2.2.2 Water and oil repellent finishing

Fluorocarbon polymers have been chosen to satisfy both water- and oil-repellency demands. Their main characteristic is a low surface tension (aprox. 15 mNm^-1) which causes excellent water and oil repellency effects. For good oil-repellency effects the orientation of hydrophobic atoms is of primary concern. Perfluorinated groups should be lined parallel which makes thick water and oil repellent layer [16, 17]. Because of the influence of alternating electric field it is assumed that hydrophobic fluoroalkyl groups could rotate into the polymer substrate what will decrease the repellency. For the purpose of thermal activation of hydrophobic FC groups microwave device have been modified with additional heated cylinder incorporated in the system [18]. In this study FC polymer with extender included in a formulation was applied with following concentration:

Durability of water- and oil-repellency to laundering and dry cleaning was tested after washing and cleaning cycles. Washing was performed in apparatus: Linitest, with 5 g/l of detergent and ratio 1 : 20, at 50 C, for 30 min. Dry cleaning was performed according to HRN.F.S3.027; AATCC 132-1998; ISO 105-DO1. Water repellency was tested by unstandardized Du Pont method. Tests were performed with drops of isopropanol/water mixure in ratios: from 0/100 (W as minimal degree) till 100/0 (10 as maximal degree). Oil repellency was tested according to AATCC 118-2002 (ISO 14419).

2.2.3. Flame retardant (FR) finishing

FR finishing was performed with high concentrations of organophosphorus reactant on cellulose material used for working clothes, whose surface mass was 250 g/m².

First bath (6) contains organophosphorus reactant (OFR) with conventional type of cross-linking agent based on melamine formaldehyde (MF). This type of binding agent between celullose and organophosphorus reactant was tried to be replaced with BTCA, which does not contain formaldehyde [19].

Effects of flame retardancy have been tested according to the method: ASTM D 626-68T. Durability to laundering was performed according to the Soaking test method: BS 5651:1978.

3. Results and discussion

Possibility of microwave treatment application for different finishing processes was determined in the present study.

3.1. Durable press finishing

From the results of WRA shown in tables 2 and 3 noticeable improvements can be seen in a case of treatment with microwaves. At the same time tensile strength retention has been improved, meaning that there is no usual negative interference with mechanical strength. Reasons of such an improvement have been presented earlier [20], giving an explanation with more uniform crosslinking obtained with microwaves.

According to Yang mechanical strength loss can be attributed to the choice of catalyst and its concentration rather than to the differences in the molecular structure and reagent reactivity.

Further improvement can be seen from the results of free formaldehyde release. Under the influence of microwaves formaldehyde release has been reduced by 50% compared to conventional thermal treatment what certainly gives an advantage to this method of treatment. Obtained reduction of formaldehyde content has been explained with the influence of microwaves to polar formaldehyde molecules. Because of the rapid charge changes molecules are heated resulting with expansion of the heat from the inside of the material to the surface. Liberated formaldehyde has the same flow what causes its reduction on the textile material.