Mass Deacidification of Papers and Books
III: Study of a Paper Strengthening and Deacidification Process with Amino Alkyl Alkoxy Silanes
by S. IPERT, E. ROUSSET & H. CHERADAME
INTRODUCTION
This series of papers deals with the mass deacidification of books and documents. In the preceding
paper, a process was described using amino alkyl alkoxy silanes as a solution in ethanol, and it was
shown that the use of 3-amino propyl trimethoxy silane and other similar silanes could be
simultaneously both an efficient deacidification treatment and provide an alkaline reserve necessary
for permanence. The degraded state of the books and documents requiring preservation means that
something must be done to maintain their mechanical properties and to allow further handling. The
Library of Congress evaluated that the cost of microfilming a badly degraded book was 500 times
more than the same operation on a book which can be easily handled1. The loss of mechanical
properties of acidic papers is the major reason for the destruction of books printed on paper containing high yield pulp. It seems that the association of lignin with acidic conditions is one of the main
starting points for poor permanence of paper-based documents.
PREVIOUS PROCESSES SIMULTANEOUSLY DEACIDIFYING AND STRENGTHENING
It is not the first time that a process able to deacidify is also able to improve mechanical properties.
The gas phase process with a mixture of ammonia and ethylene oxide is one example. Ethanol
amine is formed in situ in the paper and the hydrogen bonding given by ethanol amine seems to be
responsible for the increased interfiber bonding energy. However, the use of a mixture of these two
dangerous gases is not trivial.
As for the liquid phase processes, two different variations have to be considered, i.e. whether to
choose aqueous solutions or organic solvents. Of these, aqueous calcium hydroxide must be
mentioned, since it gives a pH of around pH 8 to the treated paper, with an alkaline reserve of more
than 100 meq/kg. An improvement of the mechanical properties is observed as shown by an
increase in the folding resistance2. In order to deacidify, a calcium hydroxide concentration of 10-2
mole/L is apparently satisfactory. However, these solutions are not stable in open air, and give a
precipitate of insoluble calcium carbonate. It must also be noted that many documents cannot be
exposed to contact with water without the danger of damage. Similarly, treatment with aqueous
barium hydroxide has been reported to give good results3. Mechanical strength of samples after
treatment has been shown to be higher than that of the controls, whatever the paper composition4. It
has also been reported that aqueous solutions
In the case of deacidification with organic solvent solutions it has been shown that the diethyl zinc
(DEZ) treatment did not cause any decrease in the tensile strength of acidic mechanical paper. After
thermal ageing, there was in most of the cases, no significant decrease or containing magnesium
salts such as magnesium acetate, carbonate or bicarbonate have improved the mechanical properties
of paper, with the pH of the paper reaching the range pH 9-9.5, and producing an alkaline reserve of
around 0.8% w/w magnesium carbonate after treatment. Folding endurance was seen to have
improved by a factor of 2 or more, according to measurements carried out at the Institut Royal du
Patrimoine Artistique of Bruxelles (Belgium)5. This improvement was obtained, whatever the paper
(wood pulp, chemical pulp, etc.), with a Mg(HCO3)2 concentration of 0.04 mole/L. However, a
yellowing effect was sometimes observed, increase of the tensile strength of the DEZ treated
papers6. It was mentioned that after the DEZ treatment no significant decrease in folding endurance
was found, but after thermal ageing the folding endurance decreased in all cases.
Three deacidification methods have been tested recently, namely DEZ (Akzo), magnesium butoxy
glycolate (FMC) and methoxy ethoxy methyl magnesium (Sablé process)7. In tests for these three
methods it has been shown that the de-acidified papers had a general tendency to be slightly weaker
than the references, especially those treated by the FMC process.
It is also possible to find, in the literature, processes in solvent phase which do not seem to be
detrimental to the mechanical properties of paper. This is the case with a solution of barium
hydroxide in methanol at a concentration of 1% (w/w) whereby deacidification, an alkaline reserve
and better folding endurance are simultaneously observed. However, this treatment has the
drawback of using a toxic heavy metal of the alkaline earth family. The process based on methyl
magnesium carbonate would seem to be more interesting8. The use of this one is reported to have
improved folding endurance when applied in pure methanol or in a mixture of methanolchlorofluoro carbon or in trichloro trifluoro ethane (Freon 113). However, it was mentioned that
papers containing mechanical pulp suffered a loss of folding resistance8. It is clear that processes
involving fluorine containing volatile compounds cannot be recommended. In contrast, some
reports have mentioned that the FMC process based on magnesium glycolate dissolved in tri-chloro
trifluoro ethane does not improve mechanical properties, measured as the resistance to elongation
stress (breaking length), though it does not have any detrimental effect.
