h e branching frequency i n a LDPE sample.Size e x c l u s i o n chromatography (SEC), SEC-on-line v i s c o s i t y (OLV) measurements, DSC-, NMR-, v i s c o s i t y measurements, as w e l l as SEC-onl i n e low angle l a s e r l i g h t s c a t t e r i n g (LALLS) measurements and o f fl i n e LALLS measurements, were performed on b o t h t h e whole sample and on f r a c t i o n s . The f r a c t i o n s were obtained by temperature r i s i n g e l u t i o n f r a c t i o n a t i o n (TREF) and by l i q u i d -l i q u i d phase s e p a r a t i o n (L-L), r e s p e c t i v e l y . D i f f e r e n t long c h a i n branching (LCB)-parameters can be derived. Their d i f f e r e n c e s were explained and some o f them were used i n gation. Also, d i f f e r e n t 8-values i n t h e expression 9' = g were used and discussed. A B-value o f 0.9 was obtained for t h e g l o b a l sample. The conclusion o f t h e f r a c t i o n a t i o n work on t h e LDPE was t h a t TREF f r a c t i o n a t e s according t o s h o r t c h a i n branching (SCB) and t h a t L-L f r a c t i o n a t e s according t o LCB.h i s i n v e s t ik J

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Trimethylolpropane trimethacrylate (TRIM) was suspension-polymerized with toluene as poreforming agent. The concentration of the monomer (TRIM) in the porogen was varied between 20 and 50 v01.-' 4' 0 of the organic phase. The poly(TR1M) particles had narrow particle-size distributions. The porosity of the dry gels was studied with scanning electron microscopy, nitrogen adsorption/desorption and mercury porosimetry. All gels had bimodal pore-size distributions.The size distribution of large pores (r > 50 A) of solvent free poly(TR1M) broadened when the amount of TRIM was decreased. The pore-size distributions of the swollen poly(TR1M) gel particles were calculated from size-exclusion chromatography (SEC) results. The separation range for poly(TR1M) particles of polystyrene standards varied with the monomer concentration. A relationship between the pore-size distributions of dry poly(TR1M) gels and those of swollen gels is proposed. Whether or not the structure of poly(TR1M) gels could be described as fractals is discussed. 100 (V(swo1len gel) -V(dry gel) S = gel) CCC 0025-1 16X/91/$03.00 0 1991, Hiithig & Wepf Verlag, Basel 1224 A. Schmid, L.4. Kulin, P. Flodin P A K D Partition coefficient Skeletal density of the dry polymer Area beneath the differential pore-size distribution curve, proportional to the percentage of the total separating volume vR -vR2700000 vR 250 -vR 2700000 K D = R S P Specific resolution R ,Resolution of two peaks HETP Height equivalent to a theoretical plate *) Systematic IUPAC nomenclature: 2-Ethyl-2-hydroxymethyl-1,3-propanediol.

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