| Abstract | Bešavna forma uveza godinama se smatrala manje kvalitetnom i manje trajnom opcijom u
odnosu na šivane forme. Napredak tehnologije lijepljenja, smanjenje vremena isporuke i
uvođenje novih inovativnih materijala utjecali su na popularizaciju ove forme uveza. Odabir
vrste adheziva u doradnim procesima ovisi o svojstvima adherenata, zahtjevima krajnje
upotrebe, veličini proizvodnje te dostupnim procesima lijepljenja. Kako bi polivinil-acetatni
(PVAc) adheziv, korišten u proizvodnji malih naklada grafičkih proizvoda, postao učinkovitiji
i pouzdaniji te kako bi se povećala kvaliteta gotovih grafičkih proizvoda, provedena je
modifikacija PVAc adheziva dodavanjem nanočestica silika (SiO2) i titan-dioksida (TiO2).
Uspješnost utjecaja modifikacije PVAc adheziva nanočesticama sustavno je istražena, a kriteriji
kvalitete gotovih bešavno uvezanih knjigoveških proizvoda jasno su definirani čvrstoćom
uveza bešavno uvezanih knjiga, otpornošću adhezijskih spojeva na ljuštenje te definiranjem i
dodjeljivanjem oznaka za vizualnu evaluaciju stupnja otvaranja knjižnog bloka i ukupnog
vizualnog dojma. Uspješnost modifikacije PVAc adheziva nanočesticama uvjetovana je
zadržavanjem već postojećih pozitivnih svojstava ispitivanog adheziva, kao što su elastičnost
osušenog filma, nevidljivost linije lijepljenja i zadovoljavajuća otpornost na starenja te
pozitivnim djelovanjem nanočestica na njegova limitirajuća svojstva – čvrstoću gotovog
proizvoda, dugo vrijeme sušenja i nisku otpornost na promjene temperature i vlage. Optimalni
udio nanočestica u PVAc adhezivu određen je nakon analize morfološke strukture papiradheziv uzoraka pretražnom elektronskom mikroskopijom i infracrvenom spektroskopijom s
Fourierovom transformacijom te procjenom slobodne površinske energije metodom
određivanja kontaktnih kutova. Dodatkom 1% SiO2 nanočestica u PVAc adheziv čvrstoća
uveza znatno se povećala (do 27,50%), a 1% TiO2 nanočestica neznatno smanjila ili povećala.
Također, zabilježeno je povećanje postojanosti kvalitete uveza prilikom dodatka obiju vrsta
nanočestica (do 75,14%), kao i povećanje otpornosti adhezijskih spojeva na ljuštenje
(do 23,88%). Razlika u boji osušenog filma PVAc i nanomodificiranih PVAc adheziva nije
vidljiva golim okom, a sve vrste ispitivanih adheziva zadovoljavajuće su otpornosti na starenje.
Elastičnost nano-SiO2 PVAc adheziva veća je u odnosu na ostale ispitivane adhezive, a nanoTiO2 PVAc adheziv najbrže se suši. Dodatno, dodatak nanočestica pozitivno je utjecao na
povećanje otpornosti PVAc adhezijskih spojeva na promjene temperature i vlage. |
| Abstract (english) | Adhesives are non-metal materials that are used to join two or more components based on
their chemical and physical properties during the application of adhesive. The adhesion bonding
process is possible primarily due to the adhesion and cohesion attraction forces between the
adhesive and the adherent. The adhesive binding type, despite its high representation and
cost-effectiveness, was for years considered to be a lower quality and less durable option than
the sewn binding type. Adhesive binding is growing in popularity due to advancements in
adhesive binding technology, shorter delivery time and the introduction of innovative materials.
It is suitable for medium volume books (50 – 250 pages) and enables the production of durable
and flexible end-products in accordance with today’s market needs.
