Styrene crosslinks

The term IPN was first used in 1960 to describe the apparently homogeneous product obtained from styrene crosslinked with divinylbenzene. IPNs were prepared from this system by taking a crosslinked poly(styrene) network and allowing it to absorb a controlled amount of styrene and a 50% divinylbenzene-toluene solution containing initiator. Polymerisation of this latter component led to the formation of an IPN, the density of which was... 

Oil-Based SINs. The SINs produced were based on a castor oil polyester-urethane and styrene crosslinked with 1 mole percent of technical grade (55%) divinyl benzene (DVB) (7). This structure may be written poly[(castor oil, sebacic acid, TDI)-SIN-(Styfene, DVB)], poly[(CO,SA,TDI)-SIN-(S,DVB)]. Benzoyl peroxide (BP) (0.48%) was used as the free radical initiator for the styrene and 1,4-tolylene-diisocyanate (TDI) was used as the crosslinker for the polyester prepolymer. A 500 ml resin kettle equipped with a N inlet, condenser, thermometer, and high torque stirrer was used as the polymerization reactor. 

Styrene Acrylonitrile a-Methylstyrene Divinylbenzene Basic monomer Basic monomer Instead of styrene Crosslinking agent... 

The distribution of styrene crosslinks in cured unsaturated polyesters based on maleic anhydride, phthalic anhydride, propylene glycol and dipropylene glycol is found to be dependent on the molar ratio of styrene vs. maleic/fumaric unit. If the molar ratio is higher than 1, the dyad distribution is predominant lower molar ratios yield mostly styrene microdomains, i.e. n-ads with more than 2 styrene repeating units 232>. 

W. F. Graydon and R. J. Stewart (41) also compared the membrane potentials with the values according to equation (46). The membrane investigated was a copolymer of p-styrene sulfonic acid and styrene crosslinked with divinyl benzene. In the large majority of cases the experimental values were lower than those according to equation (46). The smaller part of this difference could be attributed to the transport of the co-ions and was calculated roughly. The greater part was attributed to water transport. From this the transport number of water was calculated it varied from 1 to about 60. It was found that the water transport was proportional to the water content and inversely proportional to the number of crosslinks. A provisional direct measurement was effected of a water transport number. The value corresponded rather well with the indirect determination as described above. 

Ultrasonic measurements (5 MHz) made at ambient temperature on amine-crosslinked epoxies (Morel et al., 1989), or styrene-crosslinked vinyl esters (Bellenger et al., 1994), show that K is effectively proportional to the cohesive energy density ... 

Then, the knowledge of K and v allows us to calculate all the other elastic constants. Typically, the Poisson s ratio of glassy thermosets at temperatures close to 20°C ranges between 0.37 (styrene-crosslinked polyesters) and 0.42 (certain amine-crosslinked epoxies), which corresponds to tan Ap values ranging between about 0.01 and 0.1. 

For styrene-crosslinked unsaturated polyesters and vinyl esters, v is considerably higher v (20 5)10 4 KT1 and v/G —3. It is noteworthy that in such networks (Tg 100°C) the temperature interval between ambient temperature and Tg is a diffuse transition region in which tan 8 increases almost continuously with temperature. 

Some styrene crosslinked Increase with ester... 

Figure 14.7 Rubbery modulus against dangling chains concentration in styrene crosslinked unsaturated polyester. (After Mortaigne et a/., 1992.)...

Table 14.3 Characteristics of the hydrolysis kinetics at 100°C, 100% HR for styrene crosslinked unsaturated polyester and vinyl esters. (After Ganem et a ., 1994.

The solid supports used in this study were macroporous co-polymers of vinylpyridine and styrene crosslinked with divinylbenzene. Polymers of this type in the form of beads are available commercially (e.g. Reillex 425) and were also prepared for this study by Purolite. For spectroscopic studies, a more convenient sample morphology was required and thin-film polymers of similar stoichiometry were synthesised by the group of Sherrington at the University of Strathclyde. Full details of the methods used to prepare thin film polymers are reported elsewhere.11 To generate the ion exchange resin, the pyridyl functionalities of the polymer were quatemised with methyl iodide (Eq 1). 

The styrene crosslinking of unsaturated polyester resins is perhaps one of the most widely used reactions to form the matrix for fibreglass-reinforced composite materials. (The... 

Although we found other examples with a roughly statistical distribution of the clusters (e.g., for styrene crosslinked by Ta404(0Et)8(0Mc)4)," " we also observed SAXS curves with two maxima instead of one. This indicates a different distribution of the clusters with two different intercluster distances. One possible explanation of the double-maximum is that the anisotropic shape (elongated disks) of some cluster types results in a kind of discotic arrangement. The shorter distance would then correspond to the inter-cluster distances within a pile of disks, and the longer distance to the distance between clusters of neighboring piles (Fig. 4). 

Typical density values for networks are 1150 1330 kg m for amine-crosslinked epoxies (Ma 7 1) 1120-1180 kg m for styrene-crosslinked vinyl esters (Ma 6.3-7.1) and 1170-1220 kg m for styrene-crosslinked... 

---