Thermal and Photo-chemical Degradation of Nylon 6,6 Polymer: Part III Influence of Iron and Metal Deactivators

Transcription

1 Polymer Degradation and Stability 23 (1989) Thermal and Photo-chemical Degradation of Nylon 6,6 Polymer: Part nfluence of ron and Metal Deactivators Norman S. Allen, Michael J. Harrison, Michelle Ledward Department of Chemistry, Faculty of Science and Engineering, John Dalton Building, Manchester Polytechnic, Chester Street, Manchester M1 5GD, UK & Gordon W. Follows Research and Development, C (Fibres), PO Box 90, Wilton, Middlesborough, Cleveland TS6 8JE, UK (Received 4 May 1988; accepted 9 May 1988) ABSTRACT The effects of red and black oxides of iron on the photo-oxidation of nylon 6,6 film at 5 ppm concentration have been studied using viscometry and ultraviolet absorption at 294 nm together with the stabilising effect of three commercial metal deactivators; namely, Mark CDA-1, Naugard XL-1 and rganox MD Both metal oxides are sensitizers of nylon 6,6 photo-oxidation. The presence of the metal deactivators effectively inhibits the photo-sensitising effect of the iron in the order rganox MD-1024 > Naugard XL-1 > Mark CDA-1. The metal deactivators are also very effective light stabilisers in the absence of the added iron. There is a good correlation between the initial ultra-violet absorption at 294 nm of the polymer samples and their subsequent rates of photo-oxidation. t is concluded that the iron is a catalyst for the generation of ultra-violet absorbing impurities during the manufacture of the polymer and preparation of the film. NTRODUCTON t is now well established that impurity chromophores are responsible for initiating the sun-light induced photo-oxidation of nylon polymers. 1 - ~ The 165 Polymer Degradation and Stability /89/$03" Elsevier Science Publishers Ltd, England. Printed in Great Britain

2 166 Norman S. Allen et al. nature and importance of the impurity, as in many other polymers, is uncertain, but various species which have been identified include hydroperoxides, 8 iron, 9 carbonyl groups a and ~,fl-unsaturated carbonyl groups.l 1-14 n part of this series, 15 whilst there were indications that the luminescent ~, fl-unsaturated carbonyl groups may be important initiators in the photooxidation of nylon 6,6 polymer, other factors, such as the manufacturing and processing history, appeared to be more important in controlling polymer stability by influencing the number of terminal amine end-groups. n part the influence of hindered piperidine stabilisers, both as free molecules and bound to the chain-ends, was examined on nylon 6,6 photo-stability. 16 n both cases good light stability was achieved. Of all the chromophores considered, however, the nature and importance of photocatalytic metal ions such as iron have not previously been studied. We therefore report here on our observations on the effect of two types of iron on the photo-sensitised oxidation of nylon 6,6 film, together with the effect of three commercial metal deactivators, Mark CDA-1, Naugard XL-1 and rganox MD The two types of iron chosen for study were red ferric oxide (Fe203) and black magnetic oxide (Fe304). The photo-stability of the nylon 6,6 polymer was monitored using viscometry number and UV absorption at 294 nm. The latter was found in earlier work 15.a 6 to be a useful method and will usefully broaden such correlations to the field of photostabilisation. t is interesting to note that no previous work has appeared on the effect of metal deactivators on the photo-stability of nylon polymers. This may well be associated with the high temperature autoclave conditions and nature of the condensation polymerisation process which can result in some conversion and loss of the stabiliser. Our preparative conditions have minimised these effects. Unlike the polyolefins, nylon polymers are mainly stabilised by the addition of salts and compounds of copper and manganese a7 and in this respect this study should make an interesting comparison as well as support our previous work 15'16 on the stabilising activity of terminal amine groups and hindered piperidine stabilisers. Materials EXPERMENTAL Samples of partially (Mn = --~ 8000) and fully polymerised (Mn =,-~ ) additive free nylon 6,6 polymer were supplied by C Fibres. The chemical formulae and suppliers of the metal deactivators used in this study are shown in structures 1 to 3. The partially polymerised nylon 6,6 chip was