The selection of adhesive type for graphic postprocesses depends on the nature of the
adherents, the end-use performance requirements, the production volume and the available
adhesive bonding processes. Polyvinyl acetate (PVAc) adhesives are widely used adhesives in
the graphic industry for paper, board, leather and cloth. In this study, the modification of PVAc
adhesive, suitable for the short runs of graphic products, by adding silica (SiO2) and titanium
dioxide (TiO2) nanoparticles was carried out in order to produce more reliable, high-performing
adhesive and to increase the end-product quality. The efficacy of PVAc adhesive modification
with nanoparticles was systematically investigated. The quality criteria for adhesive bound
books are clearly defined by the bookbinding strength, by the peel resistance of adhesive joints
and by the definition and assignment of marks for the book opening behaviour and the overall
visual impression evaluation.
The modification of PVAc adhesive with nanoparticles is successful if the adhesive retains
its existing positive properties, such as satisfactory resistance to aging and elasticity and
invisibility of the dry adhesive film, with a positive effect of nanoparticles on its limiting
properties: end-product strength, long drying time and low resistance to temperature and
humidity changes. The optimum nanoparticle concentration in PVAc adhesive was defined by
determining the surface free energy and by analysing the morphological structure of the paperadhesive samples by scanning electron microscopy and Fourier transform infrared
spectroscopy.The page-pull binding strength results showed a significant increase in binding strength by
the addition of 1% SiO2 nanoparticles in PVAc adhesive (10.34% – 27.50%), regardless of the
paper type used in a book block. By the addition of 1% TiO2 nanoparticles, the binding strength
was slightly decreased or increased (-7.5% – 6.49%), depending on the paper type used for
making the book blocks. In addition, the modification of PVAc adhesive caused a significant
consistency improvement in binding quality, i.e. a reduction in the coefficient of variation
(43.18% – 75.14% [SiO2]; 8.72% – 48.37% [TiO2]). All uncoated book blocks, regardless of
the PVAc adhesive type used, achieved very good durability, while the coated book blocks had
poor durability and were not suitable for adhesive bookbinding with PVAc adhesives. The
modification of PVAc adhesive with SiO2 and TiO2 nanoparticles increased the peel resistance
of adhesive joints (6.00% – 23.88% [SiO2]; 2.38% – 9.10% [TiO2]). The addition of SiO2
nanoparticles to the PVAc adhesive had a positive impact on the visual evaluation of the
adhesive bookbinding quality. The visual evaluation of the book blocks after adding TiO2
nanoparticles remained almost unchanged or was slightly improved. The elasticity of the
adhesive, based on the material toughness, was increased by 9.15% by adding SiO2
nanoparticles. TiO2 nanoparticles significantly reduced the elasticity of PVAc adhesive, by
44.47%. The colour difference between dried PVAc adhesive film and dried nanomodified
PVAc adhesive films was not visible, but it was slightly larger for adhesive modified with TiO2
nanoparticles. All adhesives tested showed satisfactory resistance to UV radiation, i.e.
accelerated aging. The drying time of nano-TiO2 PVAc adhesive was much shorter than the
drying time of unmodified PVAc adhesive. Nano-SiO2 PVAc adhesive had a slightly longer
drying time than the original PVAc adhesive. The addition of nanoparticles had a positive effect
on increasing the resistance of adhesive joints to temperature and humidity changes. Nano-TiO2
PVAc adhesive joints were the most resistant to these changes.
Given that the quality of adhesive joints largely depends on the consistency of the
materials, procedures, methods and testing conditions used, it is necessary to define them
precisely to (if they are not defined in international standards or is standards do not exist) to
ensure the reliability and reproducibility of the results obtained. The guidelines for the
systematic investigation of adhesive joint quality are clearly defined in the first data package
(PP_01), along with an expected numerical range of the results and the coefficient of variation
for each quality test performed, in order to reduce measurement uncertainty and ensure correct
evaluation of the results in further research. The second data package (PP_02) provides thequality comparison of all the adhesive joints tested in this study, while the third data package
(PP_03) provides a simple quality comparison of all tested groups of adhesive bound books.
Based on the results presented, it can be concluded that there is no universal PVAc
adhesive that can fulfil all the postpress graphic processes, and it is usually necessary to
compromise when selecting the most appropriate adhesive according to a practical adhesive
system and the requirements of the end user. |