It is worth mentioning that in some instances a process able to improve mechanical properties is
absolutely necessary, the state of degradation of some items being extreme. A comparison between
the effect of the two processes based on alkoxy magnesium glycolate having different behavior
demonstrates that the mechanism of improvement is not completely understood. However, besides
fluorine-containing hydrocarbons, it can also be considered desirable to give up reactants based on
alkali cations for reasons which have been mentioned in the preceding paper: alkaline earth cations
such as magnesium cations can constitute a source of problems on long term aging9,10.
Consequently, new deacidification processes have had to be investigated.
Another process that has been described is impregnating the cellulosic material with a suitable
monomer, such as ethyl acrylate and ethyl methacrylate as a mixture, which is further polymerized
by a radical mechanism on exposure to a suitable irradiation. This process has been developed by
the British Library, and sometimes a dramatic increase of a paper's mechanical properties has been
observed. However, its general use cannot be envisaged because of the necessity to employ y
irradiation under nitrogen and because it is not a deacidification process.
It is not enough to bring some protection to the paper after a deacidification treatment, but its
behavior upon ageing must also be considered. Of course, accelerated ageing techniques have to be
used to appraise this aspect. For instance, it is sometimes mentioned that three weeks in an oven at
90°C and 50% RH are equivalent to 1200 years at room temperature (20°C). For the FMC process
using magnesium glycolate it was reported that this ageing treatment did not modify the breaking
length: a rather satisfactory result, and as the ageing condition is quite aggressive, the reliability of
the assumed equivalent to 1200 years is not necessarily brought into question.
The various aspects of the mechanical properties are not of equal value. Among them, tensile
strength and folding endurance are of utmost importance, since they give an indication of the
resistance to mechanical degradation upon handling. The problem is complicated by the fact that
these two parameters often vary in the opposite direction: the more rigid the paper, the lower the
folding endurance and the higher the tensile strength.
This article is devoted to the study and understanding of the effects on paper and its mechanical
properties when treated with amino alkyl alkoxy silanes.
EXPERIMENTAL
Chemicals used for paper reinforcement
In order to examine the general behavior of amino alkyl alkoxy silanes, the effect of some of the
silanes used as agents for mass deacidification treatment in the preceding paper was investigated:
• ATMS: 3-amino propyl trimethoxy silane - NH2-(-CH2-)3-Si(O-CH3)3 (Al-drich);
• AMTMS: 3-amino-2,2-dimethyl propyl trimethoxy silane - NH2-CH2-C(CH3) 2-CH2-Si(O-CH3)3
(Crompton-Witco Corp.);
• DMATMS: 3-(N,N-dimethyl amino) propyl trimethoxy silane - (CH3)2 N(-CH2-)3-Si(OCH3)3(Gelest-ABCR);
• AMDES: 3-amino propyl methyl diethoxy silane - NH2-(-CH2-)3-Si(O-CH2-CH3)2-CH3 (GelestABCR).
• A new bifunctional amino derivative was also examined:
• AATMS: 3-(2-amino ethyl) amino propyl trimethoxy silane - NH2-CH2-CH2NH-(-CH2-)3-Si(O-CH3)3 (Gelest-ABCR). It contains two amine functions.
The silanes were used as received.
Ethanol was used in the absolute state unless otherwise stated. Sometimes a pure grade at 95% was
also used without noticeable change. These solvents were used as received.
Treatment of papers, documents and books
It was decided to study the new deacidification process on naturally aged books already having
some acidic charge in the paper. This procedure has the advantage of imitating a real situation, but
also has some problems such as a limited page space without printing ink, etc. Several books
printed at the beginning of the 20th century were used, and some characteristics are described on
Table 1.
The treatment solutions of amino alkyl alkoxy silanes were prepared at different concentrations in
absolute ethanol in a glove box under nitrogen. After being impregnated for 10 min at room
temperature the books and documents were pressed in order to remove excess solution. Drying was
effected in an oven at 45°-50°C under slight vacuum (water pump). The duration of drying
depended on the size of the document: 20 min. for a block of 8 pages, 5 hours for a book. It was
observed that this last duration depended on the oven used and on the heat
Table 1 : Some characteristics of the various acidic books treated in this research
exchange rate between the book and the heater in the oven. For complete books, the procedure was
similar to that dealing with samples of paper, but the equipment was adapted to the size of the
document, and drying was carried out under primary vacuum with a mechanical pump.