3 Thermal and photo-chemical degradation of nylon 6,6 polymer 167 ~ HO C--N--C N P / O H N N \ / N H (!) Mark CDA-, Adeka Argus Chemical Co. Ltd, Japan X-" O HO] it ll/ H O ~ CH2CH2COCH2CH2N C-]~ 2 (2) Naugard XL-, Uniroyal Chemical Co. Ltd, USA (3) lrganox MD-1024, Ciba-Geigy Corporation, Switzerland Structures 1-3. Metal deactivators. coated with a 2-propanol solution of the metal deactivators (0"25% w/w) followed by drying under vacuum for 15 min at 120 C. Samples of the coated polymer chip were also heated in steam for 50 min at 275 C. All film samples (~ 100 #m thick) were prepared by compression moulding for 30 s at 285 C under nitrogen gas. The red and black oxides of iron were both commercially available from BDH Chemicals Ltd, UK, and were incorporated into the polymer during polymerisation. Photo-oxidation Photo-oxidation experiments were carried out in a Microscal Lightfastness Unit (Microscal Ltd, London) equipped with a 500W high pressure mercury/tungsten source.

4 168 Norman S. Allen et al. Viscosity measurements This technique was used to monitor the rate of change in molecular weight during thermal and photo-oxidation of the polymer samples. Flow times of solutions of nylon 6,6 polymer (1% w/w in 90% v/v formic acid) were measured using an Ostwald micro-viscometer at 25 C. All the solutions were filtered through glass wool prior to measurement. Viscosity number was determined from the following relationship: Nsp = t- t o to (for a dilute solution) where Nsp is the specific or relative viscosity and t o and t are the flow times (s) of the pure solvent and the nylon 6,6 solution respectively. The viscosity number is obtained using the relationship V.N- Nsp C where C is the concentration of the polymer sample in grams per cm a. The percentage decrease in viscosity number is given by the relationship: [ V. N O - V. Nt] ] %V.N= 1- ~ 100 J where V. N O and V. N t are the viscosity numbers of the polymer sample prior to and after degradation for time t. Spectroscopic measurements Ultraviolet absorption measurements at 294 nm were carried out on the 1% formic acid solutions of the polymers using a Perkin-Elmer model 554 absorption spectrometer while the fluorescence and phosphorescence analyses were carried out on the same solutions using a Perkin Elmer LS-5 Luminescence spectrometer at room temperature and 77 K, respectively. RESULTS AND DSCUSSON The preparative histories of all the nylon 6,6 film samples are shown in Table 1 together with their initial viscometry numbers and initial ultraviolet absorbance values at 294 nm.

5 Thermal and photo-chemical degradation of nylon 6,6 polymer t69 TABLE 1 Sample dentification nitial nitial UV Sample dentification viscometry absorbance number number at 294 nm Control: Partially Polymerised with 5 ppm red ferric oxide Control: Partially Polymerised with 5 ppm black iron oxide Control Partially Polymerised (1) 50m in Steam at 275 C " (3) Mark CDA % w/w (3) Naugard XL % w/w 138 0'23 6 (3) rganox MD % w/w t (2) 50m in Steam at 275 C (7) Mark CDA % w/w (7) Naugard XL % w/w 150 0'22 10 (7) rganox MD % w/w 145 0"17 11 Control Partially Polymerised (11) 50m Steam at 275 C (12) Mark CDA % w/w 134 0"69 14 (12) Naugard XL % w/w (12) rganox MD % w/w 133 0'27 16 Control Fully Polymerised (16) 50m in Steam at 275 C (17) Mark CDA % w/w 149 0'67 19 (17) Naugard XL % w/w (17) rganox MD % w/w 149 0'23 Effects of iron oxides The effect of the red and black oxides of iron at 5 ppm concentration on the photo-oxidation of nylon 6,6 film, as measured by the percentage change in viscosity number, is shown in Fig. 1. Compared with the control film sample it is seen that both oxides are photo-sensitisers with the red form being the more active. This is consistent with the higher initial absorbance at 294 nm of the polymer although the control film is higher than that containing the black oxide. However, the results in Fig. 2 demonstrate the importance of ultra-violet absorbance at 294 nm as a means of monitoring the rate of photo-oxidation of the polymer films. The rates are seen to be consistent with those for viscometry shown in Fig. 1 and implicate the importance of these light absorbing impurities in the photo-oxidation mechanism. Metal ions are well known to catalyse the thermal decomposition of hydroperoxides (Scheme 1) and promote the formation of photo-active chromophores. The effect of 5 ppm iron seen here is quite noticeable particularly

