Advances in the applied chemistry of allylic polymers

Journal of Scientific & Industrial Research Vol. 63, April 2004, pp 365-375

Advances in the applied chemistry of allylic polymers

C C Menon* Devi Nivas, Edathil Road, Tellicherry 670 101

and A Selvaraj Hindustan Aeronautics Ltd, Bangalore

Received: 21 May 2003; revised received: 22 December 2003; accepted: 30 January 2004

Investigation of diallyl phthalate polymer (DAPP) based moulding powder with partial substitution of DAPP by epoxidisied DAPP polymer (EDAPP) indicates improvement in mechanical properties without detriment to electrical strength. Peak performance is manifested at 20 per cent substitution. EDAPP is also found to be an effective reactive diluent for cold setting epoxy resin adhesives. Bond strength is observed to be unaffected by extension up to 40 per cent. Hardboard (Fibre board) modified by DAPP as an impregnant results in a novel wood-polymer composite with tangible improvement of density, electrical strength, modulus of rupture and reduced water absorption having varied applications.

Keywords: Diallyl phthalate polymer, Epoxy resin adhesive, Bond strength

IPC Code: Int. Cl.7: B 27 K 3/08, C 01 B1 13/18

Introduction

Allylic polymers constitute an obscure segment of the mammoth polymer industry. Though derived from C-3

building block with associated cost advantages the special features of allylic polymerisation erode the benefits

accruing from raw material. The industrial precursors to allylic polymers like, allyl alcohol, allyl acetate, and allyl chloride are difficult to polymerise1. Further, unlike vinyl polymerization allylic compounds polymerise to generate only dimers, trimers, tetramers, and other cyclised low molecular weight material2. Perforce conversion has to be restricted to 25 per cent to avoid the danger of catastrophic gelation3. Improvement in the economics

of the process by recovery and recycling of unreacted monomer is hampered by constraints imposed by

considerations of safety and hazards. Notwithstanding all these inconvenient features allylic polymers have

etched a niche for themselves as a "speciality polymer" in electrical and electronic applications.

Allylic polymers are generally derived from diallyl or triallyl compounds. These multifunctional monomers

have enabled the development of sophisticated products like, UV - curable printing inks for high speed printing

operations, and products for inclusion in composites which require high energy electron beam activation to

penetrate bulky objects. Diethylene glycol bis-(allyl) carbonate is used to cast ophthalmic lenses and is called optical monomer4.

Diallyl phthalate polymer based moulding powders have acquired importance in electrical and electronic

sectors.

Moulding powders obtained by blending DAP polymer with lubricant,pigment catalyst, fillers, and mould

release agents have acquired importance for making components with multiple metallic inserts made of gold,

silver, copper, and alloys . The moulded products are utilised in wide range of applications like, sockets, TV

tuners, connectors, AC switch gears, rotary switches, aviation and space control panels. Rapid production of

shapes of outstanding dimensional stability with retention of electrical properties is possible. Prolonged service

at high humidity and temperature without any deterioration is another characteristic of the product. Defence

applications encompass aircraft and guided missile parts, radomes, and submarine applications.

The main hurdle to the expansion of the market is the

------------ *Author for correspondence

high cost. It was therefore envisaged that the

366

J SCI IND RES VOL 63 APRIL 2004

development of an extender-cum-builder for the polymer may contribute to market expansion and cost reduction. Investigation of the suitability of epoxidised DAP monomer and polymer was therefore undertaken.

It was also believed that the epoxidised derivatives may acquire a foothold in the sphere of large volume plastics like, PVC as plasticiser-cum-stabilizer. Another prospective outlet envisioned was as reactive diluent for epoxy resins having a large consumption in the adhesive sector. Based on these tenets a project was conceived with the salient features5 described subsequently:

(i) Study of the variation of the properties of DAP moulding powder as a function of the concentration of epoxidised additive and the identification of the optimal concentration of the candidate product for peak performance.

(ii) Evaluation of the performance of epoxidised DAP derivatives as reactive diluent for epoxy resin adhesives and the identification of optimal dilution level.

(iii) Investigation of the potential of DAP polymer as an impregnant to wood to develop novel wood-polymer composites.

Materials and Methods (a) Diallyl Phthalate Polymer (DAPP) as well as moulding powder derived (WIPON) were obtained from

Western India Plywoods Ltd., Kannur. (b) All other ingredients involved in the formation of moulding powder like glass fibre, magnesium and

titanium oxides, blue pigment, calcium stearates and tertiary butyl per benzoate were obtained from the production wing of Western India Plywoods Ltd, Kannur.

(c) Epoxidised DAP monomer and epoxidised polymer (EDAPP) were obtained from Sri Ram Institute for Industrial Research, Delhi from their pilot plant where a project sponsored by Western India Plywoods was in progress. Epoxidised products had the under mentioned quality parameters.

Product

Oxirane oxygen Iodine

value

value

Epoxidised DAP monomer

5.5

97

Epoxidised DAP polymer

1

28

Moulding powder was made by blending the required ingredients. Moulding was done in compression moulding machine supplied by Nuchem, Mumbai Mouldings were done at 1500 C, pressure 15 kg/cm2, and cycles of 3-5 min.