The pH of the books listed in Table 1 was between pH 3.2 and pH 4.6. In addition to them a modern
paper sample was submitted to the tests.
Previously, it had been observed that the treatment of old papers with pure ethanol gave a breaking
length11 increase in the amount of ca.10%. It is to be assigned to the reorganization of the fibrils
upon drying. Also, a slight decrease of yellow index and acidity was observed. This demonstrated
that an ethanol treatment acted as a kind of paper cleaning, but that the effects were too modest to
make it attractive in itself. It will be seen below that the introduction of amino silanes has a
beneficial effect justifying their uses for the treatment of damaged, acidic papers.
Physico-mechanical determinations
The characterization of the effects of the introduction of reactants in the paper web was done
measuring the surface pH, the initial acidity or alkaline reserve and the breaking length. pH was
measured as described in part 1 of this series12, i.e. using a flat electrode for surface measuring. The
reason for using this method was discussed in the second part of this series11. It must be recalled
that the surface pH before treatment is a good indicator of the acidity state of the paper, but after
treatment by an amino silane the surface pH can decrease from a high value, in the pH 8.5 - pH 9
range, to the pH 6 - pH 7 range while the paper still keeps an alkaline reserve.
Tensile strength, given under the usual form as breaking length, was tested on samples measuring
50 mm in length and 15 mm width in the machine direction on conditioned (20°C, 50% RH)
samples using an Instron instrument, working at a rate of 10 mm/min, according to the usual
standard13. For each book a block of 8 pages was kept untreated, representing the initial state. The
folding resistance was measured according to the usual standard14.
RESULTS AND DISCUSSION
Reinforcement effect of ATMS
A preliminary study was necessary to establish the general effect of the process on the paper
properties. Amino propyl trimethoxy silane (ATMS) was one of the silanes used the most in this
study. Its effect was investigated on different acidic papers from damaged old books. The paper
acidity being neutralized, as already described in the second paper of this series, the variations of
mechanical properties were examined using mainly the breaking length (MD). Results are shown in
Table 2.
It is to be noticed that the incorporation of ATMS induced a serious increase of tensile strength.
This increase varied with the nature of the book; it was about 50% of the initial breaking length for
the treating solution containing 10-15% w/w ATMS. The absorption depended on the internal
porosity. As a general indication, papers of the type treated above absorbed around 80% (w/w) of
the solution. It is worth recalling here that the fact that the concentration of the ethanolic solution
was, e.g. 12% did not mean that the paper absorbed 0.8x12 = 10% in weight of the silane. Indeed, it
has been observed that the weight gain (around 6%) is generally lower than that expected from the
absorption of the treating solution. This can be easily determined by the weight of the solution uptake. It seems that a Chromatographic effect partly prevents the penetration of the silane into the
paper web, at least under the conditions used for the experiment, i.e. ca. 10 min contact with the
treating solution. This point will certainly deserve further investigation.
Table 2: Effect of paper treatment with a solution of amino propyl trimethoxy silane (ATMS) in
absolute ethanol on the breaking length.
Storage of the paper for 4-8 months at room temperature did not modify the mechanical properties.
Similarly, ageing the treated papers at 80°C (dry, i.e. room RH) for around 20 days did not bring
any modification to the mechanical resistance. This aspect of the process will be investigated later
using standard testing ageing procedures.
Reinforcement effect of various amino silanes
Using different amino silanes, the effect of different concentrations in an alcohol solution were
examined. Some typical results are shown in Table 3.
In general, the treatment of a paper with a solution of amino alkoxy silane in absolute ethanol
brought about a significant improvement of the breaking length as shown by the comparison
between the untreated samples Al, Bl, Cl and those that had been treated. As mentioned above, it
was verified that treatment with absolute ethanol alone only brought a modest improvement (Dl,
D2). It was also observed that the different amino alkoxy silanes did not exhibit the same efficiency.
It seems that the amino alkoxy silanes with a linear structure, namely ATMS, were slightly more
efficient than the silanes with a more bulky structure such as AMTMS or AATMS. For the small
chain compound, the improvement
Table 3: Effect of paper treatment with a solution of various amino trialkoxy silanes in absolute
ethanol on the tensile strength (given as breaking length).