6 170 Norman S. Allen et al. d F- C) (..) so 3O t~ / ( ) /// :fppm ~: Control. Fe_0. uj RRADATON TME, hrs Fig, 1. Percentage change in viscosity number versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100/~m thick) partially polymerised before (1 l) [] and after doping with (1) F1, 5 ppm red ferric oxide and (2) m, 5 ppm of black magnetic iron oxide. U rn n- O 3 to,n > 2 E3 w u~ - E J ~r go, 0 ~ V RRADATON,.,.f...--O(i) //,2, (itl O: 5ppm Fe203 Q:,, F 304 ~: Control ' 260 OQ TME) hrs Fig. 2. UV absorption at 294 nm versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100~m thick) partially polymerised before (1 l) [] and after doping with (1) 17, 5 ppm red ferric oxide and (2) m, 5 ppm black magnetic iron oxide. ROOH + Fe 2 + ~ RO. + HO- + Fe 3 + ROOH + Fe 3 + ) RO~ + H + + Fe 2 + Overall 2 ROOH ) RO" + RO~ + H20 Scheme.

7 Thermal and photo-chemical degradation of nylon 6,6 polymer 171 since previous work suggested that 8 ppm of iron was necessary to initiate photo-oxidation of nylon 6,6 polymer. 9 Effect of metal deactivators The effect of the three metal deactivators on the rates of photo-oxidation of the nylon 6,6 films containing 5 ppm of the red and black oxides of iron are shown in Figs 3 and 4, respectively. t is seen that in both cases the three compounds at 0-25% w/w stabilise the polymer in the order rganox MD > Naugard XL-1 > Mark CDA-1. The poorer efficiency of the last one may be due to its smaller molecular size. n both cases the polymer samples had been treated in steam at 275 C for 50 min and when compared with the untreated film samples it is noted that this process destabilises the polymer. This latter effect is due to further polymerisation and reaction of the amine end-groups and the possibility of further degradation. 17 A further interesting effect is the observation that the stabilising actions of the metal deactivators, especially Naugard XL-1 and rganox MD-1024, are more effective with the red than with the black oxide of iron. This may well be due to easier co-ordination in the former case. Again, for both metal oxides the initial ultra-violet absorbance values of the nylon 6,6 films at 294 nm (Table 1) correlate with the photo-stabilising action of the metal deactivators. Sppm Fe O 4O so 0: Sppm Fe203 /.1~(3} : S0min/275 o C/Steorn m//'//'0(,./~(4) + Fe203 (Sppm) / ~:(3) Mark CDA-1 (02 5 Yo) / 8: ', Nougard XL-1,, 8: " rganoxmd102t,,. > 20 Ll 0 o0 R:::ADA T ON TME, hrs 200 Fig. 3. Percentage change in viscosity number versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100/~m thick) partially polymerised with 5 ppm red ferric oxide (1) F-, no treatment and then after heating in steam at 275 C for 50min with (3), no metal deactivator and with 0"25% w/w (4) c3, Mark CDA-1; (5) ~ Naugard XL-1; (6) Ell, rganox MD-1024.

8 172 Norman S. Allen et al. 5pprn Fe~ 0,. 6 >. - 50~ 4O O 3O U L/% > _z 2O M m 0 i,i u ~A a ol RRADATON TME, hrs OO 200 0: 5ppm Fe3 0/. 1:50 rains/275 C/Steom +Fe30/. ( 5ppm)- {~: Mark CDA-1 (0"25%) e:naugard XL1., $: rgonox MD102/.. Fig. 4. Percentage change in viscosity number versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100#m thick) partially polymerised with 5 ppm black magnetic iron oxide (7) D, no treatment and then after heating in steam at 275 C for 50 min with (2) n, no metal deactivator and with 0'25% w/w (8) ~, Mark CDA-1; (9) ~, Naugard XL-1; (10) Aq, rganox MD C >- 4C > z w m uj n" u uj O 0 ol J(,2) C ~)nt ro.~; ~_~j~(,,) RRADATON TME,hrs ( 3) ~: ControL. PartiaLly PoLymerised ' 50mins/275 cj Steam O:02)Mark CDA 1(O25~ o) e:(12)nau9ard XL1 ~:(12)lrganoxMD1024. Fig. 5. Percentage change in viscosity number versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100/~m thick) partially polymerised with (11) [], no treatment and then after heating in steam at 275 C for 50min with (12),, no metal deactivator and with 0-25% w/w (13) [~, Mark CDA-1; (14) ~, Naugard XL-1; (15) Rq, rganox MD-1024.