Mechanical properties were determined using Universal Testing Machines 2 and 20 t capacity.

Bar mouldings weighing 20 g and disc moulding of 60 g were made. Impact strength was determined using Charpy FIE-IT-042 Impact Tester as per MIL-1071 procedure. Rockwell hardness was determined using Brunel FIE/74/180 tester as per MIL-108 procedure.

Electrical resistivity of disc samples was determined using AE High voltage (150 KV) Tester supplied by Automatic Electrical Ltd., Mumbai according to MIL-4031 procedure.

The rheological properties of the moulding composition were evaluated using Haake Rheocord ? 90, Computerised Torque Rheometer providing information relating to fusion rates, curing, shear heat stability, torque, melt temperature, melt flow, and rotor speed.

Molecular weight distributions of DAP polymer and EDAP polymer were obtained by using Gel permeation chromatograph supplied by Waters Inc, USA.

Araldite resin AW106 Hardner HY 953U

MENON & SELVARAJ: ADVANCES IN APPLIED CHEMISTRY OF ALLYLIC POLYMERS

367

Manufactured and marketed by Hindustan Ciba ? Geigy Ltd.

EDAPP polymer, 25 per cent, was allowed to swell in EDAP monomer (75 per cent) to obtain a homogeneous viscous system. The viscous paste was used in different proportions with Araldite resin. The variation of pot life and curing time of the composite adhesive at different concentrations were studied.

Different substrate configurations like, wood-wood, metal-metal, ceramic-ceramic, and ceramic-metal were studied. Shear strength was determined by 2 t UTM machine.

The suitability of the composite adhesive for preparation of wood based laminate was studied. The face and core veneers were Kalpine (Gurjan). Adhesive was spread on core veneer. The laminates were assembled and configuration kept under pressure for 24 h. Glue shear strength was determined, using UTM as per IS 1708.

Pot life was determined by noting the time required for the composite adhesive to lose fluidity. Cure time was indicated by the time required to reach the condition of the absence of tackiness on touching. Standard hardboard having the following characteristics was used viz.

Density Water absorption in 24 h Modulus of rupture DAP polymer of the undermentioned quality was used

Softening range: Acid value Iodine value Solubility in acetone

: 0.8 g/cc : 40 per cent : - 300 kg/cm2 :

70 ? 110o C : 450 : 55-65 : Good

Both the items were obtained from Western India Plywoods Ltd, Kannur. Acetone available commercially was used.

Immersion of hardboard in a 10 per cent solution of DAP polymer in acetone containing 1per cent t-butyl perbenzoate was the adopted procedure. Samples were taken to determine the progress of polymer absorption. When the absorptions have reached the saturation level, the board was dried at 150oC for 3 min under 10kg/cm2 pressure. Polymer uptake, density, modulus of rupture, and water absorption of samples were determined.

Results and Discussion (i) The investigation provides strong evidence to the suitability and utilization of epoxidised diallyl phthalate

polymer as an additive to diallyl phthalate polymer based moulding composition. Data relating to mechanical property improvements by substitution of DAPP polymer by EDAPP polymer have been found up to 20 per cent. Above 20 per cent there is a declining trend which militates against the usage (Tables 1-4). The electrical property is unaltered by substitution (Table 5).

Gel permeation chromotographic data of DAP polymer and EDAP polymer indicate absence of significant reduction in molecular weight (Figure 1 and 2). Hence there is likelihood of parity in performance of the derived moulding compositions. This view is further strengthened by rheological data of the moulding compositions (Figure 3 and 4). The data presented together in a diagram exhibit virtual superimposition (Figure 5).

The thermogravimetry of the two compositions indicated the absence of any significant difference in thermal resistance. DAP base moulding powder shows a weight loss of 42.7 per cent as a consequence of complete cycle of heating upto 750oC. EDAP modified composition underwent 41.7 per cent weight loss. The absence of change of decomposition point and near equality of percentage of weight loss confirm that partial substitution of DAP polymer by EDAP polymer has no adverse impact on thermal stability (Figure 6 and 7).

368

J SCI IND RES VOL 63 APRIL 2004

A tentative view can be propounded relating to critical upper limit of 20 per cent and decline at

Table 1-- Substitution of DAP polymer by EDAP polymer

Sl. No

DAP polymer content per cent

EDAP polymer content per cent

Modulus of

rupture kg/cm2

1

100

619

2

80

20

725

3

60

40

541

4

40

60

668

5

20

80

393

6

0

100

299

Table 2--Compressive strength

100 per cent DAP 80 per cent DAP + 20 per cent EDAP

1400 kg/ cm2 1652 kg/ cm2

Table 3--Impact strength

100 per cent DAP 80 per cent DAP + 20 per cent EDAP

0.180 0.128

Table 4--Hardness

100 per cent DAP

115

80 per cent DAP + 20 per cent EDAP 124

Table 5 -- Dielectric breakdown voltage and strength

Voltage kv

Dielectric strength kv/mm

100 per cent DAP

35

80 per cent DAP

35.6

+ 20 per cent EDAP

10 10.86

MENON & SELVARAJ: ADVANCES IN APPLIED CHEMISTRY OF ALLYLIC POLYMERS

369

Figure 1 -- Data relating to gel permeation chromatography of DAP powder

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download