* Results already cited in ref. 12.
was close to 50% for a treating solution at a 10% (w/w) concentration for different papers, as
becomes obvious by comparing A1/A3 with C1/C2 (Table 3) and Gl/ G2 with H1/H2 (Table 2).
It was also clear that the improvement increased with increasing silane concentration, as shown by
the comparison of Al, A2 and A3, or Bl, B2 and B3. However, the improvement did not seem to be
proportional to the silane content, at least when the concentration of the treating solution was higher
than 6% w/w. It seemed that a concentration of about 8-12% was an optimum, since it was verified
that the silane uptake was less than expected, which could be deduced from the solution absorption
before drying. As already discussed in the preceding paper, this could be due to some irregularity in
the paper uptake measurement, for instance that there was some paper extraction by the treating
solution, or that the water absorption by the paper before treatment was different from that after
treatment. Most probably, as mentioned above, it would seem rather to be due to the differences in
migration behavior of the silane and ethanol in the paper web. The solution concentration of ca.
12% is enough to provide a sufficient alkaline reserve, as mentioned in the first papers in this
series12. The behavior of the bi-functional amino alkoxy silane, AATMS, is similar to that of the
corresponding monofunctional one, ATMS.
Table 4: Effect of different chemical structures of the amine function on the variation of the
breaking length of a paper (book F) treated by different aminosilanes in absolute ethanol.
As far as the mechanical properties measured as the breaking length are concerned, the mixture of
the trialkoxysilane with a dialkoxysilane such as diethoxy diethyl silane did not bring new results as
shown by the comparison of C5 and C2 (Table 3). In the absence of any indication of the
participation of the diethoxy silane to the construction of the network in the paper, the effectiveness
of this mixture cannot be safely concluded. It is worth mentioning that for all these treatments the
pH of the treated materials was higher than pH 7.0. However, it seemed that for some unknown
reason the pH of the samples C5 was just neutral showing that when the trialkoxy silane was mixed
with the dialkoxy silane the mixture behaved as a weaker base. This point certainly deserves further
investigation. However, it can be assumed that since the silane uptake seems to be limited, the
overall amino content is lowered by the presence of the neutral dialkoxy silane.
The fact that some mixtures contained sodium borohydride (C2, C3, C4) did not seem to be
detrimental to the effect of the amino silanes on the mechanical properties. Sodium borohydride
could be used to decrease or eliminate the effect of the treatments on the optical properties of the
materials. This point will be examined in a forthcoming paper in this series15.
It was important to determine whether the nature of the amino group could influence the variation
of the mechanical properties. A comparison was effected on the same paper with different amino
silanes, one being functionalized by a tertiary amine function. The results are given in Table 4.
Despite some scatter, which is to be assigned to the fact that these papers came from different pages
of the same book, all silanes having a primary amine function gave the same result, i.e. an increase
of the breaking length together with a pH increase towards the alkaline. The silane having a tertiary
amine group (DMATMS) gave lower values for the breaking length, which means that the nature of
the amine function of this silane was involved in the increase of the breaking length. The fact that a
dialkoxy silane - AMDES - gave approximately the same result as ATMS or AATMS seems to
indicate that they were operating with the same mechanism. There are two ways of considering this
fact. The first is to state that the three products formed a cross-linked network. Since the bifunctional silane - AMDES - cannot give a cross-linked polymer only using the sila-nol condensation, it
could be suggested that the amino group participates to the formation of the network in the paper
web. This can be achieved by the reaction of the amino groups with some carbonyl functions borne
by the fibers. The second is to consider that all three products gave linear (or non-cross-linked)
polymer chains by polycondensation. Consequently, these polycondensation products should be
extractible by ethanol. Experiments were carried out and since the polymers were not significantly
extractible from these samples (G, H or A), it was possible to conclude that it was not only the
silanol groups that underwent self-condensation according to the usual chemistry of the
alkoxysilanes, but also that the amino groups were able to react with the cellulosic substrate.
It is to be noticed that the increase of the tensile strength was not always of the same amount as seen
in Table 4. The increase was often in the order of 50% or more, but sometimes a more modest
improvement of only 10% was observed. A possible explanation may be that the silane solutions
had some difficulty in penetrating papers of a compact structure.
A comment must be given on the behavior of the treated papers upon ageing at 80°C (room RH, i.e.
dry). It is clear that this ageing is by no means a true ageing showing a possible distant future
situation. The purpose of this post treatment was only to see whether it was necessary to wait a
certain time to reach a stabilized state. It was shown in the preceding paper that the surface pH
could decrease during this heating treatment11. From Table 4 it can be seen that if a small decrease
of tensile strength was observed on some samples upon heating at 80°C for three weeks, the
decrease was rather modest, and it can be concluded that paper treatment by amino alkoxy silanes is
a true strengthening process.
DISCUSSING THE STRENGTHENING EFFECT
Many samples were deacidified and strengthened by the amino alkyl alkoxy si-lanes process, and
from these experiments it can be concluded that the incorporation of ATMS and AMTMS brought a
definite increase of mechanical strength. They confirm the observations reported in Table 3 and
demonstrate that the strengthening effect can last during ageing. This is one of the most interesting
aspects of the incorporation of amino silanes into acidic papers.
Table 5: Effect of some amino silanes incorporated into papers of various initial acidity: mechanical
properties, and more particularly on folding endurance (24 hours conditioned at 24°C and 46%
RH).
* Charge = 300 g
There are several ways to improve the mechanical properties of papers. For instance, a
strengthening of the fibers themselves may produce stronger paper. Another way is to increase the
interfiber bonding energy, for instance by interpenetrating a macromolecular network into the fiber
network16. While an increase of the zero span breaking length was generally observed, it cannot be
safely concluded that this process was operating through an effect on the mechanical strength of the
individual fibers. Since the treating molecules have chemical functions, which allow selfcondensation, strengthening seems to be due to the effect of a interpenetrating network. A special
investigation on this point will be carried out in the future.
Finally, the resistance to folding was examined on two papers, one from a naturally aged acidic
book, and the other being a paper recently produced on which some determinations and ageing
effects were investigated. Results are presented in Table 5.
The reason for including a modern paper in the experiment was to investigate the problem of the
possible covalent bonding of the polysiloxane network with the fiber network through a reaction of
the amino groups with the carbonyl functions generated by a slow oxidation of the paper. As far as
oxidation was concerned, the modern paper was apparently free of its effects. It can be seen that the
presence of amino silane in the paper brought an important increase in the folding resistance. The
reason of such an effect is not completely understood, because it is clear from the breaking length
measurements that the paper had become more rigid. The fact that both mechanical characteristics
are improved could be assigned to the fact that the treatment helps to form a network penetrating
the fiber network16. The folding endurance was multiplied by a factor of 2 to 6, which showed that
the paper could recover sufficient mechanical strength to be handled again.
It is known that alkoxy silane functions are not stable in the presence of moisture. The hydrolysis of
these functions gives silanols, which in turn can self-condense into disiloxane functions, according
to the overall reaction:
2 R-Si-O-R' + H2O -> R-Si-O-Si-R + 2R'-OH
It seems that on trialkoxy silane the first hydrolysis proceeds at a lower rate than the second and the
third17. Consequently, it can be assumed that the process presented here can finally be considered as
the introduction of amino alkyl si-lanetriol into the paper web. These molecules containing
silanetriol functions can undergo self-condensation in alkaline medium to give bis-(alkyl)
tetrahydroxy disiloxane compounds. Further condensation of these latter products is likely, but
certainly takes a very long time in these conditions. Pohl and Osterholtz17 showed that at pH 4 and
35°C, condensation of silanetriol took several days, while the initial production of the silanetriol by
hydrolysis took only some tens of minutes. Thus, the paper web rapidly becoming rigid can be
assigned to the bifunctional-ity of the molecules, meaning that not only the reaction of the amino
group with the carbonyl functions present on the fiber surface must be observed, but also the
reaction of the silanol groups. The fact to be seen from Table 5, i.e. the more acidic the paper the
lower the folding resistance which means the more rigid the paper, supports the assumption that
there is a reaction between the primary amino groups and carbonyl functions.
It is interesting to see that the treatment of papers with amino alkyl trialkoxy silanes did not always
improve the folding endurance, while it always increased the tensile breaking resistance. This effect
can be assigned to the fact that, the more oxidized the paper, the more rigid it became after
treatment. This point could probably be adjusted by modifying the reactant concentration. Selfcondensation or reaction of the treatment product with the fiber surface could also be assumed, but
is less obvious because of the unavoidable presence of moisture: it is well known that the Si-O-C
chemical bond can be easily hydrolysed. Further work is in progress to clear up all these points.