9 Thermal and photo-chemical degradation of nylon 6,6 polymer 173 Contro[~.5O o i z20 N~o go w C3 ~ : FulLy Potymerised,T n(16l.ml( 8'1 - o ~~ Snj"~H~.'/ ':S0rr'l'i'l$/t7S C /St~:l'1"l CDA1(025~) (19)@:,, Naugard XL1,, 8:. r9an0x M DO2L,,, 00 ' RRADATON TME, hrs 26o Fig. 6. Percentage change in viscosity number versus irradiation time in the Microscal unit (h) for nylon 6,6 films (100 #m thick) fully polymerised with 16-1, no treatment and then after heating in steam at 275 C for 50 min with (17), no metal deactivator and with 0.25 % w/w (18) [], Mark CDA-1; (19) ~, Naugard XL-1; (20) FR, rganox MD The stabilising effects of the three metal deactivators in both the partially and fully polymerised nylon 6,6 films in the absence of any deliberately added iron oxides are shown in Figs 5 and 6, respectively. Again the same order in photo-stabilisation is observed with the effects being greater in the former than in the latter due to a loss of amine end-groups through further polymerisation and further degradation. 15,16 These photo-stabilising effects are quite significant and similar to the rates of photo-oxidation of the iron oxide doped films. Thus, whilst it may be argued that the metal deactivators are effective antioxidants due to their hindered phenolic groups, it is evident from these results that they are operating as metal deactivators and that metal ions already present in the nylon 6,6 may well be more important than previously thought. CONCLUSONS The results clearly show that iron oxides are sensitisers of the photooxidation of nylon 6,6 polymer with the red form being more photo-active than the black. Metal deactivators are effective in inhibiting the photosensitised reactions in the order rganox MD-1024>Naugard XL-1 > Mark CDA-1.

10 174 Norman S. Allen et al. ACKNOWLEDGEMENT The authors thank mperial Chemical ndustries PLC for financial support for MJH and ML, cooperation and facilities in carrying out this programme of work. REFERENCES 1. Achhammer, B. G., Reinhardt, F. W. & Kline, G. M., J. Res. Nat. Bur. Stnds., 4 (1951) Ford, R. A., J. Coll. Sci., 12 (1957) Moore, R. F., Polymer, 4 (1963) Burnett, G. M. & Riches, K. M., J. Chem. Soc., (B), (1966) Lock, M. V. & Sagar, B. F., J. Chem. Soc., (1966) Sharkey, W. H. & Mochel, W. E., J. Am. Chem. Soc., 81 (1959) Allen, N. S., Chem. Soc. Revs., 15 (1986) Anton, A., J. Appl. Polym. Sci., 9 (1965) Betts, A. T. & Uri, N., Chem. nd., (London) (1967) Rossback, V., Die Angew. Makromol. Chemie., 57 (1977) Allen, N. S., McKellar, J. F. & Wilson, D., J. Photochem., 6 (1976) Allen, N. S. & Parkinson, A., Poly. Deg. & Stab., 4 (1982) Allen, N. S., Poly. Deg. and Stab., 8 (1984) Allen, N. S. & Harrison, M. J., Eur. Polym. J., 21 (1985) Allen, N. S., Harrison, M. J., Follows, G. W. & Matthews, V., Poly. Deg and Stab. (n press). 16. Allen, N. S., Harrison, M. J. & Follows, G. W., Poly. Deg. and Stab. (n press). 17. Allen, N. S. & Mckellar, J. F., Macromol. Revs., 13.(1978) 241.

11 本文献由 学霸图书馆 - 文献云下载 收集自网络, 仅供学习交流使用 学霸图书馆 ( 是一个 整合众多图书馆数据库资源, 提供一站式文献检索和下载服务 的 24 小时在线不限 P 图书馆 图书馆致力于便利 促进学习与科研, 提供最强文献下载服务 图书馆导航 : 图书馆首页文献云下载图书馆入口外文数据库大全疑难文献辅助工具