CONCLUSION
To conclude on the effects amino alkyl trialkoxy silanes have on the mechanical properties of paper,
it is clear that these effects can be assigned to the formation of a macromolecular network,
interpenetrating the fibrous network. The general effect of such a reaction was demonstrated over
twenty years ago16. In principle, to give mechanical reinforcement the network must not necessarily
be covalently bound to the fiber network; the entanglement effect is sufficient for that. However,
the slight yellowing effect that has been noticed, might be assigned to a chemical reaction of the
amino group of the silanes with some chemical function of the cellulose, either with oxidized
groups formed during ageing, or with the terminal units of the cellulose macromolecular chains.
Actually, it can be assigned to the reaction of the amino groups with some carbonyl functions, most
probably coming from the lignin content in the paper, which produces aromatic imine functions.
These functions absorb light in the UV range.
It was necessary to firmly understand the origin of this effect and to determine whether it could be
possible to limit or to eliminate it. A future paper in this series will shed more light on this problem,
and a deeper study on the excellent ageing behavior of the deacidified papers is also to be
published.
ACKNOWLEDGMENTS
The Crompton (Witco) Corp. is gratefully acknowledged for a free sample of AMTMS. Authors are
grateful to S. Benziadi for technical assistance.
SUMMARIES
Mass Deacidification of Papers and Books III: Study of a Paper Strengthening and De-acidification
Process with Amino Alkyl Alkoxy Silanes
The object of this article is to study the strengthening effect of amino silanes on degraded paper, an
effect that has been observed in a previous study, focussed on amino silanes as deacidification
agents. Several paper samples of different fiber composition from the beginning of the 20 century
were treated with ethanolic solutions of several amino alkyl alkoxy silanes and submitted to
accelerated ageing 80°C dry (=room humidity). As parameters to describe mechanical strength,
breaking length and folding endurance were measured. In the main the former is enhanced by
several silane treatments, and the effect is stable during accelerated ageing. The chemical reactions
between reagent and cellulose that provide the strengthening effect are intensively discussed.
Several questions arising from this discussion will be studied in following-up research.
Neutralisation de masse des papiers et des livres III : Etude d'un procédé de renforcement et de
désacidification à l'aide d'amino-alkylalkoxy silanes
Le but de cet article est d'étudier l'effet de renforcement de l'introduction d'aminoalkylalcoxysilanes dans des papiers dégradés. Il avait été démontré par une étude préliminaire que ces composés pouvaient être des agents de désacidification. Plusieurs papiers de différentes compositions
fibreuses datant du début du 20ième siècle ont été traités par des solutions éthanoliques de divers
aminoalkylalcoxysilaneset soumis à un viellissement accéléré à 80°C, à l'humidité ambiante. La
longueur de rupture et la résistance au double pli ont été mesurées. La première est augmentée par
le traitements par divers silanes, et cet effet perdure après vieillissement. On discute de l'origine des
réactions chimiques qui peuvent prduire cet effet de renforcement, et les questions qui se posent
donnent des axes de recherche future.
Massenneutralisierung von Papier und Büchern III: Untersuchung der Festigung und der
Neutralisierung mit Amino-Alkylalkoxysilanen
Es wird die Festigungswirkung von Aminosilanverbindungen auf Papier untersucht, die bei einer
früheren Untersuchung zur Neutralisierung mit Aminosilanen beobachtet worden war. Papiere
verschiedener Zusammensetzung aus dem Anfang des 20. Jh. wurden mit äthanolischen Lösungen
verschiedener Amino-Alkylalkoxysilanen behandelt und einer beschleunigten Alterung (80°C,
trocken, d.h. Raumfeuchte) unterworfen. Zur Beschreibung der mechanischen Festigkeit wurden die
Zugfestigkeit, ausgedrückt als Reißlänge, und die Falzzahl gemessen. Vor allem er-sterer Parameter
wird durch die Silanbehandlung angehoben, und der Effekt bleibt bei der Alterung erhalten. Die
chemischen Reaktionen zwischen Behandlungssubstanz und Cellulose, welche die Festigung
bewirken, werden ausführlich diskutiert. Die Fragen, die sich dabei ergeben, werden Gegenstand
einer Folgeuntersuchung sein.
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S. Ipert
Centre Interrégional de Conservation du Livre
18 rue de la Calade
13200 Arles, France.
E. Rousset
Laboratoire du Génie des Procédés Papetiers
I.N.P.G., E.F.P.G., BP 65
38402 Saint-Martin d'Hères, France
H. Cheradame
Laboratoire Matériaux polymères aux Interface, UMR CNRS 7581,
Université d'Evry
Bid F. Mitterrand
91025 Evry